draft-ietf-idr-rfc2858bis-08.txt   draft-ietf-idr-rfc2858bis-09.txt 
Network Working Group Tony Bates (Cisco Systems) Network Working Group Tony Bates (Cisco Systems)
Internet Draft Ravi Chandra (Sonoa Systems) Internet Draft Ravi Chandra (Sonoa Systems)
Expiration Date: July 2006 Dave Katz (Juniper Networks) Expiration Date: September 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-08.txt draft-ietf-idr-rfc2858bis-09.txt
Status of this Memo Status of this Memo
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
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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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.
(c) to allow a given router to report some or all of the
Subnetwork Points of Attachment (SNPAs) that exist within the
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) |
+---------------------------------------------------------+ +---------------------------------------------------------+
| Network Address of Next Hop (variable) | | Network Address of Next Hop (variable) |
+---------------------------------------------------------+ +---------------------------------------------------------+
| Number of SNPAs (1 octet) | | Reserved (1 octet) |
+---------------------------------------------------------+
| Length of first SNPA(1 octet) |
+---------------------------------------------------------+
| First SNPA (variable) |
+---------------------------------------------------------+
| Length of second SNPA (1 octet) |
+---------------------------------------------------------+
| Second SNPA (variable) |
+---------------------------------------------------------+
| ... |
+---------------------------------------------------------+
| Length of Last SNPA (1 octet) |
+---------------------------------------------------------+
| Last SNPA (variable) |
+---------------------------------------------------------+ +---------------------------------------------------------+
| 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 (AFI): Address Family Identifier (AFI):
This field in combination with the Subsequent Address Family This field in combination with the Subsequent Address Family
Identifier field identifies the Network Layer protocol Identifier field identifies the Network Layer protocol
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"Network Address of Next Hop" field as measured in octets. "Network Address of Next Hop" field as measured in octets.
Network Address of Next Hop: Network Address of Next Hop:
A variable length field that contains the Network Address of A variable length field that contains the Network Address of
the next router on the path to the destination system. The the next router on the path to the destination system. The
Network Layer protocol associated with the Network Address of Network Layer protocol associated with the Network Address of
the Next Hop is identified by a combination of <AFI, SAFI> the Next Hop is identified by a combination of <AFI, SAFI>
carried in the attribute. carried in the attribute.
Number of SNPAs: Reserved:
A 1 octet field which contains the number of distinct SNPAs to
be listed in the following fields. The value 0 SHALL be used
to indicate that no SNPAs are listed in this attribute.
Length of Nth SNPA:
A 1 octet field whose value expresses the length of the "Nth
SNPA of Next Hop" field as measured in semi-octets
Nth SNPA of Next Hop:
A variable length field that contains an SNPA of the router A 1 octet field that SHOULD be set to 0.
whose Network Address is contained in the "Network Address of
Next Hop" field. The field length is an integral number of
octets in length, namely the rounded-up integer value of one
half the SNPA length expressed in semi-octets; if the SNPA
contains an odd number of semi-octets, a value in this field
MUST be padded with a trailing all-zero semi-octet.
Network Layer Reachability Information (NLRI): Network Layer Reachability Information (NLRI):
A variable length field that lists NLRI for the feasible routes A variable length field that lists NLRI for the feasible routes
that are being advertised in this attribute. The semantics of that are being advertised in this attribute. The semantics of
NLRI is identified by a combination of <AFI, SAFI> carried in NLRI is identified by a combination of <AFI, SAFI> carried in
the attribute. the 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
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This document removes the definition of SAFI 3, and deprecates SAFI This document removes the definition of SAFI 3, and deprecates SAFI
3. 3.
This document changes partitioning of the SAFI space. Specifically, This document changes partitioning of the SAFI space. Specifically,
in RFC2858 SAFI values 128 through 240 were part of the "private use" in RFC2858 SAFI values 128 through 240 were part of the "private use"
range. This document specifies that of this range, allocations which range. This document specifies that of this range, allocations which
are currently in use are to be recognized by IANA, and that unused 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 values, namely 130, 131, 135 through 139, and 141 through 240 should
be considered reserved. be considered reserved.
This document renames the Number of SNPAs field to Reserved, and
removes the rest of the SNPA-related information from the
MP_REACH_NLRI attribute.
11. Comparison with RFC2283 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.
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