Internet DRAFT - draft-ietf-idr-reserved-extended-communities
draft-ietf-idr-reserved-extended-communities
Network Working Group B. Decraene
Internet-Draft Orange
Intended status: Standards Track P. Francois
Expires: July 17, 2015 IMDEA Networks
January 13, 2015
Assigned BGP extended communities
draft-ietf-idr-reserved-extended-communities-08
Abstract
This document defines an IANA registry in order to assign non-
transitive extended communities from. These are similar to the
existing well-known BGP communities defined in RFC 1997 but provide a
control over inter-AS community advertisement as, per RFC RFC 4360,
they are not transitive across Autonomous System boundaries.
For that purpose, this document defines the use of the reserved
Autonomous System number 0.65535 in the non-transitive generic four-
octet AS specific extended community type.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 17, 2015.
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Copyright Notice
Copyright (c) 2015 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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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
[RFC1997] defines the BGP community attribute and some BGP well-known
communities whose meaning SHALL be understood by all compliant
implementations. New communities can be registered in the IANA "BGP
Well-known Communities" registry but it can't be assumed anymore that
they will be known by all BGP implementations. Implementations or
BGP policies which recognize them will behave as specified in the
IANA registry. Implementations which do not recognize those new IANA
assigned communities will propagate them from BGP neighbor to BGP
neighbor and from AS to AS with an unlimited scope.
There is currently no agreed way to register a non-transitive well-
known community.
On one hand, [RFC1997] defines BGP Well-known communities with no
structure to set their transitiveness across ASes. Without
structure, communities can only be filtered by explicitly enumerating
all community values that will be denied or allowed to BGP speakers
in neighboring ASes. This is not satisfactory as this would require
upgrading all border routers to understand this community before its
first usage.
On the other hand, [RFC4360] defines the BGP extended community
attribute with a structure including a type and a transitive bit "T".
This transitive bit, when set, allows to restrict the scope of the
community within an AS. But there is no IANA registry to allocate
one well-known extended community. [RFC4360] defines IANA registries
to allocate BGP Extended Communities types. Each type is able to
encode 2^48 or 2^56 values depending on the type being extended or
regular. Therefore, one needing to reserve a single non-transitive
extended community would need to reserve an extended subtype which
represents 2^48 communities, while a single value is used. This
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would both waste the resources and disable the ability to define
global policies on reserved communities, such as to accept them or to
filter them out. In addition, using a new community type typically
requires a software upgrade on both the router setting the community
and the router using it in a BGP policy. So this would not allow the
networking community to quickly define and use a new community.
To address this limitation, this document defines an IANA registry in
order to allow the registration of non-transitive extended
communities. These are similar to the existing Well-known BGP
communities defined in [RFC1997] but provides a control on inter-AS
community advertisement. Indeed, as per [RFC4360] non-transitive
communities are removed from routes propagated to another AS.
2. Assigned non-transitive extended communities
[I-D.ietf-idr-as4octet-extcomm-generic-subtype] defines a generic
sub-type for the four-octet AS specific extended community. The
value of the four-octets Global Administrator sub-field contains a
four-octet Autonomous System number. The value of their two-octet
Local Administrator sub-field has semantics defined by the Autonomous
System set in the Global Administrator sub-field.
This document updates [I-D.ietf-idr-as4octet-extcomm-generic-subtype]
and defines the use of the Local Administrator sub-field of the "non-
transitive generic four-octet AS specific" extended community type
when the AS number has the reserved value 0.65535 (0x0000FFFF).
When the AS number, encoded in the Global Administrator sub-field,
has the reserved value 0.65535, the communities have global
significance. The lists of those communities are maintained by the
IANA in the registry "Assigned non-transitive extended communities".
Note that this use of the reserved AS number 0.65535 in the AS field
of the communities is similar to the one defined by [RFC1997] for the
BGP Well-Known communities. In particular, [RFC1997] also uses the
reserved AS number 65535.
3. Assigned transitive extended communities
As per [RFC6793], a 2-octet Autonomous System number can be converted
into a 4-octet Autonomous System number by setting the two high-order
octets of the 4-octet field to zero. This applies to the reserved
2-octet Autonous System number 65535 which could use either a
standard community or the 4-octet AS specific generic extended
community. As noted in
[I-D.ietf-idr-as4octet-extcomm-generic-subtype], this is undesirable
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as they would be treated as different communities, even if they had
the same values.
Therefore, this document does not define a transitive extended
community registry. Transitive communities are to be assigned as per
[RFC1997].
4. IANA Considerations
The IANA is requested to create and maintain a registry entitled
"Assigned non-transitive extended communities" with the following
registration procedure:
Registry Name: Assigned non-transitive extended communities
with Global Significance
Range Registration Procedures
----------- -------------------------
0x0000-8000 First Come First Served
0x8001-FFFF Standards Action/Early IANA Allocation
An application may need both a transitive and a non-transitive
community and it may be beneficial to have the same value for both
communities. Therefore, the IANA SHOULD try to accommodate such
request to get both a non-transitive community from the above
"Assigned non transitive extended communities" and a transitive
community from [RFC1997] BGP Well-known Communities with the same
(lower two-octets) value for both.
5. Security Considerations
This document defines IANA actions. In itself, it has no impact on
the security of the BGP protocol.
It allows the allocation of non-transitive global communities which
are not propagated across Autonomous System boundaries. Compared to
a transitive well-known community, a non-transitive community can
provide some security benefit both for the sender and the receiver of
the community.
6. Acknowledgements
We would like to acknowledge John Scudder, Jeffrey Haas and Yakov
Rekhter for their contribution to this document.
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7. Normative References
[I-D.ietf-idr-as4octet-extcomm-generic-subtype]
Rao, D., Mohapatra, P., and J. Haas, "Generic Subtype for
BGP Four-octet AS specific extended community", draft-
ietf-idr-as4octet-extcomm-generic-subtype-07 (work in
progress), July 2014.
[RFC1997] Chandrasekeran, R., Traina, P., and T. Li, "BGP
Communities Attribute", RFC 1997, August 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
Communities Attribute", RFC 4360, February 2006.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC6793] Vohra, Q. and E. Chen, "BGP Support for Four-Octet
Autonomous System (AS) Number Space", RFC 6793, December
2012.
Appendix A. Appendix A. Changes / Author Notes
[RFC Editor: Please remove this section before publication ]
Changes -01:
o Name changed from 'Reserved BGP extended communities' to 'Assigned
BGP extended communities'
o Addition of section 'Assigned extended communities'
Changes -02: no change, refresh only.
Changes -03:
o Use of AS number 0.65535 (0x0000FFFF) instead of AS 0. This is
better aligned with RFC 1997 which also uses AS 65535.
o Remove the transitive flavor of assigned extended communities.
RFC 1997 well-known standard communities to be used instead.
Changes -04: no change, refresh only.
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Changes -05: minor editorial change (RFC 4893 obsoleted by 6793).
Changes -06: typo fixed, minor editorial change.
Changes -07, 08: no change, refresh only.
Authors' Addresses
Bruno Decraene
Orange
38 rue du General Leclerc
Issy Moulineaux cedex 9 92794
France
Email: bruno.decraene@orange.com
Pierre Francois
IMDEA Networks
Avda. del Mar Mediterraneo, 22
Leganese 28918
ES
Email: pierre.francois@imdea.org
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