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rfc:rfc4990

Network Working Group K. Shiomoto Request for Comments: 4990 NTT Category: Informational R. Papneja

                                                               Isocore
                                                             R. Rabbat
                                                                Google
                                                        September 2007
                         Use of Addresses
   in Generalized Multiprotocol Label Switching (GMPLS) Networks

Status of This Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Abstract

 This document clarifies the use of addresses in Generalized
 Multiprotocol Label Switching (GMPLS) networks.  The aim is to
 facilitate interworking of GMPLS-capable Label Switching Routers
 (LSRs).  The document is based on experience gained in
 implementation, interoperability testing, and deployment.
 The document describes how to interpret address and identifier fields
 within GMPLS protocols, and how to choose which addresses to set in
 those fields for specific control plane usage models.  It also
 discusses how to handle IPv6 sources and destinations in the MPLS and
 GMPLS Traffic Engineering (TE) Management Information Base (MIB)
 modules.
 This document does not define new procedures or processes.  Whenever
 this document makes requirements statements or recommendations, these
 are taken from normative text in the referenced RFCs.

Shiomoto, et al. Informational [Page 1] RFC 4990 Use of Addresses in GMPLS Networks September 2007

Table of Contents

 1. Introduction ....................................................3
 2. Terminology .....................................................3
 3. Support of Numbered and Unnumbered Links ........................5
 4. Numbered Addressing .............................................6
    4.1. Numbered Addresses in IGPs .................................6
         4.1.1. Router Address and TE Router ID .....................6
         4.1.2. Link ID and Remote Router ID ........................6
         4.1.3. Local Interface IP Address ..........................7
         4.1.4. Remote Interface IP Address .........................7
    4.2. Numbered Addresses in RSVP-TE ..............................7
         4.2.1. IP Tunnel End Point Address in Session Object .......7
         4.2.2. IP Tunnel Sender Address in Sender Template Object ..8
         4.2.3. IF_ID RSVP_HOP Object for Numbered Interfaces .......8
         4.2.4. Explicit Route Object (ERO) .........................9
         4.2.5. Record Route Object (RRO) ...........................9
         4.2.6. IP Packet Source Address ............................9
         4.2.7. IP Packet Destination Address .......................9
 5. Unnumbered Addressing ..........................................10
    5.1. Unnumbered Addresses in IGPs ..............................10
         5.1.1. Link Local/Remote Identifiers in OSPF-TE ...........10
         5.1.2. Link Local/Remote Identifiers in IS-IS-TE ..........11
    5.2. Unnumbered Addresses in RSVP-TE ...........................11
         5.2.1. Sender and End Point Addresses .....................11
         5.2.2. IF_ID RSVP_HOP Object for Unnumbered Interfaces ....11
         5.2.3. Explicit Route Object (ERO) ........................11
         5.2.4. Record Route Object (RRO) ..........................11
         5.2.5. LSP_Tunnel Interface ID Object .....................12
         5.2.6. IP Packet Addresses ................................12
 6. RSVP-TE Message Content ........................................12
    6.1. ERO and RRO Addresses .....................................12
         6.1.1. Strict Subobject in ERO ............................12
         6.1.2. Loose Subobject in ERO .............................14
         6.1.3. RRO ................................................14
         6.1.4. Label Record Subobject in RRO ......................15
    6.2. Component Link Identification .............................15
    6.3. Forwarding Destination of Path Messages with ERO ..........16
 7. Topics Related to the GMPLS Control Plane ......................16
    7.1. Control Channel Separation ................................16
         7.1.1. Native and Tunneled Control Plane ..................16
    7.2. Separation of Control and Data Plane Traffic ..............17
 8. Addresses in the MPLS and GMPLS TE MIB Modules .................17
    8.1. Handling IPv6 Source and Destination Addresses ............18
         8.1.1. Identifying LSRs ...................................18
         8.1.2. Configuring GMPLS Tunnels ..........................18
    8.2. Managing and Monitoring Tunnel Table Entries ..............19
 9. Security Considerations ........................................19

Shiomoto, et al. Informational [Page 2] RFC 4990 Use of Addresses in GMPLS Networks September 2007

 10. Acknowledgments ...............................................20
 11. References ....................................................20
    11.1. Normative References .....................................20
    11.2. Informative References ...................................21

1. Introduction

 This informational document clarifies the use of addresses in
 Generalized Multiprotocol Label Switching (GMPLS) [RFC3945] networks.
 The aim is to facilitate interworking of GMPLS-capable Label
 Switching Routers (LSRs).  The document is based on experience gained
 in implementation, interoperability testing, and deployment.
 The document describes how to interpret address and identifier fields
 within GMPLS protocols (RSVP-TE [RFC3473], GMPLS OSPF [RFC4203], and
 GMPLS ISIS [RFC4205]), and how to choose which addresses to set in
 those fields for specific control plane usage models.
 This document does not define new procedures or processes and the
 protocol specifications listed above should be treated as definitive.
 Furthermore, where this document makes requirements statements or
 recommendations, these are taken from normative text in the
 referenced RFCs.  Nothing in this document should be considered
 normative.
 This document also discusses how to handle IPv6 sources and
 destinations in the MPLS and GMPLS Traffic Engineering (TE)
 Management Information Base (MIB) modules [RFC3812], [RFC4802].

