Generalized Multiprotocol Label Switching (GMPLS) Ethernet Label Switching Architecture and Framework

Internet Engineering Task Force (IETF)                          D. Fedyk
Request for Comments: 5828                                Alcatel-Lucent
Category: Informational                                        L. Berger
ISSN: 2070-1721                                                     LabN
                                                            L. Andersson
                                                                Ericsson
                                                              March 2010


       Generalized Multiprotocol Label Switching (GMPLS) Ethernet
               Label Switching Architecture and Framework

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 Multiplexing
   (TDM), and Asynchronous Transfer Mode (ATM).  This document defines
   an architecture and framework for a Generalized-MPLS-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.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   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).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see 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/rfc5828.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

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

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 to support transport networks.  This activity has taken
   place in the Institute of Electrical and Electronics Engineers (IEEE)
   802.1 Working Group, the International Telecommunication Union -
   Telecommunication Standardization Sector (ITU-T) 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 transport 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 Ethernet
   forwarding plane and, in some cases, the extensions allow for a
   departure from forwarding based on a spanning tree.  For example, in
   the [802.1ah] case, greater flexibility in forwarding is achieved
   through the addition of a "provider" address space.  [802.1Qay]
   supports the use of provisioning systems and network control
   protocols that explicitly select traffic-engineered paths.

   This document provides a framework for GMPLS Ethernet Label Switching
   (GELS).  GELS will likely require more than one switching type to
   support the different models, and as the GMPLS procedures that will
   need to be extended are dependent on switching type, these will be
   covered in the technology-specific documents.

   In the 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 VID is
   referred to as the Service VID (S-VID) and is carried in a Service
   TAG (S-TAG).  In Provider Backbone Bridges (PBBs) [802.1ah], a
   Backbone VID (B-VID) and B-MAC header with a service instance (I-TAG)
   encapsulate a customer Ethernet frame or a service Ethernet frame.

   In the IEEE 802.1Q standard, the terms Provider Backbone Bridges
   (PBBs) and Provider Backbone Bridged Network (PBBN) are used in the
   context of these extensions.

   An example of Ethernet protection extensions can be found in
   [G.8031].  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 being defined within the context
   of the MEF and ITU-T.  [MEF.6] and [G.8011] provide parallel
   frameworks for defining network-oriented characteristics of Ethernet
   services in transport networks.  These framework documents discuss
   general Ethernet connection characteristics, Ethernet User-Network
   Interfaces (UNIs), and Ethernet Network-Network Interfaces (NNIs).
   [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-plane and management-plane extensions allow
   for the disabling of standard Spanning Tree Protocols but do not
   define an explicitly routed, constraint-based control plane.  For
   example, [802.1Qay] is an amendment to IEEE 802.1Q that explicitly
   allows for traffic engineering of Ethernet forwarding paths.

   The IETF's GMPLS work provides a common control plane for different
   data-plane technologies for Internet and telecommunication service
   providers.  The GMPLS architecture is specified in RFC 3945
   [RFC3945].  The protocols specified for GMPLS can be used to control
   "Transport Network" technologies, e.g., optical and TDM networks.
   GMPLS can also be used for packet and Layer 2 Switching (frame/cell-
   based networks).

   This document provides a framework for the use of GMPLS to control
   "transport" Ethernet Label Switched Paths (Eth-LSPs).  Transport
   Ethernet adds new constraints that require it to be distinguished
   from the previously specified technologies for GMPLS.  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 will build on the GMPLS architecture and related
   specifications.

   This document introduces and explains GMPLS control plane use for
   transport Ethernet and the concept of the Eth-LSP.  The data-plane
   aspects of Eth-LSPs are outside the scope of this document and IETF
   activities.

