draft-ietf-idr-bgp4-multiprotocol-v2-04.txt   rfc2858.txt 
Network Working Group Tony Bates
Internet Draft Cisco Systems
Expiration Date: August 2000 Ravi Chandra
Siara Systems
Dave Katz
Juniper Networks
Yakov Rekhter
Cisco Systems
Multiprotocol Extensions for BGP-4
draft-ietf-idr-bgp4-multiprotocol-v2-04.txt Network Working Group T. Bates
Request for Comments: 2858 Y. Rekhter
1. Status of this Memo Obsoletes: 2283 Cisco Systems
Category: Standards Track R. Chandra
Redback Networks Inc
D. Katz
Juniper Networks
June 2000
This document is an Internet-Draft and is in full conformance with Multiprotocol Extensions for BGP-4
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Status of this Memo
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months This document specifies an Internet standards track protocol for the
and may be updated, replaced, or obsoleted by other documents at any Internet community, and requests discussion and suggestions for
time. It is inappropriate to use Internet-Drafts as reference improvements. Please refer to the current edition of the "Internet
material or to cite them other than as ``work in progress.'' Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
The list of current Internet-Drafts can be accessed at Copyright Notice
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at Copyright (C) The Internet Society (2000). All Rights Reserved.
http://www.ietf.org/shadow.html.
2. Abstract Abstract
Currently BGP-4 [BGP-4] is capable of carrying routing information Currently BGP-4 [BGP-4] is capable of carrying routing information
only for IPv4 [IPv4]. This document defines extensions to BGP-4 to only for IPv4 [IPv4]. This document defines extensions to BGP-4 to
enable it to carry routing information for multiple Network Layer enable it to carry routing information for multiple Network Layer
protocols (e.g., IPv6, IPX, etc...). The extensions are backward protocols (e.g., IPv6, IPX, etc...). The extensions are backward
compatible - a router that supports the extensions can interoperate compatible - a router that supports the extensions can interoperate
with a router that doesn't support the extensions. with a router that doesn't support the extensions.
3. Overview This document obsoletes RFC 2283.
1. Overview
The only three pieces of information carried by BGP-4 that are IPv4 The only three pieces of information carried by BGP-4 that are IPv4
specific are (a) the NEXT_HOP attribute (expressed as an IPv4 specific are (a) the NEXT_HOP attribute (expressed as an IPv4
address), (b) AGGREGATOR (contains an IPv4 address), and (c) NLRI address), (b) AGGREGATOR (contains an IPv4 address), and (c) NLRI
(expressed as IPv4 address prefixes). This document assumes that any (expressed as IPv4 address prefixes). This document assumes that any
BGP speaker (including the one that supports multiprotocol BGP speaker (including the one that supports multiprotocol
capabilities defined in this document) has to have an IPv4 address capabilities defined in this document) has to have an IPv4 address
(which will be used, among other things, in the AGGREGATOR (which will be used, among other things, in the AGGREGATOR
attribute). Therefore, to enable BGP-4 to support routing for attribute). Therefore, to enable BGP-4 to support routing for
multiple Network Layer protocols the only two things that have to be multiple Network Layer protocols the only two things that have to be
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(MP_REACH_NLRI), and Multiprotocol Unreachable NLRI (MP_REACH_NLRI), and Multiprotocol Unreachable NLRI
(MP_UNREACH_NLRI). The first one (MP_REACH_NLRI) is used to carry the (MP_UNREACH_NLRI). The first one (MP_REACH_NLRI) is used to carry the
set of reachable destinations together with the next hop information set of reachable destinations together with the next hop information
to be used for forwarding to these destinations. The second one to be used for forwarding to these destinations. The second one
(MP_UNREACH_NLRI) is used to carry the set of unreachable (MP_UNREACH_NLRI) is used to carry the set of unreachable
destinations. Both of these attributes are optional and non- destinations. Both of these attributes are optional and non-
transitive. This way a BGP speaker that doesn't support the transitive. This way a BGP speaker that doesn't support the
multiprotocol capabilities will just ignore the information carried multiprotocol capabilities will just ignore the information carried
in these attributes, and will not pass it to other BGP speakers. in these attributes, and will not pass it to other BGP speakers.
