Network Working Group V. Manral
Internet-Draft HP Networking
Intended status: Standards Track D. Eastlake
Expires: November 3, 2011 Huawei
D. Ward
Juniper Networks
A. Banerjee
Cisco Systems
May 02, 2011
Rbridges: Bidirectional Forwarding Detection (BFD) support for TRILL
draft-ietf-trill-rbridge-bfd-00
Abstract
This document specifies use of the BFD (Bidirectional Forwarding
Detection) protocol in RBridge campuses based on the Rbridge Channel
extension to the TRILL (TRansparent Interconnection of Lots of Links)
protocol.
BFD is a widely deployed (Operations, Administration and Maintenance)
OAM mechanism in IP and MPLS networks. However, in the present form
a BFD packet cannot be sent over a TRILL network as it is either IP/
UDP encapsulated or encapsulated directly over Multi Protocol Label
Switching (MPLS) or using Associated Channel Header (ACH)
encapsulation. This document defines BFD encapsulation over TRILL to
address this shortcoming.
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 [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
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 3, 2011.
Copyright Notice
Copyright (c) 2011 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. BFD over TRILL . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Sessions and Initialization . . . . . . . . . . . . . . . . . . 5
5. Relationship to MPLS OAM . . . . . . . . . . . . . . . . . . . 6
6. TRILL BFD Control Protocol . . . . . . . . . . . . . . . . . . 6
6.1. One-Hop TRILL BFD Control . . . . . . . . . . . . . . . . . 7
6.2. BFD Control Frame Processing . . . . . . . . . . . . . . . 7
7. TRILL BFD Echo Protocol . . . . . . . . . . . . . . . . . . . . 8
7.1. BFD Echo Frame Processing . . . . . . . . . . . . . . . . . 8
8. Management and Operations Considerations . . . . . . . . . . . 9
9. Security Considerations . . . . . . . . . . . . . . . . . . . . 9
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 9
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
12.1. Normative References . . . . . . . . . . . . . . . . . . . 10
12.1. Informative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
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1. Introduction
Faster convergence is a very critical feature of TRILL networks. The
TRILL IS-IS Hellos [TRILLAdj] used between RBridges provide a basic
neighbor and continuity check for TRILL links. However, failure
detection by non-receipt of such Hellos is based on the holding time
parameter which is commonly set to a value of tens of seconds and, in
any case, has a minimum expressible value of one second.
Some applications, including Voice over IP, may wish, with high
probability, to detect interruptions in continuity within a much
shorter time period. In some cases physical layer failures can be
detected very rapidly but this is not always possible, such as when
there is a failure between two bridges that are in turn between two
RBridges. There are also many subtle failures possible at higher
levels. For example, some forms of failure could affect unicast
frames while still letting multicast frames through; since all TRILL
IS-IS Hellos are multicast such a failure cannot be detected with
Hellos. Thus, a low overhead method for frequently testing
continuity for the TRILL Data between neighbor RBridges is necessary
for some applications. BFD protocol provides a low-overhead, short-
duration detection of failures in the path between forwarding
engines.
This document describes a TRILL encapsulation for BFD packets between
Rbridges using the Rbridge Channel facility [TRILLChannel].
2. Terminology
ACH: Assiciated Channel Header
BFD: Bi-directional Forwarding Detection
GTSM: Generalized TTL Security Mechanism
IP: Internet Protocol
IS-IS: Intermediate-System to Intermediate-System
MPLS: Multi Protocol Label Switching
OAM: Operations, Administration, and Maintenance
PPP: Point-to-Point Protocol
TRILL: Transparent Interconnection of Lots of Links
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TTL: Time To Live
UDP: User Datagram Protocol
3. BFD over TRILL
TRILL supports neighbor BFD Echo and one-hop and multi-hop BFD
Control, as specified below, over the TRILL Rbridge Channel facility.
Multi-destination BFD is beyond the scope of this document. The
Rbridge Channel facility is specified in [TRILLChannel].
BFD over TRILL support is similar to BFD over IP support except where
it is explicitly so mentioned. When running BFD over TRILL both
Single Hop as well as in Multi Hop sessions are supported.
Asynchronous mode is supported, and the demand mode is not supported
for TRILL. BFD over TRILL supports the Echo function, however this
can be used for only Single hop sessions.
The TRILL Header Hop Count in the BFD packets is sent out with a
value of 63. To reduce spoofing attacks, the TRILL Hop Count of a
received frame is checked. For a Single Hop session if the Hop count
is less than 63 the packet is discarded if the GTSM mode [RFC5082] is
set. For Multi Hop sessions the Hop count check can be disabled or
the bfdTrillAcceptedHopCount value can be configured. If a packet is
received with a hop count of less than bfdTrillAcceptedHopCount, the
packet is discarded.
