Internet Draft Ruchi Kapoor
Expires: January 2006 Gargi Nalawade
Chandra Appanna
Cisco Systems
BGPv4 SAFI-Specific Attribute
draft-kapoor-nalawade-idr-bgp-ssa-01.txt
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Copyright (C) The Internet Society (2005). This document is subject
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except as set forth therein, the authors retain all their rights."
"This document and the information contained herein are provided on
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IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
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3. Abstract
This document defines a new BGP attribute called the SAFI-Specific
Attribute. The document also makes the attribute specific to be
used by the Tunnel SAFI. The Tunnel-SAFI Specific attribute (also
know as the Tunnel Attribute) is used to send out attributes of a
Tunnel used by routing for different routing applications. This
Tunnel attribute can contain various 'Types', where the Type
identifies what kind of Tunnel the TLV describes.
4. Introduction
This document defines a new BGP attribute called the Tunnel
Attribute. The value part of the Tunnel Attribute can contain one or
more an attribute, which can carry Tunnel Attributes for one or more
Tunnel types originating on a given router.
Also, unlike the fixed length (8 octets) extended community types,
the SAFI-Specific Attribute TLV is a variable length entity, so it
can carry data of any length, as required by the specific type of a
SAFI-Specific Attribute TLV.
5. Format of the SAFI-Specific Attribute
The format of the BGP SAFI-Specific attribute will be as follows:
| Attr. Flags | Attr.Type Code|
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|1|0|?|UNUSED | Type = TBD | Length (2 Octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Attribute Value |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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The BGP Tunnel is a variable length, optional transitive attribute.
The Value field of the attribute may contain one or more SAFI-
Speceific Attribute TLVs. The Value field of the Tunnel Attribute is
encoded as follows and may contain one or more tuples of the
following:
- Type Field : 2 octets
- Length Field: 2 octets
- Value Field : Variable
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type Field: The format of the Type Field is as shown below:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|T| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
T - Transitive bit
Value 1: The Tunnel type is transitive across ASes
Value 0: The Tunnel type is non-transitive across ASes
Remaining 15 bits: Indicate the type of the TLV.
Length Field: The Length is 2 octets long and indicates the length of
the Value field.
The value contained in this Length field MUST not exceed the total
length of the BGP Tunnel Attribute minus the total length of any
prior TLVs.
Value Field: The Value Field contains a TLV where the Types of the
TLV are defined by the respective SAFIs. The TLV in the Value field
of this Attribute will be of the form :
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- Type Field : 2 octets
- Length Field: 2 octets
- Value Field : Variable
The Value field will have a fixed part as specified by the respective
Tunnel Types and may have a variable part in the form of Sub-TLVs
encoded as follows :
- Sub-Type Field : 1 octets
- Length Field: 1 octets
- Value Field : Variable
6. Operation
A BGP speaker that supports a SAFI, MUST accept any SAFI-Specific
Attribute
TLVs that are part of the SAFI. If the SAFI-Specific Attribute TLV
is transitive, the BGP speaker MUST forward it even if it does not
understand it. Operation rules are governed by those for the SAFI.
This attribute only requires that it be forwarded even when it is not
understood.
When sending an UPDATE message for this SAFI to a peer, a BGP speaker
MUST only advertise the SAFI-Specific Attribute TLVs that are defined
and are valid for that SAFI.
A Capability has not been defined for this attribute intentionally.
For newer SAFIs, it is concieved that presence of the SAFI could
imply understanding the SAFI-Specific Attribute and the SAFI-
Specific Attribute TLVs. For existing SAFIs, a capbility may be
required.
7. Security Considerations
This extension to BGP does not change the underlying security issues.
8. Acknowledgements
We would like to thank Dan Tappan and Jim Guichard for their
significant contributions. We would also like to thank Francois
LeFaucher, Arjun Sreekantiah, Shyam Suri and John Scudder for their
comments and suggestions.
9. Normative References
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[BGP-4] Rekhter, Y. and T. Li (editors), "A Border Gateway Protocol
4 (BGP-4)", Internet Draft draft-ietf-idr-bgp4-26.txt, April 2005.
[BGP-CAP] Chandra, R., Scudder, J., "Capabilities Advertisement with
BGP-4", draft-ietf-idr-rfc2842bis-02.txt, April 2002.
[IANA-AFI] http://www.iana.org/assignments/address-family-numbers.
[IANA-SAFI] http://www.iana.org/assignments/safi-namespace.
10. Author's Addresses
Ruchi Kapoor mailto:ruchi@cisco.com
Gargi Nalawade mailto:gargi@cisco.com
Chandra Appanna mailto: achandra@cisco.com
Cisco Systems, Inc 170 West Tasman Drive San Jose, CA 95134
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Internet Draft - 6 - July 2005
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12. Full Copyright Statement
Copyright (C) The Internet Society (2005). All Rights Reserved.
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
13. Expiration Date
This memo is filed as <draft-kapoor-nalawade-idr-bgp-ssa-01.txt>
expires January, 2006.
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