Internet DRAFT - draft-smith-kandula-sxp
draft-smith-kandula-sxp
Network Working Group M. Smith
Internet-Draft R. Kandula
Intended status: Informational S. Appala
Expires: November 25, 2020 Cisco Systems
May 24, 2020
Scalable-Group Tag eXchange Protocol (SXP)
draft-smith-kandula-sxp-10
Abstract
This document discusses scalable-group tag exchange protocol (SXP), a
control protocol to propagate IP address to Scalable Group Tag (SGT)
binding information across network devices.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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This Internet-Draft will expire on November 25, 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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publication of this document. Please review these documents
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carefully, as they describe your rights and restrictions with respect
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. SXP Overview . . . . . . . . . . . . . . . . . . . . . . . . 4
3. SXP Operation . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. SXP Connection Management . . . . . . . . . . . . . . . . 5
3.1.1. SXP Connection . . . . . . . . . . . . . . . . . . . 5
3.1.2. SXP Message integrity/authenticity . . . . . . . . . 6
3.1.3. SXP Connectivity Discovery and Connection Recovery . 7
3.1.4. SXP Connection Setup Sequence . . . . . . . . . . . . 7
3.1.5. SXP Connection States . . . . . . . . . . . . . . . . 8
3.2. Binding Database . . . . . . . . . . . . . . . . . . . . 9
3.2.1. SXP Learned IP-SGT Binding recovery . . . . . . . . . 9
4. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 9
4.1. Bit and Octet Numbering Convention . . . . . . . . . . . 9
4.2. SXP Message Header . . . . . . . . . . . . . . . . . . . 10
4.3. Attribute Formats . . . . . . . . . . . . . . . . . . . . 10
4.4. SXP OPEN and OPEN_RESP Message . . . . . . . . . . . . . 13
4.4.1. Node-ID . . . . . . . . . . . . . . . . . . . . . . . 14
4.4.2. Capabilities Advertisement . . . . . . . . . . . . . 14
4.4.3. Keep-alive and Hold Time Negotiation . . . . . . . . 17
4.5. SXP UPDATE Message . . . . . . . . . . . . . . . . . . . 22
4.5.1. UPDATE Attributes . . . . . . . . . . . . . . . . . . 23
4.5.2. UPDATE Message Samples . . . . . . . . . . . . . . . 32
4.6. SXP ERROR Message . . . . . . . . . . . . . . . . . . . . 35
4.6.1. Error Codes . . . . . . . . . . . . . . . . . . . . . 36
4.7. SXP PURGE-ALL Message . . . . . . . . . . . . . . . . . . 37
4.8. SXP KEEPALIVE Message . . . . . . . . . . . . . . . . . . 37
5. Update Message Handling . . . . . . . . . . . . . . . . . . . 37
5.1. UPDATE Message Validation . . . . . . . . . . . . . . . . 37
5.2. UPDATE Message processing . . . . . . . . . . . . . . . . 39
5.3. Generating UPDATE Message . . . . . . . . . . . . . . . . 43
6. SXP Failure Scenarios . . . . . . . . . . . . . . . . . . . . 44
7. SXP Timers . . . . . . . . . . . . . . . . . . . . . . . . . 44
8. SXP Version Negotiation . . . . . . . . . . . . . . . . . . . 47
8.1. SXP Versions . . . . . . . . . . . . . . . . . . . . . . 47
8.2. Error Handling in Older SXP Versions . . . . . . . . . . 48
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8.2.1. SXP Version 1 . . . . . . . . . . . . . . . . . . . . 48
8.2.2. SXP Version 2 . . . . . . . . . . . . . . . . . . . . 48
9. Security Considerations . . . . . . . . . . . . . . . . . . . 48
10. Implementation Note . . . . . . . . . . . . . . . . . . . . . 49
10.1. Bi-Directional SXP . . . . . . . . . . . . . . . . . . . 49
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 49
12. IPR Disclosure . . . . . . . . . . . . . . . . . . . . . . . 49
13. Copyright Notice and Disclaimer . . . . . . . . . . . . . . . 50
14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 50
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 50
15.1. Normative References . . . . . . . . . . . . . . . . . . 50
15.2. Informative References . . . . . . . . . . . . . . . . . 51
Appendix A. SGT as MetaData in Data Plane . . . . . . . . . . . 51
A.1. CMD Format . . . . . . . . . . . . . . . . . . . . . . . 51
A.1.1. Metadata Header . . . . . . . . . . . . . . . . . . . 52
A.1.2. Metadata Payload . . . . . . . . . . . . . . . . . . 52
A.1.3. Header Protection . . . . . . . . . . . . . . . . . . 53
A.1.4. Header Insertion, Removal, and Relocation . . . . . . 53
A.2. Assigned Ethernet Type . . . . . . . . . . . . . . . . . 54
Appendix B. SGT in Network Services Header (NSH) . . . . . . . . 54
Appendix C. SGT CMD in GRE . . . . . . . . . . . . . . . . . . . 54
Appendix D. SGT NSH in GRE . . . . . . . . . . . . . . . . . . . 55
Appendix E. SGT in VXLAN . . . . . . . . . . . . . . . . . . . . 55
Appendix F. SGT tagging exemption for L2 control traffic . . . . 55
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 55
1. Introduction
SXP stands for the Scalable Group Tag (SGT) eXchange Protocol.
Scalable Group Tags are assigned to endpoints connecting to the
network that have common network policies. Each Scalable Group Tag
is identified by a unique SGT value. The SGT to which an endpoint
belongs can be assigned statically or dynamically, and the SGT can be
used as a classifier in network policies. SXP is a control-plane
mechanism used to transport an endpoint's SGT along with the IP
address from one SGT-aware network device to another. The data that
SXP transports is referred to as the IP-SGT binding in the rest of
the document.
Conveying this information allows SGT-aware network devices to make
policy decisions based on the role or intent of an endpoint, which is
expressed as a Scalable Group and represented by an SGT.
Implementations currently use SGT classifiers to apply policy
enforcement in a number of ways -
o Apply different access control decisions through an SGT-aware
access control list or firewall policy
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o Apply micro-segmentation on network devices such as switches and
WLAN access points
o Invoke different security inspection functions, such as intrusion
detection to traffic based on the SGT of the endpoint
In addition to providing policy enforcement, implementations also
currently use SGT functions to -
o Provide logging information which includes the SGT to indicate the
role of an endpoint to analytics tools
o Apply different Quality of Service policies based on the SGT of
the endpoint
o Apply a different forwarding decision based on the SGT of the
endpoint
1.1. Terminology
This document frequently uses the following terms:
SGT Scalable Group Tag
SXP Scalable-Group Tag (SGT) eXchange Protocol
IP-SGT The IP Address to SGT binding that is exchanged over SXP
connection
SXP Speaker The peer that sends the IP-SGT bindings over the SXP
connection
SXP Listener The peer that receives the IP-SGT bindings over the SXP
connection
Binding Database The database of IP-SGT bindings that the SXP Speaker
uses to export to the peer
2. SXP Overview
SXP uses TCP as its transport protocol to set up SXP connection
between 2 separate network devices. Each SXP connection has one peer
designated as SXP speaker and the other peer as SXP listener. The
peers can also be configured in a bi-directional (both) mode where
each of them act as both speaker & listener. Connections can be
initiated by either peer but binding information is always propagated
from a speaker to a listener.
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At a very high level, SXP comprises of the following -
- SXP connection establishment
- IP-SGT bindings propagation
A typical deployment scenario of SXP is illustrated below -
+---------------+ +----------------+
| | | |
| | | |
| | | |
| SXP Speaker |----------------------------->| SXP Listener |
| | IP-SGT Bindings | |
| | | |
| | | |
+---------------+ +----------------+
| |
| |
| |
| |
+------------------------------------------------+
SXP Connection
3. SXP Operation
The SXP connections are point-to-point and uses TCP as the underlying
transport protocol. The summary of operations is illustrated in each
of the sections below.
3.1. SXP Connection Management
An SXP connection consists of the following parts:
3.1.1. SXP Connection
o The peer IP address, source IP address (the best IP address of
local device used to reach the specified peer IP address)
* Used to construct TCP connection
o The connection mode
* An SXP connection can be configured for uni-directional or bi-
directional communication. For each direction, one peer must
act as an sxp speaker and the other act as an sxp listener.
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* The SXP speaker is responsible for sending the IP-SGT bindings.
* The SXP listener is responsible for collecting the IP-SGT
bindings received from the speaker peer and also merge the
bindings received from multiple connections.
o SXP connection password
* If SXP data integrity and authentication are required, then
both the peer devices must have same authentication mechanism
(MD5 or TCP-AO). The passwords should match on both the peers
in case of MD5 and similarly the key-chains in case of TCP-AO.
3.1.2. SXP Message integrity/authenticity
3.1.2.1. SXP Connection Using MD5
The connection peers on the 2 network devices supply the same SXP
password to the TCP layer which will authenticate all further
messages using the MD5 algorithm (RFC 2385). The SXP payload is not
encrypted because the main requirement is for the receiving device to
determine that the message originated from a valid source and not to
prevent snooping of message (discussed in security considerations
section) payload. SXP uses the underlying TCP MD5 option for message
integrity/authenticity. The TCP MD5 is exchanged (negotiated) during
the initial TCP 3 way handshake. Both sides (peers) are pre-
configured with the keys (password) which will be used for forming
the MD5 digest. Each packet (segment) needs to be "signed" with the
MD5 digest (16 bytes) formed using the password as the key.
Whenever the password needs to be changed for an existing TCP
connection, the peer resets the existing TCP connection and sets up a
new TCP connection with the new password. Changing the default
password will cause all SXP connections using the default password to
be re-established.
3.1.2.2. SXP Connection Using TCP-AO
The connection peers on the 2 network devices can authenticate each
other using TCP-AO (RFC 5925). SXP uses the underlying TCP-AO option
for message integrity/authenticity. The TCP-AO option is exchanged
(negotiated) during the initial TCP 3 way handshake. Both sides
(peers) are pre-configured with the keys which will be used for
forming the HMAC. The TCP module will populate the TCP-AO option in
each outgoing segment by generating the HMAC using the traffic keys.
On the receiver, TCP will generate the HMAC using the traffic keys
and incoming segment header to validate the HMAC in the incoming TCP-
AO option.
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Whenever the TCP-AO key-chain needs to be changed for an existing TCP
connection, the peer resets the existing TCP connection and sets up a
new TCP connection with the new key-chain. Changing the default key-
chain will cause all SXP connections using the default key-chain to
be re-established.
3.1.3. SXP Connectivity Discovery and Connection Recovery
SXP uses the TCP keep alive mechanism with the default behavior to
maintain SXP connectivity. A SXP device attempts to maintain
connectivity with each peer. In case of failures, the SXP device
continues to retry connection setup with all the peers with which the
SXP connections have not been established. This continues until
either a connection is established or the peer is removed from the
peer set by a change in configuration. This mechanism ensures
automatic recovery of the SXP connection once the connectivity issue
is resolved. The SXP connection can be re-established by either
device and hence the connection can be brought up sooner without
relying on the retry timers of the peer devices. Note that this is
just an optimization and not a requirement for SXP connection
recovery. If both ends of an SXP connection set up the TCP
connection at the same time, the end with source IP address higher
than the peer IP address wins: i.e. the TCP connection initiated from
that end is kept and the other TCP connection is torn down.