2. Terminology

 As described in [RFC3945], the components of a GMPLS network may be
 separated into a data plane and a control plane.  The control plane
 may be further split into signaling components and routing
 components.
 A data plane switch or router is called a data plane entity.  It is a
 node on the data plane topology graph.  A data plane resource is a
 facility available in the data plane, such as a data plane entity
 (node), data link (edge), or data label (such as a lambda).
 In the control plane, there are protocol speakers that are software
 implementations that communicate using signaling or routing
 protocols.  These are control plane entities, and may be physically
 located separately from the data plane entities that they control.
 Further, there may be separate routing entities and signaling
 entities.

Shiomoto, et al. Informational [Page 3] RFC 4990 Use of Addresses in GMPLS Networks September 2007

 GMPLS supports a control plane entity that is responsible for one or
 more data plane entities, and supports the separation of signaling
 and routing control plane entities.  For the purposes of this
 document, it is assumed that there is a one-to-one correspondence
 between control plane and data plane entities.  That is, each data
 plane switch has a unique control plane entity responsible for
 participating in the GMPLS signaling and routing protocols, and that
 each such control plane presence is responsible for a single data
 plane switch.
 The combination of control plane and data plane entities is referred
 to as a Label Switching Router (LSR).
 Note that the term 'Router ID' is used in two contexts within GMPLS.
 It may refer to an identifier of a participant in a routing protocol,
 or it may be an identifier for an LSR that participates in TE
 routing.  These could be considered as the control plane and data
 plane contexts.
 In this document, the contexts are distinguished by the following
 definitions.
 o  Loopback address: A loopback address is a stable IP address of the
    advertising router that is always reachable if there is any IP
    connectivity to it [RFC3477], [RFC3630].  Thus, for example, an
    IPv4 127/24 address is excluded from this definition.
 o  TE Router ID: A stable IP address of an LSR that is always
    reachable in the control plane if there is any IP connectivity to
    the LSR, e.g., a loopback address.  The most important requirement
    is that the address does not become unusable if an interface on
    the LSR is down [RFC3477], [RFC3630].
 o  Router ID: The OSPF protocol version 2 [RFC2328] defines the
    Router ID to be a 32-bit network-unique number assigned to each
    router running OSPF.  IS-IS [RFC1195] includes a similar concept
    in the System ID.  This document describes both concepts as the
    "Router ID" of the router running the routing protocol.  The
    Router ID is not required to be a reachable IP address, although
    an operator may set it to a reachable IP address on the same node.
 o  TE link: "A TE link is a representation in the IS-IS/OSPF Link
    State advertisements and in the link state database of certain
    physical resources, and their properties, between two GMPLS nodes"
    [RFC3945].
 o  Data plane node: A vertex on the TE graph.  It is a data plane
    switch or router.  Data plane nodes are connected by TE links that

Shiomoto, et al. Informational [Page 4] RFC 4990 Use of Addresses in GMPLS Networks September 2007

    are constructed from physical data links.  A data plane node is
    controlled through some combination of management and control
    plane actions.  A data plane node may be under full or partial
    control of a control plane node.
 o  Control plane node: A GMPLS protocol speaker.  It may be part of a
    data plane switch or may be a separate computer.  Control plane
    nodes are connected by control channels that are logical
    connection-less or connection-oriented paths in the control plane.
    A control plane node is responsible for controlling zero, one, or
    more data plane nodes.
 o  Interface ID: The Interface ID is defined in [RFC3477] and in
    Section 9.1 of [RFC3471].
 o  Data Plane Address: This document refers to a data plane address
    in the context of GMPLS.  It does not refer to addresses such as
    E.164 SAPI in Synchronous Digital Hierarchy (SDH).
 o  Control Plane Address: An address used to identify a control plane
    resource including, and restricted to, control plane nodes and
    control channels.
 o  IP Time to Live (TTL): The IPv4 TTL field or the IPv6 Hop Limit
    field, whichever is applicable.
 o  TED: Traffic Engineering Database.
 o  LSR: Label Switching Router.
 o  FA: Forwarding Adjacency.
 o  IGP: Interior Gateway Protocol.

3. Support of Numbered and Unnumbered Links

 The links in the control and data planes may be numbered or
 unnumbered [RFC3945].  That is, their end points may be assigned IP
 addresses, or may be assigned link IDs specific to the control plane
 or data plane entity at the end of the link.  Implementations may
 decide to support numbered and/or unnumbered addressing.
 The argument for numbered addressing is that it simplifies
 troubleshooting.  The argument for unnumbered addressing is to save
 on IP address resources.
 An LSR may choose to only support its own links being configured as
 numbered, or may only support its own links being configured as

Shiomoto, et al. Informational [Page 5] RFC 4990 Use of Addresses in GMPLS Networks September 2007

 unnumbered.  But an LSR must not restrict the choice of other LSRs to
 use numbered or unnumbered links since this might lead to
 interoperablity issues.  Thus, a node should be able to accept and
 process link advertisements containing both numbered and unnumbered
 addresses.
 Numbered and unnumbered addressing is described in Sections 4 and 5
 of this document, respectively.

4. Numbered Addressing

 When numbered addressing is used, addresses are assigned to each node
 and link in both the control and data planes of the GMPLS network.
 A numbered link is identified by a network-unique identifier (e.g.,
 an IP address).

