MPLS                                                       D. Frost, Ed.
Internet-Draft                                            S. Bryant, Ed.
Intended status: Standards Track                           Cisco Systems
Expires: September 13, October 24, 2010                                  M. Bocci, Ed.
                                                          Alcatel-Lucent
                                                          March 12,
                                                          April 22, 2010

             MPLS Transport Profile Data Plane Architecture
                    draft-ietf-mpls-tp-data-plane-01
                    draft-ietf-mpls-tp-data-plane-02

Abstract

   The Multiprotocol Label Switching (MPLS) Transport Profile (MPLS-TP)
   is the set of MPLS protocol functions applicable to the construction
   and operation of packet-switched transport networks.  This document
   specifies the subset of these functions that comprises the MPLS-TP
   data plane: the architectural layer concerned with the encapsulation
   and forwarding of packets within an MPLS-TP network.

   This document is a product of a joint Internet Engineering Task Force
   (IETF) / International Telecommunication Union Telecommunication
   Standardization Sector (ITU-T) effort to include an MPLS Transport
   Profile within the IETF MPLS and PWE3 architectures to support the
   capabilities and functionalities of a packet transport network.

Requirements Language

   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 RFC 2119 [RFC2119].

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 September 13, October 24, 2010.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4  3
     1.1.  Scope  . . . . . . . . . . . . . . . . . . . . . . . . . .  4  3
     1.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  MPLS-TP Packet Encapsulation and Forwarding  . . . . . . . . .  5  4
   3.  MPLS-TP Transport Entities . . . . . . . . . . . . . . . . . .  5
     3.1.  Label Switched Paths . . . . . . . . . . . . . . . . . . .  6  5
       3.1.1.  LSP Packet Encapsulation and Forwarding  . . . . . . .  6  5
       3.1.2.  LSP Payloads . . . . . . . . . . . . . . . . . . . . .  6
       3.1.3.  LSP Types  . . . . . . . . . . . . . . . . . . . . . .  7
     3.2.  Sections . . . . . . . . . . . . . . . . . . . . . . . . .  8
     3.3.  Pseudowires  . . . . . . . . . . . . . . . . . . . . . . .  9  8
   4.  MPLS-TP Generic Associated Channel . . . . . . . . . . . . . .  9
   5.  Server Layer Considerations  . . . . . . . . . . . . . . . . . 10
     5.1.  Ethernet Media . . . . . . . . . . . . . . . . . . . . . . 10
       5.1.1.  Point-to-Point Links . . . . . . . . . . . . . . . . . 10
       5.1.2.  Multipoint Links . . . . . . . . . . . . . . . . . . . 11
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12 11
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 11
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 12 11
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 14

1.  Introduction

   The MPLS Transport Profile (MPLS-TP) [I-D.ietf-mpls-tp-framework] is
   the set of protocol functions that meet the requirements [RFC5654] for the
   application of MPLS to the construction and operation of
   packet-switched packet-
   switched transport networks.  Packet  MPLS-based packet transport networks
   are defined and described in [I-D.ietf-mpls-tp-framework].

   This document specifies defines the subset set of protocol functions that
   comprises comprise the MPLS-TP
   data plane: the architectural layer concerned with the encapsulation
   and forwarding of packets within an MPLS-TP network.  This layer is
   based on the data plane architectures for MPLS ([RFC3031] and
   [RFC3032]) and for pseudowires ([RFC3985]).

   This document is a product of a joint Internet Engineering Task Force
   (IETF) / International Telecommunication Union Telecommunication
   Standardization Sector (ITU-T) effort to include an MPLS Transport
   Profile within the IETF MPLS and PWE3 architectures to support the
   capabilities and functionalities of a packet transport network.

1.1.  Scope

   This document has the following purposes:

   o  To identify the data-plane data plane functions within the MPLS Transport
      Profile;

   o  To indicate which of these data-plane data plane functions an MPLS-TP
      implementation is required to support.

   Note that the MPLS-TP functions discussed in this document are
   considered OPTIONAL unless stated otherwise.

