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Versions: 00 01 02 03 04 05 06 07 08 09 RFC 5828

Internet Draft                                         Don Fedyk, Nortel
Category: Informational                                 Lou Berger, LabN
Expiration Date: August 13, 2009              Loa Andersson, Ericsson AB

                                                       February 13, 2009

      Generalized Multi-Protocol Label Switching (GMPLS) Ethernet
               Label Switching Architecture and Framework

              draft-ietf-ccamp-gmpls-ethernet-arch-04.txt

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on August 13, 2009.

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   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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Abstract

   There has been significant recent work in increasing the capabilities
   of Ethernet switches and Ethernet forwarding models. As a
   consequence, the role of Ethernet is rapidly expanding into
   "transport networks" that previously were the domain of other
   technologies such as Synchronous Optical Network (SONET)/Synchronous
   Digital Hierarchy (SDH), Time-Division Multiplex (TDM) and



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   Asynchronous Transfer Mode (ATM). This document defines an
   architecture and framework for a Generalized GMPLS based control
   plane for Ethernet in this "transport network" capacity. GMPLS has
   already been specified for similar technologies. Some additional
   extensions to the GMPLS control plane are needed and this document
   provides a framework for these extensions.
















































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Table of Contents

 1      Introduction  ..............................................   4
 1.1    Terminology  ...............................................   6
 1.1.1  Concepts  ..................................................   6
 1.1.2  Abbreviations and Acronyms  ................................   7
 2      Background  ................................................   8
 2.1    Ethernet Switching  ........................................   9
 2.2    Operations, Administration, and Maintenance (OAM)  .........  11
 2.3    Ethernet Switching Characteristics  ........................  12
 3      Framework  .................................................  12
 4      GMPLS Routing and Addressing Model  ........................  14
 4.1    GMPLS Routing  .............................................  15
 4.2    Control Plane Network  .....................................  15
 5      GMPLS Signaling   ..........................................  15
 6      Link Management   ..........................................  16
 7      Path Computation and Selection  ............................  17
 8      Multiple VLANs  ............................................  18
 9      Security Considerations  ...................................  18
10      IANA Considerations  .......................................  18
11      References  ................................................  18
11.1    Normative References  ......................................  18
11.2    Informative References  ....................................  19
12      Acknowledgments  ...........................................  20
13      Author's Addresses  ........................................  21





















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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].



1. Introduction

   There has been significant recent work in increasing the capabilities
   of Ethernet switches. As a consequence, the role of Ethernet is
   rapidly expanding into "transport networks" that previously were the
   domain of other technologies such as SONET/SDH TDM and ATM.  The
   evolution and development of Ethernet capabilities in these areas is
   a very active and ongoing process.

   Multiple organizations have been active in extending Ethernet
   technology.  This activity has taken place in the Institute of
   Electrical and Electronics Engineers (IEEE) 802.1 Working Group, the
   International Telecommunication Union (ITU) and the Metro Ethernet
   Forum (MEF).  These groups have been focusing on Ethernet forwarding,
   Ethernet management plane extensions and the Ethernet Spanning Tree
   Control Plane, but not on an explicitly routed, constraint based
   control plane.

   In the forwarding plane context, extensions have been, or are being,
   defined to support different Ethernet forwarding models, protection
   modes and service interfaces.  Examples of such extensions include
   [802.1ah], [802.1Qay], [G.8011] and [MEF.6]. These extensions allow
   for greater flexibility in the forwarding plane and, in some cases,
   the extensions allow for a departure from forwarding based on
   Ethernet spanning tree. In the 802.1Qay case, greater flexibility in
   forwarding is achieved through the addition of a "provider" address
   space.

   This document provides a framework for GMPLS Ethernet Label switching
   (GELS). It will be followed by technology specific documents. GELS
   will likely require more than one switching type, and the GMPLS
   procedures that will need to be changed are dependent on switching,
   and thus will be covered in the technology specific documents.

   In the new provider bridge model developed in the IEEE 802.1ad
   project and amended to the IEEE 802.1Q standard [802.1Q], an extra
   Virtual Local Area Network (VLAN) identifier (VID) is added. This
   VLAN is referred to as the Service VID, (S-VID and is carried in a
   Service TAG (S-TAG). In provider backbone bridges (PBB) [802.1ah] a
   backbone VID (B-VID) and B-MAC header with a Service Instance (I-TAG)



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   encapsulates a customer Ethernet frame or a service Ethernet frame.
   An example of Ethernet protection extensions can be found in
   [G.8031]. In the IEEE 802.1Q standard the terms Provider Backbone
   Bridges (PBB) and Provider Backbone Bridged Network (PBBN) is used in
   the context of these extensions.

