--- 1/draft-ietf-idr-rfc2858bis-02.txt 2006-02-04 23:31:31.000000000 +0100 +++ 2/draft-ietf-idr-rfc2858bis-03.txt 2006-02-04 23:31:31.000000000 +0100 @@ -1,19 +1,19 @@ Network Working Group Tony Bates (Cisco Systems) Internet Draft Ravi Chandra (Redback Networks) -Expiration Date: October 2002 Dave Katz (Juniper Networks) +Expiration Date: January 2004 Dave Katz (Juniper Networks) Obsoles RFC2858 Yakov Rekhter (Juniper Networks) Multiprotocol Extensions for BGP-4 - draft-ietf-idr-rfc2858bis-02.txt + draft-ietf-idr-rfc2858bis-03.txt 1. Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. @@ -50,23 +50,25 @@ are IPv4 specific are (a) the NEXT_HOP attribute (expressed as an IPv4 address), (b) AGGREGATOR (contains an IPv4 address), and (c) NLRI (expressed as IPv4 address prefixes). This document assumes that any BGP speaker (including the one that supports multiprotocol capabilities defined in this document) has to have an IPv4 address (which will be used, among other things, in the AGGREGATOR attribute). Therefore, to enable BGP-4 to support routing for multiple Network Layer protocols the only two things that have to be added to BGP-4 are (a) the ability to associate a particular Network Layer protocol with the next hop information, and (b) the ability to - associated a particular Network Layer protocol with NLRI. To identify - individual Network Layer protocols this document uses Address Family, - as defined in [RFC1700]. + associated a particular Network Layer protocol with NLRI. To + identify individual Network Layer protocols associated with the next + hop information and semantics of NLRI this document uses a + combination of Address Family, as defined in [RFC1700], and + Subsequent Address Family (as described in this document). One could further observe that the next hop information (the information provided by the NEXT_HOP attribute) is meaningful (and necessary) only in conjunction with the advertisements of reachable destinations - in conjunction with the advertisements of unreachable destinations (withdrawing routes from service) the next hop information is meaningless. This suggests that the advertisement of reachable destinations should be grouped with the advertisement of the next hop to be used for these destinations, and that the advertisement of reachable destinations should be segregated from the @@ -123,44 +125,54 @@ | Second SNPA (variable) | +---------------------------------------------------------+ | ... | +---------------------------------------------------------+ | Length of Last SNPA (1 octet) | +---------------------------------------------------------+ | Last SNPA (variable) | +---------------------------------------------------------+ | Network Layer Reachability Information (variable) | +---------------------------------------------------------+ + The use and meaning of these fields are as follows: - Address Family Identifier: + Address Family Identifier (AFI): - This field carries the identity of the Network Layer protocol - associated with the Network Address that follows. Presently - defined values for this field are specified in RFC1700 (see the - Address Family Numbers section). + This field in combination with the Subsequent Address Family + Identifier field identifies the Network Layer protocol + associated with the Network Address of Next Hop and the + semantics of the Network Layer Reachability Information that + follows. - Subsequent Address Family Identifier: + Presently defined values for the Address Family Identifier + field are specified in RFC1700 (see the Address Family Numbers + section). - This field provides additional information about the type of - the Network Layer Reachability Information carried in the - attribute. + Subsequent Address Family Identifier (SAFI): + + This field in combination with the Address Family Identifier + field identifies the Network Layer protocol associated with the + Network Address of the Next Hop and the semantics of the + Network Layer Reachability Information that follows. Length of Next Hop Network Address: A 1 octet field whose value expresses the length of the - "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: A variable length field that contains the Network Address of - the next router on the path to the destination system + the next router on the path to the destination system. The + Network Layer protocol associated with the Network Address of + the Next Hop is identified by a combination of + carried in the attribute. Number of SNPAs: 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 @@ -169,32 +180,36 @@ Nth SNPA of Next Hop: A variable length field that contains an SNPA of the router 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 will be padded with a trailing all-zero semi-octet. - Network Layer Reachability Information: + Network Layer Reachability Information (NLRI): A variable length field that lists NLRI for the feasible routes - that are being advertised in this attribute. When the - Subsequent Address Family Identifier field is set to one of the - values defined in this document, each NLRI is encoded as - specified in the "NLRI encoding" section of this document. + that are being advertised in this attribute. The semantics of + NLRI is identified by a combination of carried in + the attribute. + + When the Subsequent Address Family Identifier field is set to + one of the values defined in this document, each NLRI is + encoded as specified in the "NLRI encoding" section of this + document. The next hop information carried in the MP_REACH_NLRI path attribute - defines the Network Layer address of the border router that should be - used as the next hop to the destinations listed in the MP_NLRI - attribute in the UPDATE message. + defines the Network Layer address of the router that should be used + as the next hop to the destinations listed in the MP_NLRI attribute + in the UPDATE message. The rules for the next hop information are the same as the rules for the information carried in the NEXT_HOP BGP attribute (see Section 5.1.3 of [BGP-4]). 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 exchanges). Moreover, in IBGP exchanges such a message MUST also carry the LOCAL_PREF attribute. @@ -216,42 +231,50 @@ The attribute is encoded as shown below: +---------------------------------------------------------+ | Address Family Identifier (2 octets) | +---------------------------------------------------------+ | Subsequent Address Family Identifier (1 octet) | +---------------------------------------------------------+ | Withdrawn Routes (variable) | +---------------------------------------------------------+ + The use and the meaning of these fields are as follows: - Address Family Identifier: + Address Family Identifier (AFI): - This field carries the identity of the Network Layer protocol - associated with the NLRI that follows. Presently defined values - for this field are specified in RFC1700 (see the Address Family - Numbers section). + This field in combination with the Subsequent Address Family + Identifier field identifies the semantics associated with the + Network Layer Reachability Information (NLRI) that follows. - Subsequent Address Family Identifier: + Presently defined values for the Address Family Identifier + field are specified in RFC1700 (see the Address Family Numbers + section). - This field provides additional information about the type of - the Network Layer Reachability Information carried in the - attribute. + Subsequent Address Family Identifier (SAFI): - Withdrawn Routes: + This field in combination with the Address Family Identifier + field identifies the semantics associated with the Network + Layer Reachability Information (NLRI) that follows. + + Withdrawn Routes Network Layer Reachability Information: A variable length field that lists NLRI for the routes that are - being withdrawn from service. When the Subsequent Address - Family Identifier field is set to one of the values defined in - this document, each NLRI is encoded as specified in the "NLRI - encoding" section of this document. + being withdrawn from service. The semantics of NLRI is + identified by a combination of carried in the + attribute. + + When the Subsequent Address Family Identifier field is set to + one of the values defined in this document, each NLRI is + encoded as specified in the "NLRI encoding" section of this + document. An UPDATE message that contains the MP_UNREACH_NLRI is not required to carry any other path attributes. 7. NLRI encoding The Network Layer Reachability information is encoded as one or more 2-tuples of the form , whose fields are described below: @@ -339,21 +362,21 @@ multiple Capabilities in the Capabilities Optional Parameter. To have a bi-directional exchange of routing information for a particular between a pair of BGP speakers, each such speaker MUST advertise to the other (via the Capability Advertisement mechanism) the capability to support that particular routes. 11. IANA Considerations - As specified in this document, the MPL_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) field. The SAFI name space is defined in this document. The IANA will maintain and register values for the SAFI namespace as follows. SAFI 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.