Internet DRAFT - draft-ietf-trill-rbridge-bfd
draft-ietf-trill-rbridge-bfd
TRILL Working Group V. Manral
INTERNET-DRAFT Hewlett Packard Co.
Intended status: Proposed Standard D. Eastlake
Huawei R&D USA
D. Ward
Cisco Systems
A. Banerjee
Cumulus Networks
Expires: January 15, 2013 July 16, 2012
TRILL (Transparent Interconnetion of Lots of Links):
Bidirectional Forwarding Detection (BFD) Support
<draft-ietf-trill-rbridge-bfd-07.txt>
Abstract
This document specifies use of the BFD (Bidirectional Forwarding
Detection) protocol in RBridge campuses based on the Rbridge Channel
extension to the the TRILL (TRansparent Interconnection of Lots of
Links) protocol.
BFD is a widely deployed OAM (Operations, Administration, and
Maintenance) mechanism in IP and MPLS (Multi Protocol Label
Switching) networks, using UDP and ACH (Associated Channel Header)
encapsulation respectively. This document specifies the BFD
encapsulation over TRILL.
Status of This Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79. Distribution of this document is
unlimited. Comments should be sent to the TRILL working group mailing
list: <rbridge@postel.org>.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
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."
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The list of current Internet-Drafts can be accessed at
http://www.ietf.org/1id-abstracts.html. The list of Internet-Draft
Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
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Table of Contents
1. Introduction............................................4
1.1 Terminology............................................4
2. BFD over TRILL.........................................6
2.1 Sessions and Initialization............................6
3. TRILL BFD Control Protocol..............................8
3.1 One-Hop TRILL BFD Control..............................8
3.2 BFD Control Frame Processing...........................8
4. TRILL BFD Echo Protocol.................................9
4.1 BFD Echo Frame Processing.............................9
5. Management and Operations Considerations...............11
6. Default Authentication.................................12
7. Security Considerations................................14
8. IANA Considerations....................................15
9. Acknowledgements.......................................15
Normative References......................................16
Informative References....................................16
Recent Changes Record.....................................18
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1. Introduction
Faster convergence is a critical feature of TRILL (Transparent
Interconnection of Lots of Links [RFC6325]) networks. The TRILL IS-
IS Hellos [RFC6327] [IS-IS] 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 that 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. The BFD (Bi-directional Forwarding Detection
[RFC5880]) protocol provides a low-overhead method for the rapid
detection of connectivity failures.
BFD is a widely deployed OAM (Operations, Administration, and
Maintenance, [RFC6291]) mechanism in IP and MPLS (Multi Protocol
Label Switching) networks, using UDP and ACH (Associated Channel
Header) encapsulation respectively. This document describes a TRILL
encapsulation for BFD packets for networks that forward based on the
TRILL Header.
1.1 Terminology
This document uses the acronyms defined in [RFC6325] along with the
following:
BFD: Bi-directional Forwarding Detection
IP: Internet Protocol
IS-IS: Intermediate-System to Intermediate-System
MH: Multi-Hop
PPP: Point-to-Point Protocol
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OAM: Operations, Administration, and Maintenance
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].
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2. BFD over TRILL
TRILL supports unicast neighbor BFD Echo and one-hop and multi-hop
BFD Control, as specified below, over the Rbridge Channel facility
[TRILLChannel]. (Multi-destination BFD is a work in progress
[MultiBFD].) BFD over TRILL support is similar to BFD over IP support
[RFC5881] except where differences are explicitly mentioned.
Asynchronous and demand modes MUST BE supported [RFC5880]. BFD over
TRILL supports the Echo function, however implementation of TRILL BFD
Echo is optional and it can only be used for single-hop sessions.
The TRILL Header hop count in the BFD packets is sent out with the
maximum value of 0x3F. To prevent spoofing attacks, the TRILL hop
count of a received session is checked [RFC5082]. For a single-hop
session if the hop count is less than 0x3F and the Rbridge Channel
Header MH flag is zero, the packet is discarded. For multihop
sessions the hop count check can be disabled if the MH flag is one.
As in BFD for IP the format of the Echo Packet content is not
defined.
New Rbridge Channel code points for BFD TRILL Control and BFD Echo
packets are specified.