3.1.4. SXP Connection Setup Sequence
When a SXP connection is configured, it initiates a TCP connection
set-up request. SXP communication starts after TCP connection has
been established between the two network devices. The end that
initiates the TCP connection starts the exchange by sending the OPEN
message to negotiate SXP version, SXP mode, and if that end is a
listener, SXP capabilities attribute. Capabilities advertisement and
Capabilities Attribute are described with additional details in
section 5.4.1. The receiving device responds with an OPEN_RESP
message that includes similar attributes. The connection can only be
set-up with one end configured as a speaker and the other end
configured as a listener. See the following sections regarding
version negotiation and capability exchange process descriptions.
Along with version negotiation, the hold time required for the
connection is also negotiated. The following sections explain the
hold time negotiation in detail.
After SXP connection is established, binding information can be sent
from speaker to listener with UPDATE message. Whenever the SXP
connection has to be closed the underlying TCP connection is closed.
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3.1.5. SXP Connection States
An SXP connection maintains following states: OFF, PENDING_ON,
DELETE_HOLD_DOWN, ON.
OFF: In this state, a connection initiation has not been started.
This is the only state that an SXP connection will retry establishing
the TCP connection.
PENDING_ON: In this state, an SXP OPEN message has been sent to the
peer and a response from the peer SXP is expected.
DELETE_HOLD_DOWN: In this state, a connection that was previously in
ON state has been terminated. Only a listener can be in this state.
ON: SXP is in ON state when SXP OPEN or SXP OPEN RESP message has
been received. SXP connection has been setup successfully. An SXP
connection will only propagates bindings in the ON state.
+-------+
T7 | |---------------+
+------------>| OFF | |T1
| | |<---------+ |
| +-------+ T2 | |
+--------+ | A +-----v-+
|DELETE | | | |PENDING |
|HOLDDOWN| T5| | T4 | ON |
+---A----+ | | +--------+
| +-v-----+ |
| T6 | ON | |T3
+-------------| |<-------------+
+-------+
T1-T7: State Transitions
T1: The connection sends a TCP connect request and an SXP OPEN
message to the peer. The connection then transits to the PENDING ON
state.
T2: TCP connection setup failure;
T3: The connection received an SXP OPEN RESPONSE or SXP OPEN message.
If the delete hold down timer is running, the timer is stopped and
the reconciliation timer is started.
T4: TCP connection failure; SXP message process failure; SXP
configuration change.
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T5: The TCP connection is setup and an SXP OPEN message is received.
If the delete hold down timer is running, the timer is stopped and
the reconciliation timer is started.
T6: TCP connection failure when a connection is in listener mode.
The delete hold down timer is started with this state transition.
T7: The delete hold down timer expired or TCP connection setup
failure.
In failure scenarios, the connection transits to OFF state and an
attempt is made to re-establish the connection.
3.2. Binding Database
A system should have a master binding database for reconciling
binding information from multiple SXP connections. The database
should consist of a single binding per IP address and there should be
a mechanism to handle same bindings from multiple SXP connections.
3.2.1. SXP Learned IP-SGT Binding recovery
When an SXP connection goes down on a network device, SXP continues
to learn/advertise IP-SGT bindings on other SXP connections that are
alive. If the device has learnt any bindings from the peer where the
SXP connection goes down, a delete hold down timer is started for
that connection:
o Once the timer expires, all binding entries that were learned from
the failed peer are deleted. The deletion of the bindings for
which the failed peer was the only source are reported to the
master binding database.
o If the connection recovers before the delete hold down timer
expiry, a reconcile timer is started to clean up old bindings that
didn't get informed to be removed because of the loss of
connectivity.
4. Message Formats
The SXP Messages and their formats are described in detail in this
section.
4.1. Bit and Octet Numbering Convention
Throughout this section, the following numbering convention is used
to depict the SXP message formats:
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Each diagram depicts the format and size of each field in bits.
Implementations MUST send the bits in each diagram as they are shown,
traversing the diagram from top to bottom and then from left to right
within each line (which represents a 32-bit quantity). Multi-byte
fields representing numeric values must be sent in network (big
endian) byte order. Descriptions of bit field (e.g., flag) values
are described referring to the position of the bit within the field.
These bit positions are numbered from the most significant bit
through the least significant bit, so a 1-octet field with only bit 0
set has the value 0x80.
4.2. SXP Message Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| SXP Message Length (4 octets) |
+---------------------------------------------------------------+
| SXP Message Type (4 octets) |
+---------------------------------------------------------------+
| SXP payload (variable) |
+---------------------------------------------------------------+
+---------+----------+----------------------------------------------+
| Field | Length | Description |
+---------+----------+----------------------------------------------+
| SXP | 4 | This 4-octet unsigned integer indicates the |
| Message | | total length of the message, |
| Length | | including the header but excluding |
| | | authentication tag. The maximum |
| | | message length is 4096 |
| SXP | 4 | This 4-octet unsigned integer indicates the |
| Message | | type code of the SXP message. The |
| Type | | following type codes are defined: 1 - OPEN 2 |
| | | - OPEN_RESP 3 - UPDATE 4 - ERROR 5 |
| | | - PURGE_ALL 6 - KEEPALIVE |
| SXP | Variable | SXP message payload is an optional field. |
| Payload | | Its content when present depends |
| | | on the message type |
+---------+----------+----------------------------------------------+
4.3. Attribute Formats
SXP payloads can contain a variable number of fields. Some fields
are fixed and mandatory to support. Other fields are called
attributes and they have an extended {Type, Length, Value} (TLV)
format in order to allows for gradual introduction of a new feature
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without requiring a protocol version change. Each attribute is
tagged and includes a length field. This allows for newer versions
of SXP to add capabilities and co-exist with old versions of SXP in
the same deployment. Each attribute includes a Flags field to
control processing. The format of an attribute {flags, type, length,
value} (TLV) is encoded as follows:
Compact TLV
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
|O|N|P|C|E| | | | Type | TLV Length | |
+-+-+-+-+-+-+-+-+---------------+---------------+ |
| Value (Variable: TLV Length octets long) |
+---------------------------------------------------------------+
Compact Extended Length TLV
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
|O|N|P|C|E| | | | Type | TLV Extended Length |
+-+-+-+-+-+-+-+-+---------------+-------------------------------+
| Value (Variable: TLV Extended Length octets long) |
+---------------------------------------------------------------+
Non-Compact TLV
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
|O|N|P|C| Type |
| |T| |0| |
+-+-+-+-+-+-+-+-+-----------------------------------------------+
| Non-Compact TLV Length |
+---------------------------------------------------------------+
| Value (Variable: Non-Compact TLV Length octets long) |
+---------------------------------------------------------------+
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+----------------+------+-------------------------------------------+
| Flags | Bits | Description |
+----------------+------+-------------------------------------------+
| Optional (O) | 0 | 1 - Attribute is optional and MAY be |
| | | ignored 0 - Attribute is |
| | | mandatory (well-known and MUST be |
| | | recognized) |
| Non-Transitive | 1 | 0 - Attribute shall be forwarded even if |
| (N) | | it is not recognized 1 - |
| | | Attribute shall not be forwarded |
| Partial (P) | 2 | 1 - When a transitive attribute is |
| | | forwarded but not recognized 0 |
| | | - Otherwise |
| Compact (C) | 3 | 1 - TLV is using compact Type and Length |
| | | encoding 0 - TLV is encoded |
| | | using all the 4 octets for Type and |
| | | Length. All other flags are 0 |
| Extended | 4 | 0 - Length is a single octet long 1 - |
| Length (E) | | Length is 2 octets long |
| Reserved | 5-7 | Reserved for future use. Must be |
| | | transmitted as 0 and ignored on |
| | | receive |
+----------------+------+-------------------------------------------+
+--------+----------+-----------------------------------------------+
| Field | Length | Description |
+--------+----------+-----------------------------------------------+
| Flags | 1 | Attribute Flags |
| Type | 1 or 4 | TLV Type |
| Length | 1, 2 or | Length (in octets) of the TLV Value field |
| | 4 | (i.e. not including the 3, 4, or |
| | | 8-octets attribute header. Unsigned integer |
| | | in the following range: [0..255] - |
| | | For Compact non-Extended Length |
| | | attribute. [256..4084] - For Compact Extended |
| | | Length attribute. |
| Value | Variable | TLV values, which depend on the TLV type |
+--------+----------+-----------------------------------------------+
If an optional non-transitive attribute is unrecognized, it is
quietly ignored.
If an optional transitive attribute is unrecognized, the Partial bit
(the third high-order bit) in the attribute flags octet is set to 1,
and the attribute is retained for export according to the scope in
which the attribute appears.
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Attribute Length field of Compact attributes SHOULD be only as large
as necessary to hold an unsigned integer that specifies the number of
octets in the attribute Value field. This implies that Extended-
Length field SHOULD contain a value greater than 256 (or the first
octet of an Extended-Length field SHOULD be non-zero). The largest
allowed value of an Extended-Length field is 4084, considering
maximum SXP message length of 4096. The largest allowed value of a
non-Compact attribute Length field is thus 4080. SXP Listener MUST
accept and process Compact Extended-Length attributes with Length
field in the range [0..255] without issuing any errors. In the rest
of this document diagrams showing usage of Compact normal and/or
Extended-Length attribute are only illustration of expected usage.
They do not imply that only the illustrated class of attribute or
attribute Length is supported.
Attribute Value field consists of well defined sub-fields which are
defined in this protocol spec. Attribute Value field MAY contain
additional, possibly optional, sub-attributes which are encoded like
other attributes.
4.4. SXP OPEN and OPEN_RESP Message
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| Version (4 octets) |
+---------------------------------------------------------------+
| SXP Mode (4 octets) |
+---------------------------------------------------------------+
| SXP Node-ID Attribute (7 octets) |
+---------------------------------------------------------------+
| Capabilities Attribute (variable) |
+---------------------------------------------------------------+
| Other Optional Attributes (variable) |
+---------------------------------------------------------------+
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+--------------+----------+-----------------------------------------+
| Field | Length | Description |
+--------------+----------+-----------------------------------------+
| Version | 4 | Unsigned integer value. The SXP Version |
| | | is set to the highest version |
| | | that is supported on the network device |
| SXP Mode | 4 | Unsigned integer value used to convey |
| | | the SXP role that the device |
| | | uses on the SXP connection. The |
| | | following values are used: 1 |
| | | - SXP Speaker 2 - SXP Listener |
| SXP Node-Id | 7 | REQUIRED non-transitive attribute (in |
| | | SXP version 4 and above) an |
| | | SXP Speaker SHALL include in OPEN or |
| | | OPEN_RESP to convey its unique |
| | | 32 bits Node ID. The attribute type |
| | | used for Node ID Attribute is |
| | | 5 |
| Capabilities | Variable | REQUIRED non-transitive attribute (in |
| | | SXP version 4 and above) an |
| | | SXP Listener SHALL include in OPEN or |
| | | OPEN_RESP to convey its |
| | | capabilities for processing data on the |
| | | connection |
+--------------+----------+-----------------------------------------+
4.4.1. Node-ID
In the OPEN or OPEN_RESP message, Node-ID has to be included only by
the speaker. The listener must not send the Node-ID in OPEN message
and the speaker has to return an error if it receives a Node-ID from
a listener.
