Bitmask Route Target

Internet-Draft	bitmask-route-target	April 2021
Zhang, et al.	Expires 23 October 2021	[Page]

Abstract

This document specifies a new type of Route Target called Bitmask Route Target as a BGP Community Container. The key element of a Bitmask Route Target is a Bitmask. Two Bitmask Route Targets are considered equivalent for the purpose of controlling route propagation (via Route Target Constraints) and importation if the result of logical "AND" operation of the Bitmask of the two is non-zero.¶

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.¶

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.¶

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."¶

This Internet-Draft will expire on 23 October 2021.¶

Copyright Notice

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.¶

1. Introduction

The importation and propagation of BGP routes can be controlled using Route Targets [RFC4364] and Constrained Route Target Distribution (RT-C) [RFC4684]. RT-C relies on matching a Route Target prefix. The typical matching use case is the full 8-octet encoding of the Route Target Extended Community.¶

For some applications, it's desirable to have a Route Target with the semantic of a bit-string. For such situations and it may be desirable to match such bit-string Route Targets that have specific bits set. This document defines a new type of Route Target for that purpose.¶

An example use case of this Bitmask Route Target is documented in [I-D.zzhang-teas-network-slicing-with-flex-te].¶

The use of Bitmask Route Target with Constrained Route Target Distribution is specified separately in [I-D.zzhang-idr-bgp-rt-constrains-extension].¶

2. Specification

The Bitmask Route Target is a Transitive BGP Community Container of type TBD1 [I-D.ietf-idr-wide-bgp-communities].¶

The semantics of Global Administrator and Local Administor are identical to those in [RFC4360].¶

The container's contents is a series of Bitmask Route Targets. Each Bitmask Route Target includes a 1-octet Global Administrator (GA) Type, a 1-octet GA Sub-Type, 1-octet GA Length, a variable length GA, a 4-octet Local Administrator (LA), a 1-octet Bitmask Length in number of octets, and a variable length Bitmask.¶


      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  GA Type        |  GA Sub-Type  |  GA Length    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Global Administrator (variable length)                       ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Local Administrator                                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Bitmask Length |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                   Bitmask (variable length)                   ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The following GA Types and corresponding lengths are defined in this document:¶

1: AS Number, 4-octets¶
2: IPv4 Address, 4-octets¶
3: IPv6 Address, 16-octets¶

The follow GA Sub-Types are defined in this document:¶

2: Route-Target¶

2.1. Matching Semantics

A Bitmask Route Target, A, is considered to match Bitmask Route Target, B, for the purpose of controlling propagation and importation of a route with an attached Bitmask Route Target B if the following conditions are met:¶

The GA Type, GA Sub-Type, GA Length, GA, and LA fields in A and B match.¶
Either:¶
- The Bitmask Length of A is 0. In other words, "match all".¶
- The result of the logical "AND" operation of the Bitmask field in A and B is not 0. When A and B have different Bitmask Lengths, the shorter Route Target's Bitmask is considered to be padded with zeroes for match purposes vs. the longer one.¶

3. Error Handling

A Bitmask Route Target MUST NOT be originated with a RESERVED GA Type. Implementations receiving BGP Routes with a RESERVED Bitmask Route Target MUST check its syntactic correctness and MAY silently discard it.¶

A Bitmask Route Target SHOULD NOT be originated with a Bitmask Length of 0.¶

A Bitmask Route Target is considered malformed if:¶

The length of the Bitmask Route Target is less than the minimum length of 8: 1-octet GA Type, 1-octet GA Sub-Type, 1-octet GA Length, 0-length GA, 4-octet LA, 0-octet Bitmask.¶
The Bitmask Route Target GA Type is known by the implementation and the GA Length is incorrect vs. the registered GA Type.¶
The total computed length of the Bitmask Route Targets in a BGP Community Container is not identical to the BGP Community Container Length. Each Bitmask Route Target's computed length is: 1-octet GA Type, 1-octet GA Length field, N-octet GA Length value, 4-octet LA field, 1-octet Bitmask Length, N-octet Bitmask Length value.¶

BGP Updates containing malformed Bitmask Route Targets should use the Treat-as-withdraw behavior for the routes in the Update according to [RFC7606].¶

5. IANA Considerations

This document requests IANA to assign a BGP Community Container Type for the Bitmask Route Target from the "BGP Community Container Types" registry for TBD1.¶

This document requests IANA to setup a "Bitmask Route Target Global Administrator Type Registry". The initial allocation and policy for this registry is:¶

Table 1: Bitmask Route Target GA-Type Registry
GA Type	GA Type Name	GA Type Length (octets)	Reference
0	RESERVED	UNSPECIFIED	This document
1	AS Number	4	This document
2	IPv4 Address	4	This document
3	IPv6 Address	16	This document
4..127	Available, Specification Required	TBD	-
128..254	Available, First Come, First Served	TBD	-
255	RESERVED	UNSPECIFIED	This document

This document requests IANA to setup a "Bitmask Route Target Global Administrator Sub-Type Registry". The initial allocation and policy for this registry is:¶

Table 2: Bitmask Route Target GA-Sub-Type Registry
GA Sub-Type	GA Sub-Type Name	Reference
0	RESERVED	This document
1	Available, Specification Required	-
2	Route-Target	This document
3..127	Available, Specification Required	-
128..254	Available, First Come, First Served	-
255	RESERVED	This document

7. References

7.1. Normative References

[I-D.ietf-idr-wide-bgp-communities]: Raszuk, R., Haas, J., Lange, A., Decraene, B., Amante, S., and P. Jakma, "BGP Community Container Attribute", Work in Progress, Internet-Draft, draft-ietf-idr-wide-bgp-communities-05, 2 July 2018, <http://www.ietf.org/internet-drafts/draft-ietf-idr-wide-bgp-communities-05.txt>.
[RFC2119]: Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>.
[RFC7606]: Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K. Patel, "Revised Error Handling for BGP UPDATE Messages", RFC 7606, DOI 10.17487/RFC7606, August 2015, <https://www.rfc-editor.org/info/rfc7606>.
[RFC8174]: Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>.

7.2. Informative References

[I-D.zzhang-idr-bgp-rt-constrains-extension]: Zhang, Z. and J. Haas, "Generic Route Constraint Distribution Mechanism for BGP", Work in Progress, Internet-Draft, draft-zzhang-idr-bgp-rt-constrains-extension-01, 11 January 2021, <http://www.ietf.org/internet-drafts/draft-zzhang-idr-bgp-rt-constrains-extension-01.txt>.
[I-D.zzhang-teas-network-slicing-with-flex-te]: Zhang, Z., Hegde, S., and A. Gulko, "Network Slicing with Flexible Traffic Engineering", Work in Progress, Internet-Draft, draft-zzhang-teas-network-slicing-with-flex-te-00, 13 July 2020, <http://www.ietf.org/internet-drafts/draft-zzhang-teas-network-slicing-with-flex-te-00.txt>.
[RFC4360]: Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended Communities Attribute", RFC 4360, DOI 10.17487/RFC4360, February 2006, <https://www.rfc-editor.org/info/rfc4360>.
[RFC4364]: Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 2006, <https://www.rfc-editor.org/info/rfc4364>.
[RFC4684]: Marques, P., Bonica, R., Fang, L., Martini, L., Raszuk, R., Patel, K., and J. Guichard, "Constrained Route Distribution for Border Gateway Protocol/MultiProtocol Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual Private Networks (VPNs)", RFC 4684, DOI 10.17487/RFC4684, November 2006, <https://www.rfc-editor.org/info/rfc4684>.