   Ethernet operations, administration, and maintenance (OAM) is another
   important area that is being extended to enable provider Ethernet
   services.  Related extensions can be found in [802.1ag] and [Y.1731].

   An Ethernet based service model is also being defined within the
   context of the Metro Ethernet Forum (MEF) and International
   Telecommunication Union (ITU).  [MEF.6] and [G.8011] provide parallel
   frameworks for defining network-oriented characteristics of Ethernet
   services in transport networks. The framework discusses general
   Ethernet connection characteristics, Ethernet User-Network Interfaces
   (UNIs) and Ethernet Network-Network Interfaces (NNIs). Within this
   framework, [G.8011.1] defines the Ethernet Private Line (EPL) service
   and [G.8011.2] defines the Ethernet Virtual Private Line (EVPL)
   service. [MEF.6] covers both service types.  These activities are
   consistent with the types of Ethernet switching defined in [802.1ah].

   The Ethernet forwarding and management plane extensions explicitly
   allow for the disabling of standard Ethernet spanning tree but do not
   define an explicitly routed, constraint based control plane.  The
   IEEE 802.1, in [802.1Qay], works on an new amendment that explicitly
   allows for traffic engineering of Ethernet forwarding paths.

   The IETF chartered the GMPLS work to specify a common control plane
   for physical path and core tunneling technologies for the Internet
   and telecommunication service providers. The GMPLS architecture is
   specified in RFC3945 [RFC3945]. The protocols specified for GMPLS
   have been used to control "Transport Networks", e.g. Optical and TDM
   networks.

   This document provides a framework for use of GMPLS to control
   "transport" Ethernet. The GMPLS architecture already handles a number
   of transport technologies but "transport" Ethernet adds a few new
   constraints that must be documented. Some additional extensions to
   the GMPLS control plane are needed and this document provides a
   framework for these extensions.  All extensions to support Eth-LSPs
   are also expected to build on the GMPLS Architecture and related
   specifications.

   This document introduces and explains GMPLS control plane deployment
   for Ethernet and the concept of the Ethernet Label Switched Path
   (Eth-LSP).  The data plane aspects of Eth-LSPs are outside the scope
   of this document and IETF activities.



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   The intent of this document is to reuse and align with as much of the
   GMPLS protocols as possible.  For example reusing the IP control
   plane addressing allows existing signaling, routing, LMP and path
   computation to be used as specified.  The GMPLS protocols support a
   set of tools for hierarchical LSPs as well as contiguous LSPs. GMPLS
   specific protocol mechanisms support a variety of networks from peer
   to peer to UNIs and NNIs. Additions to existing GMPLS capabilities
   will only be made to accommodate features unique to "transport"
   Ethernet.


1.1. Terminology

1.1.1. Concepts

   The following are basic Ethernet and GMPLS terms:

     o Asymmetric Bandwidth

       This term refers to a property of a Bidirectional service
       instance may have differing bandwidth allocation in each
       direction.

     o Bidirectional Congruent LSP

       This term refers to the property of a bi-directional LSP that
       uses only the same nodes, ports, and links in both directions.
       Ethernet data planes are normally bi-directional or reverse path
       congruent.

     o Contiguous Eth-LSP

       A contiguous Eth-LSP is an Eth-LSP that maps one to one with an
       another LSP at a VLAN boundary. Stitched LSP are contiguous LSPs.

     o Eth-LSP

       This term refers to Ethernet switched paths that may be
       controlled via GMPLS.

     o Hierarchical Eth-LSP

       Hierarchical Eth-LSPs aggregate Eth-LSPs by creating a hierarchy
       of Eth-LSPs.







