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PPP Transparent Interconnection of Lots of Links (TRILL) Protocol Control Protocol

The information below is for an old version of the document that is already published as an RFC.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 6361.
Authors Donald E. Eastlake 3rd , James D. Carlson
Last updated 2015-10-14 (Latest revision 2011-06-14)
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status Proposed Standard
Additional resources Mailing list discussion
Stream WG state WG Document
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IESG IESG state Became RFC 6361 (Proposed Standard)
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Consensus boilerplate Unknown
Telechat date (None)
Responsible AD Jari Arkko
IESG note
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Network Working Group                                      James Carlson
INTERNET-DRAFT                                               WorkingCode
Intended status: Proposed Standard                       Donald Eastlake
Expires: December 12, 2011                                 June 13, 2011

                  PPP TRILL Protocol Control Protocol


   The Point-to-Point Protocol (PPP) defines a Link Control Protocol
   (LCP) and a method for negotiating the use of multi-protocol traffic
   over point-to-point links.  This document describes PPP support for
   the Transparent Interconnection of Lots of Links (TRILL) Protocol,
   allowing direct communication between Routing Bridges (RBridges) via
   PPP links.

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 DNSEXT working group mailing list: <>.

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J. Carlson & D. Eastlake                                        [Page 1]
INTERNET-DRAFT                                            TRILL over PPP

Table of Contents

      1. Introduction............................................3

      2. PPP TRILL Negotiation...................................4
      2.1 TNCP Packet Format.....................................4
      2.2 TNP Packet Format......................................5
      2.3 TLSP Packet Format.....................................6

      3. TRILL PPP Behavior......................................7
      4. Security Considerations.................................8
      5. IANA Considerations.....................................8

      6. References..............................................9
      6.1 Normative..............................................9
      6.2 Informative............................................9
      7. Acknowledgments........................................10
      8. Authors' Addresses.....................................10

J. Carlson & D. Eastlake                                        [Page 2]
INTERNET-DRAFT                                            TRILL over PPP

1. Introduction

   The TRILL Protocol [RFCtrill] defines a set of mechanisms used to
   communicate between RBridges.  These devices can bridge together
   large 802 networks using link-state protocols in place of the
   traditional spanning tree mechanisms.

   Over Ethernet, TRILL uses two separate Ethertypes to distinguish
   between encapsulation headers, which carry user data, and link-state
   messages, which compute network topology using a protocol based on
   [IS-IS].  These two protocols must be distinguished from one another,
   and segregated from all other traffic.

   In a network where PPP [RFC1661] is used to interconnect routers
   (often over telecommunications links), it may be advantageous to be
   able to bridge between Ethernet segments over those PPP links, and
   thus integrate remote networks with an existing TRILL cloud.  The
   existing Bridging Control Protocol (BCP) [RFC3518] allows direct
   bridging of Ethernet frames over PPP.  However, this mechanism is
   inefficient and inadequate for TRILL, which can be optimized for use
   over PPP links.

   To interconnect these devices over PPP links, three protocol numbers
   are needed, and are reserved as follows:

      Value (in hex)  Protocol Name
      --------------  -------------------------------------
       TBD-00XX       TRILL Network Protocol (TNP)
       TBD-40YY       TRILL Link State Protocol (TLSP)
       TBD-80ZZ       TRILL Network Control Protocol (TNCP)

   The usage of these three protocols is described in detail in the
   following section.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

J. Carlson & D. Eastlake                                        [Page 3]
INTERNET-DRAFT                                            TRILL over PPP

2. PPP TRILL Negotiation

   The TRILL Network Control Protocol (TNCP) is responsible for
   negotiating the use of the TRILL Network Protocol (TNP) and TRILL
   Link State Protocol (TLSP) on a PPP link.  TNCP uses the same option
   negotiation mechanism and state machine as described for LCP (section
   4 of [RFC1661]).

   TNCP packets MUST NOT be exchanged until PPP has reached the Network-
   Layer Protocol phase.  Any TNCP packets received when not in that
   phase MUST be silently ignored.

   The encapsulated network layer data, carried in TNP packets, and
   topology information, carried in TLSP packets, MUST NOT be sent
   unless TNCP is in Opened state.  If a TNP or TLSP packet is received
   when TNCP is not in Opened state and LCP is Opened, an implementation
   MUST silently discard the unexpected TNP or TLSP packet.

2.1 TNCP Packet Format

   Exactly one TNCP packet is carried in the PPP Information field, with
   the PPP Protocol field set to hex TBD-80ZZ (TNCP).  A summary of the
   TNCP packet format is shown below.  The fields are transmitted from
   left to right.

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      |     Code      |  Identifier   |            Length             |
      |    Data ...