   The intent of this document is to reuse and be aligned with as much
   of the GMPLS protocols as possible.  For example, reusing the IP
   control-plane addressing allows existing signaling, routing, Link
   Management Protocol (LMP), and path computation to be used as
   specified.  The GMPLS protocols support hierarchical LSPs as well as
   contiguous LSPs.  Also, GMPLS protocol mechanisms support a variety
   of network reference points from UNIs to 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
     that has differing bandwidth allocation in each direction.

   o Bidirectional congruent LSP

     This term refers to the property of a bidirectional LSP that uses
     only the same nodes, ports, and links in both directions.  Ethernet
     data planes are normally bidirectional congruent (sometimes known
     as reverse path congruent).

   o Contiguous Eth-LSP

     A contiguous Eth-LSP is an end-to-end Eth-LSP that is formed from
     multiple Eth-LSPs, each of which is operating within a VLAN and is
     mapped one-to-one at the VLAN boundaries.  Stitched LSPs form
     contiguous LSPs.

   o Eth-LSP

     This term refers to Ethernet Label Switched Paths that may be
     controlled via GMPLS.

   o Hierarchical Eth-LSP

     Hierarchical Eth-LSPs create a hierarchy of Eth-LSPs.

   o In-band GMPLS signaling

     In-band GMPLS signaling is composed of IP-based control messages
     that 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 composed of IP-based control
     messages that are sent between Ethernet switches over links other
     than the links used by the Ethernet data plane.  Out-of-band
     signaling typically shares a different fate from the data links.

   o Point-to-point (P2P) Traffic Engineering (TE) service instance

     A TE service instance made up of a single bidirectional P2P or two
     P2P unidirectional Eth-LSPs.

   o Point-to-multipoint (P2MP) Traffic Engineering (TE) service
     instance

     A TE service instance supported by a set of LSPs that 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 + Destination MAC address) may be used for
     frames from multiple sources (Source MAC addresses).  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.  With shared forwarding, dedicated control-plane states
     for all Eth-LSPs 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
   Eth-LSP      Ethernet Label Switched Path
   I-SID        Backbone Service Identifier carried in the I-TAG
   I-TAG        A Backbone Service Instance TAG defined in the
                IEEE 802.1ah Standard [802.1ah]
   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 IEEE 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
   ongoing work taking place in the IEEE 802.1 Working Group, the ITU-T,
   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.

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 (VIDs) 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 switching types are defined in Clause 25 of [802.1ah].  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 (with the exception of the newly defined
   I-tagged service type).

   [802.1ah] defines a new I-tagged service type but does not
   specifically define the Ethernet services being defined in the
   context of [MEF.6] and [G.8011], which are also illustrated in Figure
   1.

   To summarize the definitions:

   o Port based

     This is a frame-based service that supports specific frame types;
     no Service VLAN tagging or MAC-address-based switching.

   o S-tagged

     There are multiple S-TAG-aware services, including:

     + one-to-one

       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 includes:

       * 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 types determine 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 for requesting service (service
   delimiter) and are relevant between the customer site and network
   edge.

   In most bridging cases, the header fields cannot be changed, but some
   translations of VID field values are permitted, typically at the
   network edges.

   Across all service types, the Ethernet data plane is bidirectional
   congruent.  This means that the forward and reverse paths share the
   exact same set of nodes, ports, and bidirectional links.  This
   property is fundamental.  The 802.1 group has maintained this
   bidirectional congruent property in the definition of Connectivity
   Fault Management (CFM), which is part of the overall 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 OAM message identifiers are dependent on the data plane, so
   they work equally well for provisioned or GMPLS-controlled paths.

   Ethernet OAM currently consists of:

      Defined in both [802.1ag] and [Y.1731]:
      - CCM/RDI:  Continuity Check Message / Remote Defect Indication
      - LBM/LBR:  Loopback Message/Reply
      - LTM/LTR:  Link Trace Message/Reply
      - VSM/VSR:  Vendor-Specific Message/Reply

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

   These functions are supported across all the standardized Eth-LSP
   formats.

2.3.  Ethernet Switching Characteristics

   Ethernet is similar to MPLS as it encapsulates different 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, a destination
   address, and an 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 based on a frame's destination MAC address
   and VLAN.  The VLAN identifies a virtual active set of bridges and
   LANs.  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 GMPLS
   architecture, per [RFC3945], allowed for control of Ethernet bridges
   and other Layer 2 technologies using the Layer-2 Switch Capable
   (L2SC) switching type.  But, the control of Ethernet switching was
   not explicitly defined in [RFC3471], [RFC4202], or any other
   subsequent GMPLS reference document.

   The GMPLS 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;
   - bidirectional service;

   - end-to-end and segment protection;
   - hierarchy

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

   In applying GMPLS to "transport" Ethernet, GMPLS will need to be
   extended to work with the Ethernet data plane and switching
   functions.  The definition of GMPLS support for Ethernet is
   multifaceted 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 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 made based on
   the DMAC.  When forwarding using a 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 that are tagged with that VID
   and received over one of these ports are forwarded over the other
   port without address learning.