4.1. Numbered Addresses in IGPs

 In this section, we discuss numbered addressing using two Interior
 Gateway Protocols (IGPs) that have extensions defined for GMPLS:
 OSPF-TE and IS-IS-TE.  The routing enhancements for GMPLS are defined
 in [RFC3630], [RFC3784], [RFC4202], [RFC4203], and [RFC4205].

4.1.1. Router Address and TE Router ID

 The IGPs define a field called the "Router Address".  It is used to
 advertise the TE Router ID.
 The Router Address is advertised in OSPF-TE using the Router Address
 TLV structure of the TE Link State Advertisement (LSA) [RFC3630].
 In IS-IS-TE, this is referred to as the Traffic Engineering router
 ID, and is carried in the advertised Traffic Engineering router ID
 TLV [RFC3784].

4.1.2. Link ID and Remote Router ID

 In OSPF-TE [RFC3630], the Router ID of the remote end of a TE link is
 carried in the Link ID sub-TLV.  This applies for point-to-point TE
 links only; multi-access links are for further study.
 In IS-IS-TE [RFC3784], the Extended IS Reachability TLV is used to
 carry the System ID.  This corresponds to the Router ID as described
 in Section 2.

Shiomoto, et al. Informational [Page 6] RFC 4990 Use of Addresses in GMPLS Networks September 2007

4.1.3. Local Interface IP Address

 The Local Interface IP Address is advertised in:
 o  the Local Interface IP Address sub-TLV in OSPF-TE [RFC3630]
 o  the IPv4 Interface Address sub-TLV in IS-IS-TE [RFC3784].
 This is the ID of the local end of the numbered TE link.  It must be
 a network-unique number (since this section is devoted to numbered
 addressing), but it does not need to be a routable address in the
 control plane.

4.1.4. Remote Interface IP Address

 The Remote Interface IP Address is advertised in:
 o  the Remote Interface IP Address sub-TLV in OSPF-TE [RFC3630]
 o  the IPv4 Neighbor Address sub-TLV in IS-IS-TE [RFC3784].
 This is the ID of the remote end of the numbered TE link.  It must be
 a network-unique number (since this section is devoted to numbered
 addressing), but it does not need to be a routable address in the
 control plane

4.2. Numbered Addresses in RSVP-TE

 The following subsections describe the use of addresses in the GMPLS
 signaling protocol [RFC3209], [RFC3473].

4.2.1. IP Tunnel End Point Address in Session Object

 The IP tunnel end point address of the Session Object [RFC3209] is
 either an IPv4 or IPv6 address.
 The Session Object is invariant for all messages relating to the same
 Label Switched Path (LSP).  The initiator of a Path message sets the
 IP tunnel end point address in the Session Object to one of:
 o  The TE Router ID of the egress since the TE Router ID is routable
    and uniquely identifies the egress node.
 o  The destination data plane address to precisely identify the
    interface that should be used for the final hop of the LSP.  That
    is, the Remote Interface IP Address of the final TE link, if the
    ingress knows that address.

Shiomoto, et al. Informational [Page 7] RFC 4990 Use of Addresses in GMPLS Networks September 2007

 The IP tunnel end point address in the Session Object is not required
 to be routable in the control plane, but should be present in the
 TED.

4.2.2. IP Tunnel Sender Address in Sender Template Object

 The IP tunnel sender address of the Sender Template Object [RFC3209]
 is either an IPv4 or IPv6 address.
 When an LSP is being set up to support an IPv4-numbered FA, [RFC4206]
 recommends that the IP tunnel sender address be set to the head-end
 address of the TE link that is to be created so that the tail-end
 address can be inferred as the /31 partner address.
 When an LSP is being set up that will not be used to form an FA, the
 IP tunnel sender address in the Sender Template Object may be set to
 one of:
 o  The TE Router ID of the ingress LSR since the TE Router ID is a
    unique, routable ID per node.
 o  The sender data plane address (i.e., the Local Interface IP
    Address).

4.2.3. IF_ID RSVP_HOP Object for Numbered Interfaces

 There are two addresses used in the IF_ID RSVP_HOP object.
 1. The IPv4/IPv6 Next/Previous Hop Address [RFC3473]
    When used in a Path or Resv messages, this address specifies the
    IP reachable address of the control plane interface used to send
    the messages, or the TE Router ID of the node that sends the
    message.  That is, it is a routable control plane address of the
    sender of the message and can be used to send return messages.
    Note that because of data plane / control plane separation (see
    Section 7.1) and data plane robustness in the face of control
    plane faults, it may be advisable to use the TE Router ID since it
    is a more stable address.
 2. The IPv4/IPv6 address in the Value Field of the Interface_ID TLV
    [RFC3471]
    This address identifies the data channel associated with the
    signaling message.  In all cases, the data channel is indicated by
    the use of the data plane local interface address at the upstream
    LSR, that is, at the sender of the Path message.

Shiomoto, et al. Informational [Page 8] RFC 4990 Use of Addresses in GMPLS Networks September 2007

 See Section 6.2 for a description of these fields when bundled links
 are used.

4.2.4. Explicit Route Object (ERO)

 The IPv4/IPv6 address in the ERO provides a data-plane identifier of
 an abstract node, TE node, or TE link to be part of the signaled LSP.
 See Section 6 for a description of the use of addresses in the ERO.

