Seamless Bidirectional Forwarding Detection (S-BFD) for IPv4, IPv6 and MPLS
draft-akiya-bfd-seamless-ip-04

Internet Engineering Task Force                                 N. Akiya
Internet-Draft                                              C. Pignataro
Intended status: Standards Track                                 D. Ward
Expires: February 2, 2015                                  Cisco Systems
                                                          August 1, 2014

        Seamless Bidirectional Forwarding Detection (S-BFD) for
                          IPv4, IPv6 and MPLS
                     draft-akiya-bfd-seamless-ip-04

Abstract

   This document defines procedures to use Seamless Bidirectional
   Forwarding Detection (S-BFD) for IPv4, IPv6 and MPLS environments.

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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   This Internet-Draft will expire on February 2, 2015.

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   publication of this document.  Please review these documents

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   carefully, as they describe your rights and restrictions with respect
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  S-BFD UDP Port  . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  S-BFD Echo UDP Port . . . . . . . . . . . . . . . . . . . . .   3
   4.  S-BFD Packet Demultiplexing . . . . . . . . . . . . . . . . .   3
   5.  Initiator Procedures  . . . . . . . . . . . . . . . . . . . .   3
     5.1.  Details of S-BFD Packet Sent by SBFDInitiator . . . . . .   3
     5.2.  Target vs. Remote Entity (S-BFD Discriminator)  . . . . .   4
   6.  Responder Procedures  . . . . . . . . . . . . . . . . . . . .   4
     6.1.  Details of S-BFD Packet Sent by SBFDReflector . . . . . .   5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   10. Contributing Authors  . . . . . . . . . . . . . . . . . . . .   6
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     11.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     11.2.  Informative References . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Seamless Bidirectional Forwarding Detection (S-BFD),
   [I-D.ietf-bfd-seamless-base], defines a generalized mechanism to
   allow network nodes to seamlessly perform continuity checks to remote
   entities.  This document defines necessary procedures to use S-BFD on
   IPv4, IPv6 and MPLS environments.

   The reader is expected to be familiar with the IP, MPLS BFD and S-BFD
   terminologies and protocol constructs.

2.  S-BFD UDP Port

   A new UDP port is defined for the use of the S-BFD on IPv4, IPv6 and
   MPLS environments: TBD1.  SBFDReflector session MUST listen for
   incoming S-BFD packets on the port TBD1.  SBFDInitiator sessions MUST
   transmit S-BFD packets with destination port TBD1.  The source port
   of the S-BFD packets transmitted by SBFDInitiator sessions MUST be in
   the range 49152 through 65535.  The same UDP source port number MUST
   be used for all S-BFD packets associated with a particular
   SBFDInitiator session.  The source port number MAY be unique among
   all SBFDInitiator sessions on the system.

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3.  S-BFD Echo UDP Port

   A new UDP port is defined for the use of the S-BFD Echo function on
   IPv4, IPv6 and MPLS environments: TBD2.  This document defines only
   the UDP port value for the S-BFD Echo function.

4.  S-BFD Packet Demultiplexing

   Received BFD control packet MUST be demultiplexed with the
   destination UDP port field.  If the port is TBD1, then the packet
   MUST be looked up to locate a corresponding SBFDReflector session
   based on the value from the "your discriminator" field in the table
   describing S-BFD discriminators.  If the port is not TBD1, then the
   packet MUST be looked up to locate a corresponding SBFDInitiator
   session or classical BFD session based on the value from the "your
   discriminator" field in the table describing BFD discriminators.  If
   the located session is an SBFDInitiator, then the destination IP
   address of the packet SHOULD be validated to be for self.

5.  Initiator Procedures

   S-BFD packets are transmitted with IP header, UDP header and BFD
   control header ([RFC5880]).  When S-BFD packets are explicitly label
   switched (i.e. not IP routed which happen to go over an LSP, but
   explicitly sent on a specific LSP), the former is prepended with a
   label stack.  Note that this document does not make a distinction
   between a single-hop S-BFD scenario and a multi-hop S-BFD scenario,
   both scenarios are supported.

   Necessary values in the BFD control headers are described in
   [I-D.ietf-bfd-seamless-base].  Section 5.1 describes necessary values
   in the MPLS header, IP header and UDP header when an SBFDInitiator on
   the initiator is sending S-BFD packets.

5.1.  Details of S-BFD Packet Sent by SBFDInitiator

   o  Specifications common to both IP routed S-BFD packets and
      explicitly label switched S-BFD packets:

      *  Source IP address field of the IP header MUST be set to a local
         IP address.

      *  UDP destination port MUST be set to a well-known UDP
         destination port assigned for S-BFD: TBD1.

      *  UDP source port MUST be set to a value in the range 49152
         through 65535.

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   o  Specifications for IP routed S-BFD packets:

      *  Destination IP address field of the IP header MUST set to an IP
         address of the target.

      *  TTL field of the IP header SHOULD be set to 255.

   o  Specifications for explicitly label switched S-BFD packets:

      *  S-BFD packets MUST have the label stack that is expected to
         reach the target.

