| RFC : | rfc1841 |
| Title: | |
| Date: | September 1995 |
| Status: | INFORMATIONAL |
Network Working Group J. Chapman
Request For Comments: 1841 Cisco Systems, Inc.
Category: Informational D. Coli
Cisco Systems, Inc.
A. Harvey
Cisco Systems, Inc.
B. Jensen
Cisco Systems, Inc.
K. Rowett
Cisco Systems, Inc.
September 1995
PPP Network Control Protocol for LAN Extension
Status of Memo
This memo provides information for the Internet community. This memo
does not specify an Internet standard of any kind. Distribution of
this memo is unlimited.
Abstract
Telecommunications infrastructure is improving to offer higher
bandwidth connections at lower cost. Access to the network is
changing from modems to more intelligent devices. This informational
RFC discusses a PPP Network Control Protocol for one such intelligent
device. The protocol is the LAN extension interface protocol.
Table of Contents
1.0 Introduction ........................................... 3
1.1 LAN Extension Interface Topology ..................... 4
1.2 LAN Extension Interface Architecture ................. 5
1.3 LAN Extension Interface Protocol ..................... 6
2.0 LAN Extension Interface Protocol Control Packets........ 8
2.1 Startup Options ...................................... 8
2.2 Remote Command Options ............................... 14
2.3 Conditions for Sending PPP-LEX Packet ................ 17
3.0 Filter Protocol Type ................................... 18
3.1 LEX_RCMD_REQUEST - Filter Protocol Type............... 19
3.2 Response Packets - Filter Protocol Type............... 21
4.0 Filter MAC Address ..................................... 22
4.1 LEX_RCMD_REQUEST - Filter MAC Address ................ 23
4.2 Response Packets - Filter MAC Address................. 25
Chapman, et al Informational [Page 1]
RFC 1841 LAN Extension Interface Protocol September 1995
5.0 Set Priority ........................................... 27
5.1 LEX_RCMD_REQUEST - Set Priority ...................... 27
5.2 Response Packets - Set Priority ...................... 29
6.0 Disable LAN Extension Ethernet Interface ............... 30
6.1 LEX_RCMD_REQUEST - Disable LAN Extension
Ethernet Interface ................................... 31
6.2 Response Packets - Disable LAN Extension
Ethernet Interface ................................... 32
7.0 Enable LAN Extension Ethernet Interface ................ 33
7.1 LEX_RCMD_REQUEST - Enable LAN Extension
Ethernet Interface ................................... 33
7.2 Response Packets - Enable LAN Extension
Ethernet Interface ................................... 34
8.0 Reboot LAN Extension Interface Unit .................... 35
8.1 LEX_RCMD_REQUEST - Reboot LAN Extension Interface
Unit ................................................. 35
8.2 Response Packets - Reboot LAN Extension
Interface Unit ....................................... 36
9.0 Request Statistics ..................................... 37
9.1 LEX_RCMD_REQUEST - Request Statistics ................ 37
9.2 LEX_RCMD_ACK - Request Statistics .................... 39
9.3 LEX_RCMD_NAK/LEX_RCMD_REJ - Request Statistics ....... 44
10.0 Download Request ...................................... 45
10.1 LEX_RCMD_REQUEST - Download Request ................. 46
10.2 Response Packets - Download Request.................. 48
11.0 Download Data ......................................... 49
11.1 LEX_RCMD_REQUEST - Download Request ................. 49
11.2 Response Packets - Download Data .................... 51
12.0 Download Status ....................................... 52
12.1 LEX_RCMD_REQUEST - Download Status .................. 53
12.2 LEX_RCMD_ACK - Download Status ...................... 54
12.3 LEX_RCMD_NAK/LEX_RCMD_REJ - Download Status ......... 56
13.0 Inventory Request ..................................... 56
13.1 LEX_RCMD_REQUEST - Inventory Request ................ 57
13.2 LEX_RCMD_ACK - Inventory Request .................... 58
13.3 LEX_RCMD_NAK/LEX_RCMD_REJ - Inventory Request ....... 61
14.0 LAN Extension Interface Protocol Data Packets ......... 62
14.1 Frame Format ........................................ 62
14.2 Summary Field Descriptions........................... 63
Chapman, et al Informational [Page 2]
RFC 1841 LAN Extension Interface Protocol September 1995
NOTES ...................................................... 65
REFERENCES ................................................. 65
SECURITY CONSIDERATIONS .................................... 66
AUTHORS' ADDRESSES ......................................... 66
1.0 Introduction
An increasing number of corporations allow their employees to
telecommute to work due to local government regulations on traffic
and air pollution. Additionally, many businesses are run out of
internetworked home offices and small branch offices. With these
changes in the workplace, more people and businesses require Internet
access from small LANs.
Today, routers serve the LAN-to-LAN traffic using high-speed WAN
links such as leased lines, ISDN, or Frame Relay. This new breed of
Internet users from home offices and small branch offices may have a
different, less network-literate skill set than those connecting up
to the Internet today. These new users need an alternative to the
complex and hard-to-configure routers currently employed for
connectivity. One such alternative is a LAN extension interface unit.
A LAN extension interface unit is a hardware device installed at
remote sites (such as a home office or small branch office) that
connects a LAN across a WAN link to a router at a central site. The
following sections introduce a LAN extension interface topology,
architecture, and protocol.
Chapman, et al Informational [Page 3]
RFC 1841 LAN Extension Interface Protocol September 1995
1.1 LAN Extension Interface Topology
Figure 1 shows the topology of LAN extension interfaces. The figure
shows two LAN extension interface units connected via a WAN link to a
central or "host router."
Figure 1 LAN Extension Interface Topology
-----------------------------------------
Router
-----------------------------------------
Virtual Interface Virtual Interface
123.123.78.1 123.123.89.1
.........................................
Serial 0 Serial n
-----------------------------------------
|<---- WAN Link ---->|
------------------ ------------------
| LAN Extension | | LAN Extension |
| Interface Unit | | Interface Unit |
------------------ ------------------
| |
------------------ ------------------
| |
------------ ------------
| End node | | End node |
------------ ------------
123.123.78.2 123.123.46.2
Each LAN extension interface unit maps to a virtual interface at the
host router. The virtual interface mirrors the characteristics of the
LAN extension interface unit. To the routing protocols, the virtual
interface looks just like a local interface, but with the bandwidth
of a serial line. The virtual interface keeps the state (up or down)
of the LAN extension interface unit, and identifies each LAN
extension interface unit by its MAC address.
A LAN extension interface protocol transfers MAC frames from the LAN
extension interface unit across the serial line to the host router.
At the termination point in the router, the router routes the
packets. This topology uses only one subnet per remote LAN rather
than two, as is the case when routers exist on both ends of a WAN
link. Figure 1 shows this subnetting structure. The IP addresses of
the virtual interfaces on the router are in the same subnet as the IP
addresses of the end nodes on the LAN of the LAN extension interface
unit. The LAN extension interface unit itself has no IP address.
Chapman, et al Informational [Page 4]
RFC 1841 LAN Extension Interface Protocol September 1995
LAN extension interface units resemble bridges, but with the
following distinct differences:
* LAN extension interface units always depend on a host router.
They cannot operate standalone or even back-to-back with other
LAN extension interface units.
* LAN extension interface units need not employ any spanning tree
algorithm.
* (LAN extension interface units transfer MAC frames across a
serial line (like bridges), but a router can either route or
bridge the LAN extension interface data packets.
1.2 LAN Extension Interface Architecture
Figure 2 shows the basic LAN extension interface architecture.
Figure 2 LAN Extension Interface Architecture
Router LAN Extension Interface
------------------- -------------------
| Network Layer | | MAC Layer |
------------------- -------------------
| |
------------------- -------------------
| |Virtual Interface| | Filters | |
| ------------------- ------------------- |
| | | |
| ------------------- ------------- |
| | PPP | | RCMD | |
| | | | Handler | |
| ------------------- ------------- |
| | | |
| ------------------- ------------------- |
| |Serial Interface | | PPP | |
| ------------------- ------------------- |
| | | |
| | ------------------- |
| | | Serial Interface| |
| | ------------------- |
| | WAN Link | |
| --------------------------------------- |
| |
| Outbound Inbound |
--------------> <---------------
Chapman, et al Informational [Page 5]
RFC 1841 LAN Extension Interface Protocol September 1995
In the inbound direction (from the remote LAN, to the LAN extension
interface unit, across the WAN link, to the host router), the LAN
extension interface unit can filter received frames to optimize WAN
utilization. The LAN extension interface unit can filter frames by
protocol type or by MAC address. Frames that pass through the LAN
extension interface filters go to the WAN protocol state machine. In
Figure 2, this state machine is PPP. The LAN extension interface unit
adds PPP encapsulation and forwards the packet to the router via the
WAN serial link.
Upon receiving the frame, the host router decapsulates the PPP header
and passes the packet to the virtual interface. From there the
virtual interface handles the packet like any packet received on a
local interface -- by routing or bridging the packet to another
interface, depending on configuration.
In the outbound direction (from the host router, across the WAN link,
to the LAN extension interface unit, to the LAN), the host router's
virtual interface builds the full MAC header, before adding PPP
encapsulation. The router then sends the packet across the WAN serial
link to the LAN extension interface unit. The LAN extension interface
unit strips the PPP header and forwards the packet directly onto the
LAN. The host router has already determined that the packet needs to
be forwarded to the LAN extension interface unit, hence there is no
need for additional filtering or processing at that end.
Embedded in the data stream is a control stream for configuring and
managing the LAN extension interface unit from the host router. The
virtual interface makes the remote LAN extension interface unit
appear like a local router interface to the routing protocols.
Configuration commands and statistics gathering commands are issued
on the router to the virtual interface. The virtual interface formats
the LAN extension interface remote commands into encoded messages and
transfers them in-band with the data packets. The LAN extension
interface unit decodes the remote commands and executes them.
Responses are similarly formatted messages sent by the LAN extension
interface unit to the host router. The remote command messages use a
different encapsulation type than the data packets, as described
later in this document in the "LAN Extension Interface Protocol
Control Packets" and "LAN Extension Interface Protocol Data Packets"
sections.
1.3 LAN Extension Interface Protocol
To accommodate this LAN extension interface architecture, a new
Network Control Protocol (NCP) for PPP exists. This NCP is called
PPP-LEX. The basic functionality of PPP-LEX is to encapsulate LAN
Chapman, et al Informational [Page 6]
RFC 1841 LAN Extension Interface Protocol September 1995
extension interface control and data packets. The IETF has assigned
two new protocol types for these functions, as shown in Table 1.
Table 1 IETF Protocol Types for PPP-LEX
Protocol Type Function
0x8041 Encapsulates control packets
0x0041 Encapsulates data packets (MAC frames)
PPP is a natural choice for a LAN extension interface protocol
because it allows for negotiating a specific control protocol and
options at connection time. This means that network administrators do
not have to statically configure the router interface for remote
interfaces. Rather, remote interfaces negotiate the link at
connection time.