SXP Node-ID with value 0 is reserved for denoting bindings that are
received from connections that use older versions of the SXP
protocol.
The Implementation Note Section has more details on how the Node-ID
value is selected.
4.4.2. Capabilities Advertisement
SXP Listeners are REQUIRED to include the Capabilities attribute when
they send an OPEN message or when they respond to such message with
OPEN_RESP message. The Capabilities attribute describes the SXP
features supported by the Listener. This allows the SXP Speaker to
tailor the behavior of the connection to what the Listener could
process. An SXP speaker receiving Capabilities attribute from an SXP
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Listener SHALL NOT send to that listener in UPDATE messages any
mandatory attributes that were not indicated as supported in the
Capabilities attribute. However, the Listener must be able to
process the optional attributes to act as a relay agent. If an SXP
speaker receives from its listener peer a capability that it does not
itself support or recognize, it MUST ignore that capability. In
particular, ERROR message MUST NOT be generated and the SXP session
MUST NOT be terminated in response to reception of a capability that
is not supported by the local SXP speaker.
4.4.2.1. Capabilities Attribute
This is a REQUIRED attribute that is used by an SXP Listener to
convey to its peer SXP Speaker the list of capabilities supported by
the listener. The attribute contains one or more triples <Capability
Code, Capability Length, Capability Values>:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
|O|N|P|C|E| | | | Capabilities |TLV Length (C=1| |
| | | | | | | | | Type 6 | EL=0) | |
|0|1|0|1| | | | | +---------------+---------------+
| | | | | | | | | |TLV Extended Length (C=1 EL=1) |
+-+-+-+-+-+-+-+-+---------------+-------------------------------+
|Cap Code 1 |Cap Length 1 |
|---------------+---------------+-------------------------------+
| Capability 1 Value (Variable) |
+---------------------------------------------------------------+
x ***** x
x---------------------------------------------------------------x
|Cap Code N |Cap Length N |
|---------------+---------------+-------------------------------+
| Capability N Value (Variable) |
+---------------------------------------------------------------+
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+------------+----------+-------------------------------------------+
| Field | Length | Description |
+------------+----------+-------------------------------------------+
| Capability | 1 | Unsigned integer that unambiguously |
| Code | | identifies individual |
| | | capabilities |
| Capability | 1 | Unsigned integer that contains the length |
| Length | | of the Capability Value |
| | | field in octets |
| Capability | Variable | Variable-length field that is interpreted |
| Value | | according to the value of |
| | | the Capability Code field. Could have |
| | | zero length |
+------------+----------+-------------------------------------------+
The encoding and meaning of the capabilities defines by this version
of the SXP protocol spec are as follows:
+------------+------------+------------+----------------------------+
| Capability | Capability | Capability | Description |
| Name | Code | Length | |
+------------+------------+------------+----------------------------+
| IPv4 | 1 | 0 | Listener is capable of |
| Unicast | | | receiving and handling |
| | | | IPv4 unicast |
| | | | bindings |
| IPv6 | 2 | 0 | Listener is capable of |
| Unicast | | | receiving and handling |
| | | | IPv6 unicast |
| | | | bindings |
| Subnet | 3 | 0 | Listener is capable of |
| Bindings | | | receiving and handling |
| | | | subnet |
| | | | bindings |
+------------+------------+------------+----------------------------+
4.4.2.2. Handling of Capabilities Attribute
Subnet Bindings - This capability indicates to the speaker that
subnet bindings SHOULD be exported as regular bindings without any
expansion. A listener that fully supports bindings associated with
IP prefixes other than host addresses (IPv4 /32 or IPv6/128) MUST
include the Subnet Bindings capability.
A listener that does not support subnet bindings in its forwarding
path but has the capability to expand subnet bindings locally MUST
send Subnet Bindings capability in order to prevent the listener from
unnecessarily expanding subnet bindings. A listener which does not
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support subnet bindings but might be able to support the volume of
expanded bindings MAY include Subnet Bindings capabilities.
A speaker receiving such capability MAY expand subnet bindings
exhaustively or selectively and export individual bindings within a
subnet. The expansion of subnet bindings COULD be limited by
implementation to a reasonable subnet size with a limit on the total
number of bindings expanded. Therefore there could be subnet
bindings which are not expanded.
When a speaker does not expand a subnet binding it SHOULD export it
unmodified as a subnet binding. This will allow the listener to
propagate such bindings even when it cannot use it locally.
When a speaker expands a subnet binding it MUST NOT export it as both
subnet and expanded bindings since the listener or any further SXP
peers along the SXP propagation path cannot distinguish expanded
bindings from other host bindings and relate them to the subnet
bindings they are originate from.
IPv6 Unicast - This capability indicates to the speaker that the
listener is capable of handling and using bindings associated with
IPv6 unicast addresses. A listener that support IPv6 bindings MUST
include this capability. When this capability is not included, the
speaker MUST NOT send IPv6 bindings as mandatory attributes. A
speaker, however, SHOULD send IPv6 bindings within Optional
Transitive attributes when the IPv6 Unicast capability is omitted.
This will allow an SXP node to relay IPv6 bindings even when it could
not process them locally.
IPv4 Unicast - This capability should be handled in the same way as
IPv6 Unicast capability is handled. It is unlikely for any SXP
listener to omit IPv4 Unicast capability at least until pure IPv6
networks would become common.
4.4.3. Keep-alive and Hold Time Negotiation
SXP uses TCP-based, keep-alive mechanism to determine if a connection
is live. This mechanism has been used in all prior versions of the
protocol. SXP version 4 adds a discretionary negotiated keep-alive
mechanism within the protocol itself in order to provide more
predictable and timely detection of connection loss.
SXP connections are asymmetric with almost all of the protocol
messages (except for OPEN/OPEN_RESP and ERROR) being sent from an SXP
speaker to an SXP listener.
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SXP listener could also keep potentially large volume of state per
connection which includes all the binding information learnt on a
connection. Therefore, it is only meaningful to have a keep-alive
mechanism that allows a listener to detect the loss of connection
with a speaker.
The mechanism is based on two timers:
Hold Timer - Used by a listener for detection of elapsing time
without successive KEEPALIVE and/or UPDATE messages from a speaker.
Keep-alive Timer - Used by a speaker to trigger sending of KEEPALIVE
messages during intervals when no other information is exported via
UPDATE messages.
The keep-alive timer is one-thirds of the negotiated hold-timer
value.
Hold Timer for the keep-alive mechanism MAY be negotiated during the
OPEN/OPEN_RESP exchange at connection setup.
o A listener MAY have desirable range for Hold Time period locally
configured or a default of [90..180] seconds. A value of
[0xFFFF..0xFFFF] implies that the keep-alive mechanism is not
used.
o A speaker MAY have a minimum acceptable Hold Time period locally
configured or a default of 120 seconds. This is the shortest
period of time a speaker is willing to send KEEPALIVE messages for
keeping the connection alive. Any shorter Hold Time period would
require a faster KEEPALIVE rate from the rate the speaker is ready
to support. A value of 0xFFFF implies that the keep-alive
mechanism is not used
o The negotiation succeeds when the speaker's minimum acceptable
Hold Time falls below or within the desirable Hold Time range of
the listener. If one end turns off the keep-alive mechanism, the
other end should also turn it off to make the negotiation success.
o The negotiation fails when the speaker's minimum acceptable Hold
Time is greater than the upper bound of the listener's Hold Time
range.
o The selected Hold Time period of a successful negotiation is the
maximum of the speaker's minimum acceptable Hold Time and the
lower bound of the listener's Hold Time range.
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o The speaker calculates the Keep-alive Time to 1/3 of the selected
Hold Time by default unless a different Keep-alive Time is locally
configured.
o The negotiation process is designed such that the outcome is the
same regardless of the mode of the initiator.
The diagram below illustrates the Hold Time negotiation process.
+------+ +------+
| Min | | Max |
| | | |
+------+ +------+
Listener | |
| |
-----------------V<---------------------------------->V--------
Speaker | | |
| | |
1| 2| |3
+-v---------+ +--v--------+ +--------v---+
| Selected | | Selected | |Unacceptable|
| Hold | | Hold | | Hold |
| Time | | Time | | Time |
| | | | | |
+-----------+ +-----------+ +------------+
Connection initiated by Listener
o A listener MAY include a Hold-Time Attribute in the OPEN message
with minimum and maximum values set to its configured range of
Hold Time period. Hold-Time Attribute with just a minimum value
set to 0xFFFF would indicate to the speaker that the keep-alive
mechanism is not used.
o When a speaker received an OPEN message it will react as follows:
* If the Hold-Time attribute is not present or if it contains a
minimum value that is set to 0xFFFF, the speaker will set its
Keepalive Time to 0xFFFF to indicate that keep-alive mechanism
is disabled.
* If the received Hold-Time attribute contains a valid range, the
speaker MUST include Hold-Time attribute in its OPEN_RESP
message with a minimum value set as follows:
+ 0xFFFF if the speaker does not support the keep-alive
mechanism or if the mechanism is supported but disabled due
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to local configuration which sets the Keep-alive Time to
0xFFFF
+ If the speaker's minimum acceptable Hold Time value is
greater than the upper bound of the offered range, the
speaker MUST send and Open ERROR message with sub-code set
to Unacceptable Hold Time and terminate the connection.
+ Otherwise the speaker's will set the selected Hold Time to
the maximum of its minimum acceptable Hold Time value and
the lower bound of the offered Hold Time range.
+ The speaker will calculate a new value for its Keep-alive
Time as 1/3 of that selected Hold Time.
+ The speaker will set the minimum Hold Time value of the Hold
Time attribute to the selected Hold Time.
o When the listener receives the OPEN_RESP from the speaker it will
look for Hold Time Attribute:
* If Hold-Time attribute is present and contains a minimum Hold
Time value of 0xFFFF. The listener will set its Hold Time
value to 0xFFFF to indicate that keep-alive mechanism is not
used.
* If the minimum Hold Time value is within the range offered by
the listener, the listener will set its Hold-Time period to the
selected value it has received in the OPEN_RESP.
* If the minimum Hold Time value is outside the offered range,
the listener will send Open ERROR message with sub-code set to
Unacceptable Hold Time and terminate the connection.
Connection initiated by Speaker
o A speaker MAY include a Hold-Time Attribute in the OPEN message
with minimum value set to its minimum acceptable Hold Time period.
Hold-Time Attribute with just a minimum value set to 0xFFFF would
indicate to the listener that the keep-alive mechanism is not
used.
o When a listener receives an OPEN message it will react as follows:
* If the Hold-Time attribute is not present or if it contains a
minimum value that is set to 0xFFFF, the listener will set its
Hold Time to 0xFFFF to indicate that keep-alive mechanism is
disabled.
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* If the received Hold-Time attribute contains a valid value, the
listener MUST include Hold-Time attribute in its OPEN_RESP
message with a minimum value set as follows:
+ 0xFFFF if the listener does not support the keep-alive
mechanism or if the mechanism is supported but disabled due
to local configuration which sets the Keep-alive Time to
0xFFFF
+ If the received Hold Time value is greater than the upper
bound of the listener's configured Hold Time range, the
listener MUST send an Open ERROR message with sub-code set
to Unacceptable Hold Time and terminate the connection.
+ If the received Hold Time value falls within the listener's
configured Hold Time range, the listener will make it the
selected Hold Time.
