draft-ietf-bfd-v4v6-1hop-08.txt   draft-ietf-bfd-v4v6-1hop-09.txt 
Network Working Group D. Katz Network Working Group D. Katz
Internet Draft Juniper Networks Internet Draft Juniper Networks
D. Ward Intended status: Proposed Standard D. Ward
Cisco Systems Cisco Systems
Expires: September, 2008 March, 2008 Expires: August, 2009 February 5, 2009
BFD for IPv4 and IPv6 (Single Hop) BFD for IPv4 and IPv6 (Single Hop)
draft-ietf-bfd-v4v6-1hop-08.txt draft-ietf-bfd-v4v6-1hop-09.txt
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Abstract Abstract
This document describes the use of the Bidirectional Forwarding This document describes the use of the Bidirectional Forwarding
Detection protocol over IPv4 and IPv6 for single IP hops. Comments Detection protocol over IPv4 and IPv6 for single IP hops.
on this draft should be directed to rtg-bfd@ietf.org.
Conventions used in this document Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [KEYWORDS]. document are to be interpreted as described in RFC-2119 [KEYWORDS].
1. Introduction 1. Introduction
One very desirable application for BFD [BFD] is to track IPv4 and One very desirable application for BFD [BFD] is to track IPv4 and
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[BFD-GENERIC]. [BFD-GENERIC].
2. Applications and Limitations 2. Applications and Limitations
This application of BFD can be used by any pair of systems This application of BFD can be used by any pair of systems
communicating via IPv4 and/or IPv6 across a single IP hop that is communicating via IPv4 and/or IPv6 across a single IP hop that is
associated with an incoming interface. This includes, but is not associated with an incoming interface. This includes, but is not
limited to, physical media, virtual circuits, and tunnels. limited to, physical media, virtual circuits, and tunnels.
Each BFD session between a pair of systems MUST traverse a separate Each BFD session between a pair of systems MUST traverse a separate
path in both directions. network-layer path in both directions. This is necessary for
demultiplexing to work properly, and also because (by definition)
multiple sessions would otherwise be protecting the same path.
If BFD is to be used in conjunction with both IPv4 and IPv6 on a If BFD is to be used in conjunction with both IPv4 and IPv6 on a
particular link, a separate BFD session MUST be established for each particular path, a separate BFD session MUST be established for each
protocol (and thus encapsulated by that protocol) over that link. protocol (and thus encapsulated by that protocol) over that link.
If the BFD Echo function is used, transmitted packets are immediately
routed back towards the sender on the interface over which they were
sent. This may interact with other mechanisms that are used on the
two systems that employ BFD. In particular, ingress filtering [BCP38]
is incompatible with the way Echo packets need to be sent.
Implementations that support the Echo function MUST either ensure
that ingress filtering is not used on an interface that employs the
Echo function, or need make an exception for ingress filtering Echo
packets.
An implementation of the Echo function also requires Application
Programming Interfaces (APIs) that may not exist on all systems. A
system implementing the Echo function MUST be capable of sending
packets to its own address, which will typically require bypassing
the normal forwarding lookup. This typically requires access to APIs
that bypass IP layer functionality.
3. Initialization and Demultiplexing 3. Initialization and Demultiplexing
In this application, there will be only a single BFD session between In this application, there will be only a single BFD session between
two systems over a given interface (logical or physical) for a two systems over a given interface (logical or physical) for a
particular protocol. The BFD session must be bound to this particular protocol. The BFD session must be bound to this
interface. As such, both sides of a session MUST take the "Active" interface. As such, both sides of a session MUST take the "Active"
role (sending initial BFD Control packets with a zero value of Your role (sending initial BFD Control packets with a zero value of Your
Discriminator) and any BFD packet from the remote machine with a zero Discriminator) and any BFD packet from the remote machine with a zero
value of Your Discriminator MUST be associated with the session bound value of Your Discriminator MUST be associated with the session bound
to the remote system, interface, and protocol. to the remote system, interface, and protocol.
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If BFD authentication is not in use on a session, all BFD Control If BFD authentication is not in use on a session, all BFD Control
packets for the session MUST be sent with a TTL or Hop Limit value of packets for the session MUST be sent with a TTL or Hop Limit value of
255. All received BFD Control packets that are demultiplexed to the 255. All received BFD Control packets that are demultiplexed to the
session MUST be discarded if the received TTL or Hop Limit is not session MUST be discarded if the received TTL or Hop Limit is not
equal to 255. A discussion of this mechanism can be found in [GTSM]. equal to 255. A discussion of this mechanism can be found in [GTSM].
If BFD authentication is in use on a session, all BFD Control packets If BFD authentication is in use on a session, all BFD Control packets
MUST be sent with a TTL or Hop Limit value of 255. All received BFD MUST be sent with a TTL or Hop Limit value of 255. All received BFD
Control packets that are demultiplexed the session MAY be discarded Control packets that are demultiplexed the session MAY be discarded
if the received TTL or Hop Limit is not equal to 255. if the received TTL or Hop Limit is not equal to 255. If the TTL/Hop
Limit check is made, it MAY be done before any cryptographic
authentication takes place if this will avoid unnecessary calculation
that would be detrimental to the receiving system.