Like in BFD for IP the format of the Echo Packet is not defined.
A new channel type for the BFD TRILL Control frame as well as for BFD
Echo packet is defined.
Authentication mechanisms as supported in BFD are also supported for
BFD running over TRILL.
4. Sessions and Initialization
Within an RBridge campus, there will be only a single TRILL BFD
Control session between two RBridges over a given link visible to
TRILL. This BFD session must be bound to this link. Any BFD packet
from the remote machine with a zero value of Your Discriminator MUST
be associated with the session bound to the remote system and link.
Note that TRILL BFD provides OAM facilities for the TRILL Data plane.
This is above whatever protocol is in use on a particular link, such
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as a Point-to-Point Protocol (PPP) [TrillPPP] link or an Ethernet
link. Link technology specific OAM protocols may be used on a link
between neighbor RBridges, for example Continuity Fault Management
[802.1ag] if the link is Ethernet. But such link layer OAM and
coordination between it and TRILL data plane layer OAM, such as TRILL
BFD, is beyond the scope of this document.
If lower level mechanisms, such as link aggregation [802.1AX], are in
use that present a single logical interface to TRILL IS-IS, only a
single TRILL BFD session can be established to any other RBridge over
this logical interface. However, lower layer OAM could be aware of
and/or run separately on each of the components of an aggregation.
5. Relationship to MPLS OAM
TRILL BFD uses the TRILL Rbridge Channel [TRILLChannel] in the same
way that MPLS OAM protocols use the MPLS Generic Associated Channel
[RFC5586]. However, the RBridges that implement TRILL are IS-IS
[IS-IS] based routers, not label switched routers; thus TRILL BFD is
closer to IPv4/IPv6 BFD than to MPLS BFD.
TRILL BFD optionally includes support of BFD Echo which is not
specified for MPLS BFD.
6. TRILL BFD Control Protocol
TRILL BFD Control frames are unicast TRILL OAM Message Channel frames
[TRILLChannel]. The TRILL Rbridge Protocol value is given in Section
10.
The protocol specific data associated with the TRILL BFD Control
protocol is as shown below. See [RFC5880] for further information on
these fields.
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TRILL BFD Control Protocol Data:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Vers | Diag |Sta|P|F|C|A|D|M| Detect Mult | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| My Discriminator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Your Discriminator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Desired Min TX Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Required Min RX Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Required Min Echo RX Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Optional Authentication Section:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Auth Type | Auth Len | Authentication Data... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
6.1. One-Hop TRILL BFD Control
One-hop TRILL BFD Control is typically used to rapidly detect link
and RBridge failures. TRILL BFD frames over one hop for such
purposes SHOULD be sent with priority 7.
For neighbor RBridges RB1 and RB2, each RBridge sends one-hop TRILL
BFD Control frames to the other only if TRILL IS-IS has detected bi-
directional connectivity, that is, the adjacency is in the Two-Way or
report states [TRILLAdj] and both RBridges indicate support of TRILL
BFD is enabled. The BFD Enabled TLV is used to indicate this as
specified in [RFC6213].
6.2. BFD Control Frame Processing
The following tests MUST be performed on received TRILL BFD Control
frames before generic BFD processing.
If the M bit in the TRILL Header is non-zero, discard the frame.
TRILL support of multi-destination BFD Control is beyond the scope of
this document.
If the OAM Header MH flag is zero, indicating one-hop, test that the
TRILL Header hop count received was 0x3F (i.e., is 0x3E if it has
already been decremented) and if it is any other value discard the
frame. If the MH OAM flag is one, indicating multi-hop, test that
the TRILL Header hop count received was not less than a configurable
value (bfdTrillAcceptedHopCount) that defaults to 0x30. If it is
less, discard the frame.
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7. TRILL BFD Echo Protocol
A TRILL BFD Echo frame is a unicast TRILL Rbridge Channel frame, as
specified in [TRILLChannel], which should be bounced back by an
immediate neighbor because both the ingress and egress nicknames are
set to a nickname of the originating RBridge. Normal TRILL Data
frame forwarding will cause the frame to be returned. The Rbridge
Channel protocol number for BFD Echo is given in Section 10.
TRILL BFD Echo frames SHOULD only be sent on a link if
1. A TRILL BFD Control session has been established,
2. TRILL BFD Echo support is indicated by the potentially echo
responding RBridge, and
3. The adjacency is in the Report state [TRILLAdj], and
4. The TRILL BFD Echo originating RBridge wishes to make use of this
optional feature.