1.2.  Terminology

   Term    Definition
   ------- ------------------------------------------
   G-ACh   Generic Associated Channel
   GAL     G-ACh Label
   LSP     Label Switched Path
   LSR     Label Switching Router
   MAC     Media Access Control
   MPLS-TP MPLS Transport Profile
   OAM     Operations, Administration and Maintenance
   PW      Pseudowire
   QoS     Quality of Service
   TTL     Time To Live

   Additional definitions and terminology can be found in

   [I-D.ietf-mpls-tp-framework] and [RFC5654].

2.  MPLS-TP Packet Encapsulation and Forwarding

   This document defines the encapsulation and forwarding functions
   applicable to packets traversing an MPLS-TP Label Switched Path
   (LSP), Pseudowire (PW), or Section (see Section 3 for the definitions
   of these transport entities).  Encapsulation and forwarding functions
   for packets outside an MPLS-TP LSP, PW, or Section, and mechanisms
   for delivering packets to or from MPLS-TP LSPs, PWs, and Sections,
   are outside the scope of this document.

1.2.  Terminology

   Term    Definition
   ------- ------------------------------------------
   ACH     Associated Channel Header
   G-ACh   Generic Associated Channel
   GAL     G-ACh Label
   LER     Label Edge Router
   LSP     Label Switched Path
   LSR     Label Switching Router
   MPLS-TP packet encapsulation and forwarding operates according to the MPLS data-plane architecture described in [RFC3031] and [RFC3032], Transport Profile
   OAM     Operations, Administration and Maintenance
   PW      Pseudowire
   QoS     Quality of Service
   S-PE    PW Switching Provider Edge Node
   T-PE    PW Terminating Provider Edge Node
   TTL     Time To Live

   Additional definitions and terminology can be found in
   [I-D.ietf-mpls-tp-framework] and [RFC5654].

2.  MPLS-TP Packet Encapsulation and Forwarding

   MPLS-TP packet encapsulation and forwarding SHALL operate according
   to the MPLS data plane architecture described in [RFC3031] and
   [RFC3032], and the data-plane data plane architectures for Single-Segment
   Pseudowires
   [RFC3985], Multi-Segment Pseudowires [RFC5659], and Point-to-
   Multipoint Multi-Segment Pseudowires [I-D.ietf-pwe3-p2mp-pw-requirements], (see Section 3.3), except
   as noted otherwise in this document.  The MPLS-TP data plane
   satisfies the requirements specified in [RFC5654].

   Since an MPLS-TP packet is an MPLS packet as defined in [RFC3031] and
   [RFC3032], it will have an associated label stack, and the 'push',
   'pop', and 'swap' label processing operations specified in those
   documents apply.  The label stack represents a hierarchy of Label
   Switched Paths (LSPs).  A label is pushed to introduce an additional
   level of LSP hierarchy and popped to remove it.  Such an additional
   level may be introduced by any pair of LSRs, whereupon they become
   adjacent at this new level, and are then known as Label Edge Routers
   (LERs) with respect to the new LSP.

   In contrast to, for example, Section 3.10 of [RFC3031], support for
   Internet Protocol (IP) host and router data plane functionality by
   MPLS-TP interfaces and in MPLS-TP networks is OPTIONAL.

   MPLS-TP forwarding is based on the label that identifies an LSP or
   PW.  The label value specifies the processing operation to be
   performed by the next hop at that level of encapsulation.  A  Note that
   a swap of this label is an atomic operation in which the contents of
   the packet after the swapped label are opaque to the forwarder. forwarding
   function.  The only event that interrupts a swap operation is Time To
   Live (TTL) expiry.

   Further

   At an LSR, S-PE, or T-PE, further processing occurs to determine the
   context of a packet occurs when a swap operation is interrupted in this manner, when by
   TTL expiry.  If the TTL of an LSP label expires, then the label with
   the S (Bottom of Stack) bit set is inspected to determine if it is a pop operation
   exposes
   reserved label.  If it is a specific reserved label, or when the packet is received
   with processed
   according to the rules of that reserved label.  For example, if it is
   a Generic Associated Channel Label (GAL) (see (GAL), then it is processed as a
   packet on the G-ACh; see Section 4) at 4.  If the top TTL of the stack.  Otherwise a PW expires at an
   S-PE or T-PE, then the packet is examined to determine if a Generic
   Associated Channel Header (ACH) is present immediately below the PW
   label.  If so, then the packet is processed as a packet on the G-ACh.