The LAN extension interface protocol employs PPP link operation as
described in RFC 1331, which reads as follows:
In order to establish communications of a point-to-point link,
each end of the PPP link must first send [Link Control Protocol]
LCP packets to configure and test the data link. After the link
has been established,the peer may be authenticated. Then PPP must
send NCP packets to choose and configure one or more network layer
protocols. Once each of the chosen network-layer protocols has
been configured, datagrams from each network layer protocol can be
sent over the link.
The link will remain configured for communications until explicit
LCP or NCP packets close the link down, or until some external
event occurs (an inactivity timer expires or network administrator
intervention). (References, [1])
Thus, the LAN extension interface unit and the host router exchange
PPP-LCP packets at connection time to dynamically configure and test
the WAN serial link. Once the link reaches an "opened" state, the LAN
extension interface unit and host router exchange PPP-LEX NCP packets
to configure the LAN extension interface protocol. Once it is
configured, the NCP (PPP-LEX) reaches an "opened" state, and PPP
carries the PPP-LEX control and data packets across the serial link.
At this point, link traffic is a any combination of LCPs, PPP-LEX
NCPs, PPP-LEX control packets, and PPP-LEX data packets.
Note that the LAN extension interface protocol is not a bridging
protocol. The only similarity to the PPP Bridging Control Protocol
(References. [2]) is that the LAN extension interface protocol also
encapsulates MAC frames.
Chapman, et al Informational [Page 7]
RFC 1841 LAN Extension Interface Protocol September 1995
The following sections detail PPP-LEX control packets and data
packets.
2.0 LAN Extension Interface Protocol Control Packets
There are two types of PPP-LEX control packets, as follows:
* Startup options packet
* Remote command options packets
The startup options packet is the first PPP-LEX NCP packet that the
LAN extension interface unit sends to the host router after the LCP
has reached an "opened" state. This required startup options packet
configures the LAN extension interface protocol and puts the PPP-LEX
NCP in an "opened" state.
Remote command options are the PPP-LEX NCP packets that control the
functioning and statistics gathering of the LAN extension interface
protocol.
2.1 Startup Options
The LAN extension interface unit sends a startup options packet to
the host router to negotiate the following startup options:
* MAC Type
* MAC Address
* LAN Extension
The MAC Type startup option informs the host router of the type of
media that the LAN extension interface unit is connected to. For
example, the LAN extension interface unit may be connected to an
Ethernet LAN or a Token Ring LAN. Currently, only Ethernet is
supported. The MAC type tells the host router what type of traffic
the LAN extension interface unit is prepared to receive. If the host
router rejects the MAC type, the LAN extension interface unit sends
the Configure-Request again.
The MAC Address startup option sends the MAC address of the LAN
extension interface unit to the host router to authenticate the LAN
extension interface unit and bind it to the corresponding virtual
interface at the host router. The host router also inserts the MAC
address in outbound packets. The MAC address is represented in IEEE
802.3 canonical format.
The LAN Extension startup option establishes the network layer
protocol (NCP) as PPP-LEX and provides the host router with the LAN
extension interface protocol version number.
Chapman, et al Informational [Page 8]
RFC 1841 LAN Extension Interface Protocol September 1995
Each startup option is transmitted in a series of three fields:
Option-Type, Option-Length, and Option-Data fields. The fields are
concatenated in the startup options Configure-Request packet.
Frame Format
Figure 3 shows a summary of the frame format for the startup options
packet. The LAN extension interface unit sends this startup options
packet to the host router. The LAN extension interface unit transmits
these fields from left to right.
Figure 3 Startup Options Frame Format (Configure-Request)
PPP Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address | Control | Protocol Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1 octet) (1) (2)
LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1 octet) (1) (2)
LAN Extension Interface Startup Options
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Length | Option-Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1 octet) (1)
Address
This PPP-specified field is one octet and contains the binary
sequence 11111111 (hexadecimal 0xFF), the All-Stations address. PPP
does not assign individual station addresses. The All-Stations
address must be recognized and received by all devices. For more
information on this field, refer to "The Point-to-Point Protocol
(PPP) for the Transmission of Multi-protocol Datagrams over Point-
to-Point Links." (References, [1])
Chapman, et al Informational [Page 9]
RFC 1841 LAN Extension Interface Protocol September 1995
Control
This PPP-specified field is one octet and contains the binary
sequence 00000011 (hexadecimal 0x03), the Unnumbered Information (UI)
command with the P/F bit set to zero.
For more information on this field, refer to "The Point-to-Point
Protocol (PPP) for the Transmission of Multi-protocol Datagrams over
Point-to Point Links." (References, [1])
Protocol-Type
The Protocol-Type field is two octets and contains the IETF-assigned
protocol type value. Valid LAN extension interface protocol type
values are as follows:
* 0x8041 (for control packets)
* 0x0041 (for data packets)
Because the startup options packet encapsulates LAN extension
interface control data, the valid value for this field is 0x8041.
Code
The Code field is one octet and identifies the type of LCP packet
that the LAN extension interface packet is sending. Valid values are
as follows:
* 0x01 - Configure-Request
* 0x02 - Configure-Ack
* 0x03 - Configure-Nak
* 0x04 - Configure-Rej
The LAN extension interface unit initiates the startup options
packet; therefore, the valid value for this field is 1.
Identifier
The Identifier field is one octet and contains a randomly generated
value. The value aids matching requests and replies. It is
recommended that a non-zero value be used for the identifier. That
is, zero could be used in the future for unsolicited messages from
the LAN extension interface unit. Valid values are 0x01-0xFF.
Chapman, et al Informational [Page 10]
RFC 1841 LAN Extension Interface Protocol September 1995
Length
The Length field is two octets and indicates the length of the entire
packet in octets, including the Code, Identifier, Length, and startup
options fields.
Option-Type
The Option-Type field is one octet and identifies the startup option
being negotiated. Valid values are as follows:
* 0x01 - MAC Type
* 0x03 - MAC Address
* 0x05 - LAN Extension
Option-Length
The Option-Length field is one octet and specifies the length of the
startup option fields, including the Option-Type, Option-Data, and
Option-Length fields.
Option-Data
The Option-Data field contains the data relating to the value
specified in the Option-Type field. That is, if the Option-Type field
specifies MAC type (0x01), then the Option-Data field contains the
MAC type (Ethernet, Token Ring, and so on). If the Option-Type field
specifies MAC address (0x03), then the Option-Data field contains the
actual MAC address. If the Option-Type field specifies LAN Extension
(0x05), then the Option-Data field contains LAN extension interface
software information. The following table defines the contents of the
Option-Data field for each possible Option-Type field value:
Option-Type Field Value Option-Data
0x01 (MAC Type) The most up-to-date value of the MAC type as
specified in the most recent "Assigned
Numbers" RFC. The current valid value from
that RFC follows:
* 0x01: IEEE 802.3/Ethernet with canonical
addresses
0x03 (MAC Address) The burned-in MAC address in IEEE 802.3
canonical format.
0x05 (LAN Extension) The LAN extension interface protocol version
number. 0x01 is the current protocol version
supported.
Chapman, et al Informational [Page 11]
RFC 1841 LAN Extension Interface Protocol September 1995
Example
In the Configure-Request packet that it sends to the host router, the
LAN extension interface unit concatenates the Option-Type, Option-
Data, and Option-Length fields for each startup option, as shown in
Figure 4. The LAN extension interface unit transmits these fields
from left to right.
Figure 4 Sample Startup Options Configure-Request Packet
PPP Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF | 0x03 | 0x8041 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Address Control Protocol-Type
LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x01 | 0x09 | 0x12 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Type Identifier Length
LAN Extension Interface Startup Options
<------------------------------------------------
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x01 | 0x03 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Type Option-Length
------------------------------>
4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0x01 |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Data
Chapman, et al Informational [Page 12]
RFC 1841 LAN Extension Interface Protocol September 1995
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x03 | 0x08 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Type Option-Length |
4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0A 0A 0A 0A 0B 0C |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
---------- Option-Data --------|
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x05 | 0x03 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Type Option-Length
4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0x01 |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Data
In Figure 4, the Address field always contains 0xFF, and the Control
field always contains 0x03. The Protocol-Type field value is 0x8041
because the startup options packet is a LAN extension interface
control packet. The Code field value is 0x01 because the LAN
extension interface unit is sending an LCP Configure-Request packet
to configure or negotiate PPP-LEX. The Identifier field contains a
randomly generated number. The Length field gives the total length of
the entire packet.
The first startup option is the MAC Type startup option. The Option-
Type value for MAC Type is 0x01. The Option-Length field value for
the MAC type startup option is 3 octets. The Option-Data field value
is 0x01 because, in this example, the LAN extension interface unit
connects to an Ethernet LAN using 802.3 canonical addresses.
The next startup option transmitted is the MAC Address. Its Option-
Type field value is 0x03, its Option-Length field value is 8 octets,
and its Option-Data field value is the actual MAC address.
Lastly, the LAN Extension startup option is transmitted. Its Option-
Type field value is 0x05, its Option-Length field value is 3 octets,
and its Option-Data field value is the LAN extension interface
protocol version number (0x01).
Chapman, et al Informational [Page 13]
RFC 1841 LAN Extension Interface Protocol September 1995
The host router responds to this LCP Configure-Request packet with an
LCP Configure-Ack packet, Configure-Nak packet, or Configure-Rej
packet. For more information on these packets, refer to "The Point-
to-Point Protocol (PPP) for the Transmission of Multi-protocol
Datagrams over Point-to-Point Links" RFC. (References, [1])
2.2 Remote Command Options
Once the host router responds to the startup options Configure-
Request packet with a Configure-Ack packet, the PPP-LEX NCP is in an
"opened" state, and the LAN extension interface unit and the host
router freely exchange PPP-LEX data packets and remote command
options packets.
The host router initiates PPP-LEX remote command options packets to
control the configuration of the LAN extension interface unit and to
gather statistics. There are 11 types of remote command options that
the host router can send in a LEX_RCMD_REQUEST packet to the LAN
extension interface unit. The LAN extension interface unit responds
to a LEX_RCMD_REQUEST packet with a LEX_RCMD_ACK, LEX_RCMD_NAK, or
LEX_RCMD_REJ packet.
Frame Format
Figure 5 shows a summary of the frame format for a remote command
options packet. These fields are transmitted from left to right.
Figure 5 Remote Command Options Frame Format
PPP Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address | Control | Protocol Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1 octet) (1) (2)
LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1 octet) (1) (2)
Chapman, et al Informational [Page 14]
RFC 1841 LAN Extension Interface Protocol September 1995
LAN Extension Interface Remote Command Options
<--------------------------------
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1 octet) (1)
---------------------------------------------->
6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Length | Option-Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2)
Address
This PPP-specified field is a single octet and contains the binary
sequence 11111111 (hexadecimal 0xFF), the All-Stations address. PPP
does not assign individual station addresses. The All-Stations
address must be recognized and received by all devices. For more
information on this field, refer to "The Point-to-Point Protocol
(PPP) for the Transmission of Multi-protocol Datagrams over Point-
to-Point Links." (References, [1])
Control
This PPP-specified field is a single octet and contains the binary
sequence 00000011 (hexadecimal 0x03), the Unnumbered Information (UI)
command with the P/F bit set to zero.