4.2.5. Record Route Object (RRO)

 The IPv4/IPv6 address in the RRO provides a data-plane identifier of
 either a TE node or a TE link that is part of an LSP that has been
 established or is being established.
 See Section 6 for a description of the use of addresses in the RRO.

4.2.6. IP Packet Source Address

 GMPLS signaling messages are encapsulated in IP.  The IP packet
 source address is either an IPv4 or IPv6 address and must be a
 reachable control plane address of the node sending the TE message.
 In order to provide control plane robustness, a stable IPv4 or IPv6
 control plane address (for example, the TE Router ID) can be used.
 Some implementations may use the IP source address of a received IP
 packet containing a Path message as the destination IP address of a
 packet containing the corresponding Resv message (see Section 4.2.7).
 Using a stable IPv4 or IPv6 address in the IP packet containing the
 Path message supports this situation robustly when one of the control
 plane interfaces is down.

4.2.7. IP Packet Destination Address

 The IP packet destination address for an IP packet carrying a GMPLS
 signaling message is either an IPv4 or IPv6 address, and must be
 reachable in the control plane if the message is to be delivered.  It
 must be an address of the intended next-hop recipient of the message.
 That is, unlike RSVP, the IP packet is not addressed to the ultimate
 destination (the egress).
 For a Path message, a stable IPv4 or IPv6 address of the next-hop
 node may be used.  This may be the TE Router ID of the next-hop node.
 A suitable address may be determined by examining the TE
 advertisements for the TE link that will form the next-hop data link.

Shiomoto, et al. Informational [Page 9] RFC 4990 Use of Addresses in GMPLS Networks September 2007

 A Resv message is sent to the previous-hop node.  The IPv4 or IPv6
 destination of an IP packet carrying a Resv message may be any of the
 following:
 o  The IPv4 or IPv6 source address of the received IP packet
    containing the Path message.
 o  A stable IPv4 or IPv6 address of the previous node found by
    examining the TE advertisements for the upstream data plane
    interface.
 o  The value in the received in the Next/Previous Hop Address field
    of the RSVP_HOP (PHOP) Object [RFC2205].

5. Unnumbered Addressing

 An unnumbered address is the combination of a network-unique node
 identifier and a node-unique interface identifier.
 An unnumbered link is identified by the combination of the TE Router
 ID that is a reachable address in the control plane and a node-unique
 Interface ID [RFC3477].

5.1. Unnumbered Addresses in IGPs

 In this section, we consider unnumbered address advertisement using
 OSPF-TE and IS-IS-TE.

5.1.1. Link Local/Remote Identifiers in OSPF-TE

 Link Local and Link Remote Identifiers are carried in OSPF using a
 single sub-TLV of the Link TLV [RFC4203].  They advertise the IDs of
 an unnumbered TE link's local and remote ends, respectively.  Link
 Local/Remote Identifiers are numbers unique within the scopes of the
 advertising LSR and the LSR managing the remote end of the link
 respectively [RFC3477].
 Note that these numbers are not network-unique and therefore cannot
 be used as TE link end identifiers on their own.  An unnumbered TE
 link end network-wide identifier is comprised of two elements as
 defined in [RFC3477]:
  1. A TE Router ID that is associated with the link local end
  1. The link local identifier.

Shiomoto, et al. Informational [Page 10] RFC 4990 Use of Addresses in GMPLS Networks September 2007

5.1.2. Link Local/Remote Identifiers in IS-IS-TE

 The Link Local and Link Remote Identifiers are carried in IS-IS using
 a single sub-TLV of the Extended IS Reachability TLV.  Link
 identifiers are exchanged in the Extended Local Circuit ID field of
 the "Point-to-Point Three-Way Adjacency" IS-IS Option type [RFC4205].
 The same discussion of unique identification applies here as in
 Section 5.1.1.

5.2. Unnumbered Addresses in RSVP-TE

 We consider in this section the interface ID fields of objects used
 in RSVP-TE in the case of unnumbered addressing.

5.2.1. Sender and End Point Addresses

 The IP Tunnel End Point Address in the RSVP Session Object and the IP
 Tunnel Sender Address in the RSVP Sender Template Object cannot use
 unnumbered addresses [RFC3209], [RFC3473].

5.2.2. IF_ID RSVP_HOP Object for Unnumbered Interfaces

 The interface ID field in the IF_INDEX TLV specifies the interface of
 the data channel for an unnumbered interface.
 In both Path and Resv messages, the value of the interface ID in the
 IF_INDEX TLV specifies the local interface ID of the associated data
 channel at the upstream node (the node sending the Path message and
 receiving the Resv message).
 See Section 6.2 for a description of the use bundled links.

5.2.3. Explicit Route Object (ERO)

 The ERO may use an unnumbered identifier of a TE link to be part of
 the signaled LSP.
 See Section 6 for a description of the use of addresses in the ERO.

5.2.4. Record Route Object (RRO)

 The RRO records the data-plane identifiers of TE nodes and TE links
 that are part of an LSP that has been established or is being
 established.  TE links may be identified using unnumbered addressing.
 See Section 6 for a description of the use of addresses in the RRO.