   Similarly, if a pop operation at an LER exposes a reserved label at
   the top of the label stack, then the packet is processed according to
   the rules of that reserved label.

   If no such exception occurs, the packet is forwarded according to the
   procedures in [RFC3031] and [RFC3032].

3.  MPLS-TP Transport Entities

   The MPLS Transport Profile includes the following data-plane data plane
   transport entities:

   o  Label Switched Paths (LSPs)

   o  Sections

   o  Pseudowires (PWs)

3.1.  Label Switched Paths

   MPLS-TP LSPs are ordinary MPLS LSPs as defined in [RFC3031] except as
   specifically noted otherwise in this document.

3.1.1.  LSP Packet Encapsulation and Forwarding

   Encapsulation and forwarding of packets traversing MPLS-TP LSPs MUST
   follow standard MPLS packet encapsulation and forwarding as defined
   in [RFC3031] and [RFC3031], [RFC3032], [RFC5331], and [RFC5332], except as
   explicitly stated otherwise in this document.

   Data-plane support for Internet Protocol (IP) packet encapsulation,
   addressing, and forwarding is OPTIONAL.

   Data-plane

   Data plane Quality of Service capabilities are included in the
   MPLS-TP in the form of Traffic Engineered (TE) LSPs [RFC3209] and the
   MPLS Differentiated Services (DiffServ) architecture [RFC3270].  Both
   E-LSP and L-LSP MPLS DiffServ modes are included.  The Traffic Class
   field (formerly the EXP field) of an MPLS label follows the
   definition of [RFC5462] and [RFC3270] and MUST be processed according
   to the rules specified in those documents.

   The

   Note that, except for transient packet reordering which may occur,
   for example, during fault conditions, packets are delivered in order
   on L-LSPs, and on E-LSPs within a specific ordered aggregate.

   Support for the Pipe and Short Pipe DiffServ tunneling and TTL
   processing models described in [RFC3270] and [RFC3443] are included in is REQUIRED by
   the MPLS-TP.
   The  Support for the Uniform model is outside the scope of the MPLS-TP. OPTIONAL.

   Per-platform, per-interface or other context-specific label space
   [RFC5331] MAY be used for MPLS-TP LSPs.  Downstream [RFC3031] or
   upstream [RFC5331] label allocation schemes MAY be used for MPLS-TP
   LSPs.  Note that the requirements of a particular LSP type may
   dictate which label spaces or allocation schemes it can use.

   Per-packet

   Equal-Cost Multi-Path (ECMP) load-balancing MUST NOT be performed on
   an MPLS-TP LSP.  MPLS-TP LSPs as defined in this document MAY operate
   over a server layer that supports load-balancing, but this load-
   balancing MUST operate in such a manner that it is outside transparent to
   MPLS-TP.  Note that this does not preclude the
   scope future definition of
   new MPLS-TP LSP types which have different requirements regarding the
   use of ECMP in the MPLS-TP. server layer.

   Penultimate Hop Popping (PHP) MUST be disabled by default on MPLS-TP
   LSPs.

3.1.2.  LSP Payloads

   The MPLS-TP includes support for the following LSP payload types:

   o  Network-layer protocol packets (including MPLS-labeled packets)

   o  Pseudowire packets

   The rules for processing LSP payloads that are network-layer protocol
   packets SHALL be as specified in [RFC3032].

   The rules for processing LSP payloads that are pseudowire packets
   SHALL be as specified in [RFC3985] and the attendant standards defined by in the IETF Pseudowire Emulation Edge-to-Edge (PWE3) Working
   Group. data plane pseudowire specifications (see
   Section 3.3).