In the context of this section, "authentication in use" means that In the context of this section, "authentication in use" means that
the system is sending BFD control packets with the Authentication bit the system is sending BFD control packets with the Authentication bit
set and with the Authentication Section included, and that all set and with the Authentication Section included, and that all
unauthenticated packets demultiplexed to the session are discarded, unauthenticated packets demultiplexed to the session are discarded,
per the BFD base specification. per the BFD base specification.
6. Addressing Issues 6. Addressing Issues
Implementations MUST ensure that all BFD Control packets are Implementations MUST ensure that all BFD Control packets are
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7. BFD for use with Tunnels 7. BFD for use with Tunnels
A number of mechanisms are available to tunnel IPv4 and IPv6 over A number of mechanisms are available to tunnel IPv4 and IPv6 over
arbitrary topologies. If the tunnel mechanism does not decrement the arbitrary topologies. If the tunnel mechanism does not decrement the
TTL or Hop Limit of the network protocol carried within, the TTL or Hop Limit of the network protocol carried within, the
mechanism described in this document may be used to provide liveness mechanism described in this document may be used to provide liveness
detection for the tunnel. The BFD Authentication mechanism SHOULD be detection for the tunnel. The BFD Authentication mechanism SHOULD be
used and is strongly encouraged. used and is strongly encouraged.
Normative References 8. IANA Considerations
[BFD] Katz, D., and Ward, D., "Bidirectional Forwarding Detection",
draft-ietf-bfd-base-07.txt, January, 2008.
[BFD-GENERIC] Katz, D., and Ward, D., "Generic Application of BFD",
draft-ietf-bfd-generic-04.txt, January, 2008.
[GTSM] Gill, V., et al, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, October, 2007.
[KEYWORD] Bradner, S., "Key words for use in RFCs to Indicate This document has no actions for IANA.
Requirement Levels", RFC 2119, March 1997.
Security Considerations 9. Security Considerations
In this application, the use of TTL=255 on transmit and receive, In this application, the use of TTL=255 on transmit and receive,
coupled with an association to an incoming interface, is viewed as coupled with an association to an incoming interface, is viewed as
supplying equivalent security characteristics to other protocols used supplying equivalent security characteristics to other protocols used
in the infrastructure, as it is not trivially spoofable. The in the infrastructure, as it is not trivially spoofable. The
security implications of this mechanism are further discussed in security implications of this mechanism are further discussed in
[GTSM]. [GTSM].
The security implications of the use of BFD Authentication are The security implications of the use of BFD Authentication are
discussed in [BFD]. discussed in [BFD].
The use of the TTL=255 check simultaneously with BFD Authentication The use of the TTL=255 check simultaneously with BFD Authentication
provides a low overhead mechanism for discarding a class of provides a low overhead mechanism for discarding a class of
unauthorized packets and may be useful in implementations in which unauthorized packets and may be useful in implementations in which
cryptographic checksum use is susceptable to denial of service cryptographic checksum use is susceptible to denial of service
attacks. The use or non-use of this mechanism does not impact attacks. The use or non-use of this mechanism does not impact
interoperability. interoperability.
IANA Considerations 10. References
This document has no actions for IANA. 10.1. Normative References
[BFD] Katz, D., and Ward, D., "Bidirectional Forwarding Detection",
draft-ietf-bfd-base-09.txt, February, 2009.
[BFD-GENERIC] Katz, D., and Ward, D., "Generic Application of BFD",
draft-ietf-bfd-generic-05.txt, February, 2009.
[GTSM] Gill, V., et al, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, October, 2007.
[KEYWORD] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
10.2. Informative References
[BCP38] Ferguson, P, and Senie, D., "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP Source Address
Spoofing", RFC 2827, May 2000.
Authors' Addresses Authors' Addresses
Dave Katz Dave Katz
Juniper Networks Juniper Networks
1194 N. Mathilda Ave. 1194 N. Mathilda Ave.
Sunnyvale, California 94089-1206 USA Sunnyvale, California 94089-1206 USA
Phone: +1-408-745-2000 Phone: +1-408-745-2000
Email: dkatz@juniper.net Email: dkatz@juniper.net
Dave Ward Dave Ward
Cisco Systems Cisco Systems
170 W. Tasman Dr. 170 W. Tasman Dr.
San Jose, CA 95134 USA San Jose, CA 95134 USA
Phone: +1-408-526-4000 Phone: +1-408-526-4000
Email: dward@cisco.com Email: dward@cisco.com
Changes from the previous draft Changes from the previous draft
Section 6 was changed to lump all point-to-point link types together. Only minor editorial changes were made.
Otherwise, only minor editorial changes were made.
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