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     o In-band GMPLS Signaling

       In-band GMPLS Signaling is IP based control messages which are
       sent on the native Ethernet links encapsulated by a single hop
       Ethernet header. Logical links that use a dedicated VID on the
       same physical links would be considered In-band signaling.

     o Out-of-band GMPLS Signaling

       Out-of-band GMPLS Signaling is IP based control messages which
       are sent between Ethernet switches that uses some other links
       other than the Ethernet data plane links. Out of band signaling
       typically shares a different fate from the data links.

     o Point-to-point (P2P) Traffic Engineering (TE) Service Instance

       An TE service instance made up from two P2P unidirectional Eth-
       LSPs.

     o Point-to-multipoint (P2MP) Traffic Engineering (TE) Service
       Instance

       An TE service Instance supported by a set of LSPs which comprises
       one P2MP LSP from a root to n leaves plus a Bidirectional
       Congruent point-to-point (P2P) LSP from each of the leaves to the
       root.

     o Shared forwarding

       Shared forwarding is a property of a data path where a single
       forwarding entry (VID + DMAC) may be used for frames from
       multiple sources (SMAC). Shared forwarding does not change any
       data plane behavior. Shared forwarding saves forwarding database
       (FDB) entries only.  Shared forwarding offers similar benefits to
       merging in the data plane. However in shared forwarding the
       Ethernet data packets are unchanged when using shared forwarding.
       With shared forwarding dedicated control plane states for all
       Eth-LSP are maintained regardless of shared forwarding entries.



1.1.2. Abbreviations and Acronyms

   The following abbreviations and acronyms are used in this document:

   CCM             Continuity Check Message
   CFM             Connectivity Fault Management
   DMAC            Destination MAC Address



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   Eth-LSP         Ethernet Label Switched Path
   I-SID           Service Identifier
   LMP             Link Management Protocol
   MAC             Media Access Control
   MP2MP           Multipoint to multipoint
   NMS             Network Management System
   OAM             Operations, Administration and Maintenance
   PBB             Provider Backbone Bridges [802.1ah]
   PBB-TE          Provider Backbone Bridges Traffic Engineering
                   [802.1Qay]
   P2P             Point to Point
   P2MP            Point to Multipoint
   QoS             Quality of Service
   SMAC            Source MAC Address
   S-TAG           A service TAG defined in the 802.1 Standard
                   [802.1Q]
   TE              Traffic Engineering
   TAG             An Ethernet short form for a TAG Header
   TAG Header      An extension to an Ethernet frame carrying
                   priority and other information.
   TSpec           Traffic specification
   VID             VLAN Identifier
   VLAN            Virtual LAN


2. Background

   This section provides background to the types of switching and
   services that are supported within the defined framework.  The former
   is particularly important as it identifies the switching functions
   that GMPLS will need to represent and control. The intent is for this
   document to allow for all standard forms of Ethernet switching and
   services.

   The material presented in this section is based on both finished and
   on-going work taking place in the IEEE 802.1 Working Group, the ITU
   and the MEF.  This section references and, to some degree, summarizes
   that work.  This section is not a replacement for, or an
   authoritative description of that work.












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2.1. Ethernet Switching

   In Ethernet switching terminology, the bridge relay is responsible
   for forwarding and replicating the frames.  Bridge relays forward
   frames based on the Ethernet header fields: Virtual Local Area
   Network (VLAN) Identifiers (VID) and Destination Media Access Control
   (DMAC) address. PBB [802.1ah] has also introduced a Service Instance
   tag (I-TAG).  Across all the Ethernet extensions (already referenced
   in the Introduction), multiple forwarding functions, or service
   interfaces, have been defined using the combination of VIDs, DMACs,
   and I-TAGs.  PBB [802.1ah] provides a breakdown of the different
   types of Ethernet switching services. Figure 1 reproduces this
   breakdown.

                              PBB Network
                             Service Types
                          _,,-'    |    '--.._
                    _,.-''         |          `'--.._
              _,.--'               |                 `'--..
        Port based              S-tagged              I-tagged
                               _,-     -.
                            _.'          `.
                         _,'               `.
                     one-to-one           bundled
                                         _.-   =.
                                     _.-'        ``-.._
                                 _.-'                 `-..
                            many-to-one              all-to-one
                                                          |
                                                          |
                                                          |
                                                     Transparent

                Figure 1: Ethernet Switching Service Types

   The types are defined in Clause 25 of [802.1ah], and are consistent
   with the definitions of Ethernet services supported in [G.8011] and
   [MEF.6].  To summarize the definitions:

   o Port based
     This is a frame based service that supports specific frame types,
     no Service VLAN tagging, with MAC address based switching.

   o S-tagged
     There are multiple Service VLAN tag (S-tag) aware services,
     including:

     + one-to-one



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       In this service, each VLAN identifier (VID) is mapped into a
       different service.