   Note that the payload of an MPLS-TP LSP may be a packet type that itself
   contains one or more an MPLS labels. label stack.  This is true, for instance, when the
   payload is a pseudowire or another MPLS-TP LSP.  From the
   data-plane perspective, however, an MPLS-TP packet is an MPLS packet
   as specified in [RFC3032], and so in particular has precisely one
   label stack, and one label in LSP.  In this case the stack with its S (Bottom
   of Stack) bit SHALL be set to 1.

3.1.3.  LSP Types

   The MPLS-TP includes indicate the following LSP types:

   o  Point-to-point unidirectional

   o bottom (i.e. inner-most)
   label in the label stack that is contiguous between the MPLS-TP LSP
   and its payload.  This behaviour reflects best current practice in
   MPLS but differs slightly from [RFC3032], which uses the S bit to
   identify when MPLS label processing stops and network layer
   processing starts.

3.1.3.  LSP Types

   The MPLS-TP includes the following LSP types:

   o  Point-to-point unidirectional

   o  Point-to-point associated bidirectional

   o  Point-to-point co-routed bidirectional

   o  Point-to-multipoint unidirectional

   Point-to-point unidirectional LSPs are supported by the basic MPLS
   architecture [RFC3031] and are REQUIRED to function in the same
   manner in the MPLS-TP data plane except as explicitly stated
   otherwise in this document.

   A point-to-point associated bidirectional LSP between LSRs A and B
   consists of two unidirectional point-to-point LSPs, one from A to B
   and the other from B to A, which are regarded as a pair providing a
   single logical bidirectional transport path.  The nodes A and B are
   REQUIRED to be aware of this pairing relationship, but other nodes
   need not be.

   A point-to-point co-routed bidirectional LSP is a point-to-point
   associated bidirectional LSP with the additional constraint that its
   two unidirectional component LSPs in each direction follow the same
   path in the
   network.  This means that if one (in terms of the component LSPs follows the
   path through the both nodes N0, ..., Nk, originating on N0 and terminating
   on Nk, then the path links).  An important property of the other component LSP
   co-routed bidirectional LSPs is Nk, ..., N0, and that at each node an ingress interface of one component LSP is an
   egress interface of the other.  In addition, each node along the path
   is REQUIRED to be aware of the pairing relationship between the their unidirectional component LSPs.
   LSPs share fate.

   A point-to-multipoint unidirectional LSP functions in the same manner
   in the data plane, with respect to basic label processing and packet-
   switching operations, as a point-to-point unidirectional LSP, with
   one difference: an LSR may have more than one (egress interface,
   outgoing label) pair associated with the LSP, and any packet it
   transmits on the LSP is transmitted out all associated egress
   interfaces.  Point-to-multipoint LSPs are described in [RFC4875] and
   [RFC5332].  TTL processing and exception handling for point-to-
   multipoint LSPs is the same as for point-to-point LSPs and is
   described in Section 2.

3.2.  Sections

   Two MPLS-TP LSRs are considered to be topologically adjacent at a
   particular layer n >= 0 of the MPLS-TP LSP hierarchy if there exists
   a link
   connectivity between them at the next lowest network layer.  Such a link,
   connectivity, if it exists, will be either an MPLS-TP LSP (if n > 0)
   or a data-link provided by the underlying server layer network (if n
   = 0), and is referred to as an MPLS-TP Section at layer n of the
   MPLS-TP LSP hierarchy.  Thus, the links traversed by a layer n+1
   MPLS-TP LSP are layer n MPLS-TP sections.  Such an LSP is referred to
   as a client of the section layer, and the section layer as the server
   layer with respect to its clients.

   Note that the MPLS label stack associated with an MPLS-TP section at
   layer n consists of n labels, in the absence of stack optimisation
   mechanisms such as PHP.
   mechanisms.  Note also that in order for two LSRs to exchange non-IP
   MPLS-TP control packets over a section, an additional label, the
   G-ACh Label (GAL) (see Section 4) must MUST appear at the bottom of the
   label stack.

   An MPLS-TP section may provide one or more of the following types of
   service to its client layer:

   o  Point-to-point bidirectional

   o  Point-to-point unidirectional

   o  Point-to-multipoint unidirectional

   The manner in which a section provides such a service is outside the
   scope of the MPLS-TP.

