draft-ietf-idr-rfc3392bis-05.txt   rfc5492.txt 
Internet Engineering Task Force J. Scudder Network Working Group J. Scudder
Internet-Draft Juniper Networks Request for Comments: 5492 Juniper Networks
Obsoletes: 3392 (if approved) R. Chandra Obsoletes: 3392 R. Chandra
Intended status: Standards Track Sonoa Systems Category: Standards Track Sonoa Systems
Expires: July 11, 2009 January 7, 2009 February 2009
Capabilities Advertisement with BGP-4 Capabilities Advertisement with BGP-4
draft-ietf-idr-rfc3392bis-05.txt
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Abstract Abstract
This document defines an Optional Parameter, called Capabilities, This document defines an Optional Parameter, called Capabilities,
that is expected to facilitate the introduction of new capabilities that is expected to facilitate the introduction of new capabilities
in the Border Gateway Protocol (BGP) by providing graceful capability in the Border Gateway Protocol (BGP) by providing graceful capability
advertisement without requiring that BGP peering be terminated. This advertisement without requiring that BGP peering be terminated.
document obsoletes RFC 3392.
This document obsoletes RFC 3392.
1. Introduction 1. Introduction
The base BGP-4 specification [RFC4271] requires that when a BGP The base BGP-4 specification [RFC4271] requires that when a BGP
speaker receives an OPEN message with one or more unrecognized speaker receives an OPEN message with one or more unrecognized
Optional Parameters, the speaker must terminate the BGP peering. Optional Parameters, the speaker must terminate the BGP peering.
This complicates the introduction of new capabilities in BGP. This complicates the introduction of new capabilities in BGP.
This specification defines an Optional Parameter and processing rules This specification defines an Optional Parameter and processing rules
that allow BGP speakers to communicate capabilities in an OPEN that allow BGP speakers to communicate capabilities in an OPEN
message. A pair of BGP speakers that support this specification can message. A pair of BGP speakers that supports this specification can
establish the peering even when presented with unrecognized establish the peering even when presented with unrecognized
capabilities, so long as all capabilities required to support the capabilities, so long as all capabilities required to support the
peering are supported. peering are supported.
2. Requirements Language 2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
skipping to change at page 3, line 4 skipping to change at page 2, line 45
receives from the peer. receives from the peer.
A BGP speaker that supports a particular capability may use this A BGP speaker that supports a particular capability may use this
capability with its peer after the speaker determines (as described capability with its peer after the speaker determines (as described
above) that the peer supports this capability. Simply put, a given above) that the peer supports this capability. Simply put, a given
capability can be used on a peering if that capability has been capability can be used on a peering if that capability has been
advertised by both peers. If either peer has not advertised it, the advertised by both peers. If either peer has not advertised it, the
capability cannot be used. capability cannot be used.
A BGP speaker determines that its peer doesn't support capabilities A BGP speaker determines that its peer doesn't support capabilities
advertisement, if in response to an OPEN message that carries the advertisement if, in response to an OPEN message that carries the
Capabilities Optional Parameter, the speaker receives a NOTIFICATION Capabilities Optional Parameter, the speaker receives a NOTIFICATION
message with the Error Subcode set to Unsupported Optional Parameter. message with the Error Subcode set to Unsupported Optional Parameter.
(This is a consequence of the base BGP-4 specification [RFC4271] and (This is a consequence of the base BGP-4 specification [RFC4271] and
not a new requirement.) In this case the speaker SHOULD attempt to not a new requirement.) In this case, the speaker SHOULD attempt to
re-establish a BGP connection with the peer without sending to the re-establish a BGP connection with the peer without sending to the
peer the Capabilities Optional Parameter. peer the Capabilities Optional Parameter.
If a BGP speaker that supports a certain capability determines that If a BGP speaker that supports a certain capability determines that
its peer doesn't support this capability, the speaker MAY send a its peer doesn't support this capability, the speaker MAY send a
NOTIFICATION message to the peer and terminate peering (see Section NOTIFICATION message to the peer and terminate peering (see Section
"Extensions to Error Handling" for more details). An example of when "Extensions to Error Handling" for more details). For example, a BGP
this would be done is if the BGP speaker requires that the capability speaker may need to terminate peering if it established peering to
in question be used on a peering, for instance if a BGP speaker is exchange IPv6 routes and determines that its peer does not support
attempting to establish a peering to exchange IPv6 routes but Multiprotocol Extensions for BGP-4 [RFC4760]. The Error Subcode in
determines that its peer does not support Multiprotocol Extensions the NOTIFICATION message is then set to Unsupported Capability. The
for BGP-4 [RFC4760]. The Error Subcode in the NOTIFICATION message message MUST contain the capability or capabilities that cause the
is set to Unsupported Capability. The message MUST contain the speaker to send the message. The decision to send the message and
capability (capabilities) that causes the speaker to send the terminate the peering is local to the speaker. If terminated, such
message. The decision to send the message and terminate the peering peering SHOULD NOT be re-established automatically.
is local to the speaker. If terminated, such peering SHOULD NOT be
re-established automatically.