     + Bundled
       Bundled S-tagged service supports the mapping of multiple VIDs
       into a single service and include:

       * many-to-one
         In this frame based service, multiple VIDs are mapped into the
         same service.

       * all-to-one
         In this frame based service, all VIDs are mapped into the same
         service.

         - transparent
           This is a special case, all frames are mapped from a single
           incoming port to a single destination Ethernet port.

   o I-tagged
     The edge of a PBBN consists of a combined backbone relay (B-
     component relay) and service instance relay (I-component relay).
     An I-Tag contains a service identifier (24 bit I-SID) and priority
     markings as well as some other fields.  An I-Tagged service is
     typically between the edges of the PBBN and terminated at each edge
     on an I-component that faces a customer port so the service is
     often not visible except at the edges.  However, since the I-
     component relay involves a distinct relay, it is possible to have a
     visible I-Tagged Service by separating the I component relay from
     the B-component relay.  Two examples where it makes sense to do
     this are: an I-Tagged service between two PBBNs and as an
     attachment to a customer's Provider Instance Port.

   In general, the different switching type determines which of the
   Ethernet header fields are used in the forwarding/switching function,
   e.g. VID only or VID and DMACs.  The switching type may also require
   the use of additional Ethernet headers or fields. Services defined
   for UNIs tend to use the headers on a hop-by-hop basis.

   In most bridging cases, the header fields cannot be changed hop-by-
   hop, but some translations of VID field values are permitted,
   typically at the edges. While not specifically described in
   [802.1ah], the Ethernet services being defined in the context of
   [MEF.6] and [G.8011] also fall into the types defined in Figure 1.

   Across all service types, the Ethernet data plane is bi-directional
   congruent. This means that the forward and reverse paths share the
   exact same set of nodes, ports and bi-directional links.  This



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   property is fundamental. The 802.1 group has maintained this bi-
   directional congruent property in the definition of Connectivity
   Fault Management (CFM) which is part of the overall Operations
   Administration and Management (OAM) capability.


2.2. Operations, Administration, and Maintenance (OAM)

   Robustness is enhanced with the addition of data plane OAM to provide
   both fault and performance management.

   Ethernet OAM messages [802.1ag] and [Y.1731], rely on data plane
   forwarding for both directions.  Determining a broken path or
   misdirected packet in this case relies on OAM following the Eth-LSP.
   These identifiers are dependent on the data plane so it works equally
   well for provisioned or GMPLS controlled paths.

   Ethernet OAM currently consists of:
   Defined in both [802.1ag & Y.1731]:
   - CCM/RDI: Connectivity Check, Remote Defect Indication
   - LBM/LBR: Loopback Message, Loopback Reply
   - LTM/LTR: Link trace Message, Link trace Reply
   - VSM/VSR: Vendor-specific extensions Message/Reply

   Additionally defined in [Y.1731]:
   - AIS:        Alarm Indication Signal
   - LCK:        Locked Signal
   - TST:        Test
   - LMM/LMR:    Loss Measurement Message/Reply
   - DM/DMM/DMR: Delay Measurement
   - EXM/EXR:    Experimental
   - APS, MCC:   Automatic Protection Switching, Maintenance
                 Communication Channel

   With some Eth-LSP label formats bi-directional transactions (e.g.
   LBM/LBR) and reverse direction transactions MAY have a different VID
   for each direction.  Both Y.1731 & 802.1ag assumes that bi-
   directional transactions (e.g., LBM/LBR) use the same VID in both
   directions. However in some scenarios, especially with explicitly
   routed paths [802.1Qay], it is possible that different VIDs are used
   upstream and downstream. In the context of [802.1Qay] work is ongoing
   to update [802.1ag] to support such scenarios."









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2.3. Ethernet Switching Characteristics

   Ethernet is similar to MPLS it encapsulates many packet and frame
   types for data transmission.  In Ethernet the encapsulated data is
   referred to as MAC client data.  The encapsulation is an Ethernet MAC
   frame with a header, a source address, destination address, optional
   VLAN identifier, Type and length on the front of the MAC client data
   with optional padding and a Frame Check Sequence at the end of the
   frame.