For more information on this field, refer to "The Point-to-Point
Protocol (PPP) for the Transmission of Multi-protocol Datagrams over
Point-to Point Links." (References, [1])
Note: Hereafter the Address and Control fields will be represented
together as a 2-octet field containing "0xFF03".
Protocol-Type
The Protocol-Type field is two octets and contains the IETF-assigned
protocol type value. Valid LAN extension interface protocol type
values follow:
* 0x8041 (for control packets)
* 0x0041 (for data packets)
Chapman, et al Informational [Page 15]
RFC 1841 LAN Extension Interface Protocol September 1995
Because the remote command options packet encapsulates LAN extension
interface control data, the valid value for this field is 0x8041.
Code
The Code field is one octet and identifies the type of PPP-LEX
packet. Valid values are as follows:
* 0x40 - LEX_RCMD_REQUEST packet
* 0x41 - LEX_RCMD_ ACK packet
* 0x42 - LEX_RCMD_NAK packet
* 0x43 - LEX_RCMD_REJ packet
The host router sends the LEX_RCMD_REQUEST packet, and the LAN
extension interface unit sends the LEX_RCMD_ACK, LEX_RCMD_NAK, and
LEX_RCMD_REJ packets.
Identifier
The Identifier field is one octet and contains a randomly generated
value. The value aids matching requests and replies. It is
recommended that a non-zero value be used for the identifier. That
is, zero could be used in the future for unsolicited messages from
the LAN extension interface unit. Valid values are 0x01-0xFF.
Length
The Length field is two octets and indicates the length in octets of
the entire packet, including the Code, Identifier, Length, and remote
command options fields.
Option-Type
The Option-Type field is one octet and identifies the remote command
option being transmitted. Valid values are as follows:
* 0x01 - Filter Protocol Type
* 0x02 - Filter MAC Address
* 0x03 - Set Priority
* 0x04 - Disable LAN Extension Ethernet Interface
* 0x05 - Enable LAN Extension Ethernet Interface
* 0x06 - Reboot LAN Extension Interface Unit
* 0x07 - Request Statistics
* 0x08 - Download Request
* 0x09 - Download Data
* 0x0A - Download Status
* 0x0B- Inventory Request
Chapman, et al Informational [Page 16]
RFC 1841 LAN Extension Interface Protocol September 1995
Each remote command option is discussed in detail in its own section
later in this document.
Option-Flags
This field is one octet and further specifies the remote command
option, containing specific actions that must be followed.
Option-Length
The Option-Length field is two octets and specifies the length in
octets of the remote command option fields, including the Option-
Type, Option-Flags, Option-Length, and Option-Data fields.
Option-Data
Option-Data field contains data relating to the remote command option
specified in the Option-Type field.
2.3 Conditions for Sending PPP-LEX Packet
This section describes the general conditions under which PPP-LEX
packet types are sent. For specific information by remote command,
refer to the appropriate remote command section later in this
document.
LEX RCMD_REQUEST Packet
The host router sends LEX_RCMD_REQUEST packets to the LAN extension
interface unit to initiate a remote command request. Until the host
router receives a LEX_RCMD_ACK, LEX_RCMD_NAK, or LEX_RCMD_REJ packet
from the LAN extension interface unit, the host router continues to
send the LEX_RCMD_REQUEST packet a default number of times, at which
point the host router times out.
LEX_RCMD_ACK Packet
The LAN extension interface unit responds to a LEX_RCMD_REQUEST
packet with a LEX_RCMD_ACK packet when it correctly receives the
request and is able to perform the request.
LEX RCMD_NAK Packet
The LAN extension interface unit responds to a LEX_RCMD_REQUEST
packet with a LEX_RCMD_NAK packet when the LAN extension interface
unit recognizes all the elements of the remote command option, but
some elements are not acceptable. Upon receipt of a LEX_RCMD_NAK
packet, the host router immediately stops sending the request.
Chapman, et al Informational [Page 17]
RFC 1841 LAN Extension Interface Protocol September 1995
LEX RCMD_REJ Packet
The LAN extension interface unit responds to a LEX_RCMD_REQUEST
packet with a LEX_RCMD_REJ packet when the Option-Type value in the
request packet is invalid. Invalid Option-Type values are those less
than 0x01 or greater than 0x0B. Currently, this is the only condition
under which the LAN extension interface unit sends a LEX_RCMD_REJ
packet. Upon receipt of a LEX_RCMD_REJ packet, the host router
immediately stops sending the request.
The following sections detail each of the 11 remote command options.
The sections provide a general description of the option and then
specify the option's Option-Type, Option-Flags, Option-Length, and
Option-Data fields. In addition, the sections describe the return
messages from the LAN extension interface unit.
3.0 Filter Protocol Type
The host router sends a LEX_RCMD_REQUEST packet with an Option-Type
of 0x01 to the LAN extension interface unit to configure the LAN
extension interface unit to filter inbound packets by protocol type.
A protocol type filter determines whether or not the LAN extension
interface unit forwards packets of a specific protocol type to the
host router. A protocol type filter consists of a 16-bit value, 16-
bit mask, and a permit or deny field. (See the "Option-Data Field
Descriptions" section for more information on these filter fields.)
A LEX_RCMD_REQUEST packet can contain 0 to 200 (depending on MTU
size) protocol type filters. When a LEX_RCMD_REQUEST packet contains
multiple filters, they are concatenated.
The LAN extension interface unit applies the protocol type filters to
each inbound packet's protocol type field in the order in which the
filters exist in the filter table. A packet must be permitted by one
of the filters before the LAN extension interface unit can forward
the packet across the serial link.
The following example is a filtering algorithm:
if (protocol_type_field & (~filter_mask)) == filter_value)
if (permit/deny_field == PERMIT) <forward packet on serial LAN>
else <DROP PACKET>
The protocol type filter should also be applied to the DIX type code
field of Ethernet II frames as well as to IEEE 802.2 SNAP packets.
Chapman, et al Informational [Page 18]
RFC 1841 LAN Extension Interface Protocol September 1995
3.1 LEX RCMD_REQUEST-Filter Protocol Type
Figure 6 shows a frame format summary of a LEX_RCMD_REQUEST packet
for the Filter Protocol Type remote command option. The host router
transmits the fields from left to right.
Figure 6 LEX_RCMD_REQUEST Packet Frame Format - Filter Protocol Type
PPP Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF03 | Protocol-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2 octets) (2)
LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
LAN Extension Interface Remote Command Options
<--------------------------------
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1)
---------------------------------------------->
6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Length | Option-Data |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2)
Where the Option-Data field contains the following fields:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value (16 bits) | Value (16 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Permit/Deny (16 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Chapman, et al Informational [Page 19]
RFC 1841 LAN Extension Interface Protocol September 1995
Summary Field Descriptions
For a complete description of the fields in the PPP Header, the LAN
Extension Interface Protocol Header, and the LAN Extension Interface
Remote Command Options, refer to the "Remote Command Options" section
earlier in this document. The following table provides a summary of
these fields when sending a LEX_RCMD_REQUEST packet that configures
the LAN extension interface unit to filter by protocol type.
Table 2 Field Values for LEX_RCMD_REQUEST Packet-Filter Protocol Type
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code 0x40 (LEX_RCMD_REQUEST packet)
Identifier Valid values: 0x01-0xFF
Length Minimum length = 12 octets
Maximum length = 1212 octets
Option-Type 0x01 (Filter Protocol Type)
Option-Flags None
Option-Length Minimum length = 4 octets
Maximum length = 1204 octets
Option-Data Zero or more filters to be applied at
the LAN extension interface unit. See the
following "Option-Data Field Descriptions"
for details.
Option-Data Field Descriptions
The following three Option-Data fields are used in conjunction to
specify a protocol type filter:
* Value
The Value field contains a 16-bit value that is any Ethernet type
code. Refer to the "Assigned Numbers" RFC for valid Ethernet type
codes. (References, [4]).
* Mask
The Mask field contains a 16-bit "wild card" mask. That is, this
field contains a 16-bit number whose ones bits correspond to the type
code bits to be ignored during the comparison. Thus, the mask
excludes bits from the comparison in the protocol type filter.
Chapman, et al Informational [Page 20]
RFC 1841 LAN Extension Interface Protocol September 1995
* Permit/Deny
The Permit/Deny field determines whether a protocol type filter
permits or denies inbound frames to pass to the host router. A permit
value is a non-zero value that allows frames of a specific protocol
type to pass to the host router. A deny value is a zero value that
does not allow frames of a specific protocol type to pass to the host
router.
Implementation Notes
Each LEX_RCMD_REQUEST packet is a complete specification of all
protocol type filters and replaces any previously established
filters.
Note the following special cases:
* A LEX_RCMD_REQUEST packet with an Option-Length field equal
to four (without any filter entries) instructs the LAN extension
interface unit to turn off protocol type filtering. All MAC
protocol types are forwarded.
* A LEX_RCMD_REQUEST packet with a filter entry of 0x0000 in the
Value field, 0xFFFF in the Mask field, and a positive value in the
Permit/Deny field means that if previous filters in the filter list
do not permit the inbound packet then this filter entry will. This
filter entry is typically the last filter in a list of filters
contained within the Option-Data field.
* A LEX_RCMD_REQUEST packet with a filter entry of 0x0000 in the
Value field, 0xFFFF in the Mask field, and a zero in the
Permit/Deny field, means that the LAN extension interface unit must
deny all protocol types. This filter is typically the last filter in
a list of filters contained within the Option-Data field.
3.2 Response Packets - Filter Protocol Type
The following packets are valid responses to the Filter Protocol Type
LEX_RCMD_REQUEST packet:
* LEX_RCMD_ACK - Filter Protocol Type
The LAN extension interface unit sends a LEX_RCMD_ACK packet in
response to the Filter Protocol Type LEX_RCMD_REQUEST packet when the
LAN extension interface unit correctly receives the Filter Protocol
Type remote command option and applies all filter entries to its
filter table. All filter entries are returned to the host router in
the LEX_RCMD_ACK packet.
Chapman, et al Informational [Page 21]
RFC 1841 LAN Extension Interface Protocol September 1995
* LEX_RCMD_NAK - Filter Protocol Type
The LAN extension interface unit sends a LEX_RCMD_NAK packet in
response to the Filter Protocol Type LEX_RCMD_REQUEST packet when the
request contains an incorrect number of bytes in the filter or when
there are no more filter entries available. The LAN extension
interface unit continues to use the previous filter table (that is,
the filter table that existed prior to the receipt of the request).