   [802.1Qay] allows for turning off learning and hence the broadcast
   mechanism that provides 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
   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 a key 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.  As
   such, and to allow the continued use of that switching type and those
   implementations, and to distinguish the different Ethernet switching
   paradigms, a new switching type needs to 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 Eth-LSPs is expected to
   strictly comply to the GMPLS protocol suite addressing as specified
   in [RFC3471], [RFC3473], and related documents.

4.1.  GMPLS Routing

   GMPLS routing as defined in [RFC4202] uses IP routing protocols with
   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 based on resource information obtained
   from 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 (ISC) Descriptor.  As mentioned in
   Section 3, the definition of one or more new ISCs to support Eth-LSPs
   is expected.  Again, the L2SC ISCs will not be used to represent
   interfaces capable of supporting Eth-LSPs defined by this document
   and subsequent documents in support of the transport Ethernet
   switching paradigms.  In addition, ISC-specific TE information may be
   defined as needed to support the requirements of a specific Ethernet
   Switching Service Type.

   GMPLS routing is an optional functionality 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 connectivity
   network of sufficient capacity to handle the information exchange of
   the GMPLS routing and signaling protocols is necessary.

   One way to implement this is with an IP-routed network supported by
   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, or for forwarding user traffic over this IP network.

   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 ([RFC3471] and [RFC3473]) is well suited to the
   control of Eth-LSPs and Ethernet switches.  Signaling provides 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.
   Standardized signaling also improves multi-vendor interoperability.

   GMPLS signaling supports the establishment and control of
   bidirectional and unidirectional data paths.  Ethernet is
   bidirectional by nature and CFM has been built to leverage this.
   Prior to CFM, the emulation of a physical wire and the learning
   requirements also mandated bidirectional connections.  Given this,
   Eth-LSPs need to be bidirectional 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 bidirectional LSP.  [RFC5467], an Experimental
   document, provides procedures if asymmetric bandwidth bidirectional
   LSPs are required.

6.  Link Management

   Link discovery has been specified for links interconnecting IEEE
   802.1 bridges in [802.1AB].  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.  However, the
   802.1AB capability is an optional feature, so it is not necessarily
   operating before a link is operational, and it primarily supports the
   management plane.

   In the GMPLS context, LMP [RFC4204] has been defined to support GMPLS
   control-plane link management and discovery features.  LMP also
   supports the automated creation of unnumbered interfaces for the
   control plane.  If LMP is not used, there is an additional
   configuration requirement for GMPLS link identifiers.  For large-
   scale implementations, LMP is beneficial.  LMP also has optional
   fault management capabilities, primarily for opaque and transparent
   network technology.  With IEEE's newer CFM [802.1ag] and ITU-T's
   capabilities [Y.1731], this optional capability may not be needed.
   It is the goal of the GMPLS Ethernet architecture to allow the
   selection of the best tool set for the user needs.  The full
   functionality of Ethernet CFM should be supported when using a GMPLS
   control plane.

   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 expected that LMP would be used for control-
   plane functions of link property correlation, but that Ethernet
   mechanisms for OAM such as CFM, link trace, etc., would be used for
   data-plane fault management and fault trace.

        +-------------+        +-------------+
        | +---------+ |        | +---------+ |
        | |         | |        | |         | |GMPLS
        | |  LMP    |-|<------>|-|  LMP    | |Link Property
        | |         | |        | |         | |Correlation
        | |  (opt)  | |GMPLS   | |  (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 identify a specific method for selecting paths or
   supporting path computation.  GMPLS allows for a wide range of
   possibilities to be 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].

8.  Multiple VLANs

   This document allows for the support of 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

   A GMPLS-controlled "transport" Ethernet system should assume that
   users and devices attached to UNIs may behave maliciously,
   negligently, or incorrectly.  Intra-provider control traffic is
   trusted to not be malicious.  In general, these requirements are no
   different from the security requirements for operating any GMPLS
   network.  Access to the trusted network will only occur through the
   protocols defined for 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 for 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 denial-of-service attacks
   may be required on UNI ports.

