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+Internet Engineering Task Force (IETF) L. Yong
+Request for Comments: 7173 D. Eastlake 3rd
+Category: Standards Track S. Aldrin
+ISSN: 2070-1721 Huawei
+ J. Hudson
+ Brocade
+ May 2014
+
+
+ Transparent Interconnection of Lots of Links (TRILL) Transport
+ Using Pseudowires
+
+Abstract
+
+ This document specifies how to interconnect a pair of Transparent
+ Interconnection of Lots of Links (TRILL) switch ports using
+ pseudowires under existing TRILL and Pseudowire Emulation End-to-End
+ (PWE3) standards.
+
+Status of This Memo
+
+ This is an Internet Standards Track document.
+
+ This document is a product of the Internet Engineering Task Force
+ (IETF). It represents the consensus of the IETF community. It has
+ received public review and has been approved for publication by the
+ Internet Engineering Steering Group (IESG). Further information on
+ Internet Standards is available in Section 2 of RFC 5741.
+
+ Information about the current status of this document, any errata,
+ and how to provide feedback on it may be obtained at
+ http://www.rfc-editor.org/info/rfc7173.
+
+Copyright Notice
+
+ Copyright (c) 2014 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. Please review these documents
+ carefully, as they describe your rights and restrictions with respect
+ to this document. Code Components extracted from this document must
+ include Simplified BSD License text as described in Section 4.e of
+ the Trust Legal Provisions and are provided without warranty as
+ described in the Simplified BSD License.
+
+
+
+
+Yong, et al. Standards Track [Page 1]
+
+RFC 7173 PWE3 TRILL Transport May 2014
+
+
+Table of Contents
+
+ 1. Introduction.....................................................2
+ 1.1. Conventions Used in This Document...........................2
+ 2. PWE3 Interconnection of TRILL Switches...........................3
+ 2.1. PWE3 Type-Independent Details...............................3
+ 2.2. PPP PWE3 Transport of TRILL.................................4
+ 3. Security Considerations..........................................6
+ Appendix A. Use of Other Pseudowire Types ..........................7
+ Acknowledgements ...................................................8
+ Normative References ...............................................9
+ Informative References ............................................10
+
+1. Introduction
+
+ The Transparent Interconnection of Lots of Links (TRILL) protocol
+ [RFC6325] provides optimal pair-wise data frame routing without
+ configuration in multi-hop networks with arbitrary topology. TRILL
+ supports multipathing of both unicast and multicast traffic. Devices
+ that implement TRILL are called TRILL switches or Routing Bridges
+ (RBridges).
+
+ Links between TRILL switches can be based on arbitrary link
+ protocols, for example, PPP [RFC6361], as well as Ethernet [RFC6325].
+ A set of connected TRILL switches together form a TRILL campus that
+ is bounded by end stations and Layer 3 routers.
+
+ This document specifies how to interconnect a pair of TRILL switch
+ ports using a pseudowire under existing TRILL and PWE3 (Pseudowire
+ Emulation End-to-End) standards.
+
+1.1. Conventions Used in This Document
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
+ "OPTIONAL" in this document are to be interpreted as described in
+ [RFC2119].
+
+ Acronyms used in this document include the following:
+
+ IS-IS - Intermediate System to Intermediate System [IS-IS]
+
+ MPLS - Multi-Protocol Label Switching
+
+ PPP - Point-to-Point Protocol [RFC1661]
+
+ PW - Pseudowire [RFC3985]
+
+
+
+
+Yong, et al. Standards Track [Page 2]
+
+RFC 7173 PWE3 TRILL Transport May 2014
+
+
+ PWE3 - PW Emulation End-to-End
+
+ RBridge - Routing Bridge, an alternative name for a TRILL switch
+
+ TRILL - Transparent Interconnection of Lots of Links [RFC6325]
+
+ TRILL Switch - A device implementing the TRILL protocol
+
+2. PWE3 Interconnection of TRILL Switches
+
+ When a pseudowire is used to interconnect a pair of TRILL switch
+ ports, a PPP [RFC4618] pseudowire is used as described below. The
+ pseudowire between such ports can be signaled [RFC4447] or manually
+ configured. In this context, the TRILL switch ports at the ends of
+ the pseudowire are acting as native service processing (NSP) elements
+ [RFC3985] and, assuming that the pseudowires are over MPLS or IP
+ [RFC4023] networks, as label switched or IP routers at the TRILL
+ switch ports.