The host router should signal an error to the user/network
administrator. All filter entries are returned to the host router in
the LEX_RCMD_NAK packet.
* LEX_RCMD-REJ - Filter Protocol Type
See the "Conditions for Sending PPP-LEX Packets" section earlier in
this document for more information on this packet type.
Table 3 summarizes the field values of Filter Protocol Type
LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ packets.
Table 3 Field Values for Response Packets - Filter Protocol Type
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code Valid values:
* 0x41 (LEX_RCMD_ACK packet)
* 0x42 (LEX_RCMD_NAK packet)
* 0x43 (LEX_RCMD_REJ packet)
Identifier The same value as that sent by the
LEX_RCMD_REQUEST packet
Length The same value as that sent by the
LEX_RCMD_REQUEST packet
Option-Type 0x01 (Filter Protocol Type)
Option-Flags None
Option-Length The same value as that sent by the
LEX_RCMD_REQUEST packet
Option-Data The filter entries sent in the
LEX_RCMD_REQUEST packet
4.0 Filter MAC Address
The host router sends a LEX_RCMD_REQUEST packet with an Option-Type
of 0x02 to the LAN extension interface unit to configure the LAN
extension interface unit to filter inbound packets by source MAC
address. A MAC address filter determines whether or not the LAN
extension interface unit forwards packets with a specific source MAC
Chapman, et al Informational [Page 22]
RFC 1841 LAN Extension Interface Protocol September 1995
address to the host router. A MAC address filter consists of MAC
address, a MAC address mask, and a permit or deny field. (See the
"Option-Data Field Descriptions" section later in this section for
more information on these filter fields.)
A LEX_RCMD_REQUEST packet can contain 0 to 100 (depending on MTU
size) MAC address filters. When a LEX_RCMD_REQUEST packet contains
multiple filters, they are concatenated.
The LAN extension interface unit applies MAC address filters to each
inbound packet's source MAC address in the order in which the filters
exist in the filter entry list. A packet must be permitted by one of
the filters before the LAN extension interface unit can forward the
packet across the serial link.
4.1 LEX RCMD_REQUEST - Filter MAC Address
Figure 7 shows a frame format summary of a LEX_RCMD_REQUEST packet
for the Filter MAC Address remote command option. The host router
transmits the fields from left to right.
Figure 7 LEX_RCMD_REQUEST Packet Frame Format - Filter MAC Address
PPP Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF03 | Protocol-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2 octets) (2)
LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
Chapman, et al Informational [Page 23]
RFC 1841 LAN Extension Interface Protocol September 1995
LAN Extension Interface Remote Command Options
<--------------------------------
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1)
---------------------------------------------->
6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Option-Length | Option-Data |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
(2)
Where the Option-Data field contains the following fields:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address (48 bits)....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address Mask (48 bits)....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Permit/Deny (16 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Summary Field Descriptions
For a complete description of the fields in the PPP Header, the LAN
Extension Interface Protocol Header, and the LAN Extension Interface
Remote Command Options, refer to the "Remote Command Options" section
earlier in this document. Table 4 provides a summary of these fields
when sending a LEX_RCMD_REQUEST packet that configures the LAN
extension interface unit to filter by source MAC address.
Table 4 Field Values for LEX_RCMD_REQUEST Packet - Filter MAC Address
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code 0x40 (LEX_RCMD_REQUEST packet)
Identifier Valid values: 0x01-0xFF
Length Minimum length = 12 octets
Maximum length = 1412 octets
Option-Type 0x02 (Filter MAC Address)
Option-Flags None
Option-Length Minimum length = 4 octets
Chapman, et al Informational [Page 24]
RFC 1841 LAN Extension Interface Protocol September 1995
Maximum length = 1404 octets
Option-Data Zero or more filters to be applied at the
LAN extension interface unit. See the
following "Option-Data Field Description
section for details.
Option-Data Field Descriptions
The following three Option-Data fields are used in conjunction to
specify a MAC address filter:
* MAC Address
The MAC Address field contains a 48-bit IEEE 802.3 MAC address in
canonical format.
* MAC Address Mask
The MAC Address Mask field contains a "wild card" mask. The mask is a
48-bit hexadecimal number whose ones bits correspond to the MAC
address bits to be ignored during the comparison. The mask excludes
bits from the comparison in the MAC address filter.
* Permit/Deny
The Permit/Deny field determines whether or not a MAC address filter
permits or denies inbound frames of a specific MAC address to pass to
the host router. A permit value is a non-zero value that allows
frames of a specific MAC address to pass to the host router. A deny
value is a zero value that does not allow frames of a specific MAC
address to pass to the host router.
Implementation Notes
Each LEX_RCMD_REQUEST packet is a complete specification of all MAC
address filters and replaces any previously established filters.
A LEX_RCMD_REQUEST packet with an Option-Length field equal to four
(without any filter entries) instructs the LAN extension interface
unit to turn off filtering. All MAC addresses, except local
destination addresses cached in the self-learning filter, are
forwarded.
4.2 Response Packets - Filter MAC Address
The following packets are valid responses to the Filter MAC Address
LEX_RCMD_REQUEST packet:
Chapman, et al Informational [Page 25]
RFC 1841 LAN Extension Interface Protocol September 1995
* LEX_RCMD_ACK - Filter MAC Address
The LAN extension interface unit sends a LEX_RCMD_ACK packet in
response to a Filter MAC Address LEX_RCMD_REQUEST packet when the LAN
extension interface unit correctly receives the Filter MAC Address
remote command option and applies the entries to its filter table.
All MAC address filter entries are returned in the LEX_RCMD_ACK
packet.
* LEX_RCMD_NAK - Filter MAC Address
The LAN extension interface unit sends a LEX_RCMD_NAK packet in
response to the Filter MAC Address LEX_RCMD_REQUEST packet when the
request contains an incorrect number of bytes in the filter or when
there are no more filter entries available. The LAN extension
interface unit continues to use the previous filter table (that is,
the filter table that existed prior to the receipt of the request).
The host router should signal an error to the user/network
administrator. All filter entries are returned in the LEX_RCMD_NAK
packet.
* LEX_RCMD-REJ - Filter MAC Address
See the "Conditions for Sending PPP-LEX Packets" section earlier in
this document for more information on this packet type.
Table 5 summarizes the field values of Filter MAC Address
LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ packets.
Table 5 Field Values for Response Packets - Filter MAC Address
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code Valid values:
* 0x41 (LEX_RCMD_ACK packet)
* 0x42 (LEX_RCMD_NAK packet)
* 0x43 (LEX_RCMD_REJ packet)
Identifier The same value as that sent by the
LEX_RCMD_REQUEST packet
Length The same value as that sent by the
LEX_RCMD_REQUEST packet
Option-Type 0x02 (Filter MAC Address)
Option-Flags None
Option-Length The same value as that sent by the
LEX_RCMD_REQUEST packet
Option-Data The filter entries sent in the
Chapman, et al Informational [Page 26]
RFC 1841 LAN Extension Interface Protocol September 1995
LEX_RCMD_REQUEST packet
5.0 Set Priority
The host router sends a LEX_RCMD_ REQUEST with an Option-Type of 0x03
to the LAN extension interface unit to establish the sending priority
of different protocol type packets from the LAN extension interface
unit to host router. There are four levels of priority:
* High
* Medium
* Normal
* Low
Packets are classified according to protocol type and then are queued
to one of four output queues on the LAN extension interface unit that
correspond to the above priority levels. When the LAN extension
interface unit is ready to transmit a packet, it scans the priority
queues in order, from the highest to lowest, to find the highest
priority packet.
5.1 LEX RCMD_REQUEST - Set Priority
To establish priority queues for each protocol type, the host router
sends a Set Priority LEX_RCMD_REQUEST packet. Figure 8 shows a frame
format summary of such a LEX_RCMD_REQUEST packet. The host router
transmits the fields from left to right.
Figure 8 LEX_RCMD_REQUEST Packet Frame Format - Set Priority
PPP Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF03 | Protocol-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2 octets) (2)
LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
Chapman, et al Informational [Page 27]
RFC 1841 LAN Extension Interface Protocol September 1995
LAN Extension Interface Remote Command Options
<--------------------------------
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1)
---------------------------------------------->
6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Option-Length | Option-Data |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
(2)
Where the Option-Data field contains the following fields:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol Type (16 bits) | Protocol Value (16 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Summary Field Descriptions
For a complete descriptions of the fields in the PPP Header, the LAN
Extension Interface Protocol Header, and the LAN Extension Interface
Remote Command Options, refer to the "Remote Command Options" section
earlier in this document. The following table provides a summary of
these fields when sending a LEX_RCMD_REQUEST packet that sets
priority queuing.
Table 6 Field Values for LEX_RCMD_REQUEST Packet - Set Priority
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code 0x40 (LEX_RCMD_REQUEST packet)
Identifier Valid values: 0x01-0xFF
Length Minimum length = 12 octets
Maximum length = 1028 octets
Option-Type 0x03 (Set Priority)
Option-Flags None
Option-Length Minimum length = 4 octets
Maximum length = 1020 octets
Option-Data Protocol Type and Priority Value. See the
following "Option-Data Field Description"
section for details.
Chapman, et al Informational [Page 28]
RFC 1841 LAN Extension Interface Protocol September 1995
Option-Data Field Descriptions
The following Option-Data fields set the priority queuing of
different protocol type packets.
* Protocol Type
The Protocol Type field contains a 16-bit number that is any Ethernet
type code. See the most recent "Assigned Numbers" RFC for the correct
Ethernet type code.
* Priority Value
The Priority Value field specifies the priority queue for the
protocol type specified in the Protocol Type field. Valid values are
as follows:
- 0 - High priority queue
- 1 - Medium priority queue
- 2 - Normal priority queue
- 3 - Low priority queue
Sending a LEX_RCMD_REQUEST packet with an Option-Length of four (no
priority entries) disables priority queuing. When disabled, the LAN
extension interface unit transfers all packets at a normal (2)
priority level. When a new priority is specified, it overwrites the
previous setting.
5.2 Response Packets - Set Priority
The following packets are valid responses to the Set Priority
LEX_RCMD_REQUEST packet.
* LEX_RCMD_ACK - Set Priority
See the "Conditions for Sending PPP-LEX Packets" section earlier in
this document for more information on this packet type.
* LEX_RCMD_NAK - Set Priority
The LAN extension interface unit sends a LEX_RCMD_NAK packet in
response to the Set Priority LEX_RCMD_REQUEST packet when the request
contains an incorrect number of bytes in the message, when necessary
resources are not available, or when the specified priority is
invalid.
Chapman, et al Informational [Page 29]
RFC 1841 LAN Extension Interface Protocol September 1995
* LEX_RCMD-REJ - Set Priority
See the "Conditions for Sending PPP-LEX Packets" section earlier in
this document for more information on this packet type. Table 7
summarizes the field values of Set Priority LEX_RCMD_ACK,
LEX_RCMD_NAK, and LEX_RCMD_REJ packets.
