Link Management Protocol Behavior Negotiation and Configuration Modifications

Internet Engineering Task Force (IETF)                             D. Li
Request for Comments: 6898                                        Huawei
Updates: 4204, 4207, 4209, 5818                            D. Ceccarelli
Category: Standards Track                                       Ericsson
ISSN: 2070-1721                                                L. Berger
                                                                    LabN
                                                              March 2013


           Link Management Protocol Behavior Negotiation and
                      Configuration Modifications

Abstract

   The Link Management Protocol (LMP) is used to coordinate the
   properties, use, and faults of data links in networks controlled by
   Generalized Multiprotocol Label Switching (GMPLS).  This document
   defines an extension to LMP to negotiate capabilities and indicate
   support for LMP extensions.  The defined extension is compatible with
   non-supporting implementations.

   This document updates RFC 4204, RFC 4207, RFC 4209, and RFC 5818.

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/rfc6898.

Copyright Notice

   Copyright (c) 2013 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
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   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.

Table of Contents

   1. Introduction ....................................................3
      1.1. Conventions Used in This Document ..........................4
   2. LMP Message Modifications .......................................4
      2.1. Modified Message Formats ...................................4
      2.2. Processing .................................................5
   3. LMP Behavior Negotiation ........................................6
      3.1. BehaviorConfig C-Type Format ...............................6
      3.2. Processing .................................................7
   4. Backward Compatibility ..........................................7
   5. Security Considerations .........................................8
   6. IANA Considerations .............................................9
      6.1. New LMP Class Type .........................................9
      6.2. New Capabilities Registry ..................................9
   7. Normative References ...........................................10
   8. Acknowledgments ................................................10
   9. Contributors ...................................................10

1.  Introduction

   The Link Management Protocol (LMP) [RFC4204] has been successfully
   deployed in networks controlled by Generalized Multiprotocol Label
   Switching (GMPLS).

   New LMP behaviors and protocol extensions have been introduced in a
   number of IETF documents, as set out later in this section.  It is
   likely that future extensions will be made to support additional
   functions.

   In a network, if one LMP-capable node supports a new behavior or
   protocol extension but its adjacent node does not, it is beneficial
   to have a protocol mechanism to discover the capabilities of peer
   nodes so that the right protocol extensions can be selected and the
   correct features can be enabled.  There are no such procedures
   defined in the base LMP specification [RFC4204]. [RFC4209] defined a
   specific mechanism to identify support for the functions specified in
   that document.  This document defines an LMP extension to support the
   identification of supported LMP functions in a generic fashion, as
   well as how a node supporting these extensions would communicate with
   legacy nodes.

   In [RFC4204], the basic behaviors have been defined around the use of
   the standard LMP messages, which include Config, Hello, Verify, Test,
   LinkSummary, and ChannelStatus.  Per [RFC4204], these behaviors MUST
   be supported when LMP is implemented, and the message types from 1 to
   20 have been assigned by IANA for these messages.  Support for all
   functions required by [RFC4204] is assumed by this document.

   In [RFC4207], the SONET/SDH technology-specific behavior and
   information for LMP is defined.  The Trace behavior is added to LMP,
   and the message types from 21 to 31 have been assigned by IANA for
   the messages that provide the Trace function.

   In [RFC4209], extensions to LMP are defined to allow it to be used
   between a peer node and an adjacent Optical Line System (OLS).  The
   LMP object class type and subobject class name have been extended to
   support Dense Wavelength Division Multiplexing (DWDM) behavior.

   In [RFC5818], the data channel consistency check behavior is defined,
   and the message types from 32 to 34 have been assigned by IANA for
   messages that provide this behavior.

   It is likely that future extensions to LMP for other functions or
   technologies will require the definition of further LMP messages.

   This document describes an LMP extension, referred to as behavior
   negotiation, that enables the nodes at the ends of a link to identify
   the LMP messages and functions supported by the adjacent node.  The
   extension makes use of a new CONFIG object.  The use of this new
   object does not preclude the use of existing or yet to be defined
   CONFIG objects.

