Address-Prefix-Based Outbound Route Filter for BGP-4
draft-ietf-idr-bgp-prefix-orf-05
The information below is for an old version of the document that is already published as an RFC.
| Document | Type | RFC Internet-Draft (idr WG) | |
|---|---|---|---|
| Authors | Enke Chen , Srihari R. Sangli | ||
| Last updated | 2015-10-14 (Latest revision 2008-06-23) | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | plain text htmlized pdfized bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | (None) | ||
| IESG | IESG state | RFC 5292 (Proposed Standard) | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | David Ward | ||
| Send notices to | (None) |
draft-ietf-idr-bgp-prefix-orf-05
Network Working Group E. Chen
Internet Draft S. Sangli
Expiration Date: January 2009 Cisco Systems
Address Prefix Based Outbound Route Filter for BGP-4
draft-ietf-idr-bgp-prefix-orf-05.txt
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Abstract
This document defines a new Outbound Router Filter (ORF) type for
BGP, termed "Address Prefix Outbound Route Filter", that can be used
to perform address prefix based route filtering. This ORF-type
supports prefix length or range based matching, wild-card based
address prefix matching, as well as the exact address prefix matching
for address families.
Chen & Sangli [Page 1]
Internet Draft draft-ietf-idr-bgp-prefix-orf-05.txt June 2008
1. Introduction
The Outbound Route Filtering Capability defined in [BGP-ORF] provides
a mechanism for a BGP speaker to send to its BGP peer a set of
Outbound Route Filters (ORFs) that can be used by its peer to filter
its outbound routing updates to the speaker.
This documents defines a new ORF-type for BGP, termed "Address Prefix
Outbound Route Filter (Address Prefix ORF)", that can be used to
perform address prefix based route filtering. The Address Prefix ORF
supports prefix length or range based matching, wild-card based
address prefix matching, as well as the exact address prefix matching
for address families [BGP-MP].
2. Address Prefix ORF-Type
The Address Prefix ORF-Type allows one to express ORFs in terms of
address prefixes. That is, it provides address prefix based route
filtering, including prefix length or range based matching, as well
as wild-card address prefix matching.
Conceptually an Address Prefix ORF entry consists of the fields
<Sequence, Match, Length, Prefix, Minlen, Maxlen>.
The "Sequence" field specifies the relative ordering of the entry
among all the Address Prefix ORF entries.
The "Match" field specifies whether this entry is "PERMIT" (value 0),
or "DENY" (value 1).
The "Length" field indicates the length in bits of the address
prefix. A length of zero indicates a prefix that matches all (as
specified by the address family) addresses (with prefix itself of
zero octets).
The "Prefix" field contains an address prefix of an address family.
The "Minlen" field indicates the minimum prefix length in bits that
is required for "matching". The field is considered as un-specified
with value 0.
The "Maxlen" field indicates the maximum prefix length in bits that
is required for "matching". The field is considered as un-specified
with value 0.
The fields "Sequence", "Length", "Minlen", and "Maxlen" are all
unsigned integers.
Chen & Sangli [Page 2]
Internet Draft draft-ietf-idr-bgp-prefix-orf-05.txt June 2008
This document imposes the following requirement on the values of
these fields:
0 <= Length < Minlen <= Maxlen
However, tests related to the "Minlen" or "Maxlen" value should be
omitted when the "Minlen" or "Maxlen" field (respectively) is
unspecified.
In addition, the "Maxlen" value must be no more than the maximum
length (in bits) of a host address for a given address family [BGP-
MP].
3. Address Prefix ORF Encoding
The value of the ORF-Type for the Address Prefix ORF-Type is 64.
An Address Prefix ORF entry is encoded as follows. The "Match" field
of the entry is encoded in the "Match" field of the common part
[BGP-ORF], and the remaining fields of the entry is encoded in the
"Type specific part" as shown in Figure 1.
+--------------------------------+
| Sequence (4 octets) |
+--------------------------------+
| Minlen (1 octet) |
+--------------------------------+
| Maxlen (1 octet) |
+--------------------------------+
| Length (1 octet) |
+--------------------------------+
| Prefix (variable length) |
+--------------------------------+
Figure 1: Address Prefix ORF Encoding
Note that the Prefix field contains the address prefix followed by
enough trailing bits to make the end of the field fall on an octet
boundary. The value of the trailing bits is irrelevant.
Chen & Sangli [Page 3]
Internet Draft draft-ietf-idr-bgp-prefix-orf-05.txt June 2008
4. Address Prefix ORF Matching
In addition to the general matching rules defined in [BGP-ORF],
several Address Prefix ORF specific matching rules are defined as
follows.
Consider an Address Prefix ORF entry, and a route maintained by a BGP
speaker with NLRI in the form of <Prefix, Length>.
The route is considered as "no match" to the ORF entry if the NLRI is
neither more specific than, nor equal to, the <Prefix, Length> fields
of the ORF entry.
When the NLRI is either more specific than, or equal to, the <Prefix,
Length> fields of the ORF entry, the route is considered as a match
to the ORF entry only if the NLRI match condition as listed in Table
1 is satisfied.
ORF Entry NLRI
Minlen Maxlen Match Condition
+------------------------------------------------------+
| un-spec. un-spec. NLRI.length == ORF.length |
+------------------------------------------------------+
| specified un-spec. NLRI.length >= ORF.Minlen |
+------------------------------------------------------+
| un-spec. specified NLRI.length <= ORF.Maxlen |
+------------------------------------------------------+
| specified specified NLRI.length >= ORF.Minlen |
| AND NLRI.length <= ORF.Maxlen |
+------------------------------------------------------+
Table 1: Address Prefix ORF Matching
When more than one Address Prefix ORF entry match the NLRI of the
route, the "first-match" rule applies. That is, the ORF entry with
the smallest sequence number (among all the matching ORF entries) is
considered as the sole match, and it would determine whether the
route should be advertised.
The assignment of the sequence numbers is a local matter for the BGP
speaker that sends the Address Prefix ORF entries.
Chen & Sangli [Page 4]
Internet Draft draft-ietf-idr-bgp-prefix-orf-05.txt June 2008
5. IANA Considerations
This document specifies a new Outbound Route Filtering (ORF) type,
Address Prefix ORF. The value of the ORF-type is 64.
6. Security Considerations
This extension to BGP does not change the underlying security issues
[BGP-4].
7. Normative References
[BGP-4] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway Protocol
4 (BGP-4)", RFC 4271, January 2006.
[BGP-MP] Bates, T., Chandra, R., Rekhter, Y., and D. Katz,
"Multiprotocol Extensions for BGP-4", RFC 4760, January 2007.
[BGP-ORF] Chen, E., and Rekhter, Y., "Outbound Route Filtering
Capability for BGP-4", draft-ietf-idr-route-filter-17.txt, June 2008.
8. Author Information
Enke Chen
Cisco Systems, Inc.
170 W. Tasman Dr.
San Jose, CA 95134
EMail: enkechen@cisco.com
Srihari R. Sangli
Cisco Systems, Inc.
170 W. Tasman Dr.
San Jose, CA 95134
EMail: rsrihari@cisco.com
Chen & Sangli [Page 5]
Internet Draft draft-ietf-idr-bgp-prefix-orf-05.txt June 2008
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Chen & Sangli [Page 6]