   For a more comprehensive discussion on GMPLS security please see the
   MPLS and GMPLS Security Framework [SECURITY].  Cryptography can be
   used to protect against many attacks described in [SECURITY].  One
   option for protecting "transport" Ethernet is the use of 802.1AE
   Media Access Control Security [802.1AE], which provides encryption
   and authentication.  It is expected that solution documents will
   include a full analysis of the security issues that any protocol
   extensions introduce.

10.  References

10.1.  Normative References

   [RFC3471]   Berger, L., Ed., "Generalized Multi-Protocol Label
               Switching (GMPLS) Signaling Functional Description", RFC
               3471, January 2003.

   [RFC3473]   Berger, L., Ed., "Generalized Multi-Protocol Label
               Switching (GMPLS) Signaling Resource ReserVation
               Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC
               3473, January 2003.

   [RFC3945]   Mannie, E., Ed., "Generalized Multi-Protocol Label
               Switching (GMPLS) Architecture", RFC 3945, October 2004.

   [RFC4202]   Kompella, K., Ed., and Y. Rekhter, Ed., "Routing
               Extensions in Support of Generalized Multi-Protocol Label
               Switching (GMPLS)", RFC 4202, October 2005.

10.2.  Informative References

   [802.1AB]   "IEEE Standard for Local and Metropolitan Area Networks,
               Station and Media Access Control Connectivity Discovery",
               IEEE 802.1AB, 2009.

   [802.1AE]   "IEEE Standard for Local and metropolitan area networks
               Media Access Control (MAC) Security", IEEE 802.1AE-2006,
               August 2006.

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

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

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

   [802.1Qay]  "IEEE Standard for Local and Metropolitan Area Networks -
               Virtual Bridged Local Area Networks - Amendment 10:
               Provider Backbone Bridge Traffic Engineering", IEEE Std
               802.1Qay-2009, August 2009.

   [ETH-TSPEC] Papadimitriou, D., "Ethernet Traffic Parameters", Work in
               Progress, January 2010.

   [G.8011]    ITU-T Recommendation G.8011, "Ethernet over Transport -
               Ethernet services framework", January 2009.

   [G.8011.1]  ITU-T Recommendation G.8011.1/Y.1307.1, "Ethernet private
               line service", January 2009.

   [G.8011.2]  ITU-T Recommendation G.8011.2/Y.1307.2, "Ethernet virtual
               private line service", January 2009.

   [G.8031]    ITU-T Recommendation G.8031, "Ethernet linear protection
               switching", November 2009.

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

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

   [RFC4875]   Aggarwal, R., Ed., Papadimitriou, D., Ed., and S.
               Yasukawa, Ed., "Extensions to Resource Reservation
               Protocol - Traffic Engineering (RSVP-TE) for Point-to-
               Multipoint TE Label Switched Paths (LSPs)", RFC 4875, May
               2007.

   [RFC4655]   Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
               Computation Element (PCE)-Based Architecture", RFC 4655,
               August 2006.

   [RFC4872]   Lang, J., Ed., Rekhter, Y., Ed., and D. Papadimitriou,
               Ed., "RSVP-TE Extensions in Support of End-to-End
               Generalized Multi-Protocol Label Switching (GMPLS)
               Recovery", RFC 4872, May 2007.

   [RFC4873]   Berger, L., Bryskin, I., Papadimitriou, D., and A.
               Farrel, "GMPLS Segment Recovery", RFC 4873, May 2007.

   [RFC5467]   Berger, L., Takacs, A., Caviglia, D., Fedyk, D., and J.
               Meuric, "GMPLS Asymmetric Bandwidth Bidirectional Label
               Switched Paths (LSPs)", RFC 5467, March 2009.

   [SECURITY]  Fang, L., Ed., "Security Framework for MPLS and GMPLS
               Networks", Work in Progress, October 2009.

   [Y.1731]    ITU-T Recommendation Y.1731, "OAM Functions and
               Mechanisms for Ethernet based Networks", February 2008.

11.  Acknowledgments

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

   George Swallow contributed significantly to this document.

Authors' Addresses

   Don Fedyk
   Alcatel-Lucent
   Groton, MA, 01450
   Phone: +1-978-467-5645
   EMail: donald.fedyk@alcatel-lucent.com

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

   Loa Andersson
   Ericsson
   Phone: +46 10 717 52 13
   EMail: loa.andersson@ericsson.com