+
+ Pseudowires provide transparent transport, and the two TRILL switch
+ ports appear directly interconnected with a transparent link. With
+ such an interconnection, the TRILL adjacency over the link is
+ automatically discovered and established through TRILL IS-IS control
+ messages [RFC7177].
+
+ A pseudowire is carried over a packet switched network tunnel
+ [RFC3985], for example, an MPLS or MPLS-TP label switched path tunnel
+ in MPLS networks. Either a signaling protocol or manual
+ configuration can be used to configure a label switched path tunnel
+ between two TRILL switch ports. This application needs no additions
+ to the existing pseudowire standards.
+
+2.1. PWE3 Type-Independent Details
+
+ The sending pseudowire TRILL switch port SHOULD map the inner
+ priority of the TRILL Data packets being sent to the Traffic Class
+ field of the pseudowire label [RFC5462] so as to minimize the
+ probability that higher priority TRILL Data packets will be discarded
+ due to excessive TRILL Data packets of lower priority.
+
+ TRILL IS-IS PDUs critical to establishing and maintaining adjacency
+ (Hello and MTU PDUs) SHOULD be sent with the MPLS Traffic Class that
+ calls for handling with the maximum priority. Other TRILL IS-IS PDUs
+ SHOULD be sent with the MPLS Traffic Class denoting the highest
+ priority that is less than the maximum priority. TRILL Data packets
+ SHOULD be sent with appropriate MPLS Traffic Classes, typically
+ mapped from the TRILL Data packet priority, such that TRILL Data
+ packet Traffic Classes denote priorities less than the priorities
+
+
+
+Yong, et al. Standards Track [Page 3]
+
+RFC 7173 PWE3 TRILL Transport May 2014
+
+
+ used for TRILL IS-IS PDUs. This minimizes the probability of other
+ traffic interfering with these important control PDUs and causing
+ false loss of adjacency or other control problems.
+
+ If a pseudowire supports fragmentation and reassembly (a feature that
+ has received little or no deployment), then there is no reason to do
+ TRILL MTU testing on it, and the pseudowire will not be a constraint
+ on the TRILL campus-wide MTU size (Sz) (see Section 4.3.1 of
+ [RFC6325]). If the pseudowire does not support fragmentation (the
+ more common case), then the available TRILL IS-IS packet payload size
+ over the pseudowire (taking into account MPLS encapsulation with a
+ control word) or some lower value, MUST be used in helping to
+ determine MTU size (Sz) (see Section 5 of [RFC7180]).
+
+ An intervening MPLS label switched router or similar packet switched
+ network device has no awareness of TRILL. Such devices will not
+ change the TRILL Header hop count.
+
+2.2. PPP PWE3 Transport of TRILL
+
+ For a PPP pseudowire (PW type = 0x0007), the two TRILL switch ports
+ being connected are configured to form a pseudowire with PPP
+ encapsulation [RFC4618]. After the pseudowire is established and
+ TRILL use is negotiated within PPP, the two TRILL switch ports appear
+ directly connected with a PPP link [RFC1661] [RFC6361].
+
+ If pseudowire interconnection of two TRILL switch ports is signaled
+ [RFC4447], the initiating TRILL switch port MUST attempt the
+ connection setup with pseudowire type PPP (0x0007).
+
+ Behavior for TRILL with a PPP pseudowire continues to follow that of
+ TRILL over PPP as specified in Section 3 of [RFC6361].