   The type of MAC client data is typically identified by an "Ethertype"
   value. This is an explicit type indication but Ethernet also supports
   an implicit type indication.

   Ethernet bridging switches Ethernet based on the Frame destination
   address and VLAN. The VLAN identifies an active topology.  The
   address is assumed to be unique and invariant within the VLAN. MAC
   addresses are often globally unique but this is not necessary for
   bridging.


3. Framework

   As defined in the GMPLS Architecture [RFC3945], the GMPLS control
   plane can be applied to a technology by controlling the data plane
   and switching characteristics of that technology. The architecture
   includes a clear separation between a control plane and a data plane.
   Control plane and data plane separation allows the GMPLS control
   plane to remain architecturally and functionally unchanged while
   controlling different technologies.  The architecture also requires
   IP connectivity for the control plane to exchange information, but
   does not otherwise require an IP data plane.

   All aspects of GMPLS, i.e., addressing, signaling, routing and link
   management, may be applied to Ethernet switching.  GMPLS can provide
   control for traffic engineered and protected Ethernet service paths.
   This document defines the term "Eth-LSP" to refer to Ethernet service
   paths that are controlled via GMPLS. As is the case with all GMPLS
   controlled services, Eth-LSPs can leverage common traffic engineering
   attributes such as:

   - bandwidth profile;
   - forwarding priority level;
   - connection preemption characteristics;
   - protection/resiliency capability;
   - routing policy, such as an explicit route;
   - bi-directional service;
   - end-to-end and segment protection;



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   - hierarchy

   The bandwidth profile may be used to set committed information rate,
   peak information rate, and policies based on either under-
   subscription or over-subscription.  Services covered by this
   framework MUST use a TSpec that follows the Ethernet Traffic
   parameters defined in [ETH-TSPEC].

   In applying GMPLS to "transport" Ethernet, GMPLS may be extended to
   work with the Ethernet data plane and switching functions.  The
   definition of GMPLS support for Ethernet is multi-faceted due to the
   different forwarding/switching functions inherent in the different
   service types discussed in Section 2.1. In general, the header fields
   used in the forwarding/switching function, e.g. VID and DMAC, can be
   characterized as a data plane label.  In some circumstances these
   fields will be constant along the path of the Eth-LSP, and in others
   they may vary hop-by-hop or at certain interfaces only along the
   path. In the case where the "labels" must be forwarded unchanged,
   there are a few constraints on the label allocation that are similar
   to some other technologies such as lambda labels.

   The GMPLS architecture, per [RFC3945], allowed for control of
   Ethernet bridges and other layer 2 technologies using the L2SC
   switching type.  Although, it is worth noting that the control of
   Ethernet switching was not explicitly defined in [RFC3471], [RFC4202]
   or any other subsequent GMPLS reference document.

   The characteristics of the "transport" Ethernet data plane are not
   modified in order to apply GMPLS control.  For example, consider the
   IEEE 802.1Q [802.1Q] data plane: The VID is used as a "filter"
   pointing to a particular forwarding table, and if the DMAC is found
   in that forwarding table the forwarding decision is taken based on
   the DMAC. When forwarding using an Ethernet spanning tree, if the
   DMAC is not found the frame is broadcast over all outgoing interfaces
   for which that VID is defined.  This valid MAC checking and broadcast
   supports Ethernet learning.  A special case is when a VID is defined
   for only two ports on one bridge, effectively resulting in a p2p
   forwarding constraint, in this case all frames tagged with that VID
   received over one of these ports are forward over the other port
   without address learning.

   [802.1Qay]allows for turning off learning and hence the broadcast
   mechanism providing means to create explicitly routed Ethernet
   connections.

   This document does not define any specific format for an Eth-LSP
   label. Rather, it is expected that service specific documents will
   define any signaling and routing extensions needed to support a



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   specific Ethernet service.  Depending on the requirements of a
   service, it may be necessary to define multiple GMPLS protocol
   extensions and procedures. It is expected that all such extensions
   will be consistent with this document.

   It is expected that key a requirement for service specific documents
   will be to describe label formats and encodings. It may also be
   necessary to provide a mechanism to identify the required Ethernet
   service type in signaling and a way to advertise the capabilities of
   Ethernet switches in the routing protocols. These mechanisms must
   make it possible to distinguish between requests for different
   paradigms including new, future, and existing paradigms.