Authentication mechanisms as supported in BFD are also supported for
BFD running over TRILL.
2.1 Sessions and Initialization
Within an RBridge campus, there will be no more than one TRILL BFD
Control session from any RBridge RB1 to RBridge RB2 for each RB1
TRILL port. This BFD session must be bound to this interface. As
such, both sides of a session MUST take the "Active" role (sending
initial BFD Control packets with a zero value of Your Discriminator),
and 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 interface.
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
as a PPP [RFC6361] link or an Ethernet link [RFC6325]. Link
technology specific OAM protocols may be used on a link between
neighbor RBridges, for example Continuity Fault Management [802.1Q]
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.
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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.
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3. TRILL BFD Control Protocol
TRILL BFD Control frames are unicast TRILL Rbridge Channel frames
[TRILLChannel]. The Rbridge Channel Protocol value is given in
Section 8. The protocol specific data associated with the TRILL BFD
Control protocol is as shown in Section 4.1 of [RFC5880].
3.1 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 high priority; that is, the Inner.VLAN
tag priority should be 7, they should be queued for transmission as
maximum priority frames and, if they are being sent on an Ethernet
link where the output port is configured to include an Outer.VLAN
tag, that tag should specify 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 state [RFC6327] and both RBridges indicate support of TRILL
BFD is enabled. The BFD Enabled TLV is used to indicate this as
specified in [RFC6213].
3.2 BFD Control Frame Processing
The following tests SHOULD be performed on received TRILL BFD Control
frames before generic BFD processing.
Is the M-bit in the TRILL Header non-zero? If so, discard the frame.
(Multi-destination BFD is a work in progress [MultiBFD].) Failure to
perform this test would make a denial-of-service attack using bogus
multi-destination BFD Control frames easier.
If the Channel 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 Channel flag is one, indicating multi-hop, test
that the TRILL Header hop count received was not less than a
configurable value that defaults to 0x30. If it is less, discard the
frame. Failure to perform these tests would make it easier to spoof
BFD Control frames. However, if forged BFD Control frames are a
concern, then BFD Authentication [RFC5880] should be used.
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4. TRILL BFD Echo Protocol
A TRILL BFD Echo frame is a unicast Rbridge Channel frame, as
specified in [TRILLChannel], which should be forwarded 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 unless micro-
loop suppression logic in the neighbor RBrdge prohibits sending a
frame back out the port on which it was received or the like.
RBridges with such prohibitions cannot support BFD Echo. The TRILL
OAM protocol number for BFD Echo is given in Section 8.
TRILL BFD Echo frames SHOULD be sent on a link only if the following
conditions are met. An Echo originated under other circumstances will
consume bandwidth and CPU resources but is unlikely to be returned.
- A TRILL BFD Control session has been established,
- TRILL BFD Echo support is indicated by the potentially echo
responding RBridge,
- The adjacency is in the Report state [RFC6327], and
- 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 suggested 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.
4.1 BFD Echo Frame Processing
The following tests MUST be performed on returned TRILL BFD Echo
frames before other processing. The RBridge Channel document
requires that the information in the TRILL Header be given to the BFD
protocol.
Is the M-bit in the TRILL Header non-zero? If so, discard the frame.
(Multi-destination BFD is a work in progress [MultiBFD].)
The TRILL BFD Echo frame should have gone exactly two hops so test
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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 Rbridge Channel Header in the frame MUST have the MH
bit equal to one and if it is zero, the frame is discarded.
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5. 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 [RFC5881], except where
specified in this document such as for Hop Count.
It is up to the operator of an RBridge campus to 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. See
also the discussion of congestion in Section 2 of [RFC5881].
As stated in [RFC5880]:
It is worth noting that a single BFD session does not consume a
large amount of bandwidth. An aggressive session that achieves a
detection time of 50 milliseconds, by using a transmit interval of
16.7 milliseconds and a detect multiplier of 3, will generate 60
packets per second. The maximum length of each packet on the wire
is on the order of 100 bytes, for a total of around 48 kilobits
per second of bandwidth consumption in each direction.