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Yong, et al. Standards Track [Page 4]
+
+RFC 7173 PWE3 TRILL Transport May 2014
+
+
+ The following figures show what a TRILL Data packet and TRILL IS-IS
+ packet look like over such a pseudowire in the MPLS case, assuming no
+ TRILL Header extensions:
+
+ +--------------------------------+
+ | Server MPLS Tunnel Label(s) | n*4 octets (4 octets per label)
+ +--------------------------------+
+ | PW Label | 4 octets
+ +--------------------------------+
+ | Control Word | 4 octets
+ +--------------------------------+
+ | PPP Header 0x005d | 2 octets
+ +--------------------------------+
+ | TRILL Header | 6 octets
+ +--------------------------------+
+ | Destination MAC Address | 6 octets
+ +--------------------------------+
+ | Source MAC Address | 6 octets
+ +--------------------------------+
+ | Data Label | 4 or 8 octets
+ +--------------------------------+
+ | Payload Body | variable
+ +--------------------------------+
+
+ Figure 1: TRILL Data Packet in Pseudowire
+
+ "Data Label" is the VLAN Label or Fine-Grained Label [RFC7172] of the
+ payload.
+
+ +--------------------------------+
+ | Server MPLS Tunnel Label(s) | n*4 octets (4 octets per label)
+ +--------------------------------+
+ | PW Label | 4 octets
+ +--------------------------------+
+ | Control Word | 4 octets
+ +--------------------------------+
+ | PPP Header 0x405d | 2 octets
+ +--------------------------------+
+ | Common IS-IS Header | 8 octets
+ +--------------------------------+
+ | IS-IS PDU Type Specific Header | variable
+ +--------------------------------+
+ | IS-IS TLVs | variable
+ +--------------------------------+
+
+ Figure 2: TRILL IS-IS Packet in Pseudowire
+
+
+
+
+
+Yong, et al. Standards Track [Page 5]
+
+RFC 7173 PWE3 TRILL Transport May 2014
+
+
+ The PPP Header fields (0x005d and 0x405d, respectively) for TRILL
+ Data and IS-IS packets shown above are specified in [RFC6361].
+
+3. Security Considerations
+
+ TRILL-level security mechanisms, such as the ability to use
+ authentication with TRILL IS-IS PDUs [RFC6325], are not affected by
+ link technology, such as the use of pseudowire links as specified in
+ this document.
+
+ Link security may be useful in improving TRILL campus security.
+ TRILL is transported over pseudowires as TRILL over PPP over
+ pseudowires, pseudowires are over MPLS or IP, and MPLS and IP are
+ over some lower-level link technology. Thus, link security below the
+ TRILL level for a pseudowire link could be provided by PPP security,
+ pseudowire security, MPLS or IP security, or security of the link
+ technology supporting MPLS or IP.
+
+ PPP TRILL security considerations are discussed in [RFC6361]. For
+ security considerations introduced by carrying PPP TRILL links over
+ pseudowires, see [RFC3985], which discusses the risks introduced by
+ sending protocols that previously assumed a point-to-point link on a
+ pseudowire built on a packet switched network (PSN). However, the
+ PPP layer in TRILL transport by pseudowire is somewhat vestigial and
+ intended primarily as a convenient way to use existing PPP code
+ points to identify TRILL Data packets and TRILL IS-IS packets.
+ Furthermore, existing PPP security standards are arguably
+ questionable in terms of current security criteria. For these
+ reasons, it is NOT RECOMMENDED to use PPP security in the transport
+ of TRILL by pseudowires as specified in this document.
+
+ It is RECOMMENDED that link security be provided at the layers
+ supporting pseudowires transporting TRILL, that is, at the MPLS or IP
+ layer or the link layer transporting MPLS or IP.
+
+ For applications involving sensitive data, end-to-end security should
+ always be considered, in addition to link security, to provide
+ security in depth. In this context, such end-to-end security should
+ be between the end stations involved so as to protect the entire path
+ to, through, and from the TRILL campus.
+
+ For general TRILL protocol security considerations, see [RFC6325].
+
+
+
+
+
+
+
+
+
+Yong, et al. Standards Track [Page 6]
+
+RFC 7173 PWE3 TRILL Transport May 2014
+
+
+Appendix A. Use of Other Pseudowire Types
+
+ This informational appendix briefly discusses the use of pseudowire
+ types other than PPP for the transport of TRILL.