+ If the received Hold Time value is less than the lower bound
of the listener's configured Hold Time range, the listener
will set the selected Hold Time to the lower bound of its
Hold Time range.
+ The listener will set the minimum Hold Time value of the
Hold Time attribute to the selected Hold Time.
o When the speaker receives the OPEN_RESP from the listener it will
look for Hold Time Attribute:
* If Hold-Time attribute is present and contains a minimum Hold
Time value of 0xFFFF. The speaker will set its Hold Time value
to 0xFFFF to indicate that keep-alive mechanism is not used.
* If the received Hold Time value is greater or equal to the
speaker minimum acceptable Hold Time, the speaker will
calculate a new value for its Keep-alive Time as 1/3 of that
received Hold Time.
* If the received Hold Time value is lower than the minimum
acceptable Hold Time, the speaker MUST send and Open ERROR
message with sub-code set to Unacceptable Hold Time and
terminate the connection.
4.4.3.1. Hold-Time Attribute
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
|O|N|P|C|E| | | |Hold-Time (7) | TLV Length 2/4|
+-+-+-+-+-+-+-+-+---------------+-------------------------------+
| Hold Time Minimum Value | Hold Time Maximum Value |
+---------------------------------------------------------------+
+-------------------+--------+--------------------------------------+
| Field | Length | Description |
+-------------------+--------+--------------------------------------+
| Optional(O) | 1 Bit | Value is 0 |
| Non-Transitive(N) | 1 Bit | Value is 0 |
| Partial (P) | 1 Bit | Value is 0 |
| Compact (C) | 1 Bit | Value is 1 |
| Extended Length | 1 Bit | Value is 0 |
| (E) | | |
| Attribute Type | 1 | Hold-Time (7) |
| Attribute Value | 1 | 2 - when only Hold Time Minimum |
| Length | | Value is present. 4 - |
| | | when both Hold Time Minimum and |
| | | Maximum values are present |
| Hold Time Minimum | 2 | Unsigned integer indicating the |
| Value | | number of seconds the sender |
| | | proposes as a lower bound for the |
| | | Hold Timer period or the Hold |
| | | Time period selected by a responder. |
| | | 0 or at least 3 seconds |
| Hold Time Maximum | 2 | Unsigned integer indicating the |
| Value | | number of seconds the sender |
| | | proposes as a upper bound for the |
| | | Hold Timer period. MUST be |
| | | greater than Hold Time Minimum Value |
+-------------------+--------+--------------------------------------+
Hold-Time is a well-known discretionary attribute an initiator of a
connection MAY include in an OPEN message and a responder MAY be
REQUIRED to include in an OPEN_RESP in order to negotiate the timer
periods used for keep-alive mechanism. The Hold-Time attribute has
to be marked as Non-Transitive and an error has to be returned if
it's not marked as Non-Transitive.
4.5. SXP UPDATE Message
Prior versions of SXP protocol specify that an UPDATE message
contains one or more SXP mappings. This version of SXP protocol
generalizes the UPDATE message. An UPDATE message MAY contain one or
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more attributes. Some attributes are well-known and additional
attributes COULD be added in the future without affecting existing
implementations of SXP version 4. This document defines the format
of the attributes used within UPDATE message and how they are
combined to carry the SXP binding information.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+---------------------------------------------------------------+
| Attribute 1 (Variable) |
+---------------------------------------------------------------+
x ***** x
+---------------------------------------------------------------+
| Attribute N (Variable) |
+---------------------------------------------------------------+
4.5.1. UPDATE Attributes
4.5.1.1. IPv4-Delete-Prefix Attribute
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
|O|N|P|C|E| | | |IPv4-Delete- | TLV Length |Reserved |
| | | | | | | | | Prefix | C = 1 EL = 0 | |
|0|0|0|1| | | | | Type = 13 +-------------------------------+
| | | | | | | | | |TLV Extended Length (C=1 EL=1) |
+-+-+-+-+-+-+-+-+---------------+-------------------------------+
| IPv4 Prefix 1 (Variable) |
+---------------------------------------------------------------+
x ***** x
+---------------------------------------------------------------+
| IPv4 N Value (Variable) |
+---------------------------------------------------------------+
This attribute is used to convey the withdrawal of one or more IPv4
bindings which are unambiguously identified by their IPv4 prefix.
This attribute contains a set of IPv4 prefixes. Each IPv4 prefix is
encoded as a 2-tuple of the form <length, prefix>, whose fields are
encoded as:
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| Length = | Reserved |
| [0..32] | |
+---------------+-----------------------------------------------+
| Prefix |
+---------------------------------------------------------------+
| 0 < Length | 9 <= Length | 17 <= Length |25 <= Length |
+---------------+---------------+---------------+---------------+
+--------+------------+---------------------------------------------+
| Field | Length (in | Description |
| | Octets) | |
+--------+------------+---------------------------------------------+
| Length | 1 | Unsigned integer. The length in bits of the |
| | | IP address prefix. A length |
| | | of zero indicates a prefix that matches all |
| | | IP addresses (with Prefix |
| | | field filled with zero in all octets) |
| Prefix | Variable | An IP address prefix, followed by the |
| | (Length/8) | minimum number of trailing |
| | | bits needed to make the end of the field |
| | | fall on an octet boundary. |
| | | The value of trailing bits is irrelevant |
+--------+------------+---------------------------------------------+
4.5.1.2. IPv6-Delete-Prefix Attribute
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
|O|N|P|C|E| | | |IPv4-Delete- | TLV Length |Reserved |
| | | | | | | | | Prefix | C = 1 EL = 0 | |
|0|0|0|1| | | | | Type = 14 +-------------------------------+
| | | | | | | | | |TLV Extended Length (C=1 EL=1) |
+-+-+-+-+-+-+-+-+---------------+-------------------------------+
| IPv6 Prefix 1 (Variable) |
+---------------------------------------------------------------+
x ***** x
+---------------------------------------------------------------+
| IPv6 N Value (Variable) |
+---------------------------------------------------------------+
This attribute is used to convey the withdrawal of one or more IPv6
bindings which are unambiguously identified by their IPv6 prefix.
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This attribute contains a set of IPv6 prefixes. Each IPv6 prefix is
encoded as a 2-tuple of the form <length, prefix>, whose fields are
encoded as:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| Length = | Reserved |
| [0..128] | |
+---------------+-----------------------------------------------+
| Prefix[1..4] |
+---------------------------------------------------------------+
| 0 < Length | 9 <= Length | 17 <= Length |25 <= Length |
+---------------+---------------+---------------+---------------+
| Prefix[5..8] |
+---------------------------------------------------------------+
| 33 < Length | 41 <= Length | 49 <= Length |57 <= Length |
| | | | |
+---------------+---------------+---------------+---------------+
| Prefix[9..12] |
+---------------------------------------------------------------+
| 65 < Length | 73 <= Length | 81 <= Length |89 <= Length |
+---------------+---------------+---------------+---------------+
| Prefix[13..16] |
+---------------------------------------------------------------+
| 97 < Length | 105 <= Length | 113 <= Length |121 <= Length |
+---------------+---------------+---------------+---------------+
+--------+------------+---------------------------------------------+
| Field | Length (in | Description |
| | Octets) | |
+--------+------------+---------------------------------------------+
| Length | 1 | Unsigned integer. The length in bits of the |
| | | IP address prefix. A length |
| | | of zero indicates a prefix that matches all |
| | | IP addresses (with Prefix |
| | | field filled with zero in all octets) |
| Prefix | Variable | An IP address prefix, followed by the |
| | (Length/8) | minimum number of trailing |
| | | bits needed to make the end of the field |
| | | fall on an octet boundary. |
| | | The value of trailing bits is irrelevant |
+--------+------------+---------------------------------------------+
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4.5.1.3. Peer-Sequence Attribute
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
|O|N|P|C|E| | | |Peer-Sequence | TLV Length |
|0|0|0|1|0| | | | Type = 16 | 4 * N |
+-+-+-+-+-+-+-+-+---------------+-------------------------------+
| SXP ID 1 |
+---------------------------------------------------------------+
| SXP ID 2 |
+---------------------------------------------------------------+
x ***** x
+---------------------------------------------------------------+
| SXP ID N |
+---------------------------------------------------------------+
This attribute contains the SXP nodes through which exported bindings
has traversed. Each SXP node is identified by a 4 octet SXP ID. SXP
ID MUST be unique for every SXP node in an SXP deployment. As
exported bindings are propagated by an SXP Speaker, the speaker SHALL
prepend its own SXP ID to the sequence of SXP IDs of the Peer-
Sequence attribute that was received by an SXP Listener on the same
node. If the exported binding is originated by the local node, the
Peer-Sequence will contain a single SXP ID identifying the local
node. When an UPDATE message is received by an SXP Listener, the
first SXP ID within each Peer-Sequence attribute is the SXP node ID
of the SXP Speaker on the remote end of the connection the message is
received on. The last SXP ID is the node ID of the SXP Speaker that
originates the bindings associated with a Peer-Sequence attribute.
UPDATE message SHALL contain one Peer-Sequence attribute and MAY
contain multiple Peer-Sequence attributes. Each Peer-Sequence
attribute is associated with the bindings that follow it up to the
next Peer-Sequence attribute if more than one Peer-Sequence attribute
is present or up to the end of the UPDATE message.
4.5.1.4. Source-Group-Tag Attribute
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
|O|N|P|C|E| | | |SGT Type = 17 | TLV Length 2 | Reserved |
|0|0|0|1|0| | | | Group Tag | 2 | |
+-+-+-+-+-+-+-+-+---------------+---------------+---------------+
| SGT Value | Reserved |
+-------------------------------+-------------------------------+
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+-------------------+-----------------+-----------------------------+
| Field | Length (in | Description |
| | Octets) | |
+-------------------+-----------------+-----------------------------+
| Attribute Type | 1 | Scalable-Group-Tag (17) |
| Attribute Value | 1 | |
| Length | | |
| SGT Value | 2 | Unsigned integer value of |
| | | an SGT |
+-------------------+-----------------+-----------------------------+
4.5.1.5. IPv4-Add-Prefix Attribute
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | |IPv4-Add-Prefix|TLV Length (C=1| Reserved |
|O|N|P|C|E| | | | Type = 11 | EL=0) | |
| | | | | | | | | +---------------+---------------+
|0|0|0|1| | | | | |TLV Extended Length (C=1 EL=1) |
+-+-+-+-+-+-+-+-+---------------+-------------------------------+
| IPv4 Prefix 1 (Variable) |
+---------------------------------------------------------------+
x ***** x
|---------------------------------------------------------------+
| IPv4 N Value (Variable) |
+---------------------------------------------------------------+
This attribute is used to convey the binding of one or more IPv4
prefixes with an SGT value or other information. The encoding of
each IPv4 prefix is described above in IPv4-Delete-Prefix Attribute
section.
The unbundling of IP prefixes from the information associated with
them achieves two major objectives:
o Allows for efficient sharing of common attributes such as Peer-
Sequence, and Scalable-Group-Tag with multiple IP prefixes.
o Allows for future introduction of new information for association
with IP prefixes via optional attributes.