   Note that an LSP of any of the types listed in Section 3.1.3 may
   serve as a section for a client-layer transport entity as long as it
   supports the type of service the client requires.

   An important difference exists between data-link-based sections and
   LSP-based sections.  A data-link-based section can carry additional
   packet context information such as a protocol type indication.  If an
   LSP-based section requires such context, then a service label (see
   [I-D.ietf-mpls-tp-framework]) must be used to provide it.

3.3.  Pseudowires

   The data-plane data plane architectures for Single-Segment Pseudowires
   [RFC3985], Multi-Segment Pseudowires [RFC5659], [RFC3985]
   and Point-to-
   Multipoint Multi-Segment Pseudowires [I-D.ietf-pwe3-p2mp-pw-requirements], and the
   associated data-plane pseudowire protocol functions, as defined by
   the IETF Pseudowire Emulation Edge-to-Edge (PWE3) Working Group, [RFC5659] are included in the MPLS-TP.

   Data plane processing procedures for pseudowires SHALL be as defined
   in the following documents and in any future pseudowire data plane
   specifications:

   o  [RFC4717]

   o  [RFC4816]

   o  [RFC4385]

   o  [RFC4448]

   o  [RFC4619]

   o  [RFC4618]

   o  [RFC4553]

   o  [RFC4842]

   o  [RFC5087]

   o  [I-D.ietf-pwe3-fc-encap]

   o  [RFC5086]

   This document specifies no modifications or extensions to pseudowire
   data-plane
   data plane architectures or protocols.

4.  MPLS-TP Generic Associated Channel

   The MPLS Generic Associated Channel (G-ACh) mechanism is specified in
   [RFC5586] and included in the MPLS-TP.  The G-ACh provides an
   auxiliary logical data channel associated with MPLS-TP Sections,
   LSPs, and PWs in the data plane.  The primary purpose of the G-ACh in
   the context of MPLS-TP is to support control, management, and OAM
   Operations, Administration and Maintenance (OAM) traffic associated
   with MPLS-TP transport entities.  The G-ACh MUST NOT be used to
   transport client layer network traffic in MPLS-TP networks.

   For pseudowires, the G-ACh uses the first four bits of the PW control
   word to provide the initial discrimination between data packets and
   packets belonging to the associated channel, as described in
   [RFC4385].  When this first nibble of a packet, immediately following
   the label at the bottom of stack, has a value of '1', then this
   packet belongs to a G-ACh.  The first 32 bits following the bottom of
   stack label then have a defined format called an Associated Channel
   Header (ACH), which further defines the content of the packet.  The
   ACH is therefore both a demultiplexer for G-ACh traffic on the PW,
   and a discriminator for the type of G-ACh traffic.

   When the the control message is carried over a section or an LSP,
   rather than over a PW, it is necessary to provide an indication in
   the packet that the payload is something other than a client data
   packet.  This is achieved by including a reserved label with a value
   of 13 in at the bottom of the label stack.  This reserved label is
   referred to as the G-ACh Label (GAL), and is defined in [RFC5586].
   When a GAL is found, it indicates that the payload begins with an
   ACH.  The GAL is thus a demultiplexer for G-ACh traffic on the
   section or the LSP, and the ACH is a discriminator for the type of
   traffic carried on the G-ACh.  Note however that MPLS-TP forwarding
   follows the normal MPLS model, and that a GAL is invisible to an LSR
   unless it is the top label in the label stack.  The only other
   circumstance under which the label stack may be inspected for a GAL
   is when the TTL has expired.  Any
   MPLS-TP component that intentionally performs this inspection must
   assume  Note that it is asynchronous with respect to the normal packet forwarding of
   other packets. MAY
   continue concurrently with this inspection.  All operations on the
   label stack are in accordance with [RFC3031] and [RFC3032].

   An application processing a packet received over the G-ACh may
   require packet-specific context (such as the receiving interface or
   received label stack).  Data plane implementations MUST therefore
   provide adequate context to the application which is to process a
   G-ACh packet.  The definition of the context required MUST be
   provided as part of the specification of the application using the
   G-ACh.