   This document also modifies the format of messages that carry the
   CONFIG object to allow for multiple objects.  Multiple CONFIG objects
   allow behavior negotiation concurrent with existing usage of the
   CONFIG object, i.e., HelloConfig C-Type defined in [RFC4204] and
   LMP-WDM_CONFIG C-Type defined in [RFC4209].  This document modifies
   the ConfigAck message to include CONFIG objects so that acceptable
   parameters are explicitly identified.  It also describes how a node
   that supports the extensions defined in this document interacts with
   a legacy LMP-capable node.

1.1.  Conventions Used in This Document

   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 [RFC2119].

2.  LMP Message Modifications

   LMP Config, ConfigNack, and ConfigAck messages are modified by this
   document to allow for the inclusion of multiple CONFIG objects.  The
   Config and ConfigNack messages were only defined to carry one CONFIG
   object in [RFC4204].  The ConfigAck message, which was defined
   without carrying any CONFIG objects in [RFC4204], is modified to
   enable explicit identification of negotiated configuration
   parameters.  The inclusion of CONFIG objects in ConfigAck messages is
   triggered by the use of the BehaviorConfig object (defined below) in
   a received Config message.

   The message formats in the sections that follow use Backus-Naur Form
   (BNF) encoding as defined in [RFC5511].

2.1.  Modified Message Formats

   The format of the Config message as updated by this document is as
   follows:
    <Config Message> ::= <Common Header> <LOCAL_CCID> <MESSAGE_ID>
                         <LOCAL_NODE_ID> <CONFIG> [ <CONFIG> ... ]

   The format of the ConfigAck message as updated by this document is as
   follows:

    <ConfigAck Message> ::= <Common Header> <LOCAL_CCID> <LOCAL_NODE_ID>
                            <REMOTE_CCID> <MESSAGE_ID_ACK>
                            <REMOTE_NODE_ID>[ <CONFIG> ... ]

   The format of the ConfigNack message as updated by this document is
   as follows:

    <ConfigNack Message> ::= <Common Header> <LOCAL_CCID>
                             <LOCAL_NODE_ID>  <REMOTE_CCID>
                             <MESSAGE_ID_ACK> <REMOTE_NODE_ID>
                             <CONFIG> [ <CONFIG> ... ]

2.2.  Processing

   Nodes that support the extensions defined in this document MAY
   include multiple CONFIG objects when sending a Config, ConfigAck, and
   ConfigNack message.  A maximum of a single object of any particular
   C-type SHALL be included.  A node that receives a message with
   multiple CONFIG objects of the same C-type SHALL process the first
   object of a particular C-type and ignore any subsequent CONFIG
   objects of the same C-type.  Unless specified as part of the CONFIG
   object definition, ordering of CONFIG objects with different C-type
   values is not significant.

   Nodes that support the extensions defined in this document MUST
   include a BehaviorConfig type object when sending a Config message to
   a neighbor whose support for the extensions is either known or
   unknown.  When the neighbor is known to not support the extensions,
   the object MUST NOT be sent.  Inclusion of other CONFIG objects in a
   Config message is at the discretion of the message sender and is
   based on the rules defined as part of CONFIG object definition.
   Nodes MAY include HelloConfig, LMP-WDM_CONFIG, BehaviorConfig object
   types in a single message.

   Inclusion of multiple CONFIG objects in a ConfigNack message is based
   on the processing of a received Config message.  Per [RFC4204],
   "Parameters where agreement was reached MUST NOT be included in the
   ConfigNack Message."  As such, a ConfigNack message MUST NOT include
   CONFIG objects that are acceptable and MUST include any CONFIG
   objects which are not acceptable.  When a CONFIG object is included
   in a ConfigNack message, per [RFC4204], the object is to include
   "acceptable alternate values for negotiable parameters".

