Internet DRAFT - draft-cheng-manet-dlep-multi-hop-extension
draft-cheng-manet-dlep-multi-hop-extension
Network Working Group B. Cheng
Internet-Draft Lincoln Laboratory
Intended status: Standards Track L. Berger, Ed.
Expires: April 30, 2017 LabN Consulting, L.L.C.
October 27, 2016
DLEP Multi-Hop Forwarding Extension
draft-cheng-manet-dlep-multi-hop-extension-00
Abstract
This document defines an extension to the DLEP protocol that enables
a the reporting and control of Multi-Hop Forwarding by DLEP capable
modems.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Key Words . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Extension Usage and Identification . . . . . . . . . . . . . 3
3. Extension Data Items . . . . . . . . . . . . . . . . . . . . 3
3.1. Hop Count . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2. Hop Control . . . . . . . . . . . . . . . . . . . . . . . 5
3.2.1. Reset . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2.2. Terminate . . . . . . . . . . . . . . . . . . . . . . 6
3.2.3. Direct Connection . . . . . . . . . . . . . . . . . . 6
3.2.4. Suppress Forwarding . . . . . . . . . . . . . . . . . 7
4. Security Considerations . . . . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5.1. Extension Type Value . . . . . . . . . . . . . . . . . . 7
5.2. Data Item Values . . . . . . . . . . . . . . . . . . . . 8
5.3. Hop Control Actions Registry . . . . . . . . . . . . . . 8
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.1. Normative References . . . . . . . . . . . . . . . . . . 9
6.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
The Dynamic Link Event Protocol (DLEP) is defined in
[I-D.ietf-manet-dlep]. It provides the exchange of link related
control information between DLEP peers. DLEP peers are comprised of
a modem and a router. DLEP defines a base set of mechanisms as well
as support for possible extensions. This document defines one such
extension.
Some modem technologies support connectivity to destinations via
multi-hop forwarding. DLEP Destination messages can be used to
report such connectivity, see [I-D.ietf-manet-dlep], but do not
provide any information related to the number or capacity of the
hops. The extension defined in this document enables modems to
inform routers when multi-hop forwarding is being used, and routers
to request that modems change multi-hop forwarding behavior. The
extension defined in this document is referred to as "Multi-Hop
Forwarding".
This document defines a new DLEP Extension Type Value in Section 2
which is used to indicate the use of the extension, and three new
DLEP Data Items in Section 3.
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1.1. Key Words
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14, RFC 2119 [RFC2119].
2. Extension Usage and Identification
The use of the Multi-Hop Forwarding Extension SHOULD be configurable.
To indicate that the extension is to be used, an implementation MUST
include the Multi-Hop Forwarding Extension Type Value in the
Extensions Supported Data Item. The Extensions Supported Data Item
is sent and processed according to [I-D.ietf-manet-dlep].
The Multi-Hop Forwarding Extension Type Value is TBA1, see Section 5.
3. Extension Data Items
Three data items are defined by this extension. The Hop Count Data
Item is used by a modem to provide the number of network hops
traversed to reach a particular destination. The Hop Control Data
Item is used by a router to request that a modem alter connectivity
to a particular destination. The Suppress Forwarding Data Item is
used by a router to request that a modem disable multi-hop forwarding
on either a device or destination basis.
3.1. Hop Count
The Hop Count Data Item is used by a modem to indicate the number of
physical hops between the modem and a specific destination. In other
words, each hop represents a transmission and the number of hops is
equal to the number of transmissions required to go from a router
connected modem to the destination's connected modem. The minimum
number of hops is 1, which represents the router's locally connected
modem.
The data item also contains an indication of when a destination which
currently has a hop count of greater than one (1) could be made
direcly reachable by a modem, e.g., by re-aiming an antenna.
The Hop Count Data Item SHOULD be carried in the Destination Up,
Destination Update, Destination Announce Response, and Link
Characteristics Response Messages when the Hop Count to a destination
is greater than one (1).
A router receiving a Hop Count Data Item MAY use this information in
its forwarding and routing decisions, and specific use is out of
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scope of this document. The absence of the Hop Count Data Item MUST
be interpreted by the router as a Hop Count value of one (1).
The format of the Hop Count Data Item is:
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hop Count |P| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBA2
Length: 4
Hop Count:
An unsigned 8-bit integer indicating the number of network hops
required (i.e., number of times a packet will be transmitted) to
reach the destination indicated in the message. The special value
of 255 (0xFF) is used to indicate that the number of hops is an
unknown number greater than one (1). This field MUST contain a
value of at least one (1) if the associated destination is
reachable.
A value of zero (0) is used to indicated that processing of a Hop
Control action, see Section 3.2, has resulted in a destination no
longer being reachable. A zero value MUST NOT be used in any
message other then a Destination Announce Response Message.
P:
The P-bit indicates that a destination is potentially directly
reachable. When the P-bit is set, the router MAY request a direct
link to the associated destination using the Hop Control Data Item
described below.
Reserved:
MUST be set to zero by the sender (a modem) and ignored by the
receiver (a router).
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3.2. Hop Control
The Hop Control Data Item is used by a router to request a change in
connectivity to a particular destination, or in multi-hop processing
on a device wide basis. A router can request multi-hop reachable
destination be changed to a single hop. A router can also indicate
that the modem terminate connectivity to a particular destination.
The Hop Control Data Item MAY be carried in the Session Update
Message or Destination Announce Message.
