draft-ietf-idr-bgp4-multiprotocol-00.txt   draft-ietf-idr-bgp4-multiprotocol-01.txt 
Network Working Group Tony Bates Network Working Group Tony Bates
Internet Draft Cisco Systems Internet Draft Cisco Systems
Expiration Date: February 1998 Ravi Chandra Expiration Date: March 1998 Ravi Chandra
Cisco Systems Cisco Systems
Dave Katz Dave Katz
Juniper Networks Juniper Networks
Yakov Rekhter Yakov Rekhter
Cisco Systems Cisco Systems
Multiprotocol Extensions for BGP-4 Multiprotocol Extensions for BGP-4
draft-ietf-idr-bgp4-multiprotocol-00.txt draft-ietf-idr-bgp4-multiprotocol-01.txt
1. Status of this Memo 1. Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts. working documents as Internet-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
skipping to change at page 3, line 50 skipping to change at page 3, line 50
| Length of second SNPA (1 octet) | | Length of second SNPA (1 octet) |
+---------------------------------------------------------+ +---------------------------------------------------------+
| Second SNPA (variable) | | Second SNPA (variable) |
+---------------------------------------------------------+ +---------------------------------------------------------+
| ... | | ... |
+---------------------------------------------------------+ +---------------------------------------------------------+
| Length of Last SNPA (1 octet) | | Length of Last SNPA (1 octet) |
+---------------------------------------------------------+ +---------------------------------------------------------+
| Last SNPA (variable) | | Last SNPA (variable) |
+---------------------------------------------------------+ +---------------------------------------------------------+
| Network Layer Reachability Information Length (2 octets)|
+---------------------------------------------------------+
| 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 RFC1700 (see the
Address Family Numbers section). Address Family Numbers section).
Subsequent Address Family Identifier: Subsequent Address Family Identifier:
skipping to change at page 5, line 7 skipping to change at page 4, line 50
Nth SNPA of Next Hop: Nth SNPA of Next Hop:
A variable length field that contains an SNPA of the router A variable length field that contains an SNPA of the router
whose Network Address is contained in the "Network Address of whose Network Address is contained in the "Network Address of
Next Hop" field. The field length is an integral number of Next Hop" field. The field length is an integral number of
octets in length, namely the rounded-up integer value of one octets in length, namely the rounded-up integer value of one
half the SNPA length expressed in semi-octets; if the SNPA half the SNPA length expressed in semi-octets; if the SNPA
contains an odd number of semi-octets, a value in this field contains an odd number of semi-octets, a value in this field
will be padded with a trailing all-zero semi-octet. will be padded with a trailing all-zero semi-octet.
Network Layer Reachability Information Length:
This 2-octets unsigned integer indicates the total length of
the Network Layer Reachability Information field in octets.
Network Layer Reachability Information: Network Layer Reachability Information:
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. When the that are being advertised in this attribute. When the
Subsequent Address Family Identifier field is set to one of the Subsequent Address Family Identifier field is set to one of the
values defined in this document, each NLRI is encoded as values defined in this document, each NLRI is encoded as
specified in the "NLRI encoding" section of this document. specified in the "NLRI encoding" section of this document.
The next hop information carried in the MP_REACH_NLRI path attribute The next hop information carried in the MP_REACH_NLRI path attribute
defines the Network Layer address of the border router that should be defines the Network Layer address of the border router that should be
skipping to change at page 6, line 18 skipping to change at page 6, line 8
An UPDATE message that carries the MP_REACH_NLRI must also carry the An UPDATE message that carries the MP_REACH_NLRI must also carry the
ORIGIN and the AS_PATH attributes (both in EBGP and in IBGP ORIGIN and the AS_PATH attributes (both in EBGP and in IBGP
exchanges). Moreover, in IBGP exchanges such a message must also exchanges). Moreover, in IBGP exchanges such a message must also
carry the LOCAL_PREF attribute. If such a message is received from an carry the LOCAL_PREF attribute. If such a message is received from an
external peer, the local system shall check whether the leftmost AS external peer, the local system shall check whether the leftmost AS
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.
When an UPDATE message carries the MP_REACH_NLRI attribute, the
attribute shall be placed after all other attributes in the message.
5. Multiprotocol Unreachable NLRI - MP_UNREACH_NLRI (Type Code 15): 5. 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 contains one or more triples <Address Family The attribute contains one or more triples <Address Family
Information, Unfeasible Routes Length, Withdrawn Routes>, where each Information, Unfeasible Routes Length, Withdrawn Routes>, where each
triple is encoded as shown below: triple 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) |
+---------------------------------------------------------+ +---------------------------------------------------------+
| Unfeasible Routes Length (2 octets) |
+---------------------------------------------------------+
| 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 RFC1700 (see the Address Family
Numbers section). 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.
Unfeasible Routes Length:
This 2-octets unsigned integer indicates the total length of
the Withdrawn Routes field in octets.
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.
 End of changes. 

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