4. Multiprotocol Reachable NLRI - MP_REACH_NLRI (Type Code 14): 2. Multiprotocol Reachable NLRI - MP_REACH_NLRI (Type Code 14):
This is an optional non-transitive attribute that can be used for the This is an optional non-transitive attribute that can be used for the
following purposes: following purposes:
(a) to advertise a feasible route to a peer (a) to advertise a feasible route to a peer
(b) to permit a router to advertise the Network Layer address of (b) to permit a router to advertise the Network Layer address of
the router that should be used as the next hop to the destinations the router that should be used as the next hop to the
listed in the Network Layer Reachability Information field of the destinations listed in the Network Layer Reachability
MP_NLRI attribute. Information field of the MP_NLRI attribute.
(c) to allow a given router to report some or all of the (c) to allow a given router to report some or all of the
Subnetwork Points of Attachment (SNPAs) that exist within the Subnetwork Points of Attachment (SNPAs) that exist within the
local system local system
The attribute is encoded as shown below: The attribute is encoded as shown below:
+---------------------------------------------------------+ +---------------------------------------------------------+
| Address Family Identifier (2 octets) | | Address Family Identifier (2 octets) |
+---------------------------------------------------------+ +---------------------------------------------------------+
| Subsequent Address Family Identifier (1 octet) | | Subsequent Address Family Identifier (1 octet) |
+---------------------------------------------------------+ +---------------------------------------------------------+
| Length of Next Hop Network Address (1 octet) | | Length of Next Hop Network Address (1 octet) |
+---------------------------------------------------------+ +---------------------------------------------------------+
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+---------------------------------------------------------+ +---------------------------------------------------------+
| Network Layer Reachability Information (variable) | | Network Layer Reachability Information (variable) |
+---------------------------------------------------------+ +---------------------------------------------------------+
The use and meaning of these fields are as follows: The use and meaning of these fields are as follows:
Address Family Identifier: Address Family Identifier:
This field carries the identity of the Network Layer protocol This field carries the identity of the Network Layer protocol
associated with the Network Address that follows. Presently associated with the Network Address that follows. Presently
defined values for this field are specified in RFC1700 (see the defined values for this field are specified in RFC 1700 (see
Address Family Numbers section). the Address Family Numbers section).
Subsequent Address Family Identifier: Subsequent Address Family Identifier:
This field provides additional information about the type of This field provides additional information about the type of
the Network Layer Reachability Information carried in the the Network Layer Reachability Information carried in the
attribute. attribute.
Length of Next Hop Network Address: Length of Next Hop Network Address:
A 1 octet field whose value expresses the length of the A 1 octet field whose value expresses the length of the
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in the AS_PATH attribute is equal to the autonomous system number of in the AS_PATH attribute is equal to the autonomous system number of
the peer than sent the message. If that is not the case, the local the peer than sent the message. If that is not the case, the local
system shall send the NOTIFICATION message with Error Code UPDATE system shall send the NOTIFICATION message with Error Code UPDATE
Message Error, and the Error Subcode set to Malformed AS_PATH. Message Error, and the Error Subcode set to Malformed AS_PATH.
An UPDATE message that carries no NLRI, other than the one encoded in An UPDATE message that carries no NLRI, other than the one encoded in
the MP_REACH_NLRI attribute, should not carry the NEXT_HOP attribute. the MP_REACH_NLRI attribute, should not carry the NEXT_HOP attribute.
If such a message contains the NEXT_HOP attribute, the BGP speaker If such a message contains the NEXT_HOP attribute, the BGP speaker
that receives the message should ignore this attribute. that receives the message should ignore this attribute.
5. Multiprotocol Unreachable NLRI - MP_UNREACH_NLRI (Type Code 15): 3. Multiprotocol Unreachable NLRI - MP_UNREACH_NLRI (Type Code 15):
This is an optional non-transitive attribute that can be used for the This is an optional non-transitive attribute that can be used for the
purpose of withdrawing multiple unfeasible routes from service. purpose of withdrawing multiple unfeasible routes from service.
