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rfc:rfc4202

Network Working Group K. Kompella, Ed. Request for Comments: 4202 Y. Rekhter, Ed. Category: Standards Track Juniper Networks

                                                          October 2005
                 Routing Extensions in Support of
         Generalized Multi-Protocol Label Switching (GMPLS)

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2005).

Abstract

 This document specifies routing extensions in support of carrying
 link state information for Generalized Multi-Protocol Label Switching
 (GMPLS).  This document enhances the routing extensions required to
 support MPLS Traffic Engineering (TE).

Kompella & Rekhter Standards Track [Page 1] RFC 4202 Routing Extensions for GMPLS October 2005

Table of Contents

 1.  Introduction. . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements for Layer-Specific TE Attributes . . . . .   4
     1.2.  Excluding Data Traffic from Control Channels. . . . . .   6
 2.  GMPLS Routing Enhancements. . . . . . . . . . . . . . . . . .   7
     2.1.  Support for Unnumbered Links. . . . . . . . . . . . . .   7
     2.2.  Link Protection Type. . . . . . . . . . . . . . . . . .   7
     2.3.  Shared Risk Link Group Information. . . . . . . . . . .   9
     2.4.  Interface Switching Capability Descriptor . . . . . . .   9
           2.4.1.  Layer-2 Switch Capable. . . . . . . . . . . . .  11
           2.4.2.  Packet-Switch Capable . . . . . . . . . . . . .  11
           2.4.3.  Time-Division Multiplex Capable . . . . . . . .  12
           2.4.4.  Lambda-Switch Capable . . . . . . . . . . . . .  13
           2.4.5.  Fiber-Switch Capable. . . . . . . . . . . . . .  13
           2.4.6.  Multiple Switching Capabilities per Interface .  13
           2.4.7.  Interface Switching Capabilities and Labels . .  14
           2.4.8.  Other Issues. . . . . . . . . . . . . . . . . .  14
     2.5.  Bandwidth Encoding. . . . . . . . . . . . . . . . . . .  15
 3.  Examples of Interface Switching Capability Descriptor . . . .  15
     3.1.  STM-16 POS Interface on a LSR . . . . . . . . . . . . .  15
     3.2.  GigE Packet Interface on a LSR. . . . . . . . . . . . .  15
     3.3.  STM-64 SDH Interface on a Digital Cross Connect with
           Standard SDH. . . . . . . . . . . . . . . . . . . . . .  15
     3.4.  STM-64 SDH Interface on a Digital Cross Connect with
           Two Types of SDH Multiplexing Hierarchy Supported . . .  16
     3.5.  Interface on an Opaque OXC (SDH Framed) with Support
           for One Lambda per Port/Interface . . . . . . . . . . .  16
     3.6.  Interface on a Transparent OXC (PXC) with External
           DWDM that understands SDH framing . . . . . . . . . . .  17
     3.7.  Interface on a Transparent OXC (PXC) with External
           DWDM That Is Transparent to Bit-Rate and Framing. . . .  17
     3.8.  Interface on a PXC with No External DWDM. . . . . . . .  18
     3.9.  Interface on a OXC with Internal DWDM That Understands
           SDH Framing . . . . . . . . . . . . . . . . . . . . . .  18
     3.10. Interface on a OXC with Internal DWDM That Is
           Transparent to Bit-Rate and Framing . . . . . . . . . .  19
 4.  Example of Interfaces That Support Multiple Switching
     Capabilities. . . . . . . . . . . . . . . . . . . . . . . . .  20
     4.1.  Interface on a PXC+TDM Device with External DWDM. . . .  20
     4.2.  Interface on an Opaque OXC+TDM Device with External
           DWDM. . . . . . . . . . . . . . . . . . . . . . . . . .  21
     4.3.  Interface on a PXC+LSR Device with External DWDM. . . .  21
     4.4.  Interface on a TDM+LSR Device . . . . . . . . . . . . .  21
 5.  Acknowledgements. . . . . . . . . . . . . . . . . . . . . . .  22
 6.  Security Considerations . . . . . . . . . . . . . . . . . . .  22

