Internet Engineering Task Force                                 N. Akiya
Internet-Draft                                       Big Switch Networks
Intended status: Standards Track                            C. Pignataro
Expires: August 25, October 15, 2016                                        D. Ward
                                                           Cisco Systems
                                                       February 22,
                                                          April 13, 2016

        Seamless Bidirectional Forwarding Detection (S-BFD) for
                          IPv4, IPv6 and MPLS
                     draft-ietf-bfd-seamless-ip-03
                     draft-ietf-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
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   This Internet-Draft will expire on August 25, October 15, 2016.

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Table of Contents

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

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 [RFC0791]
   [RFC2460], BFD [RFC5880], MPLS BFD [RFC5884], and S-BFD
   [I-D.ietf-bfd-seamless-base] 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: 7784.  SBFDReflector session MUST listen for
   incoming S-BFD control packets on the port 7784.  SBFDInitiator
   sessions MUST transmit S-BFD control packets with destination port
   7784.  The source port of the S-BFD control packets transmitted by
   SBFDInitiator sessions can be any but MUST NOT be 7784.  The same UDP
   source port number MUST be used for all S-BFD control packets
   associated with a particular SBFDInitiator session.  The source port
   number is unique among all SBFDInitiator sessions on the system.

3.  S-BFD Echo UDP Port

   The BFD Echo port defined by [RFC5881], port 3785, is used for the
   S-BFD Echo function on IPv4, IPv6 and MPLS environments.
   SBFDInitiator sessions MUST transmit S-BFD echo packets with
   destination port 3785.  This document defines only the UDP port value
   for the S-BFD Echo function.  The source port and the procedures for
   the S-BFD Echo function are outside the scope of this document.

4.  S-BFD Control Packet Demultiplexing

   The S-BFD Control Packet demultiplexing follows the procedure
   specified in Section 7.1. of [I-D.ietf-bfd-seamless-base].  Received
   S-BFD control packet MUST be demultiplexed with the destination UDP
   port field.

   This procedure for an S-BFD packet is executed on both the initiator
   and the reflector.  If the port is 7784 (i.e., S-BFD packet for
   S-BFDReflector)), 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 7784, 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.  If the packet is a classical BFD
   session, then the procedures from [RFC5880] apply.

5.  Initiator Procedures

   S-BFD control packets are transmitted with IP header, UDP header and
   BFD control header ([RFC5880]).  When S-BFD control 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 control packets.

5.1.  Details of S-BFD Control Packet Sent by SBFDInitiator

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

      *  Source IP address field of the IP header MUST be set to a local
         IP address that is expected to be routable by the target (i.e.
         not IPv6 link-local address when the target is multiple hops
         away).

      *  UDP destination port MUST be set to a well-known UDP
         destination port assigned for S-BFD: 7784.

      *  UDP source port MUST NOT be set to 7784.

   o  Specifications for IP routed S-BFD control 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 control
      packets:

      *  S-BFD control 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,
         as with [RFC5884].

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

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

   Typically, an S-BFD control 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 and not to the target itself.

   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 control packets not be dropped by the
   responder node due to TTL expiry.  Thus implementations on the
   responder MUST allow received S-BFD control packets taking TTL expiry
   exception path to reach corresponding reflector BFD session.

6.  Responder Procedures

   S-BFD control packets are IP routed back to the initiator, and will
   have IP header, UDP header and BFD control header.  If an
   SBFDReflector receives an S-BFD control packet with UDP source port
   as 7784, the packet MUST be discarded.  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
   control packets.

6.1.  Details of S-BFD Control 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 control packet.

   o  Source IP address field of the IP header MUST be set to a local IP
      address that is expected to be visible by the initiator (i.e. not
      IPv6 link-local address when the initiator is multiple hops away).
      The source IP address SHOULD be copied from the destination IP
      address field of the received S-BFD control packet, except when it
      is from the 127/8 range for IPv4 or from the
      0:0:0:0:0:FFFF:7F00/104 range for IPv6.

   o  TTL field of the IP header MUST 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 control packets: [RFC2827].

   o  Implementations MUST NOT act on received S-BFD control packets
      containing source Martian IP addresses (i.e., address that, by
      application of the current forwarding tables, would not have its
      return traffic routed back to the sender.)

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

8.  IANA Considerations

   A new value 7784 was allocated from the "Service Name and Transport
   Protocol Port Number Registry".  The allocated registry entry is:

     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
       RFC.this (RFC Editor, please update at publication)
     Port Number (OPTIONAL)
       7784

9.  Acknowledgements

   The authors would like to thank the BFD WG members for helping to
   shape the contents of this document.  In particular, significant
   contributions were made by following people: Marc Binderberger,
   Jeffrey Haas, Santosh Pallagatti, Greg Mirsky, Sam Aldrin, Vengada
   Prasad Govindan, Mallik Mudigonda and Srihari Raghavan.

10.  Contributing Authors

   Tarek Saad
   Cisco Systems
   Email: tsaad@cisco.com

   Siva Sivabalan
   Cisco Systems
   Email: msiva@cisco.com

   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-07 draft-ietf-bfd-seamless-base-08 (work in
              progress), February 2016.

   [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>.

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
              <http://www.rfc-editor.org/info/rfc5880>.

   [RFC5881]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881,
              DOI 10.17487/RFC5881, June 2010,
              <http://www.rfc-editor.org/info/rfc5881>.

11.2.  Informative References

   [RFC0791]  Postel, J., "Internet Protocol", STD 5, RFC 791,
              DOI 10.17487/RFC0791, September 1981,
              <http://www.rfc-editor.org/info/rfc791>.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
              December 1998, <http://www.rfc-editor.org/info/rfc2460>.

   [RFC2827]  Ferguson, P. and D. Senie, "Network Ingress Filtering:
              Defeating Denial of Service Attacks which employ IP Source
              Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827,
              May 2000, <http://www.rfc-editor.org/info/rfc2827>.

   [RFC5884]  Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
              "Bidirectional Forwarding Detection (BFD) for MPLS Label
              Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884,
              June 2010, <http://www.rfc-editor.org/info/rfc5884>.

Authors' Addresses

   Nobo Akiya
   Big Switch Networks

   Email: nobo.akiya.dev@gmail.com

   Carlos Pignataro
   Cisco Systems

   Email: cpignata@cisco.com

   Dave Ward
   Cisco Systems

   Email: wardd@cisco.com