+
+ The use of Ethernet pseudowires [RFC4448] was examined by the authors
+ and would be possible without change to such pseudowires; however,
+ this would require an additional 12 or 16 bytes per packet within the
+ payload being transmitted over the pseudowire for a TRILL Data packet
+ (Figure 3) and a TRILL IS-IS packet (Figure 4) over such an Ethernet
+ pseudowire in the MPLS case, assuming no TRILL Header extensions
+ (compare with Figures 1 and 2):
+
+ +--------------------------------+
+ | Server MPLS Tunnel Label(s) | n*4 octets (4 octets per label)
+ +--------------------------------+
+ | PW Label | 4 octets
+ +--------------------------------+
+ | Optional Control Word | 4 octets
+ +--------------------------------+
+ | TRILL Hop Dest. MAC Address | 6 octets
+ +--------------------------------+
+ | TRILL Hop Source MAC Address | 6 octets
+ +--------------------------------+
+ |Optional VLAN and/or other tags | variable
+ +--------------------------------+
+ | TRILL Ethertype (0x22f3) | 2 octets
+ +--------------------------------+
+ | TRILL Header | 6 octets
+ +--------------------------------+
+ | Destination MAC Address | 6 octets
+ +--------------------------------+
+ | Source MAC Address | 6 octets
+ +--------------------------------+
+ | Data Label | 4 or 8 octets
+ +--------------------------------+
+ | Payload Body | variable
+ +--------------------------------+
+
+ Figure 3: TRILL Data Packet in Ethernet Pseudowire
+
+ "Data Label" is the VLAN Label or Fine-Grained Label [RFC7172] of the
+ payload.
+
+
+
+
+
+
+
+
+Yong, et al. Standards Track [Page 7]
+
+RFC 7173 PWE3 TRILL Transport May 2014
+
+
+ +--------------------------------+
+ | Server MPLS Tunnel Label(s) | n*4 octets (4 octets per label)
+ +--------------------------------+
+ | PW Label | 4 octets
+ +--------------------------------+
+ | Optional Control Word | 4 octets
+ +--------------------------------+
+ | TRILL Hop Dest. MAC Address | 6 octets
+ +--------------------------------+
+ | TRILL Hop Source MAC Address | 6 octets
+ +--------------------------------+
+ |Optional VLAN and/or other tags | variable
+ +--------------------------------+
+ | Layer 2 IS-IS Ethertype 0x22f4 | 2 octets
+ +--------------------------------+
+ | Common IS-IS Header | 8 octets
+ +--------------------------------+
+ | IS-IS PDU Type Specific Header | variable
+ +--------------------------------+
+ | IS-IS TLVs | variable
+ +--------------------------------+
+
+ Figure 4: TRILL IS-IS Packet in Ethernet Pseudowire
+
+ It would also be possible to specify a new pseudowire type for TRILL
+ traffic, but the authors feel that any efficiency gain over PPP
+ pseudowires would be too small to be worth the complexity of adding
+ such a specification. Furthermore, using PPP pseudowire encoding
+ means that any traffic dissector that understands TRILL PPP encoding
+ [RFC6361] and PPP pseudowires [RFC4618] will automatically be able to
+ recursively decode TRILL transported by pseudowire.
+
+Acknowledgements
+
+ Thanks for the valuable comments from the following, who are listed
+ in alphabetic order:
+
+ Stewart Bryant, Stephen Farrell, Brian Haberman, Christer
+ Holmberg, Joel Jaeggli, Barry Leiba, Erik Nordmark, Yaron Sheffer,
+ and Yaakov (J) Stein.
+
+
+
+
+
+
+
+
+
+
+
+Yong, et al. Standards Track [Page 8]
+
+RFC 7173 PWE3 TRILL Transport May 2014
+
+
+Normative References
+
+ [RFC1661] Simpson, W., Ed., "The Point-to-Point Protocol (PPP)",
+ STD 51, RFC 1661, July 1994.