   The Switching Type and Interface Switching Capability Descriptor
   share a common set of values and are defined in [RFC3945], [RFC3471],
   and [RFC4202] as indicators of the type of switching that should
   ([RFC3471]) and can ([RFC4202]) be performed on a particular link for
   an LSP.  The L2SC switching type may already be used by
   implementations performing layer 2 switching including Ethernet. To
   support the continued use of that switching type and those
   implementations, a new switching type MUST be defined for each new
   Ethernet switching paradigm that is supported.

   For discussion purposes, we decompose the problem of applying GMPLS
   into the functions of Routing, Signaling, Link Management and Path
   Selection. It is possible to use some functions of GMPLS alone or in
   partial combinations. In most cases using all functions of GMPLS
   leads to less operational overhead than partial combinations.


4. GMPLS Routing and Addressing Model

   The GMPLS Routing and Addressing Model is not modified by this
   document.  GMPLS control for Eth-LSPs uses the Routing and Addressing
   Model described in [RFC3945].  Most notably this includes the use of
   IP addresses to identify interfaces and LSP end-points.  It also
   includes support for both numbered and unnumbered interfaces.

   In the case where another address family or type of identifier is
   required to support an Ethernet service, extensions may be defined to
   provide mapping to an IP address.  Support of Ethernet MUST strictly
   comply to the GMPLS protocol suite addressing as specific in RFC3471,
   RFC3473 and related.








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4.1. GMPLS Routing

   GMPLS routing as defined in [RFC4202] is IP routing with the opaque
   TLV extensions for the purpose of distributing GMPLS related TE
   (router and link) information. As is always the case with GMPLS, TE
   information is populated with TE resources coordinated with LMP or
   from configured information. The bandwidth resources of the links are
   tracked as Eth-LSPs are set up. Interfaces supporting the switching
   of Eth-LSPs are identified using the appropriate Interface Switching
   Capabilities. As mentioned in Section 3, the definition of one or
   more new Interface Switching Capabilities to support Eth-LSPs is
   expected.  The L2SC Interface Switching Capabilities MUST NOT be used
   to represent interfaces capable of supporting Eth-LSPs.  Interface
   Switching Capability specific TE information may be defined as needed
   to support the requirements of a specific Ethernet Switching Service
   Type.

   GMPLS Routing is an optional piece but it is highly valuable in
   maintaining topology and distributing the TE database for path
   management and dynamic path computation.


4.2. Control Plane Network

   In order for a GMPLS control plane to operate, an IP network of
   sufficient capacity to handle the information exchange between the
   GMPLS routing and signaling protocols is necessary.

   One way to implement this is with an IGP that views each switch as a
   terminated IP adjacency. In other words, IP traffic and a simple
   routing table are available for the control plane but there is no
   requirement for a high performance IP data plane.

   This IP connectivity can be provided as a separate independent
   network (out of band) or integrated with the Ethernet switches (in-
   band).


5. GMPLS Signaling

   GMPLS signaling, see [RFC3471][RFC3473], is well suited to the
   control of Eth-LSPs and Ethernet switches.  Signaling enables the
   ability to dynamically establish a path from an ingress node to an
   egress node.  The signaled path may be completely static and not
   change for the duration of its lifetime. However, signaling also has
   the capability to dynamically adjust the path in a coordinated
   fashion after the path has been established. The range of signaling
   options from static to dynamic are under operator control.



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   Standardized signaling also improves multi-vendor interoperability
   over simple management.

   GMPLS signaling supports the establishment and control of bi-
   directional and unidirectional data paths. Ethernet is bi-directional
   by nature and the CFM has been built to leverage this. Prior to CFM
   the emulation of a physical wire and the learning requirements also
   mandated bi-directional connections. Given this, Eth-LSPs MUST be bi-
   directional congruent. Eth-LSPs may be either P2P or P2MP (see
   [RFC4875]).  GMPLS signaling also allows for full and partial LSP
   protection; see [RFC4872] and [RFC4873].

   Note that standard GMPLS does not support different bandwidth in each
   direction of a bi-directional LSP. See [GMPLS-ASYM] if asymmetric
   bandwidth bi-directional LSPs are required.