Table 7 Field Values for Response Packets - Set Priority
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code Valid values:
* 0x41 (LEX_RCMD_ACK packet)
* 0x42 (LEX_RCMD_NAK packet)
* 0x43 (LEX_RCMD_REJ packet)
Identifier A randomly generated value that aids in
matching requests with replies
Length Minimum length = 12 octets
Maximum length = 1028 octets
Option-Type 0x03 (Set Priority)
Option-Flags None
Option-Length Minimum length = 4 octets
Maximum length = 1020 octets
Option-Data Protocol Type and Priority Value sent
in the LEX_RCMD_REQUEST packet
6.0 Disable LAN Extension Ethernet Interface
The host router sends a LEX_RCMD_ REQUEST with an Option-Type of 0x04
to the LAN extension interface unit to disable the LAN extension
Ethernet interface. This remote command option stops data traffic
from the LAN extension interface unit to the host router for
troubleshooting or for reconfiguring the LAN extension interface
unit. This remote command option only affects data traffic. PPP-LEX
control packets can still be transferred over the serial link.
Chapman, et al Informational [Page 30]
RFC 1841 LAN Extension Interface Protocol September 1995
6.1 LEX RCMD_REQUEST - Disable LAN Extension Ethernet Interface
Figure 9 shows a frame format summary of a LEX_RCMD_REQUEST packet
for the Disable LAN Extension Ethernet Interface remote command
option. The host router transmits the fields from left to right.
Figure 9 LEX_RCMD_REQUEST Packet Frame Format -
Disable LAN Extension Ethernet Interface
PPP Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF03 | Protocol-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2 octets) (2)
LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
LAN Extension Interface Remote Command Options
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Flags | Option-Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
Summary Field Descriptions
For complete descriptions of the fields in the PPP Header, the LAN
Extension Interface Protocol Header, and the LAN Extension Interface
Remote Command Option, refer to the "Remote Command Options" section
earlier in this document. The following table provides a summary of
these fields when sending a LEX_RCMD_REQUEST packet that disables the
LAN extension interface unit.
Chapman, et al Informational [Page 31]
RFC 1841 LAN Extension Interface Protocol September 1995
Table 8 Field Values for LEX_RCMD_REQUEST Packet -
Disable LAN Extension Ethernet Interface
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code 0x40 (LEX_RCMD_REQUEST packet)
Identifier Valid values: 0x01-0xFF
Length 12 octets
Option-Type 0x04 (Disable LAN Extension Ethernet
Interface)
Option-Flags None
Option-Length 4 octets
Option-Data None
6.2 Response Packets - Disable LAN Extension Ethernet Interface
LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD-REJ packets are valid
responses to the Disable LAN Extension Ethernet Interface
LEX_RCMD_REQUEST packet. Refer to the "Conditions for Sending PPP-LEX
Packets" section earlier in this document for more information on
when the LAN extension interface unit sends each of these response
packets. Note that the LAN extension interface unit sends the
LEX_RCMD_ACK packet after shutting down the interface.
Table 9 summarizes the field values of Disable LAN Extension Ethernet
Interface LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ packets.
Table 9 Field Values for Response Packets -
Disable LAN Extension Ethernet Interface
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code Valid values:
* 0x41 (LEX_RCMD_ACK packet)
* 0x42 (LEX_RCMD_NAK packet)
* 0x43 (LEX_RCMD_REJ packet)
Identifier The same value as that sent by the
LEX_RCMD_REQUEST packet
Length 12 octets
Option-Type 0x04 (Disable LAN Extension Ethernet
Interface)
Option-Flags None
Option-Length 4 octets
Option-Data None
Chapman, et al Informational [Page 32]
RFC 1841 LAN Extension Interface Protocol September 1995
7.0 Enable LAN Extension Ethernet Interface
The host router sends a LEX_RCMD_ REQUEST with an Option-Type of 0x05
to the LAN extension interface unit to enable the LAN extension
Ethernet interface. This remote command option allows LAN traffic to
flow into the LAN extension interface unit after the interface has
been disabled.
7.1 LEX RCMD_REQUEST - Enable LAN Extension Ethernet Interface
Figure 10 shows a frame format summary of a LEX_RCMD_REQUEST packet
for an Enable LAN Extension Ethernet Interface remote command option.
The host router transmits the fields from left to right.
Figure 10 LEX_RCMD_REQUEST Packet Frame Format - Enable LAN Extension
Ethernet Interface
PPP Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF03 | Protocol-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2 octets) (2)
LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
LAN Extension Interface Remote Command Options
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Flags | Option-Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
Summary Field Descriptions
For complete descriptions of the fields in the PPP Header, the LAN
Extension Interface Protocol Header, and the LAN Extension Interface
Remote Command Option, refer to the "Remote Command Options" section
earlier in this document. Table 10 provides a summary of these fields
when sending a LEX_RCMD_REQUEST packet that enables the LAN extension
Chapman, et al Informational [Page 33]
RFC 1841 LAN Extension Interface Protocol September 1995
Ethernet interface.
Table 10 Field Values for LEX_RCMD_REQUEST Packet -
Enable LAN Extension Ethernet Interface
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code 0x40 (LEX_RCMD_REQUEST packet)
Identifier Valid values: 0x01-0xFF
Length 12octets
Option-Type 0x05 (Enable LAN Extension Ethernet
Interface)
Option-Flags None
Option-Length 4 octets
Option-Data None
7.2 Response Packets - Enable LAN Extension Ethernet Interface
LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD-REJ packets are valid
responses to the Enable LAN Extension Ethernet Interface
LEX_RCMD_REQUEST packet. Refer to the "Conditions for Sending PPP-LEX
Packets" section earlier in this document for more information on
when the LAN extension interface unit sends each of these response
packets. Note that the LAN extension interface unit sends the
LEX_RCMD_ACK packet after enabling the interface.
The frame format of the response packets mirrors that of the request.
Table 11 summarizes the field values of Enable LAN Extension Ethernet
Interface LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ packets.
Table 11 Field Values for Response Packets -
Enable LAN Extension Ethernet Interface
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code Valid values:
* 0x41 (LEX_RCMD_ACK packet)
* 0x42 (LEX_RCMD_NAK packet)
* 0x43 (LEX_RCMD_REJ packet)
Identifier The same value as that sent by the
LEX_RCMD_REQUEST packet
Length 12 octets
Option-Type 0x05 (Enable LAN Extension Ethernet
Interface)
Chapman, et al Informational [Page 34]
RFC 1841 LAN Extension Interface Protocol September 1995
Option-Flags None
Option-Length 4 octets
Option-Data None
8.0 Reboot LAN Extension Interface Unit
The host router sends a LEX_RCMD_REQUEST packet with an Option-Type
of 0x06 to the LAN extension interface unit to cause the LAN
extension interface unit to reboot itself. The Option-Flags field
specifies the boot mode for the LAN extension interface unit. There
are two boot modes:
* The first boot mode (Option-Flag 0x00) is the default. The
default boot mode causes the LAN extension interface unit to
check for a valid Flash image and to boot from it if it exists.
If a valid Flash image does not exist, the default boot mode
causes the LAN extension interface unit to boot from the PROM
image. Similarly, if the Flash image is bad, then the LAN
extension interface unit recovers by booting from the PROM image.
* The second boot mode (Option-Flag 0x01) forces the LAN extension
interface unit to boot from the PROM image.
8.1 LEX RCMD_REQUEST - Reboot LAN Extension Interface Unit
Figure 11 shows a frame format summary of a LEX_RCMD_REQUEST packet
for a Reboot LAN Extension Interface Unit remote command option. The
host router transmits the fields from left to right.
Figure 11 LEX_RCMD_REQUEST Packet Frame Format -
Reboot LAN Extension Interface Unit
PPP Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF03 | Protocol-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2 octets) (2)
LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
Chapman, et al Informational [Page 35]
RFC 1841 LAN Extension Interface Protocol September 1995
LAN Extension Interface Remote Command Options
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Flags | Option-Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
Summary Field Descriptions
For complete descriptions of the fields in the PPP Header, the LAN
Extension Interface Protocol Header, and the LAN Extension Interface
Remote Command Option, refer to the "Remote Command Options" section
earlier in this document. Table 12 provides a summary of these fields
when sending a LEX_RCMD_REQUEST packet that instructs the LAN
extension interface unit to reboot.
Table 12 Field Values for LEX_RCMD_REQUEST Packet -
Reboot LAN Extension Interface Unit
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code 0x40 (LEX_RCMD_REQUEST packet)
Identifier Valid values: 0x01-0xFF
Length 12 octets
Option-Type 0x06 (Reboot LAN Extension Interface Unit)
Option-Flags Valid values:
* 0x00 - Reboot from Flash image if it
exists. If not, reboot from PROM. (This
value does not force the LAN extension
interface unit to reboot from PROM.)
* 0x01 - Reboot from PROM explicitly.
Option-Length 4 octets
Option-Data None
8.2 Response Packets - Reboot LAN Extension Interface Unit
LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD-REJ packets are valid
responses to the Reboot LAN Extension Interface Unit LEX_RCMD_REQUEST
packet. Refer to the "Conditions for Sending PPP-LEX Packets" section
earlier in this document for more information on when the LAN
extension interface unit sends each of these response packets. Note
that the LAN extension interface unit reboots after sending the
LEX_RCMD_ACK packet.
Chapman, et al Informational [Page 36]
RFC 1841 LAN Extension Interface Protocol September 1995
The frame format for the response packets mirrors that of the
request. Table 13 summarizes the field values for Reboot LAN
Extension Interface Unit LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ
packets.
Table 13 Field Values for Response Packets -
Reboot LAN Extension Interface Unit
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code Valid values:
* 0x41 (LEX_RCMD_ACK packet)
* 0x42 (LEX_RCMD_NAK packet)
* 0x43 (LEX_RCMD_REJ packet)
Identifier The same value as that sent in the
LEX_RCMD_REQUEST packet
Length 12 octets
Option-Type 0x06 (Reboot LAN Extension Interface Unit)
Option-Flags Valid values:
* 0x00 - Reboot from Flash image if it
exists. If not, reboot from PROM. (This
value does not force the LAN extension
interface unit to reboot from PROM.)
* 0x01 - Reboot from PROM explicitly.
Option-Length 4 octets
Option-Data None
9.0 Request Statistics
The host router issues a LEX_RCMD_REQUEST packet with an Option-Type
of 0x07 to obtain statistics information from the LAN extension
interface unit. The host router may want statistics information about
the following:
* Serial interface only
* LAN interface only
* Both the serial and LAN interfaces
The host router may also send a Statistics Request LEX_RCMD_REQUEST
packet to reset statistics in the LAN extension interface unit.
9.1 LEX RCMD_REQUEST - Request Statistics
Figure 12 shows a summary frame format of a LEX_RCMD_REQUEST packet
for a Statistics Request remote command option. The host router
transmits the fields from left to right.