Shiomoto, et al. Informational [Page 11] RFC 4990 Use of Addresses in GMPLS Networks September 2007

5.2.5. LSP_Tunnel Interface ID Object

 The LSP_TUNNEL_INTERFACE_ID Object includes the LSR's Router ID and
 Interface ID, as described in [RFC3477], to specify an unnumbered
 Forward Adjacency Interface ID.  The Router ID of the GMPLS-capable
 LSR must be set to the TE Router ID.

5.2.6. IP Packet Addresses

 IP packets can only be addressed to numbered addresses.

6. RSVP-TE Message Content

 This section examines the use of addresses in RSVP EROs and RROs, the
 identification of component links, and forwarding addresses for RSVP
 messages.

6.1. ERO and RRO Addresses

 EROs may contain strict or loose hop subobjects.  These are discussed
 separately below.  A separate section describes the use of addresses
 in the RRO.
 Implementations making limited assumptions about the content of an
 ERO or RRO when processing a received RSVP message may cause or
 experience interoperability issues.  Therefore, implementations that
 want to ensure full interoperability need to support the receipt for
 processing of all ERO and RRO options applicable to their hardware
 capabilities.
 Note that the phrase "receipt for processing" is intended to indicate
 that an LSR is not expected to look ahead in an ERO or process any
 subobjects that do not refer to the LSR itself or to the next hop in
 the ERO.  An LSR is not generally expected to process an RRO except
 by adding its own information.
 Note also that implementations do not need to support the ERO options
 containing Component Link IDs if they do not support link bundling
 [RFC4201].
 ERO processing at region boundaries is described in [RFC4206].

6.1.1. Strict Subobject in ERO

 Depending on the level of control required, a subobject in the ERO
 includes an address that may specify an abstract node (i.e., a group
 of nodes), a simple abstract node (i.e., a specific node), or a
 specific interface of a TE link in the data plane [RFC3209].

Shiomoto, et al. Informational [Page 12] RFC 4990 Use of Addresses in GMPLS Networks September 2007

 A hop may be flagged as strict (meaning that the LSP must go directly
 to the identified next hop without any intervening nodes), or loose.
 If a hop is strict, the ERO may contain any of the following.
 1. Address prefix or AS number specifying a group of nodes.
 2. TE Router ID identifying a specific node.
 3. Link ID identifying an incoming TE link.
 4. Link ID identifying an outgoing TE link, optionally followed by a
    Component Interface ID and/or one or two Labels.
 5. Link ID identifying an incoming TE link, followed by a Link ID
    identifying an outgoing TE link, optionally followed by a
    Component Interface ID and/or one or two Labels.
 6. TE Router ID identifying a specific node, followed by a Link ID
    identifying an outgoing TE link, optionally followed by a
    Component Interface ID and/or one or two Labels.
 7. Link ID identifying an incoming TE link, followed by a TE Router
    ID identifying a specific node, followed by a Link ID identifying
    an outgoing TE link, optionally followed by Component Interface ID
    and/or one or two Labels.
 The label value that identifies a single unidirectional resource
 between two nodes may be different from the perspective of upstream
 and downstream nodes.  This is typically the case in fiber switching
 because the label value is a number indicating the port/fiber.  It
 may also be the case for lambda switching, because the label value is
 an index for the lambda in the hardware and may not be a globally
 defined value such as the wavelength in nanometers.
 The value of a label in any RSVP-TE object indicates the value from
 the perspective of the sender of the object/TLV [RFC3471].
 Therefore, any label in an ERO is given using the upstream node's
 identification of the resource.

Shiomoto, et al. Informational [Page 13] RFC 4990 Use of Addresses in GMPLS Networks September 2007

6.1.2. Loose Subobject in ERO

 There are two differences between Loose and Strict subobjects.
 o  A subobject marked as a loose hop in an ERO must not be followed
    by a subobject indicating a label value [RFC3473].
 o  A subobject marked as a loose hop in an ERO should never include
    an identifier (i.e., address or ID) of the outgoing interface.
 There is no way to specify in an ERO whether a subobject identifies
 an incoming or outgoing TE link.  Path computation must be performed
 by an LSR when it encounters a loose hop in order to resolve the LSP
 route to the identified next hop.  If an interface is specified as a
 loose hop and is treated as an incoming interface, the path
 computation will select a path that enters an LSR through that
 interface.  If the interface was intended to be used as an outgoing
 interface, the computed path may be unsatisfactory and the explicit
 route in the ERO may be impossible to resolve.  Thus a loose hop that
 identifies an interface should always identify the incoming TE link
 in the data plane.

6.1.3. RRO

 The RRO is used on Path and Resv messages to record the path of an
 LSP.  Each LSR adds subobjects to the RRO to record information.  The
 information added to an RRO by a node should be the same in the Path
 and the Resv message although there may be some information that is
 not available during LSP setup.
 One use of the RRO is to allow the operator to view the path of the
 LSP.  At any transit node, it should be possible to construct the
 path of the LSP by joining together the RRO from the Path and the
 Resv messages.
 It is also important that a whole RRO on a Resv message received at
 an ingress LSR can be used as an ERO on a subsequent Path message to
 completely recreate the LSP.
 Therefore, when a node adds one or more subobjects to an RRO, any of
 the following options is valid.
 1. TE Router ID identifying the LSR.
 2. Link ID identifying the incoming (upstream) TE link.
 3. Link ID identifying the outgoing (downstream) TE link, optionally
    followed by a Component Interface ID and/or one or two Labels.