The attribute is encoded as shown below: The attribute is encoded as shown below:
+---------------------------------------------------------+ +---------------------------------------------------------+
| Address Family Identifier (2 octets) | | Address Family Identifier (2 octets) |
+---------------------------------------------------------+ +---------------------------------------------------------+
| Subsequent Address Family Identifier (1 octet) | | Subsequent Address Family Identifier (1 octet) |
+---------------------------------------------------------+ +---------------------------------------------------------+
| Withdrawn Routes (variable) | | Withdrawn Routes (variable) |
+---------------------------------------------------------+ +---------------------------------------------------------+
The use and the meaning of these fields are as follows: The use and the meaning of these fields are as follows:
Address Family Identifier: Address Family Identifier:
This field carries the identity of the Network Layer protocol This field carries the identity of the Network Layer protocol
associated with the NLRI that follows. Presently defined values associated with the NLRI that follows. Presently defined values
for this field are specified in RFC1700 (see the Address Family for this field are specified in RFC 1700 (see the Address
Numbers section). Family Numbers section).
Subsequent Address Family Identifier: Subsequent Address Family Identifier:
This field provides additional information about the type of This field provides additional information about the type of
the Network Layer Reachability Information carried in the the Network Layer Reachability Information carried in the
attribute. attribute.
Withdrawn Routes: Withdrawn Routes:
A variable length field that lists NLRI for the routes that are A variable length field that lists NLRI for the routes that are
being withdrawn from service. When the Subsequent Address being withdrawn from service. When the Subsequent Address
Family Identifier field is set to one of the values defined in Family Identifier field is set to one of the values defined in
this document, each NLRI is encoded as specified in the "NLRI this document, each NLRI is encoded as specified in the "NLRI
encoding" section of this document. encoding" section of this document.
An UPDATE message that contains the MP_UNREACH_NLRI is not required An UPDATE message that contains the MP_UNREACH_NLRI is not required
to carry any other path attributes. to carry any other path attributes.
6. NLRI encoding 4. NLRI encoding
The Network Layer Reachability information is encoded as one or more The Network Layer Reachability information is encoded as one or more
2-tuples of the form <length, prefix>, whose fields are described 2-tuples of the form <length, prefix>, whose fields are described
below: below:
+---------------------------+ +---------------------------+
| Length (1 octet) | | Length (1 octet) |
+---------------------------+ +---------------------------+
| Prefix (variable) | | Prefix (variable) |
+---------------------------+ +---------------------------+
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prefix. A length of zero indicates a prefix that matches all prefix. A length of zero indicates a prefix that matches all
(as specified by the address family) addresses (with prefix, (as specified by the address family) addresses (with prefix,
itself, of zero octets). itself, of zero octets).
b) Prefix: b) Prefix:
The Prefix field contains an address prefix followed by enough The Prefix field contains an address prefix followed by enough
trailing bits to make the end of the field fall on an octet trailing bits to make the end of the field fall on an octet
boundary. Note that the value of trailing bits is irrelevant. boundary. Note that the value of trailing bits is irrelevant.
7. Subsequent Address Family Identifier 5. Subsequent Address Family Identifier
This document defines the following values for the Subsequent Address This document defines the following values for the Subsequent Address
Family Identifier field carried in the MP_REACH_NLRI and Family Identifier field carried in the MP_REACH_NLRI and
MP_UNREACH_NLRI attributes: MP_UNREACH_NLRI attributes:
1 - Network Layer Reachability Information used for unicast 1 - Network Layer Reachability Information used for unicast
forwarding forwarding
2 - Network Layer Reachability Information used for multicast 2 - Network Layer Reachability Information used for multicast
forwarding forwarding
3 - Network Layer Reachability Information used for both unicast 3 - Network Layer Reachability Information used for both unicast
and multicast forwarding and multicast forwarding
8. Error Handling 6. Error Handling
If a BGP speaker receives from a neighbor an Update message that If a BGP speaker receives from a neighbor an Update message that
contains the MP_REACH_NLRI or MP_UNREACH_NLRI attribute, and the contains the MP_REACH_NLRI or MP_UNREACH_NLRI attribute, and the
speaker determines that the attribute is incorrect, the speaker must speaker determines that the attribute is incorrect, the speaker must
delete all the BGP routes received from that neighbor whose AFI/SAFI delete all the BGP routes received from that neighbor whose AFI/SAFI
is the same as the one carried in the incorrect MP_REACH_NLRI or is the same as the one carried in the incorrect MP_REACH_NLRI or
MP_UNREACH_NLRI attribute. For the duration of the BGP session over MP_UNREACH_NLRI attribute. For the duration of the BGP session over
which the Update message was received, the speaker then should ignore which the Update message was received, the speaker then should ignore
all the subsequent routes with that AFI/SAFI received over that all the subsequent routes with that AFI/SAFI received over that
session. session.