5.  Server Layer Considerations

   This section discusses considerations for support of the MPLS-TP data
   plane by server layer technologies and media.

   In general, the

   The MPLS-TP network has no awareness of the internals of the server
   layer of which it is a client, requiring only that the server layer
   be capable of delivering the type of service required by the MPLS-TP
   transport entities that make use of it.  Note that what appears to be
   a single server layer link to the MPLS-TP network may be a
   complicated construct underneath, such as an LSP or a collection of
   underlying links operating as a bundle.  Special care may be needed
   in network design and operation when such constructs are used as a
   server layer for MPLS-TP.

5.1.  Ethernet Media

5.1.1.  Point-to-Point Links

   When two

   Encapsulation of MPLS-TP nodes are connected by a point-to-point Ethernet
   link, the question arises as to what destination Ethernet Media
   Access Control (MAC) address should be specified in Ethernet frames
   transmitted to the peer node packets for transport over specific server-
   layer media is outside the link.  The problem scope of
   determining this address document.

6.  Security Considerations

   The MPLS data plane (and therefore the MPLS-TP data plane) does not arise in IP/MPLS networks because
   of the presence of the Ethernet Address Resolution Protocol (ARP)
   [RFC0826] or IP version 6 Neighbor Discovery protocol [RFC4861],
   which allow the unicast MAC address of the peer device to be learned
   dynamically.

   If existing
   provide any security mechanisms are available in an MPLS-TP network to
   determine the destination unicast MAC addresses and of peer nodes - itself.  The following
   behaviour, however, is considered a best current practise for
   example if the network MPLS
   LSRs which is also happens applicable to be an IP/MPLS network - such
   mechanisms MPLS-TP:

   An LSR SHOULD be used.  The remainder discard a packet received from a particular neighbour
   unless one of this section discusses the available options when this is not the case.

   One possibility is for each node to be statically configured with following two conditions holds:

   1.  Any MPLS label processed at the
   MAC address of its peer.  Static MAC address configuration MAY be
   used in an MPLS-TP network, but can present an administrative burden
   and lead to operational problems.  For example, replacement of receiving LSR, such as an
   Ethernet interface to resolve LSP or
       PW label, has a hardware fault when this approach is
   used requires label value that the peer node be manually reconfigured with the
   new MAC address.  This is especially problematic if the peer is
   operated by another provider.

   Another possibility is to use the Ethernet broadcast address, but
   this may lead receiving LSR has
       distributed to excessive frame distribution and processing that neighbour; or

   2.  Any MPLS label processed at the
   Ethernet layer.  Broadcast traffic may also be treated specially by
   some devices and this may not be desirable for MPLS-TP data frames.

   The preferred approach is therefore to use receiving LSR, such as the destination MAC
   address an Ethernet multicast address reserved for MPLS-TP for use
   over point-to-point links.  The address allocated for this purpose by
   the Internet Assigned Numbers Authority (IANA) is 01-00-5E-XX-XX-XX.
   An MPLS-TP implementation MUST process Ethernet frames received over
   a point-to-point link with this destination MAC address by default.

   Note that this approach is applicable only when the attached Ethernet
   link is known to be point-to-point.  If a link is not known to be
   point-to-point, the reserved MAC address noted above MUST NOT be
   used.

   A further alternative is to adapt LSP or introduce
       PW label, has a protocol mechanism
   for learning the Ethernet unicast MAC addresses of MPLS-TP peers label value that
   are not also IP peers.  This topic is for further study.

5.1.2.  Multipoint Links

   When a multipoint Ethernet link serves as a section for a point-to-
   multipoint MPLS-TP LSP, and multicast destination MAC addressing at the Ethernet layer is used for the LSP, the addressing and
   encapsulation procedures specified in [RFC5332] SHALL be used.

   When a multipoint Ethernet link - that is, a link which is not known receiving LSR has previously
       distributed to be point-to-point - serves as a section for a point-to-point
   MPLS-TP LSP, unicast destination MAC addresses must be used for
   Ethernet frames carrying packets of the LSP.  Note peer beyond that neighbour (i.e., when it is
       known that according to the discussion in path from the previous section, this implies system to which the use of
   either static MAC address configuration or a protocol label was
       distributed to the receiving system is via that enables
   peer MAC address discovery.