Chapman, et al Informational [Page 37]
RFC 1841 LAN Extension Interface Protocol September 1995
Figure 12 LEX_RCMD_REQUEST Packet Frame Format - Request Statistics
PPP Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF03 | Protocol-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2 octets) (2)
LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
LAN Extension Interface Remote Command Option
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 0 1 2
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Flags | Option-Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
Summary Field Descriptions
For complete descriptions of the fields in the PPP Header, the LAN
Extension Interface Protocol Header, and the LAN Extension Interface
Remote Command Option, refer to the "Remote Command Options" section
earlier in this document. Table 14 provides a summary of these fields
when sending a LEX_RCMD_REQUEST packet that requests statistics of
the LAN extension interface unit.
Table 14 Field Values for LEX_RCMD_REQUEST Packet -
Request Statistics
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code 0x40 (LEX_RCMD_REQUEST packet)
Identifier Valid values: 0x01-0xFF
Length 12 octets
Option-Type 0x07 (Request Statistics)
Option-Flags Valid values:
* 0x01 - Resets serial statistics in the LAN
Chapman, et al Informational [Page 38]
RFC 1841 LAN Extension Interface Protocol September 1995
extension interface unit
* 0x02 - Returns serial statistics from the
LAN extension interface unit
* 0x04 - Returns LAN statistics from the LAN
extension interface unit
* 0x08 - Resets LAN statistics in the LAN
* extension interface unit
If both serial and LAN statistics are
desired, the corresponding bits of this
field should be set (that is, 0x06). The
serial interface statistics appear in the
response packet before the LAN statistics.
Option-Length 4 octets
Option-Data None
9.2 LEX RCMD_ACK - Request Statistics
The normal response to a Statistics Request LEX_RCMD_REQUEST packet
is a LEX_RCMD_ACK packet. This acknowledgment packet has an Option-
Type, an Option-Flags, and an Option-Length field followed by one or
two blocks of statistics data. The value in the Option-Flags field
indicates whether the packet has one or two blocks of statistics. For
more information on these values, see the following "Summary Field
Descriptions" section.
The frame format for the Statistics Request LEX_RCMD_ACK packet
follows. The LAN extension interface unit transmits the fields from
left to right.
Figure 13 LEX_RCMD_ACK Packet Frame Format - Request Statistics
PPP Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF03 | Protocol-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2 octets) (2)
LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
Chapman, et al Informational [Page 39]
RFC 1841 LAN Extension Interface Protocol September 1995
LAN Extension Interface Remote Command Options
<--------------------------------
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1)
----------------------------------------------->
6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Length | Option-Data |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2)
Where the Option-Data fields contains one or both of the following
statistics blocks:
Serial Interface Statistics Block:
(32 bits)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Packets Received |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of CRC Erros |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Framing Errors |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Overruns |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Packets Dropped |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Frame Aborts |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Packets in Error |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Packets Dropped Due to Lack of |
| Buffer Descriptors |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Time of Last Packet Received |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Average Data Rate |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Average Packet Rate |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Octets Received |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Packets Dropped Due to No Buffers|
Chapman, et al Informational [Page 40]
RFC 1841 LAN Extension Interface Protocol September 1995
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets Transmitted |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets with Error Transmissions|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Under-run Errors |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets in Low Priority Queue |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Size of Low Priority Queue |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets Dropped in Low Priority |
| Queue |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets in Normal Priority Queue|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Size of Normal Priority Queue |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets Dropped in Normal |
| Priority Queue |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets in Medium Priority Queue|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Size of Medium Priority Queue |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets Dropped in |
| Medium Priority Queue |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets in High Priority Queue |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Size of High Priority Queue |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets Dropped in High |
| Priority Queue |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Time of Last Packet Transmitted |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Carrier Transitions |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Transmitted Data Rate |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Octets Transmitted |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Chapman, et al Informational [Page 41]
RFC 1841 LAN Extension Interface Protocol September 1995
Lan Interface Statistics Block:
(32 bits)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Received |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Received with CRC Errors |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Received with Framing Errors |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Overruns |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Dropped Due to Congestion |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Frame Aborts |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Broadcast Packets Received |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Received with Errors |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Dropped Due to Lack of Buffer |
| Descriptors |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Runts (Too Small Packets) Received |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Time of Last Packet Received |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Average Data Rate |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Average Packet Rate |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Octets Received |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Dropped Due to Lack of Buffers |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Packets Transmitted |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Packets Transmitted with Errors |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Under-runs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Collisions (Ethernet) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Packets in Queue |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Chapman, et al Informational [Page 42]
RFC 1841 LAN Extension Interface Protocol September 1995
| LAN Output, Queue Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Packets Dropped in Queue |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Time of Last Packet Transmitted |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Transmit Data Rate |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Transmit Packet Rate |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Octets Transmitted |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN, Number of Interface Resets |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Note: Counts are cumulative since last counter reset. Time stamps
are in milliseconds since last given event. Packet rates are in
packets per second (averaged).
Summary Field Descriptions
For complete descriptions of the fields in the PPP Header, the LAN
Extension Protocol Header, and the LAN Extension Remote Command
Option, refer to the "Remote Command Options" section earlier in this
document. The following table provides a summary of these fields for
a LEX_RCMD_ACK packet that sends statistics to the host router.
Table 15 Field Values for LEX_RCMD_ACK Packet - Request Statistics
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code 0x41 (LEX_RCMD_ACK packet)
Identifier The same value as that sent by the
LEX_RCMD_REQUEST packet
Length Minimum length = 120 octets
Maximum length = 140 octets
Option-Type 0x07 (Request Statistics)
Option-Flags The LAN extension interface unit always sets
this field to reflect the actions taken in
response to the LEX_RCMD_ACK packet. Valid
values:
* 0x01 - Reset serial statistics in the LAN
extension interface unit
* 0x02 - Return serial statistics from the
LAN extension interface unit
* 0x04 - Return LAN statistics from the LAN
Chapman, et al Informational [Page 43]
RFC 1841 LAN Extension Interface Protocol September 1995
extension interface unit
* 0x08 - Reset LAN statistics in the LAN
extension interface unit
If both serial and LAN statistics are
returned, the corresponding bits of this
field should are set (that is, 0x06). The
serial interface statistics appear in the
response packet before the LAN statistics.
Option-Length Minimum length = 116 octets
Maximum length = 136 octets
Option-Data The Serial Interface Statistics Block, the
LAN Interface Statistics Block, or both the
Serial Interface and LAN Interface
Statistics blocks. When the Option-Data
contains both blocks, the Serial Interface
Block precedes the LAN Interface Block.
Statistics values that the LAN extension
interface unit does not collect/support
are retuned with a value of zero.
Implementation Notes
If the LAN extension interface unit does not implement the capability
of sending the serial and LAN interface statistics blocks separately,
the implementation may always return both statistics blocks (with the
Option-Flags and Option-Length fields containing the appropriate
corresponding values).
An implementation, such as a Token Ring LAN implementation, can
collect a different set of statistics than shown above by defining a
new statistics request type remote command option.
9.3 LEX RCMD_NAK/LEX RCMD_REJ - Request Statistics
The LAN extension interface unit sends a LEX_RCMD_NAK packet when the
Statistics Request LEX_RCMD_REQUEST packet did not specify the type
of statistics the host router wants. That is, the request's Option-
Flags field equals zero.
Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
in this document for information on when the LAN extension interface
unit sends a Request Statistics LEX_RCMD_REJ packet.
The frame format for the LEX_RCMD_NAK and LEX_RCMD_REJ packets is the
same as that of the Statistics Request LEX_RCMD_REQUEST packet. Table
16 summarizes the appropriate field values for the Statistics Request
LEX_RCMD_NAK and LEX_RCMD_REJ packets.
Chapman, et al Informational [Page 44]
RFC 1841 LAN Extension Interface Protocol September 1995
Table 16 Field Values for LEX_RCMD_NAK/LEX_RCMD_REJ Packets -
Request Statistics
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code Valid values:
* 0x42 (LEX_RCMD_NAK packet)
* 0x43 (LEX_RCMD_REJ packet)
Identifier The same value as that sent by the
LEX_RCMD_REQUEST packet
Length 12 octets
Option-Type 0x07 (Request Statistics)
Option-Flags The same value as that sent by the
LEX_RCMD_REQUEST packet
Option-Length 4 octets
Option-Data None
10.0 Download Request
The host router sends a LEX_RCMD_REQUEST packet with an Option-Type
of 0x08 to alert the LAN extension interface unit that the host
router will be issuing a software download to Flash memory. When the
LAN extension interface unit acknowledges the command, the host
router starts sending download data.
Chapman, et al Informational [Page 45]
RFC 1841 LAN Extension Interface Protocol September 1995
10.1 LEX RCMD_REQUEST - Download Request
Figure 14 shows a summary frame format of a LEX_RCMD_REQUEST packet
for a Download Request remote command option. The host router
transmits the fields from left to right.
Figure 14 LEX_RCMD_REQUEST Packet Frame Format - Download Request
PPP Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF03 | Protocol-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2 octets) (2)
LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
LAN Extension Interface Remote Command Option
<--------------------------------
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1)
----------------------------------------------->
6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Length | Option-Data |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2)
Where the Option-Data field contains the following fields:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Block Number (16 bits) | File Size (32 bits)....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Filename (Max. 64 octets).......
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Chapman, et al Informational [Page 46]
RFC 1841 LAN Extension Interface Protocol September 1995
Summary Field Descriptions
For a complete description of the fields in the PPP Header, the LAN
Extension Interface Protocol Header, and the LAN Extension Interface
Remote Command Option, refer to the "Remote Command Options" section
earlier in this document. Table 17 provides a summary of these fields
when sending a LEX_RCMD_REQUEST packet that informs the LAN extension
interface unit of an upcoming software download to Flash memory.
Table 17 Field Values for LEX_RCMD_REQUEST Packet - Download Request
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code 0x40 (LEX_RCMD_REQUEST packet)
Identifier Valid values: 0x01-0xFF
Length Variable depending on size of filename in
the Filename field. Valid range:
Minimum length = 19 octets
Maximum length = 82 octets
Option-Type 0x08 (Download Request)
Option-Flags None
Option-Length Variable depending on size of filename in
the Filename field. Valid range:
Minimum length = 11 octets
Maximum length = 74 octets
Option-Data Block Number, File Size, and Filename of
the code/image to be downloaded. See the
following "Option-Data Field Descriptions"
section for details.
Option-Data Field Descriptions
The Option-Data field contains the following fields:
* Block Number
The Block Number field contains a value that identifies a contiguous
group of code bits to be downloaded to the LAN extension interface
unit. In the LEX_RCMD_REQUEST packet, the Block Number is always
zero.
* File Size
The File Size field contains the size (in octets) of the code to be
downloaded to the LAN extension interface unit.
Chapman, et al Informational [Page 47]
RFC 1841 LAN Extension Interface Protocol September 1995
* Filename
The Filename field contains the name of the image to be transferred
to the LAN extension interface unit.
