Clarification of the Flowspec Redirect Extended Community
draft-ietf-idr-flowspec-redirect-rt-bis-01
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Jeffrey Haas
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Internet Engineering Task Force J. Haas, Ed.
Internet-Draft Juniper Networks
Updates: 5575 (if approved) October 20, 2014
Intended status: Standards Track
Expires: April 23, 2015
Clarification of the Flowspec Redirect Extended Community
draft-ietf-idr-flowspec-redirect-rt-bis-01
Abstract
This document clarifies the formatting of the the BGP Flowspec
Redirect Extended Community, originally documented in RFC 5575
(Dissemination of Flow Specification Rules).
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 23, 2015.
Copyright Notice
Copyright (c) 2014 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
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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described in the Simplified BSD License.
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Internet-Draft draft-ietf-idr-flowspec-redirect-rt-bis October 2014
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
3. Security Considerations . . . . . . . . . . . . . . . . . . . 4
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
5. Normative References . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
Dissemination of Flow Specification Rules [RFC5575], commonly known
as BGP Flowspec, provided for a BGP Extended Community [RFC4360] that
served to redirect traffic to a VRF routing instance that matched the
flow specification NLRI. In that RFC, the Redirect Extended
Community was documented as follows:
: +--------+--------------------+--------------------------+
: | type | extended community | encoding |
: +--------+--------------------+--------------------------+
: | 0x8008 | redirect | 6-byte Route Target |
: +--------+--------------------+--------------------------+
:
: [...]
:
: Redirect: The redirect extended community allows the traffic to be
: redirected to a VRF routing instance that lists the specified
: route-target in its import policy. If several local instances
: match this criteria, the choice between them is a local matter
: (for example, the instance with the lowest Route Distinguisher
: value can be elected). This extended community uses the same
: encoding as the Route Target extended community [RFC4360].
: [...]
:
: 11. IANA Considerations
: [...]
:
: The following traffic filtering flow specification rules have been
: allocated by IANA from the "BGP Extended Communities Type -
: Experimental Use" registry as follows:
: [...]
:
: 0x8008 - Flow spec redirect
The IANA registry of BGP Extended Communities clearly identifies
communities of specific formats. For example, "Two-octet AS Specific
Extended Community" [RFC4360], "Four-octet AS Specific Extended
Community" [RFC5668] and "IPv4 Address Specific Extended Community"
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[RFC4360]. Route Targets [RFC4360] identify this format in the high-
order (Type) octet of the Extended Community and set the value of the
low-order (Sub-Type) octet to 0x02. The Value field of the Route
Target Extended Community is intended to be interpreted in the
context of its format.
Since the Redirect Extended Community only registered a single code-
point in the IANA BGP Extended Community registry, a common
interpretation of the redirect extended community's "6-byte route
target" has been to look, at a receiving router, for a route target
value that matches the route target value in the received redirect
extended community, and import the advertised route to the
corresponding VRF instance subject to the rules defined in RFC 5575
[RFC 5575]. However, because the route target format in the redirect
extended community is not clearly defined, the wrong match may occur.
This "value wildcard" matching behavior, that does not take into
account the format of the route target defined for a local VRF and
may result in the wrong matching decision, does not match deployed
implementations of BGP flowspec. Deployed implementations of BGP
flowspec solve this problem by defining different redirect extended
communities that are specific to the format of the route target
value. This document defines the following redirect extended
communities:
+--------+--------------------+-------------------------------------+
| type | extended community | encoding |
+--------+--------------------+-------------------------------------+
| 0x8008 | redirect AS-2byte | 2-octet AS, 4-octet Value |
| 0x8108 | redirect IPv4 | 4-octet IPv4 Address, 2-octet Value |
| 0x8208 | redirect AS-4byte | 4-octet AS, 2-octet Value |
+--------+--------------------+-------------------------------------+
It should be noted that the low-order nybble of the Redirect's Type
field corresponds to the Route Target Extended Community format field
(Type). (See [RFC4360], Secs. 3.1, 3.2 and [RFC5668], Sec. 2.) The
low order octet (Sub-Type) of the Redirect Extended Community remains
0x08, contrasted to 0x02 for Route Targets.
The IANA Registries for BGP Extended Communities [RFC7153] document
was written to update the previously-mentioned IANA registries to
better document BGP Extended Community formats. The IANA
Considerations section below further amends those registry updates in
order to properly document the flowspec redirect communities.
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2. IANA Considerations
IANA is requested to update the BGP GENERIC TRANSITIVE EXPERIMENTAL
USE EXTENDED COMMUNITY SUB-TYPES registry as follows:
0x08 - Flow spec redirect AS-2byte format.
IANA is requested to update the BGP TRANSITIVE EXTENDED COMMUNITY
TYPES registry as follows:
0x81 - Generic Transitive Experimental Use Extended Community
Part 2 (Sub-Types are defined in the "Generic Transitive
Experimental Extended Community Part 2 Sub-Types" Registry)
0x82 - Generic Transitive Experimental Use Extended Community
Part 3 (Sub-Types are defined in the "Generic Transitive
Experimental Extended Community Part 3 Sub-Types" Registry)
IANA is requested to create the GENERIC TRANSITIVE EXPERIMENTAL USE
EXTENDED COMMUNITY PART 2 SUB-TYPES registry. It should be seeded
with the following Sub-Type:
0x08 - Flow spec redirect IPv4 format.
IANA is requested to create the GENERIC TRANSITIVE EXPERIMENTAL USE
EXTENDED COMMUNITY PART 3 SUB-TYPES registry. It should be seeded
with the following Sub-Type:
0x08 - Flow spec redirect AS-4byte format.
3. Security Considerations
This document introduces no additional security considerations than
those already covered in [RFC5575].
4. Acknowledgements
The contents of this document was raised as part of implementation
discussions of BGP Flowspec with the following individuals:
Andrew Karch (Cisco)
Robert Raszuk
Adam Simpson (Alcatel-Lucent)
Matthieu Texier (Arbor Networks)
Kaliraj Vairavakkalai (Juniper)
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5. Normative References
[RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
Communities Attribute", RFC 4360, February 2006.
[RFC5575] Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J.,
and D. McPherson, "Dissemination of Flow Specification
Rules", RFC 5575, August 2009.
[RFC5668] Rekhter, Y., Sangli, S., and D. Tappan, "4-Octet AS
Specific BGP Extended Community", RFC 5668, October 2009.
[RFC7153] Rosen, E. and Y. Rekhter, "IANA Registries for BGP
Extended Communities", RFC 7153, March 2014.
Author's Address
Jeffrey Haas (editor)
Juniper Networks
1194 N. Mathida Ave.
Sunnyvale, CA 94089
US
Email: jhaas@juniper.net
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