The associated SGT is the value specified by the latest preceding
occurrence of Scalable-Group-Tag attribute within the same UPDATE
message. An IPv4-Add-Prefix attribute SHALL be preceded with an
occurrence of Peer-Sequence attribute. The latest preceding
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occurrence provides the path along which the bindings of all the
prefixes contained in the IPv4-Add-Prefix have been traversed.
4.5.1.6. IPv6-Add-Prefix Attribute
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | |IPv6-Add-Prefix|TLV Length (C=1| Reserved |
|O|N|P|C|E| | | | Type = 12 | EL=0) | |
| | | | | | | | | +---------------+---------------+
|0|0|0|1| | | | | |TLV Extended Length (C=1 EL=1) |
+-+-+-+-+-+-+-+-+---------------+-------------------------------+
| IPv6 Prefix 1 (Variable) |
+---------------------------------------------------------------+
x ***** x
|---------------------------------------------------------------+
| IPv6 N Value (Variable) |
+---------------------------------------------------------------+
This attribute is used to convey the binding of one or more IPv6
prefixes with an SGT value or other information. The encoding of
each IPv6 prefix is described above in IPv6-Delete-Prefix Attribute
section. The handling of this attribute and its relationship with
preceding attributes such as Peer-Sequence or Scalable-Group-Tag are
the same as what is described above in IPv4-Add-Prefix section except
for a different attribute type (12) and possibly longer IPv6
prefixes.
4.5.1.7. IPv4-Add-Table Attribute
This attribute provides a flexible tabular representation of bindings
information. It is provided for efficient aggregation of multiple
bindings information when an implementation cannot aggregate multiple
IP prefixes that are associated with the same SGT or other common
attributes.
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
|O|N|P|C|E| | | | IPv4-Add-Table| TLV Length | Reserved |
|0|0|0|1| | | | | Type = 21 | (C = 1 EL = 0)| |
| | | | | | | | | |-------------------------------+
| | | | | | | | | | TLV Extended Length (C=1 EL=1)|
+-+-+-+-+-+-+-+-+---------------+---------------+---------------+
| Number of | Reserved |
| Columns C | |
+---------------+---------------+---------------+---------------+
|'1'Column Type | '1'Column Type| '1'Column |'2'Column Type |
| Flags | | Width | Flags |
+---------------+---------------+---------------+---------------+
|'2'Column Type | '2'Column | |
| | Width | *** |
+---------------+---------------+---------------+---------------+
x *** x
+---------------+---------------+---------------+---------------+
|'C'Column Type | 'C'Column Type| 'C'Column | Reserved |
| Flags | | Width | |
+---------------+---------------+------------------------------+--+
| '1''1' Value | *** |'1''C'Value |'1'IPv4 Prefix |
| | *** | | (Variable) |
+---------------+---------------+---------------+-----------------+
x *** x *** x *** x *** x
x *** x *** x *** x *** x
x---------------+---------------+---------------+-----------------x
| 'R''1' Value | *** |'R''C'Value |'R'IPv4 Prefix |
| | *** | | (Variable) |
+---------------+---------------+---------------+-----------------+
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+---------+----------+----------------------------------------------+
| Field | Bits | Description |
+---------+----------+----------------------------------------------+
| Number | 1 | 1 - Unsigned integer which specifies the |
| of | | number of columns of |
| Columns | | information (not including the trailing IP |
| | | prefix) associated with each |
| | | prefix |
| [i] | 1 | 0 - An Attribute Type Flags value defining |
| Column | | the flag of the attribute in |
| Type | | the I'th column on each row |
| Flags | | |
| [i] | 1 | 1 - An Attribute Type value defining what |
| Column | | each row have in the i'th |
| Type | | column position |
| [i] | 1 | 1 - The length in octets of the attribute |
| Column | | value in the i'th column on |
| Width | | each row |
| [j] | Variable | 0 - An IP prefix which is associated with |
| IPv4 | | the C-tuple of attribute |
| Prefix | | values on the j'th row of the table. The |
| | | format of is the same as the IP prefix field |
| | | in the IPv4-Add-Prefix |
| | | attribute |
+---------+----------+----------------------------------------------+
Below is an example of an IPv4-Add-Table attribute which contain a
single SGT attribute value on each row.
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
|O|N|P|C|E| | | | IPv4-Add- | TLV Length | Reserved |
| | | | | | | | | Table | (C = 1 EL = 0)| |
|0|0|0|1| | | | | Type = 21 |-------------------------------+
| | | | | | | | | | TLV Extended Length (C=1 EL=1)|
+-+-+-+-+-+-+-+-+---------------+---------------+---------------+
| Number of | Reserved |
| Columns 1 | |
+-------------------------------+-------------------------------+
|Scalable-Group | Column | Reserved |
| Tag Type = 17 | Width = 2 | |
+-------------------------------+-------------------------------+--+
| '1'SGT Value |'1'Prefix |'1'IPv4 Prefix |
| | Length | |
+-------------------------------+---------------+------------------+
x *** x *** x *** x
x-------------------------------+---------------+------------------x
| 'R'SGT Value |'R'Prefix |'R'IPv4 Prefix |
| | Length | |
+-------------------------------+---------------+------------------+
4.5.1.8. IPv6-Add-Table Attribute
This attribute provides a flexible tabular representation of IPv6
bindings information.
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
|O|N|P|C|E| | | | IPv6-Add- | TLV Length | Reserved |
| | | | | | | | | Table | (C = 1 EL = 0)| |
|0|0|0|1| | | | | Type = 22 |-------------------------------+
| | | | | | | | | | TLV Extended Length (C=1 EL=1)|
+-+-+-+-+-+-+-+-+---------------+-------------------------------+
| Number of | Reserved |
| Columns C | |
+---------------+---------------+---------------+---------------+
|'1'Column Type | '1'Column Type| '1'Column |'2'Column Type |
| Flags | | Width | Flags |
+---------------+---------------+---------------+---------------+
|'2'Column Type | '2'Column | |
| | Width | *** |
+---------------+---------------+---------------+---------------+
x *** x
+---------------+---------------+---------------+---------------+
|'C'Column Type | 'C'Column Type| 'C'Column | Reserved |
| Flags | | Width | |
+---------------+---------------+-------------------------------+--+
| '1''1' Value | *** |'1''C'Value |'1'IPv6 Prefix |
| | *** | | (Variable) |
+---------------+---------------+---------------+------------------+
x *** x *** x *** x *** x
x---------------+---------------+---------------+------------------x
| 'R''1' Value | *** |'R''C'Value |'R'IPv6 Prefix |
| | *** | | (Variable) |
+---------------+---------------+---------------+------------------+
The format and handling of IPv6-Add-Table attribute are the same as
what is described above in IPv4-Add-Table section except that the
attribute type (22) is used and the trailing IPv6 Prefix field in
each row could be potentially longer than the corresponding trailing
IPv4 Prefix fields.
4.5.2. UPDATE Message Samples
Single IPv4 host binding as exported by the first Speaker away from
the originating node:
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+------
| SXP Message Length = 32 |SXP
+---------------------------------------------------------------+Msg
| SXP Message Type = UPDATE (3) |Header
+---------------------------------------------------------------+------
|O|N|P|C|E| | | |Peer-Sequence | TLV Length | Reserved |
|0|0|0|1|0| | | | Type = 16 | 8 | |
+-+-+-+-+-+-+-+-+---------------+-------------------------------+Peer-
| Local SXP ID |Seq-
| |Attr
+---------------------------------------------------------------+
|SXP ID of Speaker end of the connection on which it was |
| originally received |
+---------------------------------------------------------------+-----
|O|N|P|C|E| | | |Scalable-Group-| TLV Length | Reserved |
| | | | | | | | | Tag | 2 | |Src-
|0|0|0|1|0| | | | Type = 17 | | |Grp-
+-+-+-+-+-+-+-+-+---------------+-------------------------------+Tag
| SGT Value = <sgt#> | Reserved |Attr
| | |
+---------------------------------------------------------------+-----
|O|N|P|C|E| | | |IPv4-Add-Prefix| TLV Length |Prefix Length |IPv4-
| | | | | | | | | Type = 11 | 5 | 32 |Add-
|0|0|0|1|0| | | | | | |Pre-
+-+-+-+-+-+-+-+-+---------------+-------------------------------+fix
| IPv4 Host Address |Attr
+---------------------------------------------------------------+-----
Multiple IPv4 host and subnet bindings sharing the same Peer-Sequence
as exported by the first Speaker away from the originating node. 11
subnets bindings of length between 17 and 24 and as many host
bindings as SXP total message size allowed are packed into this
message:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+------
| SXP Message Length = 4096 |SXP
+---------------------------------------------------------------+Msg
| SXP Message Type = UPDATE (3) |Header
+---------------------------------------------------------------+------
|O|N|P|C|E| | | |Peer-Sequence | TLV Length | Reserved |
|0|0|0|1|0| | | | Type = 16 | 8 | |
+-+-+-+-+-+-+-+-+---------------+-------------------------------+Peer-
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| Local SXP ID |Seq-
| |Attr
+---------------------------------------------------------------+
|SXP ID of Speaker end of the connection on which it was |
| originally received |
+---------------------------------------------------------------+-----
|O|N|P|C|E| | | |IPv4-Add-Table | TLV Length | Reserved |IPv4-
| | | | | | | | | |3 + 11x6 +572x7| |Add-
|0|0|0|1|0| | | | Type = 21 | = 4073 | |Table
+-+-+-+-+-+-+-+-+---------------+-------------------------------+Attri-
|Number of | Reserved |-bute
|Columns 1 | |
+---------------------------------------------------------------+------
|Scalable | Column | Reserved |Col
|Group Tag | Width = 2 | |Head
|Type = 17 | | |ers
+-+-+-+-+-+-+-+-+---------------+-------------------------------+------
| '1' SGT Value |'1'Prefix | Reserved |
| |Length = | |
| | [17..24] | |
|-------------------------------+---------------+---------------+
| '1' IPv4 Subnet Prefix | Reserved |Subnet
+-----------------------------------------------+---------------+Bind-
* * |ings
* * Reserved |Rows
* '2..10' <SGT Value, IPv4 Subnet Prefix> rows * |
+-----------------------------------------------+---------------+
| '11' SGT Value |'11'Prefix | Reserved |
| |Length = | |
| | '17..24' | |
|-------------------------------+---------------+---------------+
| '11' IPv4 Subnet Prefix | Reserved |
+-----------------------------------------------+---------------+----
| '1' SGT Value |'1'Prefix | Reserved |
| |Length = 32 | |
|-------------------------------+---------------+---------------+
| '1'IPv4 Host Address |
+-----------------------------------------------+---------------+
x | Reserved |Host
x '2..571' <SGT Value, 32, IPv4 Host Address> | |Bind-
x +---------------+ing
x |Rows
x---------------------------------------------------------------+
| '572' SGT Value |'572'Prefix | Reserved |
| |Length = 32 | |
+-------------------------------+---------------+---------------+
| '572'IPv4 Host Address |
+---------------------------------------------------------------+-----
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4.6. SXP ERROR Message
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | 0 (E=0) | 0 (E=0) | non-Extended Error Code (E=0)|
|E+-------------+---------------+-------------------------------|
| |Error Code |Error Sub-code | |
| | (E=1) | (E=1) | |
+-+-----------------------------+ |
| Data (Variable) |
+---------------------------------------------------------------+
+--------------+--------+----------+--------------------------------+
| Field | Bits | Length | Description |
| | | (in | |
| | | Octets) | |
+--------------+--------+----------+--------------------------------+
| Extended | 0 | | 1 - Extended Error format, |
| | | | which includes code, sub-code, |
| | | | and variable data 0 - Legacy |
| | | | non-Extended Error |
| Error Code | [1..7] | 0 | Unsigned integer in the range |
| | | | [0..127] - indicates the type |
| | | | of ERROR |
| Error Sub- | | 1 | Unsigned integer in the range |
| Code | | | [0..255] - Provides extended |
| | | | information about the nature |
| | | | of the reported error. Each |
| | | | Error code may have |
| | | | one or more Error Sub-codes |
| | | | associated with it. If no |
| | | | appropriate Error Sub-code is |
| | | | defined, then zero |
| | | | (Unspecified) value |
| | | | is used |
| non-Extended | | 2 | Error code values: 0 - No |
| Error Code | | | error 1 - Version Mismatch 2 - |
| | | | Message Parse Error |
| Data | | Variable | Additional data for diagnosing |
| | | Message | the reason for the ERROR |
| | | Length - | message. The content |
| | | 10 | depends on the values of Error |
| | | | Code and Error Sub- |
| | | | code |
+--------------+--------+----------+--------------------------------+
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4.6.1. Error Codes
+-----------+-----------+-------------------------------------+
| Error | Error | Symbolic Name |
| Code | Sub-code | |
+-----------+-----------+-------------------------------------+
| 1 | - | Message Header Error |
| | | |
+-----------+-----------+-------------------------------------+
| 2 | - | OPEN Message Error |
| | | |
+-----------+-----------+-------------------------------------+
| 3 | - | UPDATE Message Error |
| | | |
+-----------+-----------+-------------------------------------+
| | 1 | Malformed Attribute List |
| | | |
+ +-----------+-------------------------------------+
| | 2 | Unexpected Attribute |
| | | |
+ +-----------+-------------------------------------+
| | 3 | Missing Well-known Attribute |
| | | |
+ +-----------+-------------------------------------+
| | 4 | Attribute Flags Error |
| | | |
+ +-----------+-------------------------------------+
| | 5 | Attribute Length Error |
| | | |
+ +-----------+-------------------------------------+
| | 6 | Malformed Attribute |
| | | |
+ +-----------+-------------------------------------+
| | 7 | Optional Attribute Error |
| | | |
+ +-----------+-------------------------------------+
| | 8 | Unsupported Version Number |
| | | |
+ +-----------+-------------------------------------+
| | 9 | Unsupported Optional Attribute |
| | | |
+ +-----------+-------------------------------------+
| | 10 | Unacceptable Hold Time |
| | | |
+-----------+-----------+-------------------------------------+
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The error codes and the error sub-codes are used to interpret the
type of error and the specific attributes that have caused the error
need not be sent back with the error message.