10.2 Response Packets - Download Request
The following packets are valid responses to a Download Request
LEX_RCMD_REQUEST packet:
* LEX_RCMD_ACK - Download Request
Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
in this document for more information on when the LAN extension
interface unit sends this packet.
* LEX_RCMD_NAK - Download Request
The LAN extension interface unit sends a Download Request
LEX_RCMD_NAK packet when the LAN Extension interface unit is
currently programming Flash, when the File Size field value in the
request is greater than the unit's available Flash bytes, when the
LAN extension interface unit is out of memory, or when the Block
Number field value in the request is not zero.
* LEX_RCMD_REJ - Download Request
Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
in this document for more information on when the LAN extension
interface unit sends this packet.
Table 18 summarizes the field values of the Download Request
LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ packets.
Table 18 Field Values for Response Packets - Download Request
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code Valid values:
* 0x41 (LEX_RCMD_ACK packet)
* 0x42 (LEX_RCMD_NAK packet)
* 0x43 (LEX_RCMD_REJ packet)
Identifier The same value as that sent by the
LEX_RCMD_REQUEST packet
Length The same value as that sent by the
LEX_RCMD_REQUEST packet
Chapman, et al Informational [Page 48]
RFC 1841 LAN Extension Interface Protocol September 1995
Option-Type 0x08 (Download Request)
Option-Flags None
Option-Length The same value as that sent by the
LEX_RCMD_REQUEST packet
Option-Data Block Number, File Size, and Filename of
the code/image to be downloaded.
11.0 Download Data
Once the host router receives a Download Request LEX_RCMD_ACK packet
from the LAN extension interface unit, the host router downloads the
data to be written to Flash memory by sending a LEX_RCMD_REQUEST
packet with an Option-Type of 0x09. The host router sends multiple
Download Data LEX_RCMD_REQUEST packets, each with 512 octets of
Option-Data containing the binary data to be programmed into Flash
memory.
A packet containing Option-Data with less than 512 octets signals the
end of the download data (that is, the end of tile). If the size of
the file being downloaded is an even multiple of 512 bytes, then the
last packet transferred should have an Option-Length of 6. That is,
the last packet transferred should have Option-Data containing the
Block Number field value but no data. A Block Number field value
without data alerts the LAN extension interface unit that this is the
last block to be transmitted.
11.1 LEX RCMD_REQUEST - Download Data
The frame format for the Download Data LEX_RCMD_REQUEST packet is
similar to a TFTP frame format. Figure 15 shows a summary frame
format. The host router transmits the fields from left to right.
Figure 15 LEX_RCMD_REQUEST Packet Frame Format - Download Data
PPP Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF03 | Protocol-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2 octets) (2)
Chapman, et al Informational [Page 49]
RFC 1841 LAN Extension Interface Protocol September 1995
LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
LAN Extension Interface Remote Command Option
<--------------------------------
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1)
----------------------------------------------->
6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Length | Option-Data |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2)
Where the Option-Data field contains the following fields:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Block Number (16 bits) | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| Binary Download Data (Max. 512 octets)..... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Summary Field Descriptions
For a complete descriptions of the fields in the PPP Header, the LAN
Extension Interface Protocol Header, and the LAN Extension Interface
Remote Command Option, refer to the "Remote Command Options" section
earlier in this document. The following table provides a summary of
these fields when sending a LEX_RCMD_REQUEST packet that download
software to the LAN extension interface unit.
Table 19 Field Values for LEX_RCMD_REQUEST Packet - Download Data
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code 0x40 (LEX_RCMD_REQUEST packet)
Chapman, et al Informational [Page 50]
RFC 1841 LAN Extension Interface Protocol September 1995
Identifier Valid values: 0x01-0xFF
Length Minimum length = 14 octets
Maximum length = 526 octets
Option-Type 0x09 (Download Data)
Option-Flags None
Option-Length Minimum length = 6 octets (signals end of
data transfer for a file with a file size
of an even multiple of 512 bytes)
Maximum length = 518 octets
Option-Data Block Number and Download Data. See the
following "Option-Data Field Descriptions"
section for details.
Option-Data Field Descriptions
The following Option-Data fields provide the LAN extension interface
unit with download data:
* Block Number
The Block Number identifies the contiguous group of code bits to be
downloaded. The host router automatically generates this number. The
first Download Data packet gets a block number of one. The host
router increments this Block Number value by one with every Download
Data LEX_RCMD_REQUEST packet sent to the LAN extension interface
unit. The maximum value of the Block Number is dependent on the
unit's Flash memory size.
* Download Data
The Download Data are the actual code bits being downloaded to the
LAN extension interface unit. A maximum of 512 octets of download
data can sent in one Download Data LEX_RCMD_REQUEST packet.
11.2 Response Packets - Download Data
The following packets are valid responses to a Download Data
LEX_RCMD_REQUEST packet:
* LEX_RCMD_ACK - Download Data
Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
in the document for more information on this packet.
Chapman, et al Informational [Page 51]
RFC 1841 LAN Extension Interface Protocol September 1995
* LEX_RCMD_NAK - Download Data
The LAN extension interface unit sends a Download Data LEX_RCMD_NAK
packet when the LAN extension interface unit is not in the proper
state or when accepting the data will over-run the download buffer.
* LEX_RCMD_REJ - Download Data
Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
in the document for more information on this packet.
Table 20 summarizes the field values of the Download Data
LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ packets.
Table 20 Field Values for Response Packets - Download Data
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code Valid values:
* 0x41 (LEX_RCMD_ACK packet)
* 0x42 (LEX_RCMD_NAK packet)
* 0x43 (LEX_RCMD_REJ packet)
Identifier The same value as that sent by the
LEX_RCMD_REQUEST packet
Length 14 octets
Option-Type 0x09 (Download Data)
Option-Flags None
Option-Length 6 octets
Option-Data Block Number only
12.0 Download Status
Upon completion of a Download Data sequence, the host router issues a
LEX_RCMD_REQUEST packet with an Option-Type of 0x0A to request status
of the success or failure of the download. A bad checksum of the
image or a malfunctioning Flash memory could cause the download to
fail.
Chapman, et al Informational [Page 52]
RFC 1841 LAN Extension Interface Protocol September 1995
12.1 LEX RCMD_REQUEST - Download Status
Figure 16 shows the frame format summary of a LEX_RCMD_REQUEST packet
for a Download Status remote command option. The host router
transmits the fields from left to right.
Figure 16 LEX_RCMD_REQUEST Packet Frame Format - Download Status
PPP Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF03 | Protocol-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2 octets) (2)
LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
LAN Extension Interface Remote Command Option
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Flags | Option-Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
Summary Field Descriptions
For a complete descriptions of the fields in the PPP Header, the LAN
Extension Interface Protocol Header, and the LAN Extension Interface
Remote Command Option, refer to the "Remote Command Options" section
earlier in this document. Table 21 provides a summary of these fields
when sending a LEX_RCMD_REQUEST packet that requests the download
status of the LAN extension interface unit.
Table 21 Field Values for LEX_RCMD_REQUEST Packet - Download Status
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code 0x40 (LEX_RCMD_REQUEST packet)
Chapman, et al Informational [Page 53]
RFC 1841 LAN Extension Interface Protocol September 1995
Identifier Valid values: 0x01-0xFF
Length 12 octets
Option-Type 0x0A (Download Status)
Option-Flags None
Option-Length 4 octets
Option-Data None
12.2 LEX RCMD_REQUEST - Download Status
When the LAN extension interface unit correctly receives the Download
Status LEX_RCMD_REQUEST packet, it returns a LEX_RCMD_ACK packet
containing the appropriate status information in the Option-Data
field.
Figure 17 shows the frame format for the Download Status LEX_RCMD_ACK
packet. The LAN extension interface unit transmits the fields from
left to right.
Figure 17 LEX_RCMD_ACK Packet Frame Format - Download Status
PPP Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF03 | Protocol-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2 octets) (2)
LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
Chapman, et al Informational [Page 54]
RFC 1841 LAN Extension Interface Protocol September 1995
LAN Extension Interface Remote Command Option
<--------------------------------
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1)
----------------------------------------------->
6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Length | Option-Data |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2)
Where the Option-Data field contains the following fields:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status (16 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Summary Field Descriptions
For a complete descriptions of the fields in the PPP Header, the LAN
Extension Interface Protocol Header, and the LAN Extension Interface
Remote Command Option, refer to the "Remote Command Options" section
earlier in this document. Table 22 provides a summary of these fields
when sending a status information to the host router.
Table 22 Field Values for LEX_RCMD_ACK Packet - Download Status
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code 0x41 (LEX_RCMD_ACK packet)
Identifier The same value as that sent by the
LEX_RCMD_REQUEST packet
Length 14 octets
Option-Type 0x0A (Download Status)
Option-Flags None
Option-Length 6 octets
Option-Data Status information. See the following
"Option-Data Field Descriptions" section
for details.
Chapman, et al Informational [Page 55]
RFC 1841 LAN Extension Interface Protocol September 1995
Option-Data Field Descriptions
The Option-Data field uses the Status field to send the download
status to the host router. The Status field reports the following
status information:
* 1 - Acknowledgment that no errors occurred
* 3 - Sequence error occurred
* 6 - Flash write error occurred
* 7 - Checksum error
12.3 LEX RCMD_NAK/LEX RCMD_REJ - Download Status
Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
in this document for information on when the LAN extension interface
unit sends a Download Status LEX_RCMD_NAK packet and Download Status
LEX_RCMD_REJ packet.
The frame format for these two response packets mirror the frame
format of the Download Status LEX_RCMD_REQUEST packet. Table 23
summarizes the field values of the Download Status LEX_RCMD_NAK and
LEX_RCMD_REJ packets.
Table 23 Field Values for LEX_RCMD_NAK/LEX_RCMD_REJ Packets - Download
Status
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code Valid values:
* 0x42 (LEX_RCMD_NAK packet)
* 0x43 (LEX_RCMD_REJ packet)
Identifier The same value as that sent by the
LEX_RCMD_REQUEST packet
Length 12 octets
Option-Type 0x0A (Download Status)
Option-Flags None
Option-Length 4 octets
Option-Data None
13.0 Inventory Request
The host router sends a LEX_RCMD_REQUEST packet with an Option-Type
of 0x0B to the LAN extension interface unit to request inventory
information. The host router may use this remote command option to
accomplish the following:
Chapman, et al Informational [Page 56]
RFC 1841 LAN Extension Interface Protocol September 1995
* Distinguish between different versions of the LAN extension
interface unit for determining their capabilities
* Determine whether a new version of Flash code should be downloaded
13.1 LEX RCMD_REQUEST - Inventory Request
Figure 18 shows the frame format for a LEX_RCMD_REQUEST packet with
an Inventory Request remote command option. The host router transmits
the fields from left to right.