A router that receives the Hop Control in a Session Update Message
SHOULD attempt to make the change indicated by the data item for the
whole device. Results of any changes made are reflected in
Destination Down and Destination Update Messages. The modem MUST
notify the router of each destination that is no longer reachable via
a Destination Down Message. The modem MUST notify the router of any
changes in Hop Counts via Destination Update Messages.
A router that receives the Hop Control in a Destination Announce
Message SHOULD attempt to make the change indicated by the data item
for the associated destination MAC address. Once the change is made,
or fails or is rejected, the modem MUST respond with a Destination
Announce Response Message containing an updated Hop Count Data Item.
The format of the Hop Control Data Item is:
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hop Control Actions | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBA3
Length: 4
Hop Control Actions:
An unsigned 16-bit value with the following meaning:
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+-------+---------------------+
| Value | Action |
+-------+---------------------+
| 0 | Reset |
| | |
| 1 | Terminate |
| | |
| 2 | Direct Connection |
| | |
| 3 | Suppress Forwarding |
+-------+---------------------+
Table 1: Hop Control Actions Values
3.2.1. Reset
The Reset Action requests that the default behavior be restored.
When received in a Session Update Message message, a modem SHOULD
clear all control actions that have previously been processed on a
device wide basis, and revert to its configured behavior. When
received in a Destination Announce Message, a modem SHOULD clear all
control actions that have previously been processed for the
destination indicated in the message.
3.2.2. Terminate
The Terminate Action is only valid on a per destination basis and
MUST NOT be sent in a Session Update Message message. It indicates
that the modem SHOULD attempt to terminate communication with the
destination identified in the message. This request has no impact
for multi-hop destinations and may fail even in a single hop case,
i.e. MAY result in the Hop Count to the destination not being
impacted by the processing of the request
3.2.3. Direct Connection
The Direct Connection is only valid on a per destination basis and
MUST NOT be sent in a Session Update Message message. It indicates
that the modem SHOULD attempt to establish a direct connection with
the destination identified in the message. This action SHOULD only
be sent for destinations for which the Hop Count is greater than 1
and has the P-Bit set in the previously received Hop Count Data Item.
Results of the request for the destination identified in the message
are provided as described above. If any other destination is
impacted in the processing of this action, the modem MUST send a
Destination Update Message for each impacted destination.
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3.2.4. Suppress Forwarding
The Suppress Forwarding Action is used by a router to indicate to its
peer that multi-hop forwarding is to be suppressed. A router may
request that multi-hop forwarding may be suppressed on a device wide
or destination specific basis.
A modem which receives the Suppress Forwarding Data Item in a Session
Update Message MUST suppress multi-hop forwarding on a device wide
basis. Impact to destination hop counts are provided to the router
by the modem as described above.
A modem which receives the Suppress Forwarding Data Item in a
Destination Announce Message MUST suppress multi-hop forwarding for
only the destination indicated in the message. Results are provided
as described above.
4. Security Considerations
The extension introduces a new mechanism for flow control between a
router and modem using the DLEP protocol. The extension does not
inherently introduce any additional threats above those documented in
[I-D.ietf-manet-dlep]. The approach taken to Security in that
document applies equally when running the extension defined in this
document.
5. IANA Considerations
This document requests the assignment of 3 values by IANA. All
assignments are to registries defined by [I-D.ietf-manet-dlep]. It
also requests creation of one new registry.
5.1. Extension Type Value
This document requests 1 new assignment to the DLEP Extensions
Registry named "Extension Tyoe Values" in the range with the
"Specification Required" policy. The requested value is as follows:
+------+----------------------+
| Code | Description |
+------+----------------------+
| TBA1 | Multi-Hop Forwarding |
+------+----------------------+
Table 2: Requested Extension Type Value
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5.2. Data Item Values
This document requests 2 new assignments to the DLEP Data Item
Registry named "Data Item Values" in the range with the
"Specification Required" policy. The requested values are as
follows:
+-----------+-------------+
| Type Code | Description |
+-----------+-------------+
| TBA2 | Hop Count |
| | |
| TBA3 | Hop Control |
+-----------+-------------+
Table 3: Requested Data Item Values
5.3. Hop Control Actions Registry
Upon approval of this document, IANA is requested to create a new
DLEP registry, named "Hop Control Actions Values". The following
table provides initial registry values and the [RFC5226]. defined
policies that should apply to the registry:
+-------------+------------------------+
| Value | Action/Policy |
+-------------+------------------------+
| 0 | Reset |
| | |
| 1 | Terminate |
| | |
| 2 | Direct Connection |
| | |
| 3 | Suppress Forwarding |
| | |
| 4-65519 | Specification Required |
| | |
| 65520-65534 | Private Use |
| | |
| 65535 | Reserved |
+-------------+------------------------+
Table 4: Hop Control Actions Values
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6. References
6.1. Normative References
[I-D.ietf-manet-dlep]
Ratliff, S., Jury, S., Satterwhite, D., Taylor, R., and (.
(Unknown), "Dynamic Link Exchange Protocol (DLEP)", draft-
ietf-manet-dlep-24 (work in progress), July 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
6.2. Informative References
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
Authors' Addresses
Bow-Nan Cheng
Lincoln Laboratory
Massachusetts Institute of Technology
244 Wood Street
Lexington, MA 02420-9108
Email: bcheng@ll.mit.edu
Lou Berger (editor)
LabN Consulting, L.L.C.
Email: lberger@labn.net
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