      Only LCP Code values 1 through 7 (Configure-Request, Configure-
      Ack, Configure-Nak, Configure-Reject, Terminate-Request,
      Terminate-Ack, and Code-Reject) are used.  All other codes SHOULD
      result in a TNCP Code-Reject reply.

   Identifier and Length

      These are as documented for LCP.


      This field contains data formatted as described in section 5 of

J. Carlson & D. Eastlake                                        [Page 4]
INTERNET-DRAFT                                            TRILL over PPP

      [RFC1661].  Codes 1-4 use Type-Length-Data sequences, Codes 5 and
      6 use uninterpreted data, and Code 7 uses a Rejected-Packet, all
      as described in [RFC1661].

   Because no Configuration Options have been defined for TNCP,
   negotiating the use of TRILL Protocol with IS-IS for the link state
   protocol is the default when no options are specified.  A future
   document may specify the use of Configuration Options to enable
   different TRILL operating modes, such as the use of a different link
   state protocol.

2.2 TNP Packet Format

   When TNCP is in Opened state, TNP packets are sent by setting the PPP
   Protocol field to hex TBD-00XX (TNP) and placing TRILL-encapsulated
   data representing exactly one encapsulated packet in the PPP
   Information field.

   A summary of this format is provided below:

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      | V | R |M|Op-Length| Hop Count | Egress (RB2) Nickname         |
      | Ingress (RB1) Nickname        | Inner Destination MAC ...

   This is identical to the TRILL Ethernet format (section 4.1 of
   [RFCtrill], "Ethernet Data Encapsulation,") except that the Outer MAC
   header and Ethertype are replaced by the PPP headers and Protocol
   Field, and the Ethernet FCS is not present.  Both user data and ESADI
   packets are encoded in this format.

   The PPP FCS follows the encapsulated data on links where the PPP FCS
   is in use.

   Unlike the TRILL Ethernet encapsulation, PPP nodes do not have MAC
   addresses, so no outer MAC is present.  (HDLC addresses MAY be
   present in some situations; such usage is outside the scope of this

J. Carlson & D. Eastlake                                        [Page 5]
INTERNET-DRAFT                                            TRILL over PPP

2.3 TLSP Packet Format

   When TNCP is in Opened state, TLSP packets are sent by setting the
   PPP Protocol field to hex TBD-40YY (TLSP) and placing exactly one IS-
   IS Payload (section 4.2.3 of [RFCtrill], "TRILL IS-IS Frames") in the
   PPP Information field.

   Note that point-to-point IS-IS links have only an arbitrary Circuit
   ID, and do not use MAC addresses for identification.

J. Carlson & D. Eastlake                                        [Page 6]
INTERNET-DRAFT                                            TRILL over PPP

3. TRILL PPP Behavior

   1. On a PPP link, TRILL always uses P2P Hellos.  There is no need for
      TRILL-Hello frames, nor is per-port configuration necessary.  P2P
      Hello messages, per "Point-to-Point IS to IS Hello PDU" (section
      9.7 of [IS-IS]), do not use Neighbor IDs in the same manner as on
      Ethernet. However, per section of [RFCtrill], three-way
      IS-IS handshake using extended circuit IDs is required on point-
      to-point links, such as PPP.

   2. RBridges are never appointed forwarders on PPP links.  If an
      implementation includes BCP [RFC3518], then it MUST ensure that
      only one of BCP or TNCP is negotiated on a link, and not both.  If
      the peer is an RBridge, then there is no need to pass
      unencapsulated frames, as the link can have no TRILL-ignorant peer
      to be concerned about.  If the peer is not an RBridge, then TNCP
      negotiation fails and TRILL is not used on the link.

   3. An implementation that has only PPP links might have no
      Organizationally Unique Identifier (OUI) that can form an IS-IS
      System ID.  Resolving that issue is outside the scope of this
      document, however it is strongly RECOMMENDED that all TRILL
      implementations have at least one zero-configuration mechanism to
      obtain a valid System ID.  Refer to ISO/IEC 10589 regarding System
      ID uniqueness requirements.

   4. TRILL MTU-probe and TRILL MTU-ack messages (section 4.3.2 of
      [RFCtrill]) are not needed on a PPP link.  Implementations MUST
      NOT send MTU-probe and SHOULD NOT reply to these messages.  The
      MTU computed by LCP SHOULD be used instead.  Negotiating an LCP
      MTU of at least 1524, to allow for an inner Ethernet payload of
      1500 octets, is RECOMMENDED.

J. Carlson & D. Eastlake                                        [Page 7]
INTERNET-DRAFT                                            TRILL over PPP

4. Security Considerations

   Existing PPP and IS-IS security mechanisms may play important roles
   in a network of RBridges interconnected by PPP links. The IS-IS
   authentication mechanism [RFC5304] [RFC5310], at the TRILL IS-IS
   layer, prevents fabrication of link-state control messages.