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6. Default Authentication
Consistent with TRILL's goal of being able to operate with minimum
configuration, the default for BFD authentication between neighbor
RBridges is based on the state of IS-IS shared secret authentication
for Hellos between those RBridges as detaled below. The BFD
authentication algorithm and methods in this section MUST be
implemented at an RBridge if TRILL IS-IS authentication and BFD are
implemented at that RBrdge. If such BFD authentication is configured
then its configuration is not restricted by the configuration of IS-
IS security.
If IS-IS authentication is not in effect between neighbor RBridges
then, by default, TRILL BFD between those RBridges is also unsecured.
If such IS-IS authentication is in effect then, unless configured
otherwise, TRILL BFD Control frames sent between those RBridges MUST
use BFD Meticulous Keyed SHA1 authentication [RFC5880]. The BFD
authentication keys between neighbor RBridges by default are derived
from the IS-IS shared secret authentication keys for Hellos between
those RBridges as detailed below. However, such BFD authentication
keys MAY be configured to some other value.
HMAC-SHA256 ( ( "TRILL BFD Control" | originPortID | originSysID ),
IS-IS-shared-key )
In the above "|" indicates concatenation, HMAC-SHA256 is as described
in [FIPS180] [RFC6234], "TRILL BFD Control" is the seventeen byte US
ASCII [ASCII] string indicated that is then concatenated with the
2-byte Port ID of the originating port and the 6-bytes IS-IS SystemID
of the originating RBridge, the last two items being in network byte
order. The Port and System IDs are included to minimize exposure of
the same key to improve resistance to cryptanalysis. IS-IS-shared-key
is secret keying material being used for IS-IS authentication on the
link.
The use of the above derived key is accomplished by associating the
above default authentication type and key with the Key ID of the IS-
IS-shared key used in the derivation and then using that Key ID in
the Authentication Section of the BFD Control frame OAM protocol
specific data. Also Auth Type would be 5 and Auth Len would be 28 in
the Authentication Section. RBridges MAY be configured to use other
BFD security modes or keying material or configured to use no
security.
Authentication for TRILL BFD Echo is a local implementation issue as
BFD Echo frames are authenticated by their sender when returned by by
a neighbor. However, if TRILL IS-IS and BFD Control are being
authenticated to a neighbor and BFD Echo is in use, BFD Echo frames
to be returned by that neighbor should be authenticated and such
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authentication should use different keying material from other types
of authentication. For example, it could use keying material derived
as follows, where "|" indicates concatenation:
HMAC-SHA256 ( ( "TRILL BFD Echo" | originPortID | originSysID ),
IS-IS-shared-key )
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7. Security Considerations
BFD over TRILL utilizes the RBridge Channel extension to the TRILL
protocol and is generally analogous to BFD over IP. As such, the BFD
authentication faciliity is available to authenticate BFD over TRILL
packet payloads but no encryption or other security features are
provided at the BFD over TRILL level. See the following:
- [RFC5881] for general BFD security considerations,
- [TRILLChannel] for general RBridge Channel security
considerations, and
- [RFC6325] for general TRILL protocol security considerations.
Section 3.2 above describes seurity concerns with multi-hop BFD
Control packets and failure to check the TRILL Header M bit in BFD
Control packets.
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8. IANA Considerations
IANA is requested to allocate two Rbridge Channel Protocol numbers
[TRILLChannel] from the range allocated by Standards Actions, as
follows:
Protocol Number
-------- ------
BFD Control TBD (2 suggested)
BFD Echo TBD (3 suggested)
9. Acknowledgements
The authors would like to specially thank Dave Katz, an author of
[RFC5880] and [RFC5881], from which some material herein has been
reproduced.
The following are thanked for their comments and suggestions: Scott
Bradner, Stewart Bryant, Stephen Farrell, Eric Gray, Brian Haberman,
Barry Leiba, Erik Nordmark, John Scudder, Robert Sparks, Martin
Stiemerling, an Sean Turner.
This documnt was prepared using raw nroff. All macros used were
defined in the source file.
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Normative References
[ASCII] - American National Standards Institute (formerly United
States of America Standards Institute), "USA Code for
Information Interchange", ANSI X3.4-1968, 1968. ANSI X3.4-1968
has been replaced by newer versions with slight modifications,
but the 1968 version remains definitive for the Internet.