6.  Security Considerations

   This document serves primarily neighbour).

   Client layers that wish to secure data carried over MPLS-TP transport
   entities are REQUIRED to specify which aspects of existing
   MPLS data-plane functionality apply their own security mechanisms.

   Where management or control plane protocols are used to MPLS-TP.  As such it
   introduces no new install label
   switching operations necessary to establish MPLS-TP transport paths,
   those protocols are equipped with security considerations in itself, but features and network
   operators may use those features to securely create the transport
   paths.

   Further details of MPLS security
   considerations documented can be found in the specifications to which it refers
   apply as well to MPLS-TP.
   [I-D.ietf-mpls-mpls-and-gmpls-security-framework].

7.  IANA Considerations

   The authors request that

   This document introduces no new IANA allocate an Ethernet Multicast Address
   from the Ethernet Multicast Addresses table in the ethernet-numbers
   registry for use by MPLS-TP LSRs over point-to-point links as
   described in Section 5.1.1.  The entry should specify an address of
   the form 01-00-5E-XX-XX-XX, a Type Field of 8847/8848, and a usage
   "MPLS-TP point-to-point (this draft)". considerations.

8.  References

8.1.  Normative References

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

   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031, January 2001.

   [RFC3032]  Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
              Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
              Encoding", RFC 3032, January 2001.

   [RFC5654]  Niven-Jenkins, B., Brungard,

   [RFC3209]  Awduche, D., Betts, M., Sprecher, N.,
              and S. Ueno, "Requirements of an MPLS Transport Profile",
              RFC 5654, September 2009.

   [RFC5586]  Bocci, M., Vigoureux, M., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and S. Bryant, "MPLS Generic
              Associated Channel", G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 5586, June 2009. 3209, December 2001.

   [RFC3270]  Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen,
              P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi-
              Protocol Label Switching (MPLS) Support of Differentiated
              Services", RFC 3270, May 2002.

   [RFC3443]  Agarwal, P. and B. Akyol, "Time To Live (TTL) Processing
              in Multi-Protocol Label Switching (MPLS) Networks",
              RFC 3443, January 2003.

   [RFC5462]  Andersson, L. 3443, January 2003.

   [RFC4385]  Bryant, S., Swallow, G., Martini, L., and D. McPherson,
              "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
              Use over an MPLS PSN", RFC 4385, February 2006.

   [RFC4448]  Martini, L., Rosen, E., El-Aawar, N., and G. Heron,
              "Encapsulation Methods for Transport of Ethernet over MPLS
              Networks", RFC 4448, April 2006.

   [RFC4553]  Vainshtein, A. and YJ. Stein, "Structure-Agnostic Time
              Division Multiplexing (TDM) over Packet (SAToP)",
              RFC 4553, June 2006.

   [RFC4618]  Martini, L., Rosen, E., Heron, G., and A. Malis,
              "Encapsulation Methods for Transport of PPP/High-Level
              Data Link Control (HDLC) over MPLS Networks", RFC 4618,
              September 2006.

   [RFC4619]  Martini, L., Kawa, C., and A. Malis, "Encapsulation
              Methods for Transport of Frame Relay over Multiprotocol
              Label Switching (MPLS) Networks", RFC 4619,
              September 2006.

   [RFC4717]  Martini, L., Jayakumar, J., Bocci, M., El-Aawar, N.,
              Brayley, J., and R. Asati, "Multiprotocol Label Switching
              (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic
              Class" Field", G. Koleyni, "Encapsulation Methods for
              Transport of Asynchronous Transfer Mode (ATM) over MPLS
              Networks", RFC 5462, 4717, December 2006.

   [RFC4816]  Malis, A., Martini, L., Brayley, J., and T. Walsh,
              "Pseudowire Emulation Edge-to-Edge (PWE3) Asynchronous
              Transfer Mode (ATM) Transparent Cell Transport Service",
              RFC 4816, February 2009.