   Not all implementations need to include specific security mechanisms
   at the PPP layer, for example if they are designed to be deployed
   only in cases where the networking environment is trusted or where
   other layers provide adequate security. A complete enumeration of
   possible deployment scenarios and associated threats and options is
   not possible and is outside the scope of this document. For
   applications involving sensitive data, end-to-end security should
   always be considered in addition to link security to provide security
   in depth.

   However, in case a PPP layer authentication mechanism to protect the
   establishment of a link and identify a link with a known peer is
   needed, implementation of PPP CHAP [RFC1994] is RECOMENDED. Should
   greater flexibility be required than that provided by CHAP, EAP
   [RFC3748] is a good alternative.

   If TRILL over PPP packets also require confidentiality, the PPP ECP
   link encryption mechanisms [RFC1968] can protect the confidentiality
   and integrity of all packets on the PPP link.

   And when PPP is run over tunneling mechanisms, such as L2TP
   [RFC3931], tunnel security protocols may be available.

   For general TRILL protocol security considerations, see [RFCtrill].

5. IANA Considerations

   IANA is requested to assigned three PPP Protocol field values,
   TBD-00XX, TBD-40YY, and TBD-80ZZ, as described in Section 1 of this

   IANA is requested to create a new "PPP TNCP Configuration Option
   Types" in the PPP-Numbers registry using the same format as the
   existing "PPP LCP Configuration Option Types" table.

   All TNCP Configuration Option Types except 00 are "Unassigned" and
   available for future use, based on "IETF Review," as described in BCP
   26 [RFC5226].  Option 00 is allocated for use with Vendor Specific
   Options, as described in [RFC2153].

J. Carlson & D. Eastlake                                        [Page 8]
INTERNET-DRAFT                                            TRILL over PPP

6. References

   Normative and Informational references are listed below.

6.1 Normative

   [RFC1661] - W. Simpson, Editor, "The Point-to-Point Protocol (PPP),"
         RFC 1661, July 1994

   [RFC2119] - S. Bradner, "Key words for use in RFCs to Indicate
         Requirement Levels," BCP 14 and RFC 2119, March 1997

   [RFC5226] - T. Narten and H. Alvestrand, "Guidelines for Writing an
         IANA Considerations Section in RFCs," BCP 26 and RFC 5226, May

   [RFCtrill] - R. Perlman, et al., "RBridges: Base Protocol
         Specification," draft-ietf-trill-rbridge-protocol-16.txt, in
         RFC Editor queue

6.2 Informative

   [IS-IS] - International Organization for Standardization,
         "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)", ISO/IEC 10589:2002, Second Edition, Nov

   [RFC1968] - G. Meyer, "The PPP Encryption Control Protocol (ECP),"
         RFC 1968, June 1996

   [RFC1994] - W. Simpson, "PPP Challenge Handshake Authentication
         Protocol (CHAP)," RFC 1994, August 1996

   [RFC2153] - W. Simpson, "PPP Vendor Extensions," RFC 2153, May 1997

   [RFC3518] - M. Higashiyama, et al., "Point-to-Point Protocol (PPP)
         Bridging Control Protocol (BCP)," RFC 3518, April 2003

   [RFC3748] - B. Aboba, et al., "Extensible Authentication Protocol
         (EAP)," RFC 3748, June 2004

J. Carlson & D. Eastlake                                        [Page 9]
INTERNET-DRAFT                                            TRILL over PPP

   [RFC3931] - J. Lau, Ed., et al., "Layer Two Tunneling Protocol -
         Version 3 (L2TPv3)," RFC 3931, March 2005

   [RFC5304] - T. Li and R. Atkinson, "IS-IS Cryptographic
         Authentication," RFC 5304, October 2008

   [RFC5310] - Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
         and M. Fanto, "IS-IS Generic Cryptographic Authentication", RFC
         5310, February 2009.

7. Acknowledgments

   The authors thanks Jari Arkko, Stewart Bryant, Ralph Droms, Linda
   Dunbar, Adrian Farrel, Stephen Farrell, Radia Perlman, Mike Shand,
   and William A. Simpson for their comments and help.

8. Authors' Addresses

   James Carlson
   25 Essex Street
   North Andover, MA 01845 USA

   Phone: +1-781-301-2471

   Donald Eastlake, 3rd
   Huawei Technologies
   155 Beaver Street
   Milford, MA 01757 USA

   Phone: +1-508-333-2270

J. Carlson & D. Eastlake                                       [Page 10]
INTERNET-DRAFT                                            TRILL over PPP

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J. Carlson & D. Eastlake                                       [Page 11]