Figure 18 LEX_RCMD_REQUEST Packet Frame Format - Inventory Request
PPP Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF03 | Protocol-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2 octets) (2)
LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
LAN Extension Interface Remote Command Option
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Flags | Option-Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
Summary Field Descriptions
For a complete description of the fields in the PPP Header, the LAN
Extension Interface Protocol Header, and the LAN Extension Interface
Remote Command Option, refer to the "Remote Command Options" section
earlier in this document. Table 24 provides a summary of these fields
when sending a LEX_RCMD_REQUEST packet that requests inventory
information.
Chapman, et al Informational [Page 57]
RFC 1841 LAN Extension Interface Protocol September 1995
Table 24 Field Values for LEX_RCMD_REQUEST Packet-Inventory Request
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code 0x40 (LEX_RCMD_REQUEST packet)
Identifier Valid values: 0x01-0xFF
Length 12 octets
Option-Type 0x0B (Inventory Request)
Option-Flags None
Option-Length 4 octets
Option-Data None
13.2 LEX RCMD_ACK - Inventory Request
When it correctly receives the Inventory Request remote command
option and retrieves the inventory information, the LAN extension
interface unit responds with an acknowledgment. This acknowledgment
contains the requested inventory information in the Option-Data
field.
Figure 19 shows the frame format for the Inventory Request
LEX_RCMD_ACK packet.
Figure 19 LEX_RCMD_ACK Packet Frame Format - Inventory Request
PPP Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF03 | Protocol-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2 octets) (2)
LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
Chapman, et al Informational [Page 58]
RFC 1841 LAN Extension Interface Protocol September 1995
LAN Extension Interface Remote Command Option
<--------------------------------
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1)
----------------------------------------------->
6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Length | Option-Data |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2)
Where the Option-Data field contains the following fields:
(32 bits)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flash Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HW Version | PROM Major Ver| PROM Minor Ver|Flash Major Ver|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Flash Minor Ver| FLAGS | RAM Major Ver | RAM Minor Ver |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Mac Address (6 octets) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Summary Field Descriptions
For a complete description of the fields in the PPP Header, the LAN
Extension Interface Protocol Header, and the LAN Extension Interface
Remote Command Option, refer to the "Remote Command Options" section
earlier in this document. Table 25 provides a summary of these fields
when acknowledging a LEX_RCMD_REQUEST packet that requests inventory
information.
Table 25 Field Values for LEX_RCMD_ACK Packet - Inventory Request
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code 0x41 (LEX_RCMD_ACK packet)
Chapman, et al Informational [Page 59]
RFC 1841 LAN Extension Interface Protocol September 1995
Identifier The same value as that sent by
LEX_RCMD_REQUEST packet
Length 34 octets
Option-Type 0x0B (Inventory Request)
Option-Flags None
Option-Length 26 octets
Option-Data Inventory data. See the following
"Option-Data Field Descriptions" section
for details.
Option-Data Field Descriptions
The Option-Data field of the LEX_RCMD_ACK packet uses the following
fields to send inventory data to the host router about the LAN
extension interface unit.
* Flash Size
This field contains the LAN extension interface unit's Flash size in
bytes.
* Serial Number
This field provides the LAN extension interface unit's serial number.
This is an unassigned, 32-bit number.
* HW Version
This field contains the version number of the LAN extension interface
hardware unit.
* PROM Major Ver
This field contains part of the version number of the PROM image.
"Major" indicates which major software release this revision belongs
to. For example, if the PROM version number is 1.2, then the major
version number is 1.
* PROM Minor Ver
This field contains part of the version number of the PROM image.
"Minor" indicates which minor software release this revision belongs
to. For example, if the PROM version number is 1.2, then the minor
version number is 2.
Chapman, et al Informational [Page 60]
RFC 1841 LAN Extension Interface Protocol September 1995
* Flash Major Ver
This field contains the "major" version number of the Flash image.
For example, if the Flash image version number is 1.2, then the major
version number is 1.
* Flash Minor Ver
This field contains the "minor" version number of the Flash image.
For example, if the Flash image version number is 1.2, then the minor
version number is 2.
* FLAGS
FLAGS report the boot status of the LAN extension interface unit. The
flags are as follows:
- 0x01 - Running PROM image
- 0x02 - Running Flash image
- 0x04 - PROM image passed checksum
- 0x08 - Flash image passed checksum
* RAM Major Ver
This field contains the "major" version number of the running image
in RAM. For example, if the RAM image version number is 1.2, then the
major version number is 1.
* RAM Minor Ver
This field contains the "minor" version number of the running image
in RAM. For example, if the RAM image version number is 1.2, then the
minor version number is 2.
* MAC Address
The MAC Address is the LAN extension interface unit's burned-in MAC
address in canonical format. This field is six octets.
13.3 LEX RCMD_NAK/LEX RCMD_REJ - Inventory Request
Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
in this document for information on when the LAN extension interface
unit sends an Inventory Request LEX_RCMD_NAK packet and Inventory
Request LEX_RCMD_REJ packet.
The frame format of these two response packets mirrors that of the
request. Table 26 summarizes the field values for such Inventory
Chapman, et al Informational [Page 61]
RFC 1841 LAN Extension Interface Protocol September 1995
Request LEX_RCMD_NAK/LEX_RCMD_REJ packets.
Table 26 Field Values for LEX_RCMD_NAK/LEX_RCMD_REJ Packets -
Inventory Request
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code Valid values:
* 0x42 (LEX_RCMD_NAK packet)
* 0x43 (LEX_RCMD_REJ packet)
Identifier The same value as that sent by the
LEX_RCMD_REQUEST packet
Length 12 octets
Option-Type 0x0B (Inventory Request)
Option-Flags None
Option-Length 4 octets
Option-Data None
14.0 LAN Extension Interface Protocol Data Packets
When the PPP-LEX NCP is in an "opened" state, the LAN extension
interface unit and the host router also exchange PPP-LEX data packets
(as well as control packets). There is only one type of PPP-LEX data
packet. This data packet is a subset of the PPP-BCP packet format.
The format subsetting is such that a PPP-BCP implementation will
successfully process a LAN extension interface protocol packet. The
differences are as follows:
* LAN ID field will not be present.
* LAN FCS field will never be present (that is, the F flag will
always be off [=0]).
* LAN ID flag (I) will always be off.
* Pad field for the serial link will never be present, and the
count field will be 0.
For detailed information on PPP-BCP packets, refer to the "PPP
Bridging Control Protocol (BCP)" RFC. (References, [2])
14.1 Frame Format
Figure 20 shows the frame format for a PPP-LEX data packet. The MAC
frame is transferred except for the FCS field. The LAN extension
interface unit computes the FCS for packets transferred to the LAN
and strips the FCS for packets destined for the host router.
Chapman, et al Informational [Page 62]
RFC 1841 LAN Extension Interface Protocol September 1995
Figure 20 PPP-LEX Data Packet Frame Format
(8 bits) (8 bits) (8 bits) (8 bits)
+-+-+-+-+-+-+-+-+
| HDLC FLAG |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF | 0x03 | 0x0041 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| F|I|Z|0| Pad | Mac Type | Destination MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source MAC Address | Length/Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LLC Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Serial) HDLC CRC | HDLC FLAG |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
14.2 Summary Field Descriptions
HDLC FLAG
HDLC Frame delimiter.
0xFF
This Address field contains the broadcast address.
0x03
This Control field contains unnumbered information.
0x0041
This field contains the IETF-assigned protocol type value for a
PPP-LEX data packet. In this case this field will always contain
0x0041.
Flags
The flags F, I, Z, 0 have the following meanings:
Chapman, et al Informational [Page 63]
RFC 1841 LAN Extension Interface Protocol September 1995
* F: Set bit F if the LAN FCS field is present. Because PPP-LEX
data packets do not contain the LAN FCS field, this bit should
not be set (field=0).
* I: Set bit I if the LAN ID field is present. Because PPP-LEX
data packets do not contain the field, this bit should not be
set (field=0).
* Z: Set bit Z if IEEE 802.3 Pad must be zero filled to minimum
size.
* 0: Reserved, must be zero.
Pad
Any PPP frame may have padding inserted in the Optional Data Link
Layer Padding field. The value tells the receiving system how many
pad octets to strip off. The LAN extension interface protocol does
not support the Optional Data Link Layer Padding field, so the
value of this field should be zero.
MAC Type
This field contains the most up-to-date value of the MAC type as
specified in the most recent "Assigned Numbers" RFC. The current
value is as follows:
* 1: IEEE 802.3/Ethernet with canonical addresses
Destination MAC Address
This field is 6 octets and contains the MAC address of the
destination system as defined by IEEE. The MAC Type field defines
the bit ordering.
Source MAC Address
This field is 6 octets and contains the MAC address of the
destination system as defined by IEEE. The MAC Type field defines
the bit ordering.
Length/Type
This field is any Ethernet protocol type (See RFC 1700 in the
references "Assigned Numbers"). For IEEE 802.3 frames, this is a
length field.
Chapman, et al Informational [Page 64]
RFC 1841 LAN Extension Interface Protocol September 1995
LLC Data
This field is the remainder of the MAC frame which is (or would be
if it were present) protected by the LAN FCS.
(Serial) HDLC CRC
This is a 16 bit Cyclic Redundancy Check field.
For complete information on the above fields and their relationship
to PPP-BCP packets, refer to the "PPP Bridging Control Protocol
(BCP)" RFC. (References, [2])
Notes
1. The LAN extension interface protocol does allow the segmentation
of individual LAN packets across the serial link. Each LAN
packet must be transmitted across the serial link as one PPP-LEX
encapsulation.
2. MAC addresses in PPP-LEX packets should be in canonical format.
References
[1] Simpson, W., "The Point-To-Point Protocol (PPP) for the
Transmission of Multi-protocol Datagrams over Point-To-Point
Links", RFC 1331, Daydreamer, May 1992.
[2] Baker, F., and R. Bowen, "PPP Bridging Control Protocol (BCP)",
RFC 1638, ACC, IBM, June 1994.
[3] Lloyd, B., and W. Simpson, "PPP Authentication Protocols", RFC
1334, Lloyd & Associates, Daydreamer, October 1992.
[4] Reynolds, J., and J. Postel, "Assigned Numbers", STD 2, RFC 1700,
USC/Information Sciences Institute, October 1994.
[5] Reynolds, J., and J. Postel, "Standard for the transmission of IP
datagrams over IEEE 802 networks", RFC 1042, USC/Information
Sciences Institute, February 1988.
Chapman, et al Informational [Page 65]
RFC 1841 LAN Extension Interface Protocol September 1995
Security Considerations
Security issues are not discussed in this memo.
Authors' Addresses
Joelle Bafile Chapman, Technical Writer
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
EMail: joelle@cisco.com
Dave Coli, Software Engineer
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
EMail: dcoli@cisco.com
Andy Harvey, Software Engineer
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
EMail: agh@cisco.com
Bent Jensen, Engineering Manager
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
EMail: bent@cisco.com
Kevin Rowett, Software Engineer
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
EMail: krowett@cisco.com
Chapman, et al Informational [Page 66]