4.7. SXP PURGE-ALL Message
There is no payload corresponding to this message type.
When an SXP connection on which the local SXP node is a speaker is
administratively deleted, SXP MUST send a PURGE-ALL message to the
SXP listener at the remote end. This will provide the listener
timely knowledge that the connection is about to be torn down and
that it is not an intermittent loss of communication. The listener
will immediately delete all bindings that were received on that
connection and will not go through Delete Hold-Down timer before
removal of bindings.
When SXP feature gets administratively disabled, SXP MUST send PURGE-
ALL message on all the connections on which the local end is a
speaker.
Upon receiving a PURGE-ALL message, an SXP listener MUST immediately
delete all the bindings that were received on that connection.
PURGE-ALL message should have the same effect as an UPDATE message
with IPv4-Delete-Prefix or IPv6-Delete-Prefix attributes that contain
all bindings which has been exported on the connection. A PURGE-ALL
is simply an optimization of such delete at-once case.
4.8. SXP KEEPALIVE Message
There is no payload corresponding to this message type. This message
is sent by the speaker to the listener side when KEEPALIVE timer
expires.
5. Update Message Handling
An SXP UPDATE message may be received only in the ON state.
Receiving an UPDATE message in any other state is an error. When an
UPDATE message is received, each field is checked for validity.
5.1. UPDATE Message Validation
UPDATE message SHALL be organized as illustrated below:
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+-------------------------------------------------------------+
|Zero or more global optional attributes which are unrelated |
|to any of the binding delete or add attributes or groups |
| below them |
+-------------------------------------------------------------+
|At most one each IPv4-Delete-Prefix or IPv6-Delete-Prefix |
+-------------------------------------------------------------+
|Zero or more Del-IPv4 or Del-IPv6 (non-zero only when neither|
| IPv4-Delete-Prefix nor IPv6-Delete-Prefix are present) |
+-------------------------------------------------------------+
All errors detected while processing the UPDATE message MUST be
indicated by sending the ERROR message with the Error Code UPDATE
Message Error to the SXP speaker from which the UPDATE message was
received. The Error Sub-code provides additional information about
the error. UPDATE message is a sequence of attributes. Attributes
could be further classified as compact, compact with extended length,
or non-compact attributes. Each attribute consists of a fixed-size
header, 3, 4, or 8 octets long respectively, which contains TLV
Length field. The total length of each attribute is thus: Attribute
Length = 3/4/8 + TLV Length If the length of any attribute is larger
than the SXP Message length or the sum of Attribute Length of all
attributes is larger than the SXP Message length, the Error Sub-code
MUST be set to Malformed Attribute List. If any recognized attribute
has Attribute Flags that conflicts with its Attribute Type, then the
Error Sub-code MUST be set to Attribute Flags Error. The Data field
MUST contain the erroneous attribute (flags, type, length, and
value). If any recognized attribute has Attribute Length that
conflicts with the expected length (based on its Attribute Type),
then the Error Sub-code MUST be set to Attribute Length Error. The
Data field MUST contain the erroneous attribute (flags, type, length,
and value).
If any recognized attribute does not conform to the attribute
specification in UPDATE Attributes section, then Error Sub-code MUST
be set to Malformed Attribute. The Data field MUST contain the
erroneous attribute (flags, type, length, and value). Cases of
malformed attributes:
o IP Prefix length field is outside of the permitted range
[0..32]/[0..128] for IPv4/IPv6 respectively.
o Implied length of IP Prefix field which extends the prefix beyond
the extent of the containing attribute.
If any attribute appears more than once when at most one occurrence
is permitted then the Error Sub-code MUST be set to Malformed
Attribute List.
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If any attribute appears in a location where it is not expected (such
as IPv4-Add-Prefix/IPv6-Add-Prefix without preceding Scalable-Group-
Tag) then the Error Sub-code MUST be set to Malformed Attribute List.
If an optional non-transitive attribute is unrecognized, it is
quietly ignored.
If an optional transitive attribute is unrecognized, the Partial bit
(the third high-order bit) in the attribute flags octet is set to 1,
and the attribute is retained for export according to the scope in
which the attribute appears. A global attribute is exported along
every binding specified in this UPDATE message on all connections for
which the local peer is a speaker. A path attribute is exported
along the bindings from a single path. A per <path, scalable-group>
attribute is exported along bindings received from a single path
which share a single Scalable-Group-Tag attribute. If an optional
attribute is recognized and has a valid value, then, depending on the
type of the optional attribute, it is processed locally, retained,
and updated, if necessary, for possible export to listener peers. A
Peer-Sequence attributes is checked for syntactic correction. If the
path is syntactically incorrect (e.g. length is not a multiple of 4),
then an ERROR message MUST be sent to the speaker with Error Sub-code
set to Malformed Attribute. SXP listener learns the SXP Node-ID from
the SXP Node-ID in the OPEN or OPEN_RESP it receives at connection
establishment. This Node-ID is used to validate subsequent Peer-
Sequence attributes from the same peer. SXP MUST check whether the
leftmost (with respect to the position of octets in the protocol
message) SXP Node-ID in the Peer-Sequence is equal to the SXP Node-ID
of the peer that sent the UPDATE message. If the checks determines
that this is not the case, then an ERROR message MUST be sent to the
speaker with Error Sub-code set to Malformed Attribute.
5.2. UPDATE Message processing
Processing of an UPDATE message by an SXP listener follows the
organization of the message according to the following high level
steps:
1. UPDATE Message validation as described in section 5.1.
2. Processing of global optional attributes.
3. Processing of binding delete attributes. Binding delete
attributes include any of IPv4-Del-Prefix, IPv6-Del-Prefix, Del-
IPv4, or Del-IPv6 attributes.
4. Processing path-groups.
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A. Process per-path common optional attributes
B. Add-Prefix groups. Each Add-Prefix group starts with a
Scalable-Group-Tag attribute.
i. Process per <path, SGT> optional attributed.
ii. Process IPv4-Add-Prefix attribute
iii. Process IPv6-Add-Prefix attribute
C. Processing IPv4-Add-Table attribute
D. Processing IPv6-Add-Table attribute
E. Processing Add-IPv4 attributes
F. Processing Add-IPv6 attributes
5. Processing trailing optional non-transitive attributes
Each path-group starts with an instance of Peer-Sequence attribute.
Processing Binding Delete Attributes (step 3)
If the UPDATE message contains a non-empty IPv4-Del-Prefix/IPv6-Del-
Prefix or one or more Del-IPv4/Del-IPv6 attributes, the previously
received bindings from the remote speaker peer, whose IP/IPv6
addresses are contained in any of those attributes, SHALL be removed
from the SXP input bindings database. Additional processing of a
deleted binding depends on whether it was the SXP contributed binding
for its IPv4/IPv6 address and whether it was the selected and
exported binding by the master binding data-base:
o Non-contributed binding - No further processing is needed.
o Contributed but not exported - The binding was the preferred
binding by SXP and was reported to the master binding database.
However, the binding was not exported by SXP due to higher
priority contributors in the master binding database. SXP SHALL
select a new contribution for the IPv4/IPv6 address of the deleted
binding from the input bindings database, and, upon change of SGT
or other associated data that are reported to the master bindings
database, report the newly selected binding to the master binding
database. The newly selected contribution will not affect the
exported binding since this is a non-contributed binding that was
not exported to the master binding database.
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o Contributed and Exported - The binding was the preferred binding
by SXP and was the selected binding for the IPv4/IPv6 address by
the master binding database. SXP contribution was either the only
binding contributor or the highest priority contributor.
SXP SHALL select a new contribution for the IPv4/IPv6 address of the
deleted binding among the bindings for that address from other peers.
SXP SHALL apply the following rules for selecting a binding for
reporting to the master binding database:
1. Shortest Path rule
Choose a binding which has the shortest Peer-Sequence among all the
bindings for the same IP address. A binding received without Peer-
Sequence attribute (i.e. from an earlier version speaker) is
considered as being received with a Peer-Sequence that contains a
single NULL SXP Node-ID (value 0).
1. Most Recently Received rule
If there are more than one bindings with the shortest Peer-Sequence,
the binding which has been most recently received is selected.
If the deleted binding was the only binding for its IP address in the
SXP input binding database, SXP SHALL report it to the master binding
database. The external outcome when no other contributors to the
same IP address is present, is that a deletion of the binding using
IPv4-Del-Prefix/IPv6-Del-Prefix or Del-IPv4/Del-IPv6 attribute MUST
be exported on all connections on which the local end is a speaker.
