Internet DRAFT - draft-ietf-bess-pta-flags
draft-ietf-bess-pta-flags
BESS Working Group E. Rosen
Internet-Draft Juniper Networks, Inc.
Updates: 6514 (if approved) T. Morin
Intended status: Standards Track Orange
Expires: November 4, 2016 May 3, 2016
Registry and Extensions for
P-Multicast Service Interface Tunnel Attribute Flags
draft-ietf-bess-pta-flags-03.txt
Abstract
The BGP-based control procedures for Multicast Virtual Private
Networks make use of a BGP attribute known as the "P-Multicast
Service Interface (PMSI) Tunnel" attribute. The attribute contains a
one-octet "Flags" field. The purpose of this document is to
establish an IANA registry for the assignment of the bits in this
field. Since the Flags field contains only eight bits, this document
also defines a new BGP Extended Community, "Additional PMSI Tunnel
Attribute Flags", that can be used to carry additional flags for the
PMSI Tunnel attribute. This document updates RFC 6514.
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 November 4, 2016.
Copyright Notice
Copyright (c) 2016 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Extending the PMSI Tunnel Attribute Flags Field . . . . . . . 2
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
A BGP attribute known as the "P-Multicast Service Interface (PMSI)
Tunnel" attribute is defined in [RFC6514]. This attribute contains a
one-octet "Flags" field. Only one flag is defined in that RFC, but
there is now a need to define additional flags. However, that RFC
did not create an IANA registry for the assignment of bits in the
"Flags" field. This document creates a registry for that purpose.
In addition, there may be a need to define more than eight flags.
Therefore this document defines a new BGP Extended Community,
"Additional PMSI Tunnel Attribute Flags", that can be used to carry
additional flags for the PMSI Tunnel attribute. A registry is also
created for this Extended Community, allowing IANA to assign flag
bits from the Extended Community's six-octet value field.
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 [RFC2119].
2. Extending the PMSI Tunnel Attribute Flags Field
In [RFC6514], only a single octet in the "PMSI Tunnel" attribute is
defined to carry bit flags. This allows eight flags, which is
unlikely to be sufficient for all future applications.
This document defines a new Transitive Opaque Extended Community
([RFC4360], [RFC7153]), "Additional PMSI Tunnel Attribute Flags". It
also defines a new bit flag in the "PMSI Tunnel" attribute Flags
field, called the "Extension" flag.
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The "Additional PMSI Tunnel Attribute Flags" Extended Community MUST
NOT be carried by a given BGP UPDATE message unless the following
conditions both hold:
o the given BGP UPDATE message is also carrying a "PMSI Tunnel"
attribute, and
o the "Extension" flag of that "PMSI Tunnel" attribute's "Flags"
field is set.
The six-octet value field of the "Additional PMSI Tunnel Attribute
Flags" Extended Community is considered to be a string of 48 bit
flags. As shown in Figure 1, the leftmost bit (the most significant
bit of the most significant octet) is bit 0, and the rightmost bit
(the least significant bit of the least significant octet) is bit 47.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3 4
2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Value Field of the Additional PMSI Tunnel Attribute Flags
Extended Community
A BGP speaker MUST NOT attach more than one "Additional PMSI Tunnel
Attribute Flags" Extended Community to a given BGP UPDATE. If a
given BGP UPDATE already contains an "Additional PMSI Tunnel
Attribute Flags" Extended Community, a BGP speaker MUST NOT attach
any additional such Extended Communities.
If a BGP speaker receives a BGP UPDATE with more than one "Additional
PMSI Tunnel Attribute Flags" Extended Communities attached, only the
flag settings in first occurrence of the Extended Community are
significant. Flag settings in subsequent occurrences of the Extended
Community MUST be ignored. When propagating the UPDATE, all
instances of the Extended Community other than the first SHOULD be
removed.
Suppose a BGP speaker receives an UPDATE message that contains a
"PMSI Tunnel" attribute, but does not contain an "Additional PMSI
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Tunnel Attribute Flags" Extended Community. If the "Extension" flag
of the "PMSI Tunnel" attribute is set, the UPDATE is considered to be
malformed, and the "treat-as-withdraw" procedure of [RFC7606] MUST be
applied.
If a BGP speaker receives an UPDATE message that contains one or more
"Additional PMSI Tunnel Attribute Flags" Extended Communities, but
either (a) that UPDATE message does not contain a PMSI Tunnel
attribute, or (b) the Extension flag of the PMSI Tunnel attribute is
not set, then the Extended Community(ies) SHOULD be removed and
SHOULD NOT be redistributed. The BGP UPDATE message MUST be
processed (and if necessary, redistributed) as if the Extended
Community(ies) had not been present.