6. Link Management

   Link discovery has been specified for Ethernet in [802.1AB].  However
   the 802.1AB capability is an optional feature, is not necessarily
   operating before a link is operational, and it primarily supports the
   management plane. The benefits of running link discovery in large
   systems are significant. Link discovery may reduce configuration and
   reduce the possibility of undetected errors in configuration as well
   as exposing misconnections.

   In the GMPLS context, LMP [RFC4204] has been defined to support link
   management and discovery features.  LMP also supports the automated
   creation of unnumbered interfaces. If LMP is not used there is an
   additional configuration requirement to add GMPLS link identifiers.
   For large-scale implementations LMP would be beneficial. LMP also has
   fault management capabilities that overlap with CFM [802.1ag] and
   [Y.1731]. It is the goal of the architecture to allow the selection
   of the best tool set for the user needs so full functionality of
   Ethernet CFM should be allowed.

   LMP and 802.1AB are relatively independent. The LMP capability should
   be sufficient to remove the need for 802.1AB but 802.1 AB can be run
   in parallel or independently if desired.  Figure 2 provides possible
   ways of using LMP, 802.1AB and 802.1ag in combination.

   Figure 2 illustrates the functional relationship of link management
   and OAM schemes.   It is intended that LMP would use functions of
   link property correlation but that Ethernet mechanisms for OAM such
   as CFM, link trace etc would be used for fault management and fault
   trace.




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        +-------------+        +-------------+
        | +---------+ |        | +---------+ |
        | |         | |        | |         | |GMPLS
        | |  LMP    |-|<------>|-|  LMP    | |Link Property
        | |         | |        | |         | |Correlation
        | |  (opt)  | |IP      | |  (opt)  | |
        | |         | |        | |         | | Bundling
        | +---------+ |        | +---------+ |
        | +---------+ |        | +---------+ |
        | |         | |        | |         | |
        | | 802.1AB |-|<------>|-| 802.1AB | |P2P
        | |  (opt)  | |Ethernet| |  (opt)  | |link identifiers
        | |         | |        | |         | |
        | +---------+ |        | +---------+ |
        | +---------+ |        | +---------+ |
        | |         | |        | |         | |End to End
   -----|-| 802.1ag |-|<------>|-| 802.1ag |-|-------
        | | Y.1731  | |Ethernet| | Y.1731  | |Fault Management
        | |  (opt)  | |        | |  (opt)  | |Performance
        | |         | |        | |         | |Management
        | +---------+ |        | +---------+ |
        +-------------+        +-------------+
             Switch 1    link      Switch 2

                 Figure 2: Logical Link Management Options


7. Path Computation and Selection

   GMPLS does not specify a specific method for selecting paths or
   supporting path computation. GMPLS allows for a wide range of
   possibilities supported from very simple path computation to very
   elaborate path coordination where a large number of coordinated paths
   are required.  Path computation can take the form of paths being
   computed in a fully distributed fashion, on a management station with
   local computation for rerouting, or on more sophisticated path
   computation servers.

   Eth-LSPs may be supported using any path selection or computation
   mechanism. As is the case with any GMPLS path selection function, and
   common to all path selection mechanisms, the path selection process
   should take into consideration Switching Capabilities and Encoding
   advertised for a particular interface. Eth-LSPs may also make use of
   the emerging path computation element and selection work; see
   [RFC4655]






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8. Multiple VLANs

   This document allows for the support the signaling of Ethernet
   parameters across multiple VLANs supporting both contiguous Eth-LSP
   and Hierarchical Ethernet LSPs. The intention is to reuse GMPLS
   hierarchy for the support of Peer to Peer models, UNIs and NNIs.


9. Security Considerations

   The architecture for GMPLS controlled "transport" Ethernet assumes
   that the network consists of trusted devices, but does not require
   that the ports over which a UNI are defined are trusted, nor does
   equipment connected to these ports need to be trusted. Access to the
   trusted network SHALL only occur through the protocols defined in the
   UNI or NNI or through protected management interfaces.

   When in-band GMPLS signaling is used for the control plane the
   security of the control plane and the data plane may affect each
   other.  When out-of-band GMPLS signaling is used the control plane
   the data plane security is decoupled from the control plane and
   therefore the security of the data plane has less impact on overall
   security.

   Where GMPLS is applied to the control of VLAN only, the commonly
   known techniques for mitigation of Ethernet DOS attacks may be
   required on UNI ports.

   For a more comprehensive discussion on GMPLS security please see the
   MPLS and GMPLS Security Framework [SECURITY].