Since the originating RBridge is the RBridge that will be processing
a returned Echo frame, the entire TRILL BFD Echo protocol specific
data area is considered opaque and left to the discretion of the
originating RBridge. Nevertheless, it is RECOMMENDED that this data
include information by which the originating RBridge can authenticate
the returned BFD Echo frame and confirm the neighbor that echoed the
frame back. For example, it could include its own SystemID, the
neighbor's SystemID, a session identifier and a sequence count as
well as a Message Authentication Code.
7.1. BFD Echo Frame Processing
The following tests MUST be performed on returned TRILL BFD Echo
frames before other processing. The RBridge Channel document now
requires that the information in the TRILL Header be given to the OAM
protocol.
If the M-bit in the TRILL Header is non-zero, discard the frame.
TRILL support of multi-destination BFD Echo is beyond the scope of
this document.
The TRILL BFD Echo frame should have gone exactly two hops so test
that the TRILL Header hop count as received was 0x3E (i.e., 0x3D if
it has already been decremented) and if it is any other value discard
the frame. The TRILL Rbridge Channel Header in the frame should have
the MH bit equal to one and if it is zero, the frame is discarded.
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8. Management and Operations Considerations
The TRILL BFD parameters on an RBridge are configurable. The default
values are the same as in the IP BFD case, except where specified in
this document i.e. Hop Count.
It is required that the operator of an RBridge campus configure the
rates at which TRILL BFD frames are transmitted on a link to avoid
congestion (e.g., link, I/O, CPU) and false failure detection.
9. Security Considerations
This draft raises no new security considerations than those already
mentioned in the BFD [RFC5880]. By keeping a seperate flag for
Single Hop and Multihop sessions it allows the TTL check to be
performed thus making harder the spoofing of BFD packets.
However the same is possible even without the changes mentioned in
this document. A device should rate limit the BFD packets redirected
to the CPU so that the CPU is not overwhelmed.
10. IANA Considerations
IANA is request to allocate two TRILL Rbridge Channel numbers from
the range allocated by Standards Actions, as follows:
Protocol Number
-------- ------
BFD Control TBD (2 suggested)
BFD Echo TBD (3 suggested)
11. Acknowledgements
The authors would like to thank a lot of folks. Names will be
disclosed soon.
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12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., and C.
Pignataro, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, October 2007.
[RFC5586] Bocci, M., Vigoureux, M., and S. Bryant, "MPLS Generic
Associated Channel", RFC 5586, June 2009.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, June 2010.
[RFC6213] Hopps, C. and L. Ginsberg, "IS-IS BFD-Enabled TLV",
RFC 6213, April 2011.
[TRILLAdj] Eastlake, D., R. Perlman, A. Ghanwani, D. Dutt, V. Manral,
"RBridges: Adjacency", draft-ietf-trill-adj, work
in progress.
[TRILLChannel] Eastlake, D., V. Manral, Y. Li, S. Aldrin, D. Ward,
"RBridges: RBridge Channel Support in TRILL",
draft-ietf-trill-rbridge-channel, work in progress.
12.2. Informative References
[802.1AX] IEEE, "IEEE Standard for Local and metropolitan area
networks / Link Aggregation", 802.1AX-2008,
1 January 2008.
[802.1ag] IEEE, "IEEE Standard for Local and metropolitan area
networks / Virtual Bridged Local Area Networks /
Connectivity Fault Management", 802.1ag-2007, 17
December 2007.
[TrillPPP] Carlson, J., "PPP TRILL Protocol Control Protocol",
draft-ietf-pppext-trill-protocol-02.txt, work in progress,
May 2010.
[IS-IS] ISO/IEC 10589:2002, "Intermediate system to Intermediate
system routeing information exchange protocol for use in
conjunction with the Protocol for providing the
Connectionless-mode NetworkService (ISO 8473),"
ISO/IEC 10589:2002.
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Authors' Addresses
Vishwas Manral
HP Networking
19111 Pruneridge Ave.
Cupertino, CA 95014
USA
Phone: 408-777-0693
Fax:
Email: vishwas.manral@hp.com
URI:
Donald Eastlake 3rd
Huawei
155 Beaver Street
Milford, MA 01757
USA
Phone: 508-333-2270
Email: d3e3e3@gmail.com
Dave Ward
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089-1206
USA
Phone: 408-745-2000
Email: dward@juniper.net
Ayan Banerjee
Cisco Systems
170 W. Tasman Drive
San Jose, CA 95138
USA
Phone: 408-525-8781
Email: ayabaner@cisco.com
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