A BGP speaker that supports the current document, but does not
recognize a particular flag (either in the" PMSI Tunnel" attribute
"Flags" field or in the "Additional PMSI Tunnel Attribute Flags"
Extended Community) MUST simply ignore that flag. If the BGP speaker
propagates either the PMSI Tunnel attribute or the "Additional PMSI
Tunnel Attribute Flags" Extended Community or both along with the
UPDATE message, it SHOULD leave the setting of the flag unchanged.
It is possible that a particular application will require all members
of a particular set of BGP speakers to support a particular flag.
How it is determined whether all such BGP speakers support that flag
is outside the scope of this document.
In some situations, a BGP speaker may need to modify or replace the
"PMSI Tunnel" attribute before propagating an UPDATE. If the
"Extension" flag of the "PMSI Tunnel" attribute was set before the
attribute is modified or replaced, but that flag is no longer set
after the attribute is modified or replaced, any "Additional PMSI
Tunnel Attribute Flags" Extended Communities MUST be removed before
the UPDATE is propagated. If the PMSI Tunnel attribute is removed
entirely before an UPDATE is propagated, the "Additional PMSI Tunnel
Attribute Flags" Extended Communities (if any) MUST also be removed.
3. IANA Considerations
IANA is requested to create a new registry called "P-Multicast
Service Interface (PMSI) Tunnel Attribute Flags" in the "Border
Gateway Protocol (BGP) Parameters" registry.
Per [RFC6514] section 5, a "PMSI Tunnel" attribute contains a "Flags"
octet. The Flags field is a single octet, with bits numbered, left-
to-right, from 0 to 7. IANA is requested to initialize the registry
as follows:
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Bit Position Description Reference
(left to right)
0 unassigned
1 Extension This document
2 unassigned
3 unassigned
4 unassigned
5 unassigned
6 unassigned
7 Leaf Information Required (L) RFC6514
PMSI Tunnel Attribute Flags
The registration procedure for this registry is Standards Action.
IANA is also requested to assign a codepoint, from the "First Come,
First Served" range of the Transitive Opaque Extended Community Sub-
Types registry, for "Additional PMSI Tunnel Attribute Flags".
[TO BE REMOVED: This registration should take place at the following
location: http://www.iana.org/assignments/bgp-extended-communities
/bgp-extended-communities.xhtml#trans-opaque]
IANA is further requested to establish a registry for the bit flags
carried in the "Additional PMSI Tunnel Attribute Flags" Extended
Community. The bits shall be numbered 0-47, with 0 being the most
significant bit and 47 being the least significant bit. The
registration policy for this registry shall be "Standards Action".
[TO BE REMOVED: The creation of the registry should take place at the
following location: http://www.iana.org/assignments/bgp-extended-
communities/bgp-extended-communities.xhtml]
The initial registry should be as follows:
Bit Flag Name Reference
0-47 unassigned
Additional PMSI Tunnel Attribute Flags
4. Acknowledgments
The authors wish to thank Martin Vigoureux for his review of this
document. We also thank Christian Huitema and Alexey Melnikov for
their review and comments.
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5. Security Considerations
This document establishes an IANA registry, and defines a new
Transitive Opaque Extended Community ([RFC4360], [RFC7153]).
Establishment of an IANA registry does not raise any security
considerations.
While this document defines a new Extended Community for carrying bit
flags, it does not define any of the bit flags in that Extended
Community. Therefore no security considerations are raised.
This document defines a new flag, the "Extension" flag, in the "PMSI
Tunnel" attribute. If a particular UPDATE contains "PMSI Tunnel"
attribute with this flag set, but the UPDATE does not contain an
"Additional PMSI Tunnel Attribute Flags" Extended Community, then the
UPDATE is considered to be malformed, and the "treat-as-withdraw"
procedure of [RFC7606] is invoked. Thus one can cause an UPDATE to
be treated as a withdrawal by incorrectly setting this bit.
6. 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,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
Communities Attribute", RFC 4360, DOI 10.17487/RFC4360,
February 2006, <http://www.rfc-editor.org/info/rfc4360>.
[RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
Encodings and Procedures for Multicast in MPLS/BGP IP
VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012,
<http://www.rfc-editor.org/info/rfc6514>.
[RFC7153] Rosen, E. and Y. Rekhter, "IANA Registries for BGP
Extended Communities", RFC 7153, DOI 10.17487/RFC7153,
March 2014, <http://www.rfc-editor.org/info/rfc7153>.
[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,
<http://www.rfc-editor.org/info/rfc7606>.
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Authors' Addresses
Eric C. Rosen
Juniper Networks, Inc.
10 Technology Park Drive
Westford, Massachusetts 01886
United States
Email: erosen@juniper.net
Thomas Morin
Orange
2, avenue Pierre-Marzin
22307 Lannion Cedex
France
Email: thomas.morin@orange.com
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