In addition, the speaker may terminate the BGP session over which the In addition, the speaker may terminate the BGP session over which the
Update message was received. The session should be terminated with Update message was received. The session should be terminated with
the Notification message code/subcode indicating "Update Message the Notification message code/subcode indicating "Update Message
Error"/"Optional Attribute Error". Error"/"Optional Attribute Error".
9. Use of BGP Capability Negotiation 7. Use of BGP Capability Advertisement
A BGP speaker that uses Multiprotocol Extensions should use the A BGP speaker that uses Multiprotocol Extensions should use the
Capability Negotiation procedures [BGP-CAP] to determine whether the Capability Advertisement procedures [BGP-CAP] to determine whether
speaker could use Multiprotocol Extensions with a particular peer. the speaker could use Multiprotocol Extensions with a particular
peer.
The fields in the Capabilities Optional Parameter are set as follows. The fields in the Capabilities Optional Parameter are set as follows.
The Capability Code field is set to 1 (which indicates Multiprotocol The Capability Code field is set to 1 (which indicates Multiprotocol
Extensions capabilities). The Capability Length field is set to 4. Extensions capabilities). The Capability Length field is set to 4.
The Capability Value field is defined as: The Capability Value field is defined as:
The use and meaning of this field is as follow: The use and meaning of this field is as follow:
0 7 15 23 31 0 7 15 23 31
+-------+-------+-------+-------+ +-------+-------+-------+-------+
| AFI | Res. | SAFI | | AFI | Res. | SAFI |
+-------+-------+-------+-------+ +-------+-------+-------+-------+
AFI - Address Family Identifier (16 bit), encoded the same way AFI - Address Family Identifier (16 bit), encoded the same way
as in the Multiprotocol Extensions as in the Multiprotocol Extensions
Res. - Reserved (8 bit) field. Should be set to 0 by the sender Res. - Reserved (8 bit) field. Should be set to 0 by the sender
and ignored by the receiver. and ignored by the receiver.
SAFI - Subsequent Address Family Identifier (8 bit), encoded SAFI - Subsequent Address Family Identifier (8 bit), encoded
the same way as in the Multiprotocol Extensions. the same way as in the Multiprotocol Extensions.
A speaker that supports multiple <AFI, SAFI> tuples includes them as A speaker that supports multiple <AFI, SAFI> tuples includes them as
multiple Capabilities in the Capabilities Optional Parameter. multiple Capabilities in the Capabilities Optional Parameter.
To have a bi-directional exchange of routing information for a To have a bi-directional exchange of routing information for a
particular <AFI, SAFI> between a pair of BGP speakers, each such particular <AFI, SAFI> between a pair of BGP speakers, each such
speaker must advertise to the other (via the Capability Negotiation speaker must advertise to the other (via the Capability Advertisement
mechanism) the capability to support that particular <AFI, SAFI> mechanism) the capability to support that particular <AFI, SAFI>
routes. routes.
