One document matched: draft-ietf-bfd-seamless-ip-05.xml
<?xml version="1.0" encoding="US-ASCII"?>
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<rfc category="std" docName="draft-ietf-bfd-seamless-ip-05" ipr="trust200902">
<!-- category values: std, bcp, info, exp, and historic
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<!-- ***** FRONT MATTER ***** -->
<front>
<title abbrev="Seamless BFD for IP">
Seamless Bidirectional Forwarding Detection (S-BFD) for IPv4, IPv6 and MPLS
</title>
<!-- add 'role="editor"' below for the editors if appropriate -->
<!-- Another author who claims to be an editor -->
<author fullname="Nobo Akiya" initials="N."
surname="Akiya">
<organization>Big Switch Networks</organization>
<address>
<email>nobo.akiya.dev@gmail.com</email>
</address>
</author>
<author fullname="Carlos Pignataro" initials="C."
surname="Pignataro">
<organization abbrev="Cisco">Cisco Systems, Inc.</organization>
<address>
<email>cpignata@cisco.com</email>
</address>
</author>
<author fullname="Dave Ward" initials="D."
surname="Ward">
<organization abbrev="Cisco">Cisco Systems, Inc.</organization>
<address>
<email>wardd@cisco.com</email>
</address>
</author>
<date />
<area>BFD Working Group</area>
<workgroup>Internet Engineering Task Force</workgroup>
<!-- WG name at the upperleft corner of the doc,
IETF is fine for individual submissions.
If this element is not present, the default is "Network Working Group",
which is used by the RFC Editor as a nod to the history of the IETF. -->
<keyword>BFD</keyword>
<keyword>seamless BFD</keyword>
<keyword>negotiation free</keyword>
<keyword>label verification</keyword>
<keyword>segment routing</keyword>
<keyword>IP</keyword>
<!-- Keywords will be incorporated into HTML output
files in a meta tag but they have no effect on text or nroff
output. If you submit your draft to the RFC Editor, the
keywords will be used for the search engine. -->
<abstract>
<t>This document defines procedures to use Seamless Bidirectional Forwarding Detection (S-BFD) for IPv4, IPv6 and MPLS environments.</t>
</abstract>
<note title="Requirements Language">
<t>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 <xref target="RFC2119">RFC 2119</xref>.</t>
</note>
</front>
<middle>
<section title="Introduction">
<t>Seamless Bidirectional Forwarding Detection (S-BFD), <xref target="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.</t>
<t>The reader is expected to be familiar with the IP
<xref target="RFC0791" /> <xref target="RFC2460" />,
BFD <xref target="RFC5880" />,
MPLS BFD <xref target="RFC5884" />,
and S-BFD <xref target="I-D.ietf-bfd-seamless-base" />
terminologies and protocol constructs.
</t>
</section>
<section title="S-BFD UDP Port">
<t>A new UDP port is defined for the use of the S-BFD on IPv4, IPv6 and MPLS environments: 7784.
</t><t>
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 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.</t>
<t>
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.
</t>
</section>
<section title="S-BFD Echo UDP Port">
<t>The BFD Echo port defined by <xref target="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 <xref target="RFC5881" /> and the procedures <xref target="I-D.ietf-bfd-seamless-base" />
for the S-BFD Echo function are outside the scope of this document.</t>
</section>
<section title="S-BFD Control Packet Demultiplexing">
<t>
The S-BFD Control Packet demultiplexing follows the procedure specified in Section 7.1. of <xref target="I-D.ietf-bfd-seamless-base" />.
Received S-BFD control packet MUST be demultiplexed with the destination UDP port field.
</t><t>
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 <xref target="RFC5880" /> apply.