10. IANA Considerations

   No new values are specified in this document.


11. References

11.1. Normative References

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

   [RFC3471] Berger, L. (editor), "Generalized MPLS Signaling
             Functional Description", January 2003, RFC3471.





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   [RFC3473] Berger, L. (editor), "Generalized Multi-Protocol Label
             Switching (GMPLS) Signaling Resource ReserVation
             Protocol-Traffic Engineering (RSVP-TE) Extensions",
             January 2003, RFC3473.

   [RFC4202] Kompella, K., Rekhter, Y., "Routing Extensions in
             Support of Generalized MPLS", RFC 4202, October 2005


11.2. Informative References

   [G.8031] ITU-T Draft Recommendation G.8031, Ethernet Protection
            Switching.

   [G.8011] ITU-T Draft Recommendation G. 8011, Ethernet over
            Transport - Ethernet services framework.

   [RFC3945] E. Mannie, Ed., "Generalized Multi-Protocol Label
             Switching (GMPLS) Architecture", RFC 3495.

   [802.1AB] "IEEE Standard for Local and Metropolitan Area
              Networks, Station and Media Access Control
              Connectivity Discovery" (2004).

   [802.1ag] "IEEE Standard for Local and Metropolitan Area
              Networks - Virtual Bridged Local Area Networks
              - Amendment 5:Connectivity Fault Management",
              (2007).

   [802.1ah] "IEEE Standard for Local and Metropolitan Area
              Networks - Virtual Bridged Local Area Networks
              - Amendment 6: Provider Backbone Bridges", (2008)

   [802.1Qay] "IEEE standard for Provider Backbone Bridge Traffic
              Engineering", work in progress.

   [802.1Q] "IEEE standard for Virtual Bridged Local Area Networks
            802.1Q-2005", May 19, 2006

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

   [MEF.6] The Metro Ethernet Forum MEF 6 (2004), "Ethernet Services
           Definitions - Phase I".

   [MEF.10] The Metro Ethernet Forum MEF 10 (2004), "Ethernet
            Services Attributes Phase 1".




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   [RFC4875] Aggarwal, R. Ed., "Extensions to RSVP-TE for Point to
             Multipoint TE LSPs", IETF RFC 4875, May 2007

   [RFC4655] Farrel, A. et.al., "Path Computation Element (PCE)
             Architecture", RCF 4655, August 2006.

   [RFC4872] Lang et.al., "RSVP-TE Extensions in support of
             End-to-End Generalized Multi-Protocol Label Switching
             (GMPLS)-based Recovery ", RFC 4872, May 2007.

   [RFC4873] Berger, L. et.al.,"MPLS Segment Recovery", RFC 4873, May
             2007.

   [Y.1731] ITU-T Draft Recommendation Y.1731(ethoam), " OAM
            Functions and Mechanisms for Ethernet based Networks ",
            work in progress.

   [GMPLS-ASYM] Berger, L. et al., "GMPLS Asymmetric Bandwidth
                Bidirectional LSPs", work in progress.

   [ETH-TSPEC] Papadimitriou, D., "Ethernet Traffic Parameters", work
               in progress.

   [SECURITY] Luyuan Fang, Ed., " Security Framework for MPLS
              and GMPLS Networks", work in progress.


12. Acknowledgments

   There were many people involved in the initiation of this work prior
   to this document. The GELS framework draft and the PBB-TE extensions
   drafts were two drafts the helped shape and justify this work. We
   acknowledge the work of these authors of these initial drafts:
   Dimitri Papadimitriou, Nurit Sprecher, Jaihyung Cho, Dave Allan,
   Peter Busschbach, Attila Takacs, Thomas Eriksson, Diego Caviglia,
   Himanshu Shah, Greg Sunderwood, Alan McGuire, Nabil Bitar.

   George Swallow contributed significantly to this document.













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13. Author's Addresses

   Don Fedyk
   Nortel Networks
   600 Technology Park Drive
   Billerica, MA, 01821
   Phone: +1-978-288-3041
   Email: dwfedyk@nortel.com

   Lou Berger
   LabN Consulting, L.L.C.
   Phone: +1-301-468-9228
   Email: lberger@labn.net

   Loa Andersson
   Ericsson AB
   Phone:+46 8 632 77 14
   Email: loa@pi.nu

































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