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rfc:rfc7173

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] 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.

Yong, et al. Standards Track [Page 10] 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

Yong, et al. Standards Track [Page 11]

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