draft-ietf-idr-rfc2858bis-06.txt   draft-ietf-idr-rfc2858bis-07.txt 
Network Working Group Tony Bates (Cisco Systems) Network Working Group Tony Bates (Cisco Systems)
Internet Draft Ravi Chandra (Redback Networks) Internet Draft Ravi Chandra (Redback Networks)
Expiration Date: November 2004 Dave Katz (Juniper Networks) Expiration Date: February 2006 Dave Katz (Juniper Networks)
Obsoles RFC2858 Yakov Rekhter (Juniper Networks) Obsoles RFC2858 Yakov Rekhter (Juniper Networks)
Multiprotocol Extensions for BGP-4 Multiprotocol Extensions for BGP-4
draft-ietf-idr-rfc2858bis-06.txt draft-ietf-idr-rfc2858bis-07.txt
1. Status of this Memo
This document is an Internet-Draft and is in full conformance with Status of this Memo
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
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The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
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The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
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2. Abstract IPR Disclosure Acknowledgement
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.
Abstract
Currently BGP-4 is capable of carrying routing information only for Currently BGP-4 is capable of carrying routing information only for
IPv4. This document defines extensions to BGP-4 to enable it to carry IPv4. This document defines extensions to BGP-4 to enable it to carry
routing information for multiple Network Layer protocols (e.g., IPv6, routing information for multiple Network Layer protocols (e.g., IPv6,
IPX, etc...). The extensions are backward compatible - a router that IPX, etc...). The extensions are backward compatible - a router that
supports the extensions can interoperate with a router that doesn't supports the extensions can interoperate with a router that doesn't
support the extensions. support the extensions.
3. Specification of Requirements 1. Specification of Requirements
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].
4. Overview 2. Overview
The only three pieces of information carried by BGP-4 [BGP-4] that The only three pieces of information carried by BGP-4 [BGP-4] that
are IPv4 specific are (a) the NEXT_HOP attribute (expressed as an are IPv4 specific are (a) the NEXT_HOP attribute (expressed as an
IPv4 address), (b) AGGREGATOR (contains an IPv4 address), and (c) IPv4 address), (b) AGGREGATOR (contains an IPv4 address), and (c)
NLRI (expressed as IPv4 address prefixes). This document assumes that NLRI (expressed as IPv4 address prefixes). This document assumes that
any BGP speaker (including the one that supports multiprotocol any 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.
5. Multiprotocol Reachable NLRI - MP_REACH_NLRI (Type Code 14): 3. 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 destinations
listed in the Network Layer Reachability Information field of the listed in the Network Layer Reachability Information field of the
MP_NLRI attribute. MP_NLRI attribute.
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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.
An UPDATE message SHOULD NOT include the same address prefix (of the An UPDATE message SHOULD NOT include the same address prefix (of the
same <AFI, SAFI>) in more than one of the following fields: WITHDRAWN same <AFI, SAFI>) in more than one of the following fields: WITHDRAWN
ROUTES field, Network Reachability Information fields, MP_REACH_NLRI ROUTES field, Network Reachability Information fields, MP_REACH_NLRI
field, and MP_UNREACH_NLRI field. The processing of an UPDATE message field, and MP_UNREACH_NLRI field. The processing of an UPDATE message
in this form is un-defined. in this form is un-defined.
6. Multiprotocol Unreachable NLRI - MP_UNREACH_NLRI (Type Code 15): 4. 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) |
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attribute. attribute.
When the Subsequent Address Family Identifier field is set to When the Subsequent Address Family Identifier field is set to
one of the values defined in this document, each NLRI is one of the values defined in this document, each NLRI is
encoded as specified in the "NLRI encoding" section of this encoded as specified in the "NLRI encoding" section of this
document. 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.
7. NLRI encoding 5. 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.
8. Subsequent Address Family Identifier 6. 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
An implementation MAY support all, some, or none of the Subsequent An implementation MAY support all, some, or none of the Subsequent
Address Family Identifier values defined in this document. Address Family Identifier values defined in this document.
9. Error Handling 7. 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".
10. Use of BGP Capability Advertisement 8. 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 Advertisment procedures [BGP-CAP] to determine whether the Capability Advertisment procedures [BGP-CAP] to determine whether the
speaker could use Multiprotocol Extensions with a particular peer. 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:
0 7 15 23 31 0 7 15 23 31
+-------+-------+-------+-------+ +-------+-------+-------+-------+
| AFI | Res. | SAFI | | AFI | Res. | SAFI |
+-------+-------+-------+-------+ +-------+-------+-------+-------+
The use and meaning of this field is as follow:
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 Advertisement 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.
11. IANA Considerations 9. IANA Considerations
As specified in this document, the MP_REACH_NLRI and MP_UNREACH_NLRI As specified in this document, the MP_REACH_NLRI and MP_UNREACH_NLRI
attributes contain the Subsequence Address Family Identifier (SAFI) attributes contain the Subsequence Address Family Identifier (SAFI)
field. The SAFI name space is defined in this document. The IANA will field. The SAFI name space is defined in this document. The IANA will
maintain and register values for the SAFI namespace as follows. SAFI maintain and register values for the SAFI namespace as follows:
value 0 is reserved. SAFI values 1 and 2 are assigned in this
document. SAFI values 4 through 63 are to be assigned by IANA using
the "IETF Consensus" policy defined in RFC2434. SAFI values 64
through 127 are to be assigned by IANA, using the "First Come First
Served" policy defined in RFC2434. SAFI values 128 through 255 are
for "private use", and values in this range are not to be assigned by
IANA.