Shiomoto, et al. Informational [Page 14] RFC 4990 Use of Addresses in GMPLS Networks September 2007

 4. Link ID identifying the incoming (upstream) TE link, followed by a
    Link ID identifying the outgoing (downstream) TE link, optionally
    followed by a Component Interface ID and/or one or two Labels.
 5. TE Router ID identifying the LSR, followed by a Link ID
    identifying the outgoing (downstream) TE link, optionally followed
    by a Component Interface ID and/or one or two Labels.
 6. Link ID identifying the incoming (upstream) TE link, followed by
    the TE Router ID identifying the LSR, followed by a Link ID
    identifying the outgoing (downstream) TE link, optionally followed
    by a Component Interface ID and/or one or two Labels.
 An implementation may choose any of these options and must be
 prepared to receive an RRO that contains any of these options.

6.1.4. Label Record Subobject in RRO

 RRO Label recording is requested by an ingress node setting the Label
 Recording flag in the SESSION_ATTRIBUTE object and including an RRO
 is included in the Path message as described in [RFC3209].  Under
 these circumstances, each LSR along the LSP should include label
 information in the RRO in the Path message if it is available.
 As described in [RFC3209], the processing for a Resv message "mirrors
 that of the Path" and "The only difference is that the RRO in a Resv
 message records the path information in the reverse direction." This
 means that hops are added to the RRO in the reverse order, but the
 information added at each LSR is in the same order (see Sections
 6.1.1, 6.1.2, and 6.1.3).  Thus, when label recording is requested,
 labels are included in the RROs in both the Path and Resv messages.

6.2. Component Link Identification

 When a bundled link [RFC4201] is used to provide a data channel, a
 component link identifier is specified in the Interface
 Identification TLV in the IF_ID RSVP_HOP Object in order to indicate
 which data channel from within the bundle is to be used.  The
 Interface Identification TLV is IF_INDEX TLV (Type 3) in the case of
 an unnumbered component link and IPv4 TLV (Type 1) or IPv6 TLV
 (Type 2) in the case of a numbered component link.
 The component link for the upstream data channel may differ from that
 for the downstream data channel in the case of a bidirectional LSP.
 In this case, the Interface Identification TLV specifying a
 downstream interface is followed by another Interface Identification
 TLV specifying an upstream interface.

Shiomoto, et al. Informational [Page 15] RFC 4990 Use of Addresses in GMPLS Networks September 2007

 Note that identifiers in TLVs for upstream and downstream data
 channels in both Path and Resv messages are specified from the
 viewpoint of the upstream node (the node sending the Path message and
 receiving the Resv message), using identifiers belonging to the node.
 An LSR constructing an ERO may include a Link ID that identifies a
 bundled link.  If the LSR knows the identities of the component links
 and wishes to exert control, it may also include component link
 identifiers in the ERO.  Otherwise, the component link identifiers
 are not included in the ERO.
 When a bundled link is in use, the RRO may include the Link ID that
 identifies the link bundle.  Additionally, the RRO may include a
 component link identifier.

6.3. Forwarding Destination of Path Messages with ERO

 The final destination of the Path message is the Egress node that is
 specified by the tunnel end point address in the Session object.
 The Egress node must not forward the corresponding Path message
 downstream, even if the ERO includes the outgoing interface ID of the
 Egress node for Egress control [RFC4003].

7. Topics Related to the GMPLS Control Plane

7.1. Control Channel Separation

 In GMPLS, a control channel can be separated from the data channel
 and there is not necessarily a one-to-one association of a control
 channel to a data channel.  Two nodes that are adjacent in the data
 plane may have multiple IP hops between them in the control plane.
 There are two broad types of separated control planes: native and
 tunneled.  These differ primarily in the nature of encapsulation used
 for signaling messages, which also results in slightly different
 address handling with respect to the control plane address.

7.1.1. Native and Tunneled Control Plane

 A native control plane uses IP forwarding to deliver RSVP-TE messages
 between protocol speakers.  The message is not further encapsulated.
 IP forwarding applies normal rules to the IP header.  Note that an IP
 hop must not decrement the TTL of the received RSVP-TE message.
 For the case where two adjacent nodes have multiple IP hops between
 them in the control plane, then as stated in Section 9 of [RFC3945],

Shiomoto, et al. Informational [Page 16] RFC 4990 Use of Addresses in GMPLS Networks September 2007

 implementations should use the mechanisms of Section 6.1.1 of
 [RFC4206] whether or not they use LSP Hierarchy.  Note that Section
 6.1.1 of [RFC4206] applies to an "FA-LSP" as stated in that section,
 but also to a "TE link" for the case where a normal TE link is used.
 With a tunneled control plane, the RSVP-TE message is packaged in an
 IP packet that is inserted into a tunnel such that the IP packet will
 traverse exactly one IP hop.  Various tunneling techniques can be
 used including (but not limited to) IP-in-IP, Generic Routing
 Encapsulation (GRE), and IP in MPLS.
 Where the tunneling mechanism includes a TTL, it should be treated as
 for any network message sent on that network.  Implementations
 receiving RSVP-TE messages on the tunnel interface must not compare
 the RSVP-TE TTL to any other TTL (whether the IP TTL or the tunnel
 TTL).
 It has been observed that some implementations do not support the
 tunneled control plane features, and it is suggested that to enable
 interoperability, all implementations should support at least a
 native control plane.