   When sending a ConfigAck message, nodes supporting the extensions
   defined in this document MUST include all CONFIG objects received in
   the corresponding Config message when that message includes a CONFIG
   object of type BehaviorConfig.

3.  LMP Behavior Negotiation

   The Config message is used in the control channel negotiation phase
   of LMP [RFC4204].  The LMP behavior negotiation procedure is defined
   in this document as an addition to this phase.

   The Config message is defined in Section 12.3.1 of [RFC4204] and
   carries the CONFIG object (class name 6) as defined in Section 13.6
   of [RFC4204].

   Two class types have been defined:

   - C-Type = 1, HelloConfig, defined in [RFC4204]

   - C-Type = 2, LMP-WDM_CONFIG, defined in [RFC4209]

   This document defines a third C-Type to report and negotiate LMP
   mechanisms and behaviors.  Its usage indicates support for the
   extensions defined in this document.

3.1.  BehaviorConfig C-Type Format

   Class = 6

   - C-Type = 3, BehaviorConfig

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |S|D|C|                   Must Be Zero (MBZ)                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Flags:

     S: 1 bit

      This bit indicates support for the Trace behavior of SONET/SDH
      technology-specific defined in [RFC4207].

     D: 1 bit

      This bit indicates support for the DWDM behavior defined in
      [RFC4209].

     C: 1 bit

      This bit indicates support for the data channel consistency check
      behavior defined in [RFC5818].

     Must Be Zero (MBZ): Variable length

      The remaining bits in the flags field MUST be set to zero (0).
      This field MUST be sized to ensure 32-bit alignment of the object.

      Other bits may be defined in future documents, in which case the
      number of bits in the MBZ field is expected to change.

3.2.  Processing

   The inclusion of a BehaviorConfig type object in a message is
   discussed above in Section 2.2.

   When sending a BehaviorConfig type object, the N-bit (negotiable) in
   the LMP object header MUST be set (N=1) in the LMP object header.

   When sending a BehaviorConfig type object in Config and ConfigNack
   messages, the flags field SHOULD be set based on the supported
   capabilities of the sending node.  When sending a ConfigAck message,
   the flags field MUST be set to the value received in the
   corresponding Config message.

   When receiving a BehaviorConfig type object, the node compares the
   flags field against its capacities.  Any bit set in the MBZ portion
   of the flags field MUST be interpreted as unacceptable.  Processing
   related to unacceptable values in CONFIG objects is defined in
   [RFC4204] and is not modified by this document.

4.  Backward Compatibility

   The required use of the BehaviorConfig type CONFIG object enables
   nodes that support the extensions defined in this document to
   explicitly identify when a neighboring node does not.  When a non-
   supporting node receives a Config message with the BehaviorConfig
   type CONFIG object or multiple CONFIG objects, its behavior is to be
   one of the following behaviors:

   a) Reject the Config message because of the unknown BehaviorConfig
      object type and send a ConfigNack message which includes the
      unsupported C-type.

   b) Reject the message because of multiple CONFIG objects and send a
      ConfigNack message which includes all but one of the CONFIG
      objects.

   c) Silently ignore the one or more of the CONFIG object, and respond
      with a ConfigAck message that does not include any CONFIG objects.

   d) Treat the message as malformed, and discard it without any
      response.

   Behaviors (a) and (b) result in ConfigNack messages with a
   BehaviorConfig type object whose contents are identical to what was
   sent in the Config message.  Behavior (c) results in a ConfigAck
   message without a BehaviorConfig type CONFIG object.  In each of
   these cases, the node SHOULD explicitly identify that the LMP
   neighbor does not support the extensions defined in this document.

   Behavior (d) results in no response at all.  When the node reaches
   the "retry limit", defined in [RFC4204], the node SHOULD infer that
   the LMP neighbor does not support the extensions defined in this
   document.

   Once a node identifies a neighbor as not supporting the extensions
   defined in this document, the node SHOULD follow previously defined
   Config message usage.

5.  Security Considerations

   [RFC4204] describes how LMP messages between peers can be secured,
   and these measures are equally applicable to messages carrying the
   new CONFIG object defined in this document.

