wdiff rfc7881.alt-original rfc7881.txt

Internet Engineering Task Force (IETF) C. Pignataro
Internet-Draft
Request for Comments: 7881 D. Ward
Intended status:
Category: Standards Track Cisco
Expires: November 7, 2016
ISSN: 2070-1721 N. Akiya
Big Switch Networks
May 6,
July 2016

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

Abstract

This document defines procedures to use for using Seamless Bidirectional
Forwarding Detection (S-BFD) for in IPv4, IPv6 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 an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force
(IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid the IETF community. It has
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Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of six months RFC 7841.

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This Internet-Draft will expire on November 7, 2016.
http://www.rfc-editor.org/info/rfc7881.

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Table of Contents

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

1. Introduction

Seamless Bidirectional Forwarding Detection (S-BFD),
[I-D.ietf-bfd-seamless-base], (S-BFD) [RFC7880] defines
a generalized mechanism to allow network nodes to seamlessly perform
continuity checks to remote entities. This document defines
necessary procedures to use for using S-BFD on in IPv4, IPv6 IPv6, and MPLS
environments.

The reader is expected to be familiar with the IP [RFC0791] [RFC791] [RFC2460],
BFD [RFC5880], MPLS BFD [RFC5884], and S-BFD
[I-D.ietf-bfd-seamless-base] terminologies [RFC7880] terms and
protocol constructs.

2. S-BFD UDP Port

A new UDP port is defined for the use of the by S-BFD on in IPv4, IPv6 IPv6, and MPLS
environments: 7784.

In S-BFD control Control packets from the SBFDInitiator to the SBFDReflector,
the SBFDReflector session MUST listen for incoming S-BFD control Control
packets on the port 7784. SBFDInitiator sessions MUST transmit S-BFD
control
Control packets with destination port 7784. The source port of the
S-BFD control Control packets transmitted by SBFDInitiator sessions can be
any but port, with one exception: it MUST NOT be 7784. The same UDP
source port number MUST be used for all S-BFD control Control packets
associated with a particular SBFDInitiator session. The source port
number is unique among all SBFDInitiator sessions on the system.

In S-BFD control Control packets from the SBFDReflecto SBFDReflector to the SBFDInitiator,
the SBFDInitiator session MUST listen for reflected S-BFD control 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 in IPv4, IPv6 IPv6, and MPLS environments.
SBFDInitiator sessions MUST transmit S-BFD echo Echo packets with
destination port 3785. The setting of the UDP source port [RFC5881]
and the procedures [I-D.ietf-bfd-seamless-base] [RFC7880] for the S-BFD Echo function are outside
the scope of this document.

4. S-BFD Control Packet Demultiplexing

The

S-BFD Control Packet packet demultiplexing follows the procedure specified
in Section 7.1. 7.1 of [I-D.ietf-bfd-seamless-base]. Received [RFC7880]. A received S-BFD control 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., an S-BFD packet for
S-BFDReflector),
the SBFDReflector), then the packet MUST be looked up to locate a
corresponding SBFDReflector session based on the value from the "your
discriminator"
Your Discriminator field in the table describing S-BFD discriminators.
Discriminators. If the port is not 7784, 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" Your Discriminator field in the table describing
BFD discriminators. 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 Control packets are transmitted with an IP header, UDP header header,
and BFD control header Control packet ([RFC5880]). When S-BFD control Control packets are
explicitly label switched (i.e. (i.e., not IP routed which happen to go and forwarded over
an LSP, a
Label Switched Path (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, scenario; both scenarios are supported.

The necessary values in the BFD control headers are described in
[I-D.ietf-bfd-seamless-base].
[RFC7880]. Section 5.1 describes necessary values in the MPLS
header, IP header header, and UDP header when an SBFDInitiator on the
initiator is sending S-BFD control Control packets.

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

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

* The Source IP address 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.
(i.e., not an IPv6 link-local address when the target is
multiple hops away).

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

* The UDP source port MUST NOT be set to 7784.

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

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

* The TTL/Hop TTL / Hop Limit field of the IP header SHOULD be set
to 255.

o Specifications for explicitly label switched label-switched S-BFD control Control
packets:

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

* The TTL field of the top most topmost 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 0:0:0:0:0:ffff:7f00:0/104 range for IPv6,
as with per [RFC5884].

* The TTL/Hop TTL / Hop Limit field of the IP header MUST be set to 1.

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

Typically, an S-BFD control Control packet will have "your discriminator" the Your Discriminator
field corresponding to an S-BFD discriminator 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" 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.

Section 5.1 intentionally uses the word "target", "target" instead of "remote
entity",
entity" to accommodate this possible S-BFD usage through TTL expiry.
This also requires that S-BFD control Control packets not be dropped by the
responder node due to TTL expiry. Thus Thus, implementations on the
responder MUST allow received S-BFD control Control packets taking a TTL
expiry exception path to reach the corresponding reflector BFD SBFDReflector
session. This is an existing packet processing packet-processing exception practice
for OAM Operations, Administration, and Maintenance (OAM) packets, where
the control plane further identifies the type of OAM by the protocol
and port numbers.

6. Responder Procedures

S-BFD control Control packets are IP routed back to the initiator, initiator and will
have an IP header, UDP header header, and BFD control header. If an
SBFDReflector receives an S-BFD control Control packet with a UDP source port
as
of 7784, the packet MUST be discarded. Necessary values in the BFD
control header are described in [I-D.ietf-bfd-seamless-base]. [RFC7880]. Section 6.1 describes
necessary values in the IP header and UDP header when an
SBFDReflector on the responder is sending S-BFD
control Control packets.

6.1. Details of S-BFD Control Packet Packets Sent by SBFDReflector

o The Destination IP address Address field of the IP header MUST be copied
from
source the Source IP address Address field of the received S-BFD control Control
packet.

o The Source IP address Address field of the IP header MUST be set to a
local IP address that is expected the initiator expects to be visible by the initiator (i.e. (i.e.,
not an IPv6 link-local address when the initiator is multiple hops
away). The source IP address SHOULD be copied from the destination
Destination IP
address Address field of the received S-BFD control 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
0:0:0:0:0:ffff:7f00:0/104 range for IPv6.

o The TTL/Hop TTL / Hop Limit field of the IP header MUST be set to 255.

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

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

7. Security Considerations

Security considerations for S-BFD are discussed in
[I-D.ietf-bfd-seamless-base]. [RFC7880].
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: Control packets; see [RFC2827].

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

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

8. IANA Considerations

A new value 7784 port number 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>
IETF Chair <chair@ietf.org>

Description (REQUIRED)
Seamless Bidirectional Forwarding Detection (S-BFD)

Reference (REQUIRED)
RFC.this (RFC Editor, please update at publication)
RFC 7881

Port Number (OPTIONAL)
7784

11.

9. References

11.1.

9.1. 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.

[RFC7880] Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S.
Pallagatti, "Seamless Bidirectional Forwarding Detection
(S-BFD)", RFC 7880, DOI 10.17487/RFC7880, July 2016,
<http://www.rfc-editor.org/info/rfc7880>.

9.2. Informative References

[RFC0791]

[RFC791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, 10.17487/RFC791, 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>.

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 the following people: Marc Binderberger,
Jeffrey Haas, Santosh Pallagatti, Greg Mirsky, Sam Aldrin, Vengada
Prasad Govindan, Mallik Mudigonda Mudigonda, and Srihari Raghavan.

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.

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