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Versions: (draft-yong-trill-o-pw) 00 01 02 03 04 05 06 RFC 7173

TRILL Working Group                                            Lucy Yong
INTERNET-DRAFT                                           Donald Eastlake
Intended status: Proposed Standard                            Sam Aldrin
                                                     Huawei Technologies
                                                              Jon Hudson
                                                                 Brocade
Expires: July 12, 2014                                  January 13, 2014


                  Transport of TRILL Using Pseudowires
                     <draft-ietf-trill-o-pw-05.txt>


Abstract

   This document specifies how to interconnect a pair of TRILL
   (Transparent Interconnection of Lots of Links) switch ports using
   pseudowires under existing TRILL and PWE3 (Pseudowire Emulation End-
   to-End) standards.


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 authors.

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L. Yong, et al                                                  [Page 1]

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Table of Contents

      1. Introduction............................................3
      1.1 Conventions used in this document......................3

      2. PWE3 Interconnection of TRILL Switches..................4
      2.1 PWE3 Type Independent Details..........................4
      2.2 PPP PWE3 Transport of TRILL............................5

      3. IANA Considerations.....................................7
      4. Security Considerations.................................7

      Appendix A: Use of Other Pseudowire Types..................8
      Appendix Z: Change History................................10

      Acknowledgements..........................................12
      Normative References......................................12
      Informative References....................................13

      Authors' Addresses........................................14
































L. Yong, et al                                                  [Page 2]

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1. Introduction

   The TRILL (Transparent Interconnection of Lots of Links) 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 RBridges (Routing
   Bridges).

   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 which
   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]

      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








L. Yong, et al                                                  [Page 3]

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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 elements (NSP
   [RFC3985]) and, assuming 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 [RFC6327bis].

   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 Traffic Class that would be used
   for a priority 7 (maximum priority) TRILL Data packet while other
   TRILL IS-IS PDUs SHOULD be sent with the Traffic Class that would be
   used for a priority 6 TRILL Data packet.  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 re-assembly (a feature
   that have 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
   [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 [ClearCorrect]).


L. Yong, et al                                                  [Page 4]

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   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 set-up 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].

   The following figures show what a TRILL Data 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          |  4 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 [FGL] of the
   payload.



L. Yong, et al                                                  [Page 5]

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      +-------------------------------+
      |   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 Specifc Header |  variable
      +-------------------------------+
      |          IS-IS TLVs           |  variable
      +-------------------------------+

                Figure 2. TRILL IS-IS Packet in Pseudowire

   The PPP Header fields (0x005d and 0x405d respectively) for TRILL Data
   and IS-IS packets shown above are specified in [RFC6361].
































L. Yong, et al                                                  [Page 6]

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3. IANA Considerations

   No IANA actions are required by this document. RFC Editor: Please
   remove this section before publication.




4. Security Considerations

   TRILL level secuirty 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
   technolgy 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
   pseudo wire 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 sepecified 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].





L. Yong, et al                                                  [Page 7]

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Appendix A: Use of Other Pseudowire Types

   This informational Appendix briefly discusses 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 as shown in the
   following figures for a TRILL Data and TRILL IS-IS packet 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          |  4 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 [FGL] of the
   payload.









L. Yong, et al                                                  [Page 8]

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      +-------------------------------+
      |   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
      +-------------------------------+
      |     Commmon IS-IS Header      |  8 octets
      +-------------------------------+
      | IS-IS PDU Type Specifc 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 understands PPP pseudowires [RFC4618] will
   automatically be able to recursively decode TRILL transported by
   pseudowire.



















L. Yong, et al                                                  [Page 9]

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Appendix Z: Change History

   RFC Editor Note: Please remove this appendix prior to publication.

From -00 to -01

   Add information on Traffic Classes that should be used for TRILL IS-
   IS PDUs.

   Other changes to resolve WG Last Call comments:

      Change title from "TRILL Over Psuedowires".

      Change "Class of Service" to "Traffic Class".

      Expand informational paragraph about the consideration of using
      other pseudowire types for the transport of TRILL and make that
      paragraph into Appendix A.

      Add this Change History Appendix Z.

From -01 to -02

   Add packet diagrams.

   Minor editing changes.

From -02 to -03

   Editorial and minor Security Considerations changes based on the
   Shepherd review by Erik Nordmark. See
      http://www.ietf.org/mail-archive/web/trill/current/msg06029.html
   and ensuing conversation.

From -03 to -04

   Security Considerations changes based on SECDIR review.

   Minor Editorial change to the first sentence of Section 1 based on
   GENART review.

   Add final sentence to first paragraph of Section 2.1 to resolve
   COMMENT by Barry Leiba.

From -04 to -05

   Assorted changes resulting from IESG review:

      Replace "autoconfigured" with "signaled".



L. Yong, et al                                                 [Page 10]

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      Clarify that it is the inner TRILL Data packet priority that is
   used to determine pseudowire Traffic Class and that the priority is
   mapped to the Traffic Class.

      Clarify that if Ethernet pseudowires were used no change would be
   required in the Ethernet pseudowire standard.

      Expand "Sz" to "MTU size (Sz)".

      Note that pseudowire fragmentation has little if any deployment.

      Minor editorial improvements.








































L. Yong, et al                                                 [Page 11]

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Acknowledgements

   Thanks for the valuable comments from the following who are listed in
   alphabetic order:

      Stewart Bryant, Stephen Farrell, Brain Haberman, Christer
      Holmberg, Joel Jaeggli, Barry Leiba, Erik Nordmark, Yaron Sheffer,
      and Yaakov (J) Stein

   The document was prepared in raw nroff. All macros used were defined
   within the source file.



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., "Encapsulation Methods for Transport of
         PPP/High-Level Data Link Control (HDLC) over MPLS Networks",
         BCP 116, 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", RFC6325, July 2011.

   [RFC6361] - Carlson, J., and D. Eastlake, "PPP Transparent
         Interconnection of Lots of Links (TRILL) Protocol Control
         Protocol", RFC6361, August 2011.

   [ClearCorrect] - Eastlake, D., M. Zhang, A. Ghanwani, V. Manral, and
         A. Banerjee, "TRILL: Clarifications, Corrections, and Updates",
         draft-ietf-trill-clear-correct, in RFC Editor's queue.

   [FGL] - D. Eastlake, M. Zhang, P. Agarwal, R. Perlman, D. Dutt,
         "TRILL (Transparent Interconnection of Lots of Links): Fine-
         Grained Labeling", draft-ietf-trill-fine-labeling, in RFC
         Editor's queue.


L. Yong, et al                                                 [Page 12]

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Informative References

   [IS-IS] - International Organization for Standardization,
         "Intermediate system to Intermediate system intra-domain
         routing information exchange protocol for use in conjunction
         with the protocol for providing the connectionless-mode Network
         Service (ISO 8473)", ISO/IEC10589:2002, Second Edition, Nov
         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.

   [RFC6327bis] - Eastlake 3rd, D., Perlman, R., Ghanwani, A., Howard,
         Y., and V. Manral, "TRILL: Adjacency", draft-ietf-trill-
         rfc6327bis, work in progress.





























L. Yong, et al                                                 [Page 13]

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Authors' Addresses

   Lucy Yong
   Huawei Technologies
   5340 Legacy Drive
   Plano, TX 75025 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
   jon.hudson@gmail.com
















L. Yong, et al                                                 [Page 14]

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