If a BGP speaker receives from its peer a capability which it does If a BGP speaker receives from its peer a capability that it does not
not itself support or recognize, it MUST ignore that capability. In itself support or recognize, it MUST ignore that capability. In
particular, the Unsupported Capability NOTIFICATION message MUST NOT particular, the Unsupported Capability NOTIFICATION message MUST NOT
be generated in response to reception of a capability which is not be generated and the BGP session MUST NOT be terminated in response
supported by the local speaker. to reception of a capability that is not supported by the local
speaker.
4. Capabilities Optional Parameter (Parameter Type 2): 4. Capabilities Optional Parameter (Parameter Type 2):
This is an Optional Parameter that is used by a BGP speaker to convey This is an Optional Parameter that is used by a BGP speaker to convey
to its BGP peer the list of capabilities supported by the speaker. to its BGP peer the list of capabilities supported by the speaker.
The encoding of BGP Optional Parameters is specified in Section 4.2 The encoding of BGP Optional Parameters is specified in Section 4.2
of [RFC4271]. The parameter type of the Capabilities Optional of [RFC4271]. The parameter type of the Capabilities Optional
Parameter is 2. Parameter is 2.
The parameter contains one or more triples <Capability Code, The parameter contains one or more triples <Capability Code,
skipping to change at page 4, line 18 skipping to change at page 3, line 50
| Capability Length (1 octet) | | Capability Length (1 octet) |
+------------------------------+ +------------------------------+
| Capability Value (variable) | | Capability Value (variable) |
~ ~ ~ ~
+------------------------------+ +------------------------------+
The use and meaning of these fields are as follows: The use and meaning of these fields are as follows:
Capability Code: Capability Code:
Capability Code is a one octet unsigned binary integer that Capability Code is a one-octet unsigned binary integer that
unambiguously identifies individual capabilities. unambiguously identifies individual capabilities.
Capability Length: Capability Length:
Capability Length is a one octet unsigned binary integer that Capability Length is a one-octet unsigned binary integer that
contains the length of the Capability Value field in octets. contains the length of the Capability Value field in octets.
Capability Value: Capability Value:
Capability Value is a variable length field that is interpreted Capability Value is a variable-length field that is interpreted
according to the value of the Capability Code field. according to the value of the Capability Code field.
BGP speakers SHOULD NOT include more than one instance of a BGP speakers SHOULD NOT include more than one instance of a
capability with the same Capability Code, Capability Length, and capability with the same Capability Code, Capability Length, and
Capability Value. Note however, that processing of multiple Capability Value. Note, however, that processing of multiple
instances of such capability does not require special handling, as instances of such capability does not require special handling, as
additional instances do not change the meaning of the announced additional instances do not change the meaning of the announced
capability, thus a BGP speaker MUST be prepared to accept such capability; thus, a BGP speaker MUST be prepared to accept such
multiple instances. multiple instances.
BGP speakers MAY include more than one instance of a capability (as BGP speakers MAY include more than one instance of a capability (as
identified by the Capability Code) with non-zero Capability Length identified by the Capability Code) with non-zero Capability Length
field, but with different Capability Value, and either the same or field, but with different Capability Value and either the same or
different Capability Length. Processing of these capability different Capability Length. Processing of these capability
instances is specific to the Capability Code and MUST be described in instances is specific to the Capability Code and MUST be described in
the document introducing the new capability. the document introducing the new capability.
The Capabilities Optional Parameter (OPEN Optional Parameter Type 2) The Capabilities Optional Parameter (OPEN Optional Parameter Type 2)
SHOULD only be included in the OPEN message once. If the BGP speaker SHOULD only be included in the OPEN message once. If the BGP speaker
wishes to include multiple capabilities in the OPEN message, it wishes to include multiple capabilities in the OPEN message, it
SHOULD do so as discussed above, by listing all those capabilities as SHOULD do so as discussed above -- by listing all those capabilities
TLVs within a single Capabilities Optional Parameter. However, for as TLVs within a single Capabilities Optional Parameter. However,
backward compatibility a BGP speaker MUST be prepared to receive an for backward compatibility, a BGP speaker MUST be prepared to receive
OPEN message which contains multiple Capabilities Optional an OPEN message that contains multiple Capabilities Optional
Parameters, each of which contains one or more capabilities TLVs. Parameters, each of which contains one or more capabilities TLVs.
The set of capabilities should be processed in the same way in either The set of capabilities should be processed in the same way in either
case, whether it is enumerated within a single Capabilities Optional case, whether it is enumerated within a single Capabilities Optional
Parameter of the OPEN message, or split across multiple. Parameter of the OPEN message or split across multiple Capabilities
Optional Parameters.