7.2. Separation of Control and Data Plane Traffic

 Data traffic must not be transmitted through the control plane.  This
 is crucial when attempting PSC (Packet-Switching Capable) GMPLS with
 separated control and data channels.

8. Addresses in the MPLS and GMPLS TE MIB Modules

 This section describes a method of defining or monitoring an LSP
 tunnel using the MPLS-TE-STD-MIB module [RFC3812] and GMPLS-TE-STD-
 MIB module [RFC4802] where the ingress and/or egress routers are
 identified using 128-bit IPv6 addresses.  This is the case when the
 mplsTunnelIngressLSRId and mplsTunnelEgressLSRId objects in the
 mplsTunnelTable [RFC3812] cannot be used to carry the tunnel end
 point address and Extended Tunnel Id fields from the signaled Session
 Object because the IPv6 variant (LSP_TUNNEL_IPv6_SESSION object) is
 in use.
 The normative text for MIB objects for control and monitoring MPLS
 and GMPLS nodes is found in the RFCs referenced above.  This section
 makes no changes to those objects, but describes how they may be used
 to provide the necessary function.

Shiomoto, et al. Informational [Page 17] RFC 4990 Use of Addresses in GMPLS Networks September 2007

8.1. Handling IPv6 Source and Destination Addresses

8.1.1. Identifying LSRs

 For this feature to be used, all LSRs in the network must advertise a
 32-bit value that can be used to identify the LSR.  In this document,
 this is referred to as the 32-bit LSR ID.  The 32-bit LSR ID is the
 OSPFv3 router ID [RFC2740] or the ISIS IPv4 TE Router ID [RFC3784].
 Note that these are different from TE router ID (see Section 2).

8.1.2. Configuring GMPLS Tunnels

 When setting up RSVP TE tunnels, it is common practice to copy the
 values of the mplsTunnelIngressLSRId and mplsTunnelEgressLSRId fields
 in the MPLS TE MIB mplsTunnelTable [RFC3812] into the Extended Tunnel
 ID and IPv4 tunnel end point address fields, respectively, in the
 RSVP-TE LSP_TUNNEL_IPv4 SESSION object [RFC3209].
 This approach cannot be used when the ingress and egress routers are
 identified by 128-bit IPv6 addresses as the mplsTunnelIngressLSRId,
 and mplsTunnelEgressLSRId fields are defined to be 32-bit values
 [RFC3811], [RFC3812].
 Instead, the IPv6 addresses should be configured in the mplsHopTable
 as the first and last hops of the mplsTunnelHopTable entries defining
 the explicit route for the tunnel.  Note that this implies that a
 tunnel with IPv6 source and destination addresses must have an
 explicit route configured, although it should be noted that the
 configuration of an explicit route in this way does not imply that an
 explicit route will be signaled.
 In more detail, the tunnel is configured at the ingress router as
 follows.  See [RFC3812] for definitions of MIB table objects and for
 default (that is, "normal") behavior.
 The mplsTunnelIndex and mplsTunnelInstance fields are set as normal.
 The mplsTunnelIngressLSRId and mplsTunnelEgressLSRId fields should be
 set to 32-bit LSR IDs for ingress and egress LSRs, respectively.
 The mplsTunnelHopTableIndex must be set to a non-zero value.  That
 is, an explicit route must be specified.
 The first hop of the explicit route must have mplsTunnelHopAddrType
 field set to ipv6(2) and should have the mplsTunnelHopIpAddr field
 set to a global scope IPv6 address of the ingress router that is
 reachable in the control plane.

Shiomoto, et al. Informational [Page 18] RFC 4990 Use of Addresses in GMPLS Networks September 2007

 The last hop of the explicit route must have mplsTunnelHopAddrType
 field set to ipv6(2) and should have the mplsTunnelHopIpAddr field
 set to a global scope IPv6 address of the egress router that is
 reachable in the control plane.
 The ingress router should set the signaled values of the Extended
 Tunnel ID and IPv6 tunnel end point address fields, respectively, of
 the RSVP-TE LSP_TUNNEL_IPv6 SESSION object [RFC3209] from the
 mplsTunnelHopIpAddr object of the first and last hops in the
 configured explicit route.

8.2. Managing and Monitoring Tunnel Table Entries

 In addition to their use for configuring LSPs as described in Section
 8.1, the TE MIB modules (MPLS-TE-STD-MIB and GMPLS-TE-STD-MIB) may be
 used for managing and monitoring MPLS and GMPLS TE LSPs,
 respectively.  This function is particularly important at egress and
 transit LSRs.
 For a tunnel with IPv6 source and destination addresses, an LSR
 implementation should return values in the mplsTunnelTable as follows
 (where "normal" behavior is the default taken from [RFC3812]).
 The mplsTunnelIndex and mplsTunnelInstance fields are set as normal.
 The mplsTunnelIngressLSRId field and mplsTunnelEgressLSRId are set to
 32-bit LSR IDs.  That is, each transit and egress router maps from
 the IPv6 address in the Extended Tunnel ID field to the 32-bit LSR ID
 of the ingress LSR.  Each transit router also maps from the IPv6
 address in the IPv6 tunnel end point address field to the 32-bit LSR
 ID of the egress LSR.

