TRILL (Transparent Interconnetion of Lots of Links): Bidirectional Forwarding Detection (BFD) Support
Author(s): David Ward, Donald Eastlake, Ayan Banerjee, Vishwas Manral
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....
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: <email@example.com>. 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." V. Manral, et al [Page 1] INTERNET-DRAFT BFD TRILL Encapsulation 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. V. Manral, et al [Page 2] INTERNET-DRAFT BFD TRILL Encapsulation 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 V. Manral, et al [Page 3] INTERNET-DRAFT BFD TRILL Encapsulation 1. Introduction Faster convergence is a critical feature of TRILL (Transparent Interconnection of Lots of Links [RFC6325]) networks. The TRILL IS- IS Hellos [RFC 6327] [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 V. Manral, et al [Page 4] INTERNET-DRAFT BFD TRILL Encapsulation 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 [RFC 2119]. V. Manral, et al [Page 5] INTERNET-DRAFT BFD TRILL Encapsulation 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. V. Manral, et al [Page 6] INTERNET-DRAFT BFD TRILL Encapsulation 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. V. Manral, et al [Page 7] INTERNET-DRAFT BFD TRILL Encapsulation 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 [RFC 6327] 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. V. Manral, et al [Page 8] INTERNET-DRAFT BFD TRILL Encapsulation 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 [RFC 6327], 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 V. Manral, et al [Page 9] INTERNET-DRAFT BFD TRILL Encapsulation 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. V. Manral, et al [Page 10] INTERNET-DRAFT BFD TRILL Encapsulation 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. V. Manral, et al [Page 11] INTERNET-DRAFT BFD TRILL Encapsulation 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 V. Manral, et al [Page 12] INTERNET-DRAFT BFD TRILL Encapsulation 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 ) V. Manral, et al [Page 13] INTERNET-DRAFT BFD TRILL Encapsulation 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. V. Manral, et al [Page 14] INTERNET-DRAFT BFD TRILL Encapsulation 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. V. Manral, et al [Page 15] INTERNET-DRAFT BFD TRILL Encapsulation 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. [RFC 2119] - 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)", RFC5880, June 2010. [RFC5881] - Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD) for IPv4 and IPv6 (Single Hop)", RFC5881, 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", RFC6325, July 2011. [RFC 6327] - 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. V. Manral, et al [Page 16] INTERNET-DRAFT BFD TRILL Encapsulation [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)", RFC6234, 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, RFC6291, June 2011. [RFC6361] - Carlson, J. and D. Eastlake 3rd, "PPP Transparent Interconnection of Lots of Links (TRILL) Protocol Control Protocol", RFC6361, August 2011. V. Manral, et al [Page 17] INTERNET-DRAFT BFD TRILL Encapsulation Recent Changes Record [RFC Editor Note: Please delete this section before publication.] From -06 to -07: 1. Replace normative reference to RFC 0020 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. V. Manral, et al [Page 18] INTERNET-DRAFT BFD TRILL Encapsulation Authors' Addresses Vishwas Manral Hewlett Packard Co. 19111 Pruneridge Ave. Cupertino, CA 95089 USA Phone: +1-408-447-0000 Email: firstname.lastname@example.org Donald Eastlake 3rd Huawei R&D USA 155 Beaver Street Milford, MA 01757 USA Phone: +1-508-333-2270 Email: email@example.com Dave Ward Cisco Systems 170 W. Tasman Drive San Jose, CA 95138 USA Email: firstname.lastname@example.org Ayan Banerjee Cumulus Networks 1089 West Evelyn Avenue Sunnyvale, CA 94086 USA EMail: email@example.com V. Manral, et al [Page 19] INTERNET-DRAFT BFD TRILL Encapsulation Copyright and IPR Provisions Copyright (c) 2012 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 Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. 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