   Alone, the procedures described in this document do not constitute a
   security risk, since they do not cause any change in network state.
   It would be possible, if the messages were intercepted or spoofed to
   cause bogus alerts in the management plane, or to cause LMP peers to
   consider that they could or could not operate protocol extensions,
   and so the use of the LMP security measures are RECOMMENDED.

   Note, however, that [RFC4204] references for security have been
   updated with [RFC4301], and the current reference for IKEv2 is
   [RFC5996].

6.  IANA Considerations

6.1.  New LMP Class Type

   IANA maintains the "Link Management Protocol (LMP) Parameters"
   registry, which has a subregistry called "LMP Object Class name space
   and Class type (C-Type)".

   IANA has made an assignment from this registry as follows:

      6   CONFIG                              [RFC4204]

   CONFIG Object Class type name space:

      C-Type        Description            Reference
      ------------  ---------------------  ---------
      3             BehaviorConfig         RFC 6898

6.2.  New Capabilities Registry

   IANA has created a new subregistry of the "Link Management Protocol
   (LMP) Parameters" registry to track the Behavior Configuration bits
   defined in Section 2 of this document.  This registry is called "LMP
   Behavior Configuration Flags".

   Allocations from this registry are by Standards Action.

   Bits in this registry are numbered from zero as the most significant
   bit (transmitted first).  The number of bits that can be present is
   limited by the length field of the CONFIG object, which gives rise to
   (255 x 32)-8 = 8152.  IANA is strongly recommended to allocate new
   bits with the lowest available unused number.

   The registry is initially populated as follows:

      Bit    | Bit  | Meaning                                | Reference
      Number | Name |                                        |
      -------+------+----------------------------------------+----------
        0    |   S  | SONET/SDH Test support                 | RFC 6898
        1    |   D  | DWDM support                           | RFC 6898
        2    |   C  | Data Channel consistency check support | RFC 6898

7.  Normative References

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

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, December 2005.

   [RFC5996]  Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
              "Internet Key Exchange Protocol Version 2 (IKEv2)", RFC
              5996, September 2010.

   [RFC4204]  Lang, J., Ed., "Link Management Protocol (LMP)", RFC 4204,
              October 2005.

   [RFC4207]  Lang, J. and D. Papadimitriou, "Synchronous Optical
              Network (SONET)/Synchronous Digital Hierarchy (SDH)
              Encoding for Link Management Protocol (LMP) Test
              Messages", RFC 4207, October 2005.

   [RFC4209]  Fredette, A., Ed., and J. Lang, Ed., "Link Management
              Protocol (LMP) for Dense Wavelength Division Multiplexing
              (DWDM) Optical Line Systems", RFC 4209, October 2005.

   [RFC5818]  Li, D., Xu, H., Bardalai, S., Meuric, J., and D. Caviglia,
              "Data Channel Status Confirmation Extensions for the Link
              Management Protocol", RFC 5818, April 2010.

   [RFC5511]  Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
              Used to Form Encoding Rules in Various Routing Protocol
              Specifications", RFC 5511, April 2009.

8.  Acknowledgments

   Thanks to Adrian Farrel and Richard Graveman for their useful
   comments.

9.  Contributors

   Diego Caviglia
   Ericsson
   Via E. Melen, 77
   Genova - Erzelli
   Italy
   Phone: +39 010 600 3736
   EMail: diego.caviglia@ericsson.com

Authors' Addresses

   Dan Li
   Huawei Technologies
   F3-5-B R&D Center, Huawei Industrial Base,
   Shenzhen 518129
   China
   Phone: +86 755-289-70230
   EMail: huawei.danli@huawei.com

   Daniele Ceccarelli
   Ericsson
   Via E. Melen, 77
   Genova - Erzelli
   Italy
   EMail: daniele.ceccarelli@ericsson.com

   Lou Berger
   LabN Consulting, L.L.C.
   EMail: lberger@labn.net