</t>
</section>
<section title="Initiator Procedures">
<t>S-BFD control packets are transmitted with IP header, UDP header and BFD control header (<xref target="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.</t>
<t>Necessary values in the BFD control headers are described in <xref target="I-D.ietf-bfd-seamless-base" />. <xref target="_init_pak" /> describes necessary values in the MPLS header, IP header and UDP header when an SBFDInitiator on the initiator is sending S-BFD control packets.</t>
<section title="Details of S-BFD Control Packet Sent by SBFDInitiator" anchor="_init_pak">
<t>
<list style="symbols">
<t>Specifications common to both IP routed S-BFD control packets and explicitly label switched S-BFD control packets:
<list style="symbols">
<t>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).</t>
<t>UDP destination port MUST be set to a well-known UDP destination port assigned for S-BFD: 7784.</t>
<t>UDP source port MUST NOT be set to 7784.</t>
</list>
</t>
<t>Specifications for IP routed S-BFD control packets:
<list style="symbols">
<t>Destination IP address field of the IP header MUST set to an IP address of the target.</t>
<t>TTL field of the IP header SHOULD be set to 255.</t>
</list>
</t>
<t>Specifications for explicitly label switched S-BFD control packets:
<list style="symbols">
<t>S-BFD control packets MUST have the label stack that is expected to reach the target.</t>
<t>TTL field of the top most label SHOULD be 255.</t>
<t>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 <xref target="RFC5884" />.</t>
<t>TTL field of the IP header MUST be set to 1.</t>
</list>
</t>
</list>
</t>
<section title="Target vs. Remote Entity (S-BFD Discriminator)">
<t>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 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.</t>
<t><xref target="_init_pak" /> 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.</t>
</section>
</section>
</section>
<section title="Responder Procedures">
<t>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 <xref target="I-D.ietf-bfd-seamless-base" />. <xref target="_resp_pak" /> describes necessary values in the IP header and UDP header when an SBFDReflector on the responder is sending S-BFD control packets.</t>
<section title="Details of S-BFD Control Packet Sent by SBFDReflector" anchor="_resp_pak">
<t>
<list style="symbols">
<t>Destination IP address field of the IP header MUST be copied from source IP address field of received S-BFD control packet.</t>
<t>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.</t>
<t>TTL field of the IP header MUST be set to 255.</t>
<t>UDP destination port MUST be copied from received UDP source port.</t>
<t>UDP source port MUST be copied from received UDP destination port.</t>
</list>
</t>
</section>
</section>
<section anchor="Security" title="Security Considerations">
<t>Security considerations for S-BFD are discussed in <xref target="I-D.ietf-bfd-seamless-base" />. Additionally, implementing the following measures will strengthen security aspects of the mechanism described by this document:
<list style="symbols">
<t>Implementations MUST provide filtering capability based on source IP addresses of received S-BFD control packets: <xref target="RFC2827" />.</t>
<t>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.)
</t>
<t>Implementations MUST ensure that response S-BFD control packets generated to the initiator by the SBFDReflector have a reachable target (ex: destination IP address).</t>
</list>
</t>
</section>
<section anchor="IANA" title="IANA Considerations">
<t>A new value 7784 was allocated from the "Service Name and Transport Protocol Port Number Registry". The allocated registry entry is:
<figure align="left"><preamble></preamble><artwork align="left"><![CDATA[
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
]]></artwork></figure>
</t>
</section>
<section title="Acknowledgements">
<t>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.</t>
</section>
<section title="Contributors">
<t>The following are key contributors to this document:
<list style="empty">
<?rfc subcompact="yes" ?>
<t>Tarek Saad, Cisco Systems, Inc.
</t>
<t>Siva Sivabalan, Cisco Systems, Inc.
</t>
<t>Nagendra Kumar, Cisco Systems, Inc.
</t>
</list>
<?rfc subcompact="no" ?>
</t>
<!--
<t>Tarek Saad
<vspace blankLines="0" />
Cisco Systems
<vspace blankLines="0" />
Email: tsaad@cisco.com</t>
<t>Siva Sivabalan
<vspace blankLines="0" />
Cisco Systems
<vspace blankLines="0" />
Email: msiva@cisco.com</t>
<t>Nagendra Kumar
<vspace blankLines="0" />
Cisco Systems
<vspace blankLines="0" />
Email: naikumar@cisco.com</t>
-->
</section>
</middle>
<!-- *****BACK MATTER ***** -->
<back>
<!-- References split into informative and normative -->
<references title="Normative References">
<?rfc include="reference.RFC.2119"?>
<?rfc include="reference.RFC.5880"?>
<?rfc include="reference.RFC.5881"?>
<?rfc include="reference.I-D.ietf-bfd-seamless-base"?>
</references>
<references title="Informative References">
<?rfc include="reference.RFC.2827"?>
<?rfc include="reference.RFC.5884"?>
<?rfc include="reference.RFC.0791"?>
<?rfc include="reference.RFC.2460"?>
</references>
<!-- Change Log
v00-a 2013-05-20 Nobo: Initial version
v00-b 2013-05-24 Nobo: Included comments from Carlos/Nagendra
v00-c 2013-05-27 Nobo: Incorporated comments from Marc
v01-a 2013-12-04 Nobo: Minor tweak to keep draft alive
v03-a 2014-06-24 Nobo: Major rewrite to align with new base
-->
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-23 10:53:15 |