Internet Draft Expires: March 2006
Internet Draft Ruchi Kapoor
Expires: March 2006 Gargi Nalawade
Chandra Appanna
Cisco Systems
BGPv4 Tunnel Encapsulation Attribute
draft-kapoor-nalawade-idr-bgp-ssa-02.txt
1. Status of this Memo
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Internet Draft - 2 - September 2005
2. Copyright Notice
Copyright (C) The Internet Society (2005). 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
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3. Abstract
This document defines a new BGP attribute called the Tunnel
Encapsulation Attribute. This attribute is used to carry Tunnel
encapsulations, capabilities and other relevant information about a
Tunnel.
4. Introduction
In case of MPLS-VPNs, the reachability to the nexthop is provided via
LDP, which provides information about the LSP Tunnel endpoint.
However, if the reachability were to be via a Tunnel, then there is
no mechanism to be provide that reachability dynamically. One could
manually configure Tunnels on each PE and use policy to specify what
Tunnel to use for reaching what BGP nexthop. However this is too
complex and unmanageable. What is needed is a way to send the Tunnel
Encapsulation information dynamically.
This document defines a new BGP attribute called the Tunnel
Encapsulation Attribute which will be used to carry Tunnel
Encapsulations with BGP updates. The value part of the Tunnel
Encapsulation attribute can contain one or more Tunnel Encapsulation
TLVs. The TLVs can carry Tunnel Encapsulations for one or more Tunnel
types originating on a given router. The Type in the TLV identifies
what kind of Tunnel it is.
Also, unlike the fixed length (8 octets) extended community types,
the Tunnel encapsulation TLV is a variable length entity, so it can
carry data of any length, as required by the specific type of a
Tunnel Encapsulation TLV.
5. Format of the Tunnel Encapsulation Attribute
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The format of the BGP Tunnel Encapsulation attribute will be as
follows:
| Attr. Flags | Attr.Type Code|
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|1|0|?|UNUSED | Type = TBD | Length (2 Octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Attribute Value |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The BGP Tunnel Encapsulation Attribute is a variable length, optional
transitive attribute. The Value field of the attribute may contain
one or more Tunnel Encapsulation TLVs. The Value field of the Tunnel
Encapsulation 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: The Type field identifies the type of the Tunnel Eg. mGRE or
IPSEC. 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
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Internet Draft - 4 - September 2005
If the 'T' bit has a value of 1, it implies that the Tunnel type is
transitive across ASes. If the 'T' bit has a value of 0, it implies
that the Tunnel type is non-transitive across ASes.
Remaining 15 bits: Indicate the type of the TLV.
Length: The Length is 2 octets long and indicates the length of the
Value field.
Value: The Value fields for all Tunnel TLVs, will carry the
following fields :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Preference (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S| Flags | |
+-+-+-+-+-+-+-+-+ +
| Tunnel Encapsulation |
| (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where
Preference - Preference is a 2 Octet field containing a Preference
associated with the TLV. The Preference value indicates a preferred
ordering of tunneling encapsulations according to the sender (i.e.
egress PE). The recipient of the information SHOULD take the
sender's preference into account in selecting which encapsulation it
will use. A higher value indicates a higher preference.
Flags - Flags is a 1 Octet field containing flag-bits. The leftmost
bit indicates whether Sequence numbering is to be used or not. The
remaining bits are reserved for future use.
Tunnel Encapsulation: The Tunnel Encapsulation field will carry the
tunnel encapsulation information, specific for this particular tunnel
'Type'.
The Value field will have a fixed part and an optional variable part
as specified by the respective Tunnel Types. The variable part when
present will contain Sub-TLVs encoded as follows :
- Sub-Type Field: 1 octets
- Length Field : 1 octets
- Value Field : Variable
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6. Operation
A BGP speaker that supports the Tunnel Encapsulation Attribute, MUST
accept all Tunnel Encapsulation TLV types. If the Tunnel
Encapsulation TLV is transitive, The BGP speaker MUST forward it even
if it does not understand it. This attribute MUST only be carried
with the BGP Tunnel SAFI [BGP-TUN-SAFI].
If this attribute is carried with another BGP SAFI, the receiving BGP
Speaker MUST ignore this attribute.
A Capability has not been defined for this attribute intentionally.
The presence of the Tunnel SAFI implies the Capability to understand
this Tunnel Encapsulation attribute.
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
[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
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Internet Draft - 6 - September 2005
Cisco Systems, Inc 170 West Tasman Drive San Jose, CA 95134
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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
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Internet Draft - 7 - September 2005
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
13. Expiration Date
This memo is filed as <draft-kapoor-nalawade-idr-bgp-ssa-02.txt>
expires March, 2006.
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