   [RFC5331]  Aggarwal, 2007.

   [RFC4842]  Malis, A., Pate, P., Cohen, R., Rekhter, Y., and E. Rosen, "MPLS Upstream
              Label Assignment and Context-Specific Label Space", D. Zelig, "Synchronous
              Optical Network/Synchronous Digital Hierarchy (SONET/SDH)
              Circuit Emulation over Packet (CEP)", RFC 5331, August 2008. 4842,
              April 2007.

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

   [RFC5331]  Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream
              Label Assignment and Context-Specific Label Space",
              RFC 5331, August 2008.

   [RFC5332]  Eckert, T., Rosen, E., Aggarwal, R., and Y. Rekhter, "MPLS
              Multicast Encapsulations", RFC 5332, August 2008.

   [RFC4385]

   [RFC5462]  Andersson, L. and R. Asati, "Multiprotocol Label Switching
              (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic
              Class" Field", RFC 5462, February 2009.

   [RFC5586]  Bocci, M., Vigoureux, M., and S. Bryant, S., Swallow, G., Martini, L., "MPLS Generic
              Associated Channel", RFC 5586, June 2009.

   [RFC5654]  Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N.,
              and D. McPherson,
              "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
              Use over S. Ueno, "Requirements of an MPLS PSN", Transport Profile",
              RFC 4385, February 2006. 5654, September 2009.

8.2.  Informative References

   [I-D.ietf-mpls-mpls-and-gmpls-security-framework]
              Fang, L. and M. Behringer, "Security Framework for MPLS
              and GMPLS Networks",
              draft-ietf-mpls-mpls-and-gmpls-security-framework-09 (work
              in progress), March 2010.

   [I-D.ietf-mpls-tp-framework]
              Bocci, M., Bryant, S., Frost, D., Levrau, L., and L.
              Berger, "A Framework for MPLS in Transport Networks",
              draft-ietf-mpls-tp-framework-10
              draft-ietf-mpls-tp-framework-11 (work in progress),
              February
              April 2010.

   [I-D.ietf-pwe3-p2mp-pw-requirements]
              Heron, G., Wang, L., Aggarwal, R., Vigoureux,

   [I-D.ietf-pwe3-fc-encap]
              Black, D., Roth, M., Bocci, Tsurusawa, M., Jin, L., JOUNAY, F., Niger, P., Kamite, Y., DeLord,
              S., Solomon, R., and L. Martini, "Requirements
              Dunbar, "Encapsulation Methods for Point-to-Multipoint
              Pseudowire", draft-ietf-pwe3-p2mp-pw-requirements-02 Transport of Fibre
              Channel frames Over MPLS Networks",
              draft-ietf-pwe3-fc-encap-10 (work in progress), January
              February 2010.

   [RFC3985]  Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to-
              Edge (PWE3) Architecture", RFC 3985, March 2005.

   [RFC5086]  Vainshtein, A., Sasson, I., Metz, E., Frost, T., and P.
              Pate, "Structure-Aware Time Division Multiplexed (TDM)
              Circuit Emulation Service over Packet Switched Network
              (CESoPSN)", RFC 5086, December 2007.

   [RFC5087]  Stein, Y(J)., Shashoua, R., Insler, R., and M. Anavi,
              "Time Division Multiplexing over IP (TDMoIP)", RFC 5087,
              December 2007.

   [RFC5659]  Bocci, M. and S. Bryant, "An Architecture for Multi-
              Segment Pseudowire Emulation Edge-to-Edge", RFC 5659,
              October 2009.

   [RFC0826]  Plummer, D., "Ethernet Address Resolution Protocol: Or
              converting network protocol addresses to 48.bit Ethernet
              address for transmission on Ethernet hardware", STD 37,
              RFC 826, November 1982.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              September 2007.

Authors' Addresses

   Dan Frost (editor)
   Cisco Systems

   Email: danfrost@cisco.com

   Stewart Bryant (editor)
   Cisco Systems

   Email: stbryant@cisco.com

   Matthew Bocci (editor)
   Alcatel-Lucent

   Email: matthew.bocci@alcatel-lucent.com