12. Comparison with RFC2858 - SAFI values 1 and 2 are assigned in this document.
- SAFI value 3 is reserved. It was assigned by RFC 2858 for a use
that was never fully implemented, so is deprecated by this
document.
- SAFI values 5 through 63 are to be assigned by IANA using either
the Standards Action process defined in [RFC2434], or the Early
IANA Allocation process defined in [RFC4020].
- SAFI values 67 through 127 are to be assigned by IANA, using the
"First Come First Served" policy defined in RFC2434.
- SAFI values 0 and 255 are reserved.
- SAFI values 128 through 240 are part of the previous "private
use" range. Of this space, allocations which are currently in use
are to be recognized by IANA. Unused values, namely 130, 131, 135
through 139, and 141 through 240 should be considered reserved, in
order to avoid conflicts.
- SAFI values 241 through 254 are for "private use", and values in
this range are not to be assigned by IANA.
10. Comparison with RFC2858
This document makes the use of the next hop information consistent This document makes the use of the next hop information consistent
with the information carried in the NEXT_HOP BGP path attribute. with the information carried in the NEXT_HOP BGP path attribute.
This document removes the definition of SAFI = 3. This document removes the definition of SAFI 3, and deprecates SAFI
3.
13. Comparison with RFC2283 This document changes partitioning of the SAFI space. Specifically,
in RFC2858 SAFI values 128 through 240 were part of the "private use"
range. This document specifies that of this range, allocations which
are currently in use are to be recognized by IANA, and that unused
values, namely 130, 131, 135 through 139, and 141 through 240 should
be considered reserved.
11. Comparison with RFC2283
This document restricts the MP_REACH_NLRI attribute to carry only a This document restricts the MP_REACH_NLRI attribute to carry only a
single instance of <AFI, SAFI, Next Hop Information, ...>. single instance of <AFI, SAFI, Next Hop Information, ...>.
This document restricts the MP_UNREACH_NLRI attribute to carry only a This document restricts the MP_UNREACH_NLRI attribute to carry only a
single instance of <AFI, SAFI, ...>. single instance of <AFI, SAFI, ...>.
This document clarifies handling of an UPDATE message that carries no This document clarifies handling of an UPDATE message that carries no
NLRI, other than the one encoded in the MP_REACH_NLRI attribute. NLRI, other than the one encoded in the MP_REACH_NLRI attribute.
This document clarifies error handling in the presence of This document clarifies error handling in the presence of
MP_REACH_NLRI or MP_UNREACH_NLRI attributes. MP_REACH_NLRI or MP_UNREACH_NLRI attributes.
This document specifies the use of BGP Capabilities Advertisements in This document specifies the use of BGP Capabilities Advertisements in
conjunction with Multi-protocol extensions. conjunction with Multi-protocol extensions.
Finally, this document includes the "IANA Consideration" Section. Finally, this document includes the "IANA Consideration" Section.
14. Security Considerations 12. 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. inherent in the existing BGP.
13. Intellectual Property Considerations
This section is taken from Section 5 of RFC 3668.
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at ietf-
ipr@ietf.org.
14. Copyright Notice
Copyright (C) The Internet Society (2005).
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.
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 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.
15. Acknowledgements 15. 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.
16. Normative References 16. Normative References
[BGP-CAP] "Capabilities Advertisement with BGP-4", R. Chandra, J. [BGP-CAP] "Capabilities Advertisement with BGP-4", R. Chandra, J.
Scudder, RFC2842, May 2000 Scudder, RFC2842, May 2000
[BGP-4] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4 [BGP-4] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4
(BGP-4)", RFC 1771, March 1995. (BGP-4)", RFC 1771, March 1995.
[RFC1700] "Assigned Numbers", J. Reynolds, J. Postel, RFC1700, [RFC1700] "Assigned Numbers", J. Reynolds, J. Postel, RFC1700,
October 1994 (see also http://www.iana.org/iana/assignments.html) October 1994 (see also http://www.iana.org/iana/assignments.html)
[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.
[RFC2434] Narten, T., Alvestrand, H., "Guidelines for Writing an IANA
Considerations Section in RFCs", RFC2434, October 1998
[RFC4020] "Early IANA Allocation of Standards Track Code Points", K.
Kompella, A. Zinin, BCP0100, RFC 4020, February 2005.
17. Author Information 17. Author Information
Tony Bates Tony Bates
Cisco Systems, Inc. Cisco Systems, Inc.
email: tbates@cisco.com email: tbates@cisco.com
Ravi Chandra Ravi Chandra
Redback Networks Redback Networks
e-mail: rchandra@redback.com e-mail: rchandra@redback.com
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