9. Security Considerations

 In the interoperability testing we conducted, the major issue we
 found was the use of control channels for forwarding data.  This was
 due to the setting of both control and data plane addresses to the
 same value in PSC (Packet-Switching Capable) equipment.  This
 occurred when attempting to test PSC GMPLS with separated control and
 data channels.  What resulted instead were parallel interfaces with
 the same addresses.  This could be avoided simply by keeping the
 addresses for the control and data plane separate.

Shiomoto, et al. Informational [Page 19] RFC 4990 Use of Addresses in GMPLS Networks September 2007

10. Acknowledgments

 The following people made textual contributions to this document:
   Alan Davey, Yumiko Kawashima, Kaori Shimizu, Thomas D. Nadeau,
   Ashok Narayanan, Eiji Oki, Lyndon Ong, Vijay Pandian, Hari
   Rakotoranto, and Adrian Farrel.
 The authors would like to thank Adrian Farrel for the helpful
 discussions and the feedback he gave on the document.  In addition,
 Jari Arkko, Arthi Ayyangar, Deborah Brungard, Diego Caviglia, Lisa
 Dusseault, Dimitri Papadimitriou, Jonathan Sadler, Hidetsugu
 Sugiyama, and Julien Meuric provided helpful comments and
 suggestions.
 Adrian Farrel edited the final revisions of this document before and
 after working group last call.

11. References

11.1. Normative References

 [RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
           Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
           Functional Specification", RFC 2205, September 1997.
 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
           and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
           Tunnels", RFC 3209, December 2001.
 [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.
 [RFC3477] Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links
           in Resource ReSerVation Protocol - Traffic Engineering
           (RSVP-TE)", RFC 3477, January 2003.
 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
           (TE) Extensions to OSPF Version 2", RFC 3630, September
           2003.

Shiomoto, et al. Informational [Page 20] RFC 4990 Use of Addresses in GMPLS Networks September 2007

 [RFC3811] Nadeau, T., Ed., and J. Cucchiara, Ed., "Definitions of
           Textual Conventions (TCs) for Multiprotocol Label Switching
           (MPLS) Management", RFC 3811, June 2004.
 [RFC3812] Srinivasan, C., Viswanathan, A., and T. Nadeau,
           "Multiprotocol Label Switching (MPLS) Traffic Engineering
           (TE) Management Information Base (MIB)", RFC 3812, June
           2004.
 [RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label
           Switching (GMPLS) Architecture", RFC 3945, October 2004.
 [RFC4003] Berger, L., "GMPLS Signaling Procedure for Egress Control",
           RFC 4003, February 2005.
 [RFC4201] Kompella, K., Rekhter, Y., and L. Berger, "Link Bundling in
           MPLS Traffic Engineering (TE)", RFC 4201, October 2005.
 [RFC4202] Kompella, K., Ed., and Y. Rekhter, Ed., "Routing Extensions
           in Support of Generalized Multi-Protocol Label Switching
           (GMPLS)", RFC 4202, October 2005.
 [RFC4203] Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions in
           Support of Generalized Multi-protocol Label Switching", RFC
           4203, October 2005.
 [RFC4206] Kompella, K. and Y. Rekhter, "LSP Hierarchy with
           Generalized MPLS TE", RFC 4206, October 2005.

11.2. Informative References

 [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
           dual environments", RFC 1195, December 1990.
 [RFC2740] Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6", RFC
           2740, December 1999.
 [RFC3784] Smit, H. and T. Li, "Intermediate System to Intermediate
           System (IS-IS) Extensions for Traffic Engineering (TE)",
           RFC 3784, June 2004.
 [RFC4205] Kompella, K., Ed., and Y. Rekhter, Ed., "Intermediate
           System to Intermediate System (IS-IS) Extensions in Support
           of Generalized Multi-Protocol Label Switching (GMPLS)", RFC
           4205, October 2005.

Shiomoto, et al. Informational [Page 21] RFC 4990 Use of Addresses in GMPLS Networks September 2007

 [RFC4802] Nadeau, T., Ed., and A. Farrel, Ed., "Generalized
           Multiprotocol Label Switching (GMPLS) Traffic Engineering
           Management Information Base", RFC 4802, February 2007.

Authors' Addresses

 Kohei Shiomoto
 NTT Network Service Systems Laboratories
 3-9-11 Midori
 Musashino, Tokyo 180-8585
 Japan
 Phone: +81 422 59 4402
 EMail: shiomoto.kohei@lab.ntt.co.jp
 Richard Rabbat
 Google Inc.
 1600 Amphitheatre Parkway
 Mountain View, CA 94043
 Phone: +1 650-714-7618
 EMail: rabbat@alum.mit.edu
 Rajiv Papneja
 Isocore Corporation
 12359 Sunrise Valley Drive, Suite 100
 Reston, Virginia 20191
 United States of America
 Phone: +1 703-860-9273
 EMail: rpapneja@isocore.com

Shiomoto, et al. Informational [Page 22] RFC 4990 Use of Addresses in GMPLS Networks September 2007

Full Copyright Statement

 Copyright (C) The IETF Trust (2007).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
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 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
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Shiomoto, et al. Informational [Page 23]

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