idr Z. Zhang
Internet-Draft J. Haas
Updates: 4684 (if approved) Juniper Networks
Intended status: Standards Track July 12, 2020
Expires: January 13, 2021
Route Target Constrain Extension
draft-zzhang-idr-bgp-rt-constrains-extension-00
Abstract
This document specifies the extensions to Route Target Constrain
mechanism so that it works with various types of Route Targets of
arbitrary lengths.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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 January 13, 2021.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Specification . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Security Considerations . . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
6.1. Normative References . . . . . . . . . . . . . . . . . . 4
6.2. Informative References . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The importation and propagation of BGP routes can be controled using
Route Targets [RFC4364] and Route Target Constrains [RFC4684].
A Route Target (RT) could be an 8-octet BGP Extended Community (EC)
or a 20-octet IPv6 Address Sepcfic EC, though the RT Constrain
mechanism specified in [RFC4684] was designed for the 8-octet RTs
only.
[I-D.ietf-idr-bgp-ipv6-rt-constrain] extends the mechanism to handle
IPv6 Address Specific RTs by allowing the NLRI prefix to be of 0 to
24 octets (vs. 0 to 12 octets as in [RFC4684]):
+-------------------------------+
| origin as (4 octets) |
+-------------------------------+
| route target (8 or 20 octets)|
~ ~
| |
+-------------------------------+
There is a limitation with the approach in [I-D.ietf-idr-bgp-ipv6-rt-
constrain] - when the prefix is not more than 12 octets, there is no
way to determine if the route target part is a partial IPv6 Address
Sepcific RT or a full/partial AS or IPv4 Address Specific RT.
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Additional types of RTs of arbitrary lengths could also be defined,
e.g. [I-D.zzhang-idr-bitmask-route-target]. To extend the RT
Constrain mechanisms in a generic way so that any forseeable types of
RTs can be used, this document proposes the extensions specified in
the following section.
While the extended mechnism specified in this document can be used
for existing RTs including IPv6 Address Specific RTs, it is not the
intention of this document to replace or obsolete the mechansim
defined in [I-D.ietf-idr-bgp-ipv6-rt-constrain], given its current
status and potential existing implementations and deployments. An
operator may choose either way as long as there is no ambiguity.
2. Specification
To advertise Route Target Membership with various types of RTs, a new
NLRI encoding with a new SAFI "Extended Route Target constrains" is
used as following:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Origin AS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Path Attr Type | Route Target ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Route Target (continued, variable length ) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The one-octet "Path Attr Type" indicates the category of Route Target
that follows it, using the type of BGP Path Attribute for the RT.
For example, the "Path Attr Type" is 16 (Extended Community) for
regular RTs, 25 (IPv6 Address Specific Extended Community) for IPv6
Address Specific RTs, or 34 (BGP Community Container Attribute) for
any RT defined as a BGP Community Container (e.g. [I-D.zzhang-idr-
bitmask-route-target]).
Similar to [RFC4684], except for the default route target, which is
encoded as a zero-length prefix, the minimum prefix length is 40 bits
- the Origin AS field and the Path Attr Type field cannot be
interpreted as a prefix. Route targets MAY then be expressed as
prefixes, where, for instance, a prefix would encompass all regular
or IPv6 Address Specific RTs assigned by a given Global
Administrator. Semantics of adverising Route Target Membership for
other types of RTs as prefixes MUST be defined with the specfication
of those types of RTs.
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3. Security Considerations
This document does not change security aspects as discussed in
[RFC4684].
4. IANA Considerations
This document requests IANA to assign a new SAFI "Extended Route
Target constrains".
5. Acknowledgements
The authors thank John Scudder for his comments and suggestions.
6. References
6.1. Normative References
[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>.
[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>.
[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>.
6.2. Informative 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", draft-
ietf-idr-wide-bgp-communities-05 (work in progress), July
2018.
[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>.
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Authors' Addresses
Zhaohui Zhang
Juniper Networks
EMail: zzhang@juniper.net
Jeffrey Haas
Juniper Networks
EMail: jhaas@juniper.net
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