      *  TTL field of the top most label SHOULD be 255.

      *  The destination IP address MUST be chosen from the 127/8 range
         for IPv4 and from the 0:0:0:0:0:FFFF:7F00/104 range for IPv6.

      *  TTL field of the IP header MUST be set to 1.

5.2.  Target vs. Remote Entity (S-BFD Discriminator)

   Typically, an S-BFD packet will have "your discriminator" field
   corresponding to an S-BFD discriminator of the remote entity located
   on the target network node defined by the destination IP address or
   the label stack.  It is, however, possible for an SBFDInitiator to
   carefully set "your discriminator" and TTL fields to perform a
   continuity test towards a target but to a transit network node.

   Section 5.1 intentionally uses the word "target", instead of "remote
   entity", to accommodate this possible S-BFD usage through TTL expiry.
   This also requires S-BFD packets not be dropped by the responder node
   due to TTL expiry.  Thus implementations on the responder MUST allow
   received S-BFD packets taking TTL expiry exception path to reach
   corresponding reflector BFD session.

6.  Responder Procedures

   S-BFD packets are IP routed back to the initiator, and will have IP
   header, UDP header and BFD control header.  Necessary values in the
   BFD control header are described in [I-D.ietf-bfd-seamless-base].
   Section 6.1 describes necessary values in the IP header and UDP
   header when an SBFDReflector on the responder is sending S-BFD
   packets.

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6.1.  Details of S-BFD Packet Sent by SBFDReflector

   o  Destination IP address field of the IP header MUST be copied from
      source IP address field of received S-BFD packet.

   o  Source IP address field of the IP header MUST be set to a local IP
      address.

   o  TTL field of the IP header SHOULD be set to 255.

   o  UDP destination port MUST be copied from received UDP source port.

   o  UDP source port MUST be copied from received UDP destination port.

7.  Security Considerations

   Security considerations for S-BFD are discussed in
   [I-D.ietf-bfd-seamless-base].  Additionally, implementing the
   following measures will strengthen security aspects of the mechanism
   described by this document:

   o  Implementations MUST provide filtering capability based on source
      IP addresses of received S-BFD packets: [RFC2827].

   o  Implementations MUST NOT act on received S-BFD packets containing
      Martian addresses as source IP addresses.

   o  Implementations MUST ensure that response S-BFD packets generated
      to the initiator by the SBFDReflector have a reachable target (ex:
      destination IP address).

8.  IANA Considerations

   A new value TBD1 is requested from the "Service Name and Transport
   Protocol Port Number Registry".  The requested registry entry is:

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     Service Name (REQUIRED)
       s-bfd
     Transport Protocol(s) (REQUIRED)
       udp
     Assignee (REQUIRED)
       IESG <iesg@ietf.org>
     Contact (REQUIRED)
       BFD Chairs <bfd-chairs@tools.ietf.org>
     Description (REQUIRED)
       Seamless Bidirectional Forwarding Detection (S-BFD)
     Reference (REQUIRED)
       draft-akiya-bfd-seamless-ip
     Port Number (OPTIONAL)
       TBD1 (Requesting 7784)

   A new value TBD2 is requested from the "Service Name and Transport
   Protocol Port Number Registry".  The requested registry entry is:

     Service Name (REQUIRED)
       s-bfd-echo
     Transport Protocol(s) (REQUIRED)
       udp
     Assignee (REQUIRED)
       IESG <iesg@ietf.org>
     Contact (REQUIRED)
       BFD Chairs <bfd-chairs@tools.ietf.org>
     Description (REQUIRED)
       Seamless Bidirectional Forwarding Detection (S-BFD) Echo Function
     Reference (REQUIRED)
       draft-akiya-bfd-seamless-ip
     Port Number (OPTIONAL)
       TBD2 (Requesting 7785)

9.  Acknowledgements

   Authors would like to thank Marc Binderberger from Cisco Systems for
   providing valuable comments.

10.  Contributing Authors

   Tarek Saad
   Cisco Systems
   Email: tsaad@cisco.com

   Siva Sivabalan
   Cisco Systems
   Email: msiva@cisco.com

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   Nagendra Kumar
   Cisco Systems
   Email: naikumar@cisco.com

11.  References

11.1.  Normative References

   [I-D.ietf-bfd-seamless-base]
              Akiya, N., Pignataro, C., Ward, D., Bhatia, M., and J.
              Networks, "Seamless Bidirectional Forwarding Detection
              (S-BFD)", draft-ietf-bfd-seamless-base-01 (work in
              progress), June 2014.

   [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.

11.2.  Informative References

   [RFC2827]  Ferguson, P. and D. Senie, "Network Ingress Filtering:
              Defeating Denial of Service Attacks which employ IP Source
              Address Spoofing", BCP 38, RFC 2827, May 2000.

Authors' Addresses

   Nobo Akiya
   Cisco Systems

   Email: nobo@cisco.com

   Carlos Pignataro
   Cisco Systems

   Email: cpignata@cisco.com

   Dave Ward
   Cisco Systems

   Email: wardd@cisco.com

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