If there is one or more additional contributors in the master binding
database, a new binding is selected and it MUST be exported using
IPv4-Add-Prefix/IPv6-Add-Prefix, IPv4-Add-Table/IPv6-Add-Table, or
Add-IPv4/Add-IPv6 and associated with a Peer-Sequence that includes
only the SXP Node ID of the local instance.
If the binding selection rule has yielded a newly selected binding
from SXP input binding database it SHALL be compared to the binding
it is replacing, and
o upon change of SGT, or, other associated data that are reported to
the master binding database, report the newly selected binding to
the master binding database. The newly selected contribution will
become the selected contribution and will trigger export.
o If the SGT of the newly selected binding, and all other associated
data that are reported to the master binding database, remain the
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same as those of the deleted binding, SXP SHOULD NOT report a new
contribution to the master binding database. However, the newly
selected binding has a different Peer-Sequence attribute because
binding from a different peer is selected. There could also be
changes in optional transitive attributes. SXP SHALL export the
newly selected binding directly and include all transitive
attributes, thus bypassing the usual notification path from the
master bindings database.
Processing Binding Add Attributes (step 4)
I. Implicit delete of current bindings
If the UPDATE message contains a non-empty IPv4-Add-Prefix/IPv6-
Add-Prefix/IPv4-Add-Table/IPv6-Add-Table or one or more Add-IPv4/
Add-IPv6 attributes, the previously received bindings from the
remote speaker peer (if any), whose IP/IPv6 addresses are
contained in any of those attributes, SHALL be removed from the
SXP input bindings database and replaced with the new bindings for
those IPv4/IPv6 addresses. An added binding is an implicit delete
of an existing binding for the same IP address from the same peer.
The external behavior of the implicit deletion is as described for
the processing of IPv4-Del-Prefix/IPv6-Del-Prefix or Del-IPv4/Del-
IPv6 attributes where the deleted binding is the last binding for
its IP address.
II. Loop Detection
SXP MUST check the Peer-Sequence associated with each added
binding for the presence of loops before accepting the binding as
a new binding or as a replacement for an implicitly deleted
binding. SXP loop detection is done by scanning the entire Peer-
Sequence attribute, and checking that the SXP Node ID of the local
system does not appear in the Peer-Sequence.
III. New or Replaced Bindings
SXP SHALL keep the most recently received binding for each IP
address in the input binding database. SXP SHALL keep all the
mandatory attributes and any optional transitive attributes and
MAY keep other non-transitive attributes. A subset of the
attributes, such as Scalable-Group-Tag, are used locally on the
system and have to be reported to the master binding database.
The master binding database arbitrates among multiple binding
contributors for the same IP address. SXP SHALL report new
bindings to the master binding database along with the attributes
the master database is aware of. The arbitration process in the
master binding database yields a selected binding contributor for
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each IP address. The binding contributor could be a binding
source other than SXP. SXP MUST NOT export any binding it has
received in UPDATE message unless it has survived the arbitration
process in the master binding database to become the selected
binding.
SXP SHALL become aware of the outcome of the arbitration process
within the master binding database. The arbitration process could
be triggered by binding add or delete reported by SXP or binding
changes from other binding contributors. SXP NEED NOT be aware of
the presence of other binding contributors, their nature, or how
many such contributors exist. SXP is only aware of the possible
existence of such binding contributors and only need to know
whether a selected binding was contributed by SXP itself or by
some other contributor. The mechanism by which SXP becomes aware
of changes of selected bindings in the master binding database is
an implementation detail.
5.3. Generating UPDATE Message
Binding Removal Event
If SXP becomes aware of a deletion of a binding for an IPv4/IPv6
prefix it then processes the event as follows:
o The IPv4/IPv6 prefix SHALL be included in either an IPv4-Del-
Prefix/IPv6-Del-Prefix or a single Del-IPv4/Del-IPv6 attribute of
an outgoing UPDATE message. SXP MAY delay exporting of such event
for a small and bound duration in order to allow for aggregation
as long as such aggregation will not exhibit different external
behavior from individually exported events.
Binding Change Event
If SXP becomes aware of a new or changed binding for an IPv4/IPv6
prefix it then processes the event as follows:
o If the selected contributor is not SXP, SXP SHALL associate the
binding with a Peer-Sequence that contains the local SXP Node ID
as the only peer and export the binding in one of IPv4-Add-Prefix/
IPv6-Add-Prefix, IPv4-Add-Table/IPv6-Add-Table, or Add-IPv4/Add-
IPv6. SXP SHALL include in the outgoing UPDATE message the
attributes that are available from the master binding database.
o If the selected contributor is SXP, SXP MUST locate the
contributed binding in its input binding database and extract the
Peer-Sequence that was associated with the binding when it was
originally received. SXP SHALL prepend the local SXP Node ID to
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the Peer-Sequence when it is added to an outgoing UPDATE message.
SXP SHALL include in the UPDATE message the mandatory attributes
reported by the master binding database and any additional well-
known or optional transitive attributes that were associated with
the binding upon its arrival. SXP MAY add additional optional
transitive or non-transitive attributes.
SXP SHALL flag an SXP originated binding in its input bindings
database in order to support UPDATE message processing as specified
in this section.
6. SXP Failure Scenarios
The following SXP failure scenarios are analyzed in this section:
o SXP Connection Failure
o Operational (Hardware) Failures
SXP connection can fail for various reasons:
o Peer device offline
o Loss of network connectivity
o Loss message authentication key synchronization with the peer. In
this case the device re-attempts message exchange for a fixed
number of times and if the problem persists then the connection is
torn down.
o Software processing failures, e.g. SXP message decode failure.
SXP version mismatch and SXP message parse error will result in
the device sending an Error TLV. When sending an error message,
the error code is passed as part of the TLV and the action
decision is left up to the peer device. This error code COULD be
simply logged for debugging purposes. The SXP connection is
closed and retries to setup after sending the SXP ERROR message.
7. SXP Timers
There are 5 SXP timers defined in SXP protocol. The details of the
timers and the default values of them are described below:
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+------------------------+---------------------------------+
| Timer | Default Value (seconds) |
+------------------------+---------------------------------+
| Retry Open Timer | 120 |
| Delete Hold Down Timer | 120 |
| Reconciliation Timer | 120 |
| Hold Timer | 90 (actual value is negotiated) |
| Keep-alive Timer | 30 (one-third of Hold Timer) |
+------------------------+---------------------------------+
o Retry open timer
* Retry open timer is triggered as long as there is one SXP
connection on the device that is not up.
* The default timer value is 120 seconds. Value 0 means retry
timer will not be started.
* The retry continues until the SXP connection is setup or the
retry timer is configured to be 0.
o Delete Hold Down Timer
* Delete hold down timer is triggered when a connection on
listener side is torn down. The bindings learnt are not
deleted immediately but held off for the delete hold down timer
period.
* The bindings are deleted upon the expiry of this timer.
* The timer value is set to 120 seconds and it is not
configurable.
o Reconciliation Timer
* If a SXP connection is brought up within the delete hold down
timer period, bindings are re-populated from the speaker side.
At the same time, the old bindings learnt before the connection
went down still hold.
* Reconciliation timer starts right after the connection is
brought up to wait for the new bindings to be forwarded from
the peer.
* Upon timer expiry, SXP checks the bindings in its input binding
database and deletes any stale bindings. Those are bindings
that could have been deleted on the remote side while the
connection was down.
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* The default timer value is 120 seconds. Value 0 means
reconciliation timer will not be started.
o Hold Timer
* Hold Timer MAY be used by an SXP Listener to detect when a
connection is no longer live.
* The usage of Hold Timer and KEEPALIVE is negotiated during
OPEN/OPEN_RESP exchange.
* The Hold Timer is started when the connection reaches ON state.
The interval is set to the negotiated Hold Time.
* The Hold Timer is restarted whenever a listener receives a
KEEPALIVE or an UPDATE message.
* If a listener does not receive KEEPALIVE, and/or UPDATE
messages within the period negotiated for the Hold Time of a
connection, the Hold Timer expires.
* Upon the timer expiry, SXP MUST send an ERROR message with Hold
Timer Expired code and tear down the connection.
* The rest of the behavior is the same as when TCP indicates to
SXP the loss of a connection. The Delete Hold Down timer is
restarted for delayed deletion of bindings as described above.
* The suggested period of the Hold Timer is 90 seconds. SXP
implementation MAY allow for local configuration of Hold Time
for a listener. The actual value of the Hold Time used for a
connection is negotiated.
o Keepalive Timer
* Keepalive Timer MAY be used by an SXP Listener for triggering
sending KEEPALIVE messages to the listener peer which monitors
a connection using Hold Timer.
* The usage of Keepalive Timer and KEEPALIVE messages is
negotiated during OPEN/OPEN_RESP exchange.
* The Keepalive Timer is started for the first time when the
connection reaches its ON state.
* The Keepalive Timer is restarted thereafter, when a speaker
sends an UPDATE or KEEPALIVE message.
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* Upon timer expiry, SXP speaker MUST send KEEPALIVE message in
order to indicate to the listener that the connection remains
live.
* The suggested period of the Keepalive Timer is 30 seconds. SXP
implementation MAY allow for local configuration of Keepalive
Time for a speaker. The actual value of the Keepalive Time
used for a connection is set to 1/3 of the negotiated Hold
Time.
* The Keepalive Timer is restarted with a random jitter. The
actual period of the Keepalive Timer is set to a random value
between 0.75 to 1.0 of the negotiated Keepalive Time which is
re-calculated every time the timer is restarted.
8. SXP Version Negotiation
In a software release, SXP always supports the highest version in
that release and any version lower than that. SXP version
negotiation is per connection base. On the same device, the
connections established between this device and the peer devices may
have difference versions, depending on the SXP version running on the
peer devices.
If the two ends of a SXP connection run the same SXP version, the
running version is used. If the two ends are running different
versions, the version of the connection is decided with following
process:
When the initiator of a connection sends a SXP OPEN message, the
highest supported version is coded in the OPEN message.
On the receiver side, if the version in the OPEN message is higher
than the version it can support, it sends back OPEN RESPONSE message
with the highest version it supports (which is lower than the version
in OPEN message). When the OPEN RESPONSE message is received by the
initiator, it accepts the version coded in the OPEN RESPONSE. The
receiver side's version is used as the connection's version.
In summary, SXP connection picks the highest version that is
supported on both sides.
8.1. SXP Versions
SXP supports three versions starting from version 2 to 4. The
details of what is supported in each of the version follows -
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+-----+----------+----------+------------+-----------+--------------+
| Ver | IPv4 | IPv6 | Subnet | Loop | SXP |
| | Bindings | Bindings | Binding | Detection | Capability |
| | | | Expansion | | Exchange |
+-----+----------+----------+------------+-----------+--------------+
| 2 | Yes | Yes | No | No | No |
| 3 | Yes | Yes | Yes | No | No |
| 4 | Yes | Yes | Yes | Yes | Yes |
+-----+----------+----------+------------+-----------+--------------+
8.2. Error Handling in Older SXP Versions
The error handling scenarios in SXP Version1 & Version 2 are listed
below:
8.2.1. SXP Version 1
o Unknown message type causes connection to be disconnected
o Extra fileds in OPEN & OPEN_RESP messages causes connection to be
disconnected
o Unknown TLV in UPDATE message causes a parser error message sent
to the peer and connection is disconnected
o Extra parameters in the ERROR message cause a parser error message
sent to the peer and connection is disconnected
8.2.2. SXP Version 2
o Unknown message type is ignored
o Extra fileds in OPEN & OPEN_RESP messages is ignored
o Unknown TLV received in UPDATE message is ignored and no other
action is taken. Unknown opcode is also ignored
o Extra parameter in ERROR message is ignored
9. Security Considerations
SXP carries mappings between IP addresses and scalable groups. An
adversary that can modify the data can potentially gain an advantage
over the system. This specification defines the use of TCP MD5
Signature Option [RFC5925] to provide integrity protection for the
information. The key used with TCP MD5[RFC1321] should be chosen to
be long and have high entropy to provide as much protection from
dictionary attacks as possible.
