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Versions: (draft-akiya-bfd-seamless-ip) 00 01 02 03 04 05 06 RFC 7881

Internet Engineering Task Force                             C. Pignataro
Internet-Draft                                                   D. Ward
Intended status: Standards Track                                   Cisco
Expires: November 7, 2016                                       N. Akiya
                                                     Big Switch Networks
                                                             May 6, 2016


        Seamless Bidirectional Forwarding Detection (S-BFD) for
                          IPv4, IPv6 and MPLS
                     draft-ietf-bfd-seamless-ip-06

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 7, 2016.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of



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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   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 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 . . . . . . . . . . . . . . . . . . .   6
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   10. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   7
   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.

   On S-BFD control packets from the SBFDInitiator to the SBFDReflector,
   the 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



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   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.

   On S-BFD control packets from the SBFDReflecto to the SBFDInitiator,
   the SBFDInitiator MUST listen for reflected S-BFD control packets at
   its source port.

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.  The setting of the UDP source port [RFC5881]
   and the procedures [I-D.ietf-bfd-seamless-base] 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, but the packet is demultiplexed to be for an
   SBFDInitiator, then the packet MUST be looked up to locate a
   corresponding SBFDInitiator session based on the value from the "your
   discriminator" field in the table describing BFD discriminators.  In
   that case, then the destination IP address of the packet SHOULD be
   validated to be for itself.  If the packet demultiplexes to 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.



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   The 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.

      *  The TTL/Hop Limit 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:7F00:0/104 range for IPv6,
         as with [RFC5884].

      *  The TTL/Hop Limit 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 the "your discriminator" and TTL



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   fields to perform a continuity test in the direction towards a
   target, but destined 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.  This is
   an existing packet processing exception practice for OAM packets,
   where the control plane further identifies the type of OAM by the
   protocol and port numbers.

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:7F00:0/104 range for IPv6.

   o  The TTL/Hop Limit 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.








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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@ietf.org>
     Description (REQUIRED)
       Seamless Bidirectional Forwarding Detection (S-BFD)
     Reference (REQUIRED)
       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.





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10.  Contributors

   The following are key contributors to this document:

      Tarek Saad, Cisco Systems, Inc.
      Siva Sivabalan, Cisco Systems, Inc.
      Nagendra Kumar, Cisco Systems, Inc.

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-09 (work in
              progress), April 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>.





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   [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

   Carlos Pignataro
   Cisco Systems, Inc.

   Email: cpignata@cisco.com


   Dave Ward
   Cisco Systems, Inc.

   Email: wardd@cisco.com


   Nobo Akiya
   Big Switch Networks

   Email: nobo.akiya.dev@gmail.com




























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