| Internet Engineering Task Force | N. Akiya |
| Internet-Draft | C. Pignataro |
| Intended status: Standards Track | D. Ward |
| Expires: December 09, 2013 | Cisco Systems |
| June 07, 2013 |
Seamless Bidirectional Forwarding Detection (BFD) for IP
draft-akiya-bfd-seamless-ip-00
This specification defines procedures to use Seamless Bidirectional Forwarding Detection (BFD) in IP and IP signalled MPLS environments.
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].
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This Internet-Draft will expire on December 09, 2013.
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One application for Seamless Bidrectional Forwarding Detection (BFD) [I-D.akiya-bfd-seamless-base] is to perform full and partial reachability validations on IP and IP signalled MPLS environments.
This specification defines procedures to use Seamless BFD in IP and IP signalled MPLS environments.
BFD target identifier type of value 1 is used for IPv4 addresses and router IDs. This identifier type will cover Seamless BFD in following scenarios: Section 3.
Not all IPv6 aspects are covered by this specification, and details are clarified in
With IPv4 based BFD, BFD target identifier type 1 is used. BFD discriminator values corresponding to all or subset of local IPv4 addresses are to be reserved. IPv4 addresses are used as BFD discriminators. Corresponding BFD discriminators MUST be reserved and those BFD discriminators MUST NOT be used for other BFD sessions.
Example:
With IPv6 based BFD, BFD target identifier type 1 is used. BFD discriminator values corresponding to all or subset of local IGP Router IDs are to be reserved. These router IDs are used as BFD discriminators. With OSPFv3, employed 32 bit router IDs are used. Corresponding BFD discriminators MUST be reserved and those BFD discriminators MUST NOT be used for other BFD sessions. ISIS is not included as part of this identifier type, and is outside the scope of this document.
Example:
Note that it is acceptable for an IPv4 address and a router-ID to collide, mapping into a same BFD discriminator value. There will not be an issue as long as colliding BFD discriminator value is reserved for the Seamless BFD purpose.
With IP identifier type, only locally reserved BFD discriminators and corresponding information are to be in this table. No inter-node communications are needed to exchange BFD discriminator and BFD target identifier mappings.
Any IP network node can attempt to perform a full reachability validation to any BFD target identifier of type 1 (IPv4 address or router-ID) on other network nodes, as long as destination BFD target identifier is provisioned to use this mechanism. Transmitted BFD control packet by the initiator is to have "your discriminator" corresponding to destination BFD target identifier of type 1.
Initiator is to use following procedures to construct BFD control packets to perform IP full reachability validations on BFD packets that are IP routed:
To respond to received BFD control packet which was targeted to local BFD target identifier of type 1 (IP ddress or router-ID), response BFD control packet is targeted to IP address taken from received "source IP address". Responder MUST validate obtained IP address is in valid format (ex: not Martian address). Responder MUST consult local routing table to ensure obtained IP address is reachable.
Procedures described in [I-D.akiya-bfd-seamless-base] applies.
MPLS label verification mechanism is applicable to those IP based BFD which use explicit label switching techniques. However, details of what responder embeds in the lower 23 bits of localhost address, and how initiator determines correctness of label programming is outside the scope of this document.
Active IP BFD sessions, single-hop, multi-hop or MPLS can be instantiated on any network node using this mechanism to any IPv4 target addresses and OSPFv3 router IDs using this mechanism. This style of usage is particularly useful only if one side is required to perform full reachability validations (ex: static route, uni-directional tunnel). This style of usage is also particularly useful to perform validations and verifications on just subset of LSPs (ex: inter-AS, injection of partial BFD reachability validation packet on IPv4 RSVP LSP nodes).
Same security considerations as [RFC5880], [RFC5881], [RFC5883], [RFC5884], [RFC5885] and [I-D.akiya-bfd-seamless-base] apply to this document.
None
Authors would like to thank Marc Binderberger from Cisco Systems for providing valuable comments.
Tarek Saad
Cisco Systems
Email: tsaad@cisco.com
Siva Sivabalan
Cisco Systems
Email: msiva@cisco.com
Nagendra Kumar
Cisco Systems
Email: naikumar@cisco.com
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. |
| [RFC5880] | Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD)", RFC 5880, June 2010. |
| [RFC5881] | Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, June 2010. |
| [RFC5883] | Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD) for Multihop Paths", RFC 5883, June 2010. |
| [RFC5884] | Aggarwal, R., Kompella, K., Nadeau, T. and G. Swallow, "Bidirectional Forwarding Detection (BFD) for MPLS Label Switched Paths (LSPs)", RFC 5884, June 2010. |