10. IANA Considerations 8. IANA Considerations
As specified in this document, the MPL_REACH_NLRI and MP_UNREACH_NLRI As specified in this document, the MPL_REACH_NLRI and MP_UNREACH_NLRI
attributes contain the Subsequence Address Family Identifier (SAFI) attributes contain the Subsequence Address Family Identifier (SAFI)
field. SAFI value 0 is reserved. SAFI values 1, 2, and 3 are field. The SAFI name space is defined in Section 9. The IANA will
assigned in this document. SAFI values 4 through 63 are to be maintain and register values for the SAFI namespace as follows. SAFI
assigned by IANA using the "IETF Consensus" policy defined in value 0 is reserved. SAFI values 1, 2, and 3 are assigned in this
RFC2434. SAFI values 64 through 127 are to be assigned by IANA, using document. SAFI values 4 through 63 are to be assigned by IANA using
the "First Come First Served" policy defined in RFC2434. SAFI values the "IETF Consensus" policy defined in RFC 2434. SAFI values 64
128 through 255 are vendor-specific, and values in this range are not through 127 are to be assigned by IANA, using the "First Come First
to be assigned by IANA. Served" policy defined in RFC 2434. SAFI values 128 through 255 are
for "private use", and values in this range are not to be assigned by
IANA.
11. Security Considerations 9. Comparison with RFC 2283
This document restricts the MP_REACH_NLRI attribute to carry only a
single instance of <AFI, SAFI, Next Hop Information, ...>.
This document restricts the MP_UNREACH_NLRI attribute to carry only a
single instance of <AFI, SAFI, ...>.
This document clarifies handling of an UPDATE message that carries no
NLRI, other than the one encoded in the MP_REACH_NLRI attribute.
This document clarifies error handling in the presence of
MP_REACH_NLRI or MP_UNREACH_NLRI attributes.
This document specifies the use of BGP Capabilities Advertisements in
conjunction with Multi-protocol extensions.
Finally, this document includes the "IANA Consideration" Section.
10. 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 [Heffernan]. inherent in the existing BGP [Heffernan].
12. Acknowledgements 11. Acknowledgements
The authors would like to thank members of the IDR Working Group for The authors would like to thank members of the IDR Working Group for
their review and comments. their review and comments.
13. References 12. References
[BGP-CAP] "Capabilities Negotiation with BGP-4", R. Chandra, J. [BGP-CAP] Chandra, R. and J. Scudder, "Capabilities Advertisement
Scudder, draft-ietf-idr-bgp4-cap-neg-05.txt, February 1999 with BGP-4", RFC 2842, May 2000.
[BGP-4] "A Border Gateway Protocol 4 (BGP-4)", Y. Rekhter & T. Li, [BGP-4] Rekhter, Y. and T. Li, "A Border Gateway Protocol 4
RFC1771, March 1995 (BGP-4)", RFC 1771, March 1995.
[Heffernan] Heffernan, A., "Protection of BGP Sessions via the TCP [Heffernan] Heffernan, A., "Protection of BGP Sessions via the TCP
MD5 Signature Option", RFC2385, August 1998. MD5 Signature Option", RFC 2385, August 1998.
[IPv4] "Internet Protocol", J. Postel, September 1981 [IPv4] Postel, J., "Internet Protocol", STD 5, RFC 791,
September 1981.
[RFC1700] "Assigned Numbers", J. Reynolds, J. Postel, RFC1700, [RFC1700] Postel, J. and J. K. Reynolds, "Assigned Numbers", STD
October 1994 (see also http://www.iana.org/iana/assignments.html) 2, RFC 1700, October 1994. (see also
http://www.iana.org/iana/assignments.html)
14. Author Information 13. Authors' Addresses
Tony Bates Tony Bates
Cisco Systems, Inc. Cisco Systems, Inc.
170 West Tasman Drive 170 West Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
email: tbates@cisco.com
EMail: tbates@cisco.com
Ravi Chandra Ravi Chandra
Siara Systems Incorporated Redback Networks Inc.
1195 Borregas Avenue 350, Holger Way
Sunnyvale, CA 94089 San Jose, CA 95134
e-mail: rchandra@siara.com
EMail: rchandra@redback.com
Dave Katz Dave Katz
Juniper Networks, Inc. Juniper Networks, Inc.
3260 Jay St. 3260 Jay St.
Santa Clara, CA 95054 Santa Clara, CA 95054
email: dkatz@jnx.com
EMail: dkatz@jnx.com
Yakov Rekhter Yakov Rekhter
Cisco Systems, Inc. Cisco Systems, Inc.
170 West Tasman Drive 170 West Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
email: yakov@cisco.com
EMail: yakov@cisco.com
14. Full Copyright Statement
Copyright (C) The Internet Society (2000). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS 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.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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