+
+ [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC4447] Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and
+ G. Heron, "Pseudowire Setup and Maintenance Using the
+ Label Distribution Protocol (LDP)", RFC 4447, April 2006.
+
+ [RFC4618] Martini, L., Rosen, E., Heron, G., and A. Malis,
+ "Encapsulation Methods for Transport of PPP/High-Level
+ Data Link Control (HDLC) over MPLS Networks", RFC 4618,
+ September 2006.
+
+ [RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching
+ (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic
+ Class" Field", RFC 5462, February 2009.
+
+ [RFC6325] Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A.
+ Ghanwani, "Routing Bridges (RBridges): Base Protocol
+ Specification", RFC 6325, July 2011.
+
+ [RFC6361] Carlson, J. and D. Eastlake 3rd, "PPP Transparent
+ Interconnection of Lots of Links (TRILL) Protocol Control
+ Protocol", RFC 6361, August 2011.
+
+ [RFC7172] Eastlake 3rd, D., Zhang, M., Agarwal, P., Perlman, R., and
+ D. Dutt, "Transparent Interconnection of Lots of Links
+ (TRILL): Fine-Grained Labeling", RFC 7172, May 2014.
+
+ [RFC7180] Eastlake 3rd, D., Zhang, M., Ghanwani, A., Manral, V., and
+ A. Banerjee, "Transparent Interconnection of Lots of Links
+ (TRILL): Clarifications, Corrections, and Updates",
+ RFC 7180, May 2014.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Yong, et al. Standards Track [Page 9]
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+RFC 7173 PWE3 TRILL Transport May 2014
+
+
+Informative References
+
+ [IS-IS] ISO/IEC 10589:2002, Second Edition, "Information
+ technology -- Telecommunications and information exchange
+ between systems -- Intermediate System to Intermediate
+ System intra-domain routeing information exchange protocol
+ for use in conjunction with the protocol for providing the
+ connectionless-mode network service (ISO 8473)", 2002.
+
+ [RFC3985] Bryant, S., Ed., and P. Pate, Ed., "Pseudo Wire Emulation
+ Edge-to-Edge (PWE3) Architecture", RFC 3985, March 2005.
+
+ [RFC4023] Worster, T., Rekhter, Y., and E. Rosen, Ed.,
+ "Encapsulating MPLS in IP or Generic Routing Encapsulation
+ (GRE)", RFC 4023, March 2005.
+
+ [RFC4448] Martini, L., Ed., Rosen, E., El-Aawar, N., and G. Heron,
+ "Encapsulation Methods for Transport of Ethernet over MPLS
+ Networks", RFC 4448, April 2006.
+
+ [RFC7177] Eastlake 3rd, D., Perlman, R., Ghanwani, A., Yang, H., and
+ V. Manral, "Transparent Interconnection of Lots of Links
+ (TRILL): Adjacency", RFC 7177, May 2014.
+
+
+
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+Yong, et al. Standards Track [Page 10]
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+RFC 7173 PWE3 TRILL Transport May 2014
+
+
+Authors' Addresses
+
+ Lucy Yong
+ Huawei Technologies
+ 5340 Legacy Drive
+ Plano, TX 75024
+ USA
+
+ Phone: +1-469-227-5837
+ EMail: lucy.yong@huawei.com
+
+
+ Donald E. Eastlake 3rd
+ Huawei Technologies
+ 155 Beaver Street
+ Milford, MA 01757
+ USA
+
+ Phone: +1-508-333-2270
+ EMail: d3e3e3@gmail.com
+
+
+ Sam Aldrin
+ Huawei Technologies
+ 2330 Central Expressway
+ Santa Clara, CA 95050
+ USA
+
+ Phone: +1-408-330-4517
+ EMail: sam.aldrin@huawei.com
+
+
+ Jon Hudson
+ Brocade
+ 130 Holger Way
+ San Jose, CA 95134
+ USA
+
+ Phone: +1-408-333-4062
+ EMail: jon.hudson@gmail.com
+
+
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+Yong, et al. Standards Track [Page 11]
+