[FIPS180] - "Secure Hash Standard (SHS)", United States of American,
National Institute of Science and Technology, Federal
Information Processing Standard (FIPS) 180-4, March 2012,
http://csrc.nist.gov/publications/fips/fips180-4/fips-180-4.pdf
[IS-IS] - International Organization for Standardization,
"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, Second Edition, Nov 2002.
[RFC2119] - Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5880] - Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, June 2010.
[RFC5881] - Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, June 2010.
[RFC6213] - Hopps, C. and L. Ginsberg, "IS-IS BFD-Enabled TLV", RFC
6213, April 2011.
[RFC6325] - Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A.
Ghanwani, "Routing Bridges (RBridges): Base Protocol
Specification", RFC 6325, July 2011.
[RFC6327] - Eastlake, D., R. Perlman, A. Ghanwani, D. Dutt, V.
Manral, "RBridges: Adjacency", RFC 6327, July 2011.
[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.
Informative References
[802.1AX] - IEEE, "IEEE Standard for Local and metropolitan area
networks / Link Aggregation", 802.1AX-2008, 1 January 2008.
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[802.1Q] - IEEE 802.1, "IEEE Standard for Local and metropolitan area
networks - Virtual Bridged Local Area Networks", IEEE Std
802.1Q-2011, May 2011.
[MultiBFD] - Katz, D. and D. Ward, "draft-ietf-bfd-multipoint", work
in progress.
[RFC5082] - Gill, V., Heasley, J., Meyer, D., Savola, P., and C.
Pignataro, "The Generalized TTL Security Mechanism (GTSM)", RFC
5082, October 2007.
[RFC6234] - Eastlake 3rd, D. and T. Hansen, "US Secure Hash
Algorithms (SHA and SHA-based HMAC and HKDF)", RFC 6234, May
2011.
[RFC6291] - Andersson, L., van Helvoort, H., Bonica, R., Romascanu,
D., and S. Mansfield, "Guidelines for the Use of the "OAM"
Acronym in the IETF", BCP 161, RFC 6291, June 2011.
[RFC6361] - Carlson, J. and D. Eastlake 3rd, "PPP Transparent
Interconnection of Lots of Links (TRILL) Protocol Control
Protocol", RFC 6361, August 2011.
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Recent Changes Record
[RFC Editor Note: Please delete this section before publication.]
From -06 to -07:
1. Replace normative reference to RFC 20 with a refernce to [ASCII].
2. Update Author Address information.
3. In the default BFD authentication key derivation, change
"OriginatorMAC" to the concatenation of the Port ID and the
System ID. OriginatorMAC is simpler and shorter but only works
for Ethernet links. TRILL supports arbitrary technology links
between RBridges so you need to use the combination of Port ID
and System ID to get a globally unique quantity. In addition, if
an IS-IS authentication method is in use the has a Key ID field
so that multiple shared secret keys may be in place, then by
default BFD authentication with such a Key ID field should also
be used with matching Key ID for matching derived key.
4. Clarify what it means that a single hop BFD control frame in
support of link connectivity is send at high priority for cases
other than Ethernet links.
5. Add reference in Section 5 to Section 2 of [RFC5881] in
conngection with congestion control.
6. Add mandatory to implement support for Demand Mode BFD.
7. Clarify that the BFD authentication algorithm and methods in
Section 6 MUST be implemented if TRILL IS-IS Authentication and
BFD are implemented.
8. Add some small pieces of explanatory and motivational text that
make no technical changes, as suggested by the Operations
Directorate review.
9. Delete comparison between RBridge Channel and MPLS Generic
Associated Channel.
10. Update Author Info.
11. Various editorial changes.
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Authors' Addresses
Vishwas Manral
Hewlett Packard Co.
19111 Pruneridge Ave.
Cupertino, CA 95089 USA
Phone: +1-408-447-0000
Email: vishwas.manral@hp.com
Donald Eastlake 3rd
Huawei R&D USA
155 Beaver Street
Milford, MA 01757 USA
Phone: +1-508-333-2270
Email: d3e3e3@gmail.com
Dave Ward
Cisco Systems
170 W. Tasman Drive
San Jose, CA 95138 USA
Email: dward@cisco.com
Ayan Banerjee
Cumulus Networks
1089 West Evelyn Avenue
Sunnyvale, CA 94086 USA
EMail: ayabaner@gmail.com
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