5. Extensions to Error Handling 5. Extensions to Error Handling
This document defines a new Error Subcode, Unsupported Capability. This document defines a new Error Subcode, Unsupported Capability.
The value of this Subcode is 7. The Data field in the NOTIFICATION The value of this Subcode is 7. The Data field in the NOTIFICATION
message MUST list the set of capabilities that cause the speaker to message MUST list the set of capabilities that causes the speaker to
send the message. Each such capability is encoded in the same way as send the message. Each such capability is encoded in the same way as
it would be encoded in the OPEN message. it would be encoded in the OPEN message.
As explained in the Overview of Operations section, the Unsupported As explained in the "Overview of Operations" section, the Unsupported
Capability NOTIFICATION is a way for a BGP speaker to complain that Capability NOTIFICATION is a way for a BGP speaker to complain that
its peer does not support a required capability, without which the its peer does not support a required capability without which the
peering cannot proceed. It MUST NOT be used when a BGP speaker peering cannot proceed. It MUST NOT be used when a BGP speaker
receives a capability which it does not understand; such capabilities receives a capability that it does not understand; such capabilities
MUST be ignored. MUST be ignored.
6. IANA Considerations 6. IANA Considerations
This document defines a Capability Optional Parameter along with a This document defines a Capability Optional Parameter along with a
Capability Code field. IANA maintains the registry for Capability Capability Code field. IANA maintains the registry for Capability
Code values. Capability Code value 0 is reserved. Capability Code Code values. Capability Code value 0 is reserved. Capability Code
values 1 through 63 are to be assigned by IANA using the "IETF values 1 through 63 are to be assigned by IANA using the "IETF
Consensus" policy defined in [RFC5226]. Capability Code values 64 Review" policy defined in [RFC5226]. Capability Code values 64
through 127 are to be assigned by IANA, using the "First Come First through 127 are to be assigned by IANA using the "First Come First
Served" policy defined in [RFC5226]. Capability Code values 128 Served" policy defined in [RFC5226]. Capability Code values 128
through 255 are for "Private Use" as defined in [RFC5226]. through 255 are for "Private Use" as defined in [RFC5226].
IANA created and maintains a registry for OPEN message Optional
Parameters called "BGP OPEN Optional Parameter Types". Optional
Parameters are identified by the Parameter Type, which is a one-octet
unsigned integer. Values (0 reserved, 1-255) are to be allocated
according to the "IETF Review" policy as defined in [RFC5226].
The registry has been populated with the two Parameter Type codes
that are currently defined:
o Parameter Type 1: Authentication (deprecated) [RFC4271] [RFC5492]
o Parameter Type 2: Capabilities [RFC5492]
7. Security Considerations 7. Security Considerations
This extension to BGP does not change the underlying security issues This extension to BGP does not change the underlying security issues
inherent in the existing BGP [RFC4272]. inherent in the existing BGP [RFC4272].
8. Acknowledgements 8. Acknowledgments
The authors would like to thank members of the IDR Working Group and The authors would like to thank members of the IDR Working Group and
the IESG and its Directorates for their review and comments. the IESG and its Directorates for their review and comments.
9. References 9. References
9.1. Normative References 9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
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9.2. Informative References 9.2. Informative References
[RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis", [RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis",
RFC 4272, January 2006. RFC 4272, January 2006.
[RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 4760, "Multiprotocol Extensions for BGP-4", RFC 4760,
January 2007. January 2007.
Appendix A. Comparison with RFC 2842 Appendix A. Comparison between RFC 2842 and RFC 3392
In addition to several minor editorial changes, RFC 3392 also In addition to several minor editorial changes, RFC 3392 also
clarified how to handle multiple instances of the same capability. clarified how to handle multiple instances of the same capability.
Appendix B. Comparison with RFC 3392 Appendix B. Comparison between RFC 3392 and This Document
This document makes minor editorial changes and updated references, This document makes minor editorial changes and updated references,
clarifies the use of the Unsupported Optional Parameter NOTIFICATION clarifies the use of the Unsupported Optional Parameter NOTIFICATION
message, clarifies behavior when the Capabilities parameter is message, clarifies behavior when the Capabilities Parameter is
included in the OPEN message multiple times, and clarifies included in the OPEN message multiple times, and clarifies
requirements by changing a number of SHOULDs to MUSTs. requirements by changing a number of SHOULDs to MUSTs.
Authors' Addresses Authors' Addresses
John G. Scudder John G. Scudder
Juniper Networks Juniper Networks
Email: jgs@juniper.net EMail: jgs@juniper.net
Ravi Chandra Ravi Chandra
Sonoa Systems Sonoa Systems
Email: rchandra@sonoasystems.com EMail: rchandra@sonoasystems.com
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