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MD5 has been shown to contain weaknesses so this protection may not
be sufficient in many environments. In addition, an adversary who
can observe the data may be able to use the information learned to
identify weak or highly valued targets so it is desirable that
confidentiality also be provided. A future revision of this
specification will provide more robust security mechanisms such as
ones based on IPSEC or TLS.
10. Implementation Note
Current implementations of the protocol support source and peer IP
addresses to be IPv4 only. However, the implementation should take
care of being able to support IPv6 addresses as well in the future.
As such, there are not changes expected to be done in the protocol
itself to support IPv6 address based connections.
The SXP password can be upto 80 ASCII characters.
The Node-id used has to be a unique IP address on the device.
Current implementations use the highest local IP address on the
device and some use the first IP address on the device.
10.1. Bi-Directional SXP
The current implementation of SXP protocol supports bindings to be
exchanged in one direction only per connection. In scenarios where
bindings have to be sent and received with the same peer, two
connections have to be configured with one as Listener and the other
one as Speaker. In order to avoid configuring two different
connections with the same peer, the procotol supports bi-directional
mode. When a connection is configured in bi-directional mode, on
either ends only the Listener initiates the socket connection unlike
the normal case where either Speaker/Listener can initiate the
connection. Once the two socket connections are up the rest of the
connection management, bindings updates, etc are same as the uni-
directional connection.
11. IANA Considerations
TBD
12. IPR Disclosure
"By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79."
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13. Copyright Notice and Disclaimer
"Copyright (C) The IETF Trust (year). This document is subject to
the rights, licenses and restrictions contained in BCP 78, and except
as set forth therein, the authors retain all their rights."
Additional copyright notices are not permitted in IETF Documents
except in the case where such document is the product of a joint
development effort between the IETF and another standards development
organization or the document is a republication of the work of
another standards organization. Such exceptions must be approved on
an individual basis by the IAB.
"This document and the information contained herein are provided on
an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY , THE
IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL
WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY
WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY
RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE."
14. Acknowledgements
Special acknowledgements are due to the following contributors. The
protocol was originally developed by Michael Smith, Michael Fine and
Awais Nemat. Enhancements have been made over the years by Ronen
Arad, Rajesh Bhandari, Lei Fu and Paddy Nallur. Darrin Miller and
Kevin Regan provided significant inputs into requirements for later
versions of the protocol. Fabio Maino specified the data plane
format. Sandeep Rao has contributed to the SGT format in NSH, GRE,
VxLan and also the section on tagging exemption for L2 control
traffic. Thanks to Joe Salowey and Susan Thomson for edits and
review.
15. References
15.1. Normative References
[RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
DOI 10.17487/RFC1321, April 1992,
<https://www.rfc-editor.org/info/rfc1321>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
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[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
June 2010, <https://www.rfc-editor.org/info/rfc5925>.
[RFC5926] Lebovitz, G. and E. Rescorla, "Cryptographic Algorithms
for the TCP Authentication Option (TCP-AO)", June 2010,
<https://www.rfc-editor.org/info/rfc5926>.
15.2. Informative References
[I-D.draft-guichard-sfc-nsh-dc-allocation]
Guichard, J., Smith, M., Kumar, S., Majee, S., Agarwal,
P., Glavin, K., and Y. Laribi, "Network Service Header
(NSH) Context Header Allocation (Data Center)", December
2014.
[I-D.draft-quinn-sfc-nsh]
Quinn, P., Guichard, J., Surendra, S., Smith, M.,
Henderickx, W., Nadeau, T., Agarwal, P., Manur, R.,
Chauhan, A., Majee, S., Elzur, U., Melman, D., Garg, P.,
McConnell, B., Wright, C., and K. Kevin, "Network Service
Header", January 2015.
[I-D.draft-smith-vxlan-group-policy]
Guichard, J., Smith, M., Kumar, S., Majee, S., Agarwal,
P., Glavin, K., and Y. Laribi, "Network Service Header
(NSH) Context Header Allocation (Data Center)", December
2014.
Appendix A. SGT as MetaData in Data Plane
The Scalable Group Tag can be carried in the control plane (using SXP
described in the main body of this I-D), or in the data plane. SGT
can be carried inline as metadata in Cisco MetaData (CMD) or Network
Service Header (NSH). CMD can be carried in L2 or as a GRE payload.
The following sections describe format of SGT metadata in CMD and
NSH.
This section describes Cisco Metadata (CMD) Version 1, the format for
carrying SGT in the data plane at L2. Appendix B describes SGT in
NSH, while C and D describes format of SGT CMD and SGT NSH in GRE.
A.1. CMD Format
The CMD format is comprised of a header and payload. The fields are
transmitted in network byte order from left to right.
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A.1.1. Metadata Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| Metadata Ethertype | Version | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| Metadata Payload (4-12 bytes) |
+ +
| ... |
+ ... +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
Metadata Ethertype:
The Metadata field is 2 bytes and contains the ethertype assigned by
IEEE for Cisco Metadata (0x8909).
Version
The Version field is 1 byte, and is set to 1 for CMD Header version 1
described in this document.
Length
The Length field is 1 byte, and specifies the length of the CMD in
4-byte units, not including the first 4 bytes. Valid values are in
the range of 1-3.
A.1.2. Metadata Payload
Metadata payload is composed of 1 or more options. Only one option
is defined in this document.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| | | | | | | | | | |1|1|1|1|1|1|1|1|1|1|2|2|2|2|2|2|2|2|2|2|3|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
| Len | Option Type | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| Value (2-6 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+-+-+
Len
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The most significant three bits of the Option are the Option Length,
expressed in a multiple of 4 bytes not including the first 4 bytes.
Option Type
After Len, the next 13 bits are the Option Type. For SGT Option, the
value is 1.
Value
The Value field is 2-6 bytes of data. For SGT Option, the value is 2
bytes, and contains a 16-bit Scalable Group Tag (SGT). If an Option
of Type 1 (SGT Option) is present in the Metadata Payload, it must be
included as the first Option in the Payload.
A.1.3. Header Protection
The CMD header does not have a checksum or CRC, and relies on the
underlying ethernet CRC for integrity protection.
A.1.4. Header Insertion, Removal, and Relocation
The useful lifespan of a metadata header is expected to be a single
zone of authority, such as an enterprise or service provider, where
all routers and switches within that zone are under the control of
that authority. CMD headers should be inserted upon entrance to a
zone of authority or while traversing the zone, and removed just
prior to exit from the zone.
A.1.4.1. Insertion
A CMD header can be inserted in a packet at any point during network
traversal. Any device wishing to add metadata to a packet should
check for a pre-existing header, and add a new header if one is not
present.
When used at layer 2, in order to simplify parsing and allow bridging
of frames through CMD-unaware bridges, the CMD header shall be
inserted after the .1Q tag, if present. If the .1Q tag is not
present the CMD header will immediately follow the MAC Source
Address. Below is a non-exhaustive list of L2 frames with CMD.
CMD Insertion only:
DA,SA,L3pld -> DA,SA,CMD,L3pld
DA,SA,1Q,L3pld -> DA,SA,1Q,CMD,L3pld
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DA,SA,1Q,1Q,L3pld -> DA,SA,1Q,1Q,CMD,L3pld
DA,SA,1Q,MPLS,L3pld -> DA,SA,1Q,CMD,MPLS,L3pld
CMD and MACsec Insertion:
DA,SA,L3pld -> DA,SA,MACsec,CMD,L3pld
DA,SA,1Q,L3pld -> DA,SA,MACsec,1Q,CMD,L3pld
DA,SA,1Q,1Q,L3pld -> DA,SA,MACsec,1Q,1Q,CMD,L3pld
A.1.4.2. Removal
A CMD header should be removed prior to exit from the zone of
authority, regardless of contents.
A.2. Assigned Ethernet Type
IEEE has assigned the Ethernet Type Field Number 0x8909 to the CMD
protocol.
Appendix B. SGT in Network Services Header (NSH)
NSH Is defined in [I-D.draft-quinn-sfc-nsh].
[I-D.draft-guichard-sfc-nsh-dc-allocation] provides a recommended
default allocation for the fixed context headers within NSH. Using
the recommended default, SGT is carried as follows in the NSH:
Source Class: Set to SGT associated with source IP address in packet
Destination Class: Set to SGT associated with destination IP address
in packet (when known)
Appendix C. SGT CMD in GRE
The format of SGT CMD in GRE (IPv4 Packet) is as shown below:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+
| L2 Header | L3 Header, proto=47| GRE Header, PT=0x8909 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------------------+
| CMD |
+---------------+-----------------+
| PT=0x800 | Original Packet |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---+
The format of CMD is as per Appendix A.
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Appendix D. SGT NSH in GRE
The format of SGT NSH in GRE (IPv4 Packet) is as shown below:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-++-+-+-+-+-+-+-+
| L2 Header | L3 Header, proto=47| GRE Header, PT=0x8909 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------------------+
| NSH |
+---------------+-----------------+
| PT=0x800 | Original Packet |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---+
Appendix E. SGT in VXLAN
The VXLAN Group Based Policy (VXLAN-GBP) Extension is defined in
[I-D.draft-smith-vxlan-group-policy]. SGT can be carried in VXLAN-
GBP Extension header in the Group Policy ID field with the G-bit set
as shown below:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+
|G|R|R|R|I|R|R|R|R|D|R|R|A|R|R|R| Group Policy ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-----------+----------------+
| VXLAN Network Identifier (VNI) | Reserved |
+---------------+-----------------+---------+----------------+
Appendix F. SGT tagging exemption for L2 control traffic
There are many Ethernet L2 control protocols (L2CP) that govern
various operational and link states on a device. This includes
protocols such as Spanning Tree BPDUs, EPoL, LACP, VTP, PVST, UDLD,
LLDP, PAUSE Frames and so on. Typically these protocols have
predesignated destination MAC address or ranges. In order to
facilitate seamless flow and native processing of these control
protocols, insertion of CMD to these protocols SHOULD be exempted.
Authors' Addresses
Michael Smith
Cisco Systems
210 West Tasman Drive
San Jose, California 95134
United States
Email: michsmit@cisco.com
Smith, et al. Expires November 25, 2020 [Page 55]
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Rakesh Reddy Kandula
Cisco Systems
Cessna Business Park, Kadubeesanahalli Village
Sarjapur/Marathahalli Outer Ring Road
Bangalore, Karnataka 560103
India
Email: krreddy@cisco.com
Syam Appala
Cisco Systems
510 McCarthy Blvd.
Milpitas, California 95035
United States
Email: syam1@cisco.com
Smith, et al. Expires November 25, 2020 [Page 56]