Kompella & Rekhter Standards Track [Page 2] RFC 4202 Routing Extensions for GMPLS October 2005

 7.  References. . . . . . . . . . . . . . . . . . . . . . . . . .  23
     7.1.  Normative References. . . . . . . . . . . . . . . . . .  23
     7.2.  Informative References. . . . . . . . . . . . . . . . .  24
 8.  Contributors. . . . . . . . . . . . . . . . . . . . . . . . .  24

1. Introduction

 This document specifies routing extensions in support of carrying
 link state information for Generalized Multi-Protocol Label Switching
 (GMPLS).  This document enhances the routing extensions [ISIS-TE],
 [OSPF-TE] required to support MPLS Traffic Engineering (TE).
 Traditionally, a TE link is advertised as an adjunct to a "regular"
 link, i.e., a routing adjacency is brought up on the link, and when
 the link is up, both the properties of the link are used for Shortest
 Path First (SPF) computations (basically, the SPF metric) and the TE
 properties of the link are then advertised.
 GMPLS challenges this notion in three ways.  First, links that are
 not capable of sending and receiving on a packet-by-packet basis may
 yet have TE properties; however, a routing adjacency cannot be
 brought up on such links.  Second, a Label Switched Path can be
 advertised as a point-to-point TE link (see [LSP-HIER]); thus, an
 advertised TE link may be between a pair of nodes that don't have a
 routing adjacency with each other.  Finally, a number of links may be
 advertised as a single TE link (perhaps for improved scalability), so
 again, there is no longer a one-to-one association of a regular
 routing adjacency and a TE link.
 Thus we have a more general notion of a TE link.  A TE link is a
 "logical" link that has TE properties.  The link is logical in a
 sense that it represents a way to group/map the information about
 certain physical resources (and their properties) into the
 information that is used by Constrained SPF for the purpose of path
 computation, and by GMPLS signaling.  This grouping/mapping must be
 done consistently at both ends of the link.  LMP [LMP] could be used
 to check/verify this consistency.
 Depending on the nature of resources that form a particular TE link,
 for the purpose of GMPLS signaling, in some cases the combination of
 <TE link identifier, label> is sufficient to unambiguously identify
 the appropriate resource used by an LSP.  In other cases, the
 combination of <TE link identifier, label> is not sufficient; such
 cases are handled by using the link bundling construct [LINK-BUNDLE]
 that allows to identify the resource by <TE link identifier,
 Component link identifier, label>.

Kompella & Rekhter Standards Track [Page 3] RFC 4202 Routing Extensions for GMPLS October 2005

 Some of the properties of a TE link may be configured on the
 advertising Label Switching Router (LSR), others which may be
 obtained from other LSRs by means of some protocol, and yet others
 which may be deduced from the component(s) of the TE link.
 A TE link between a pair of LSRs doesn't imply the existence of a
 routing adjacency (e.g., an IGP adjacency) between these LSRs.  As we
 mentioned above, in certain cases a TE link between a pair of LSRs
 could be advertised even if there is no routing adjacency at all
 between the LSRs (e.g., when the TE link is a Forwarding Adjacency
 (see [LSP-HIER])).
 A TE link must have some means by which the advertising LSR can know
 of its liveness (this means may be routing hellos, but is not limited
 to routing hellos).  When an LSR knows that a TE link is up, and can
 determine the TE link's TE properties, the LSR may then advertise
 that link to its (regular) neighbors.
 In this document, we call the interfaces over which regular routing
 adjacencies are established "control channels".
 [ISIS-TE] and [OSPF-TE] define the canonical TE properties, and say
 how to associate TE properties to regular (packet-switched) links.
 This document extends the set of TE properties, and also says how to
 associate TE properties with non-packet-switched links such as links
 between Optical Cross-Connects (OXCs).  [LSP-HIER] says how to
 associate TE properties with links formed by Label Switched Paths.
 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 BCP 14, RFC 2119
 [RFC2119].

1.1. Requirements for Layer-Specific TE Attributes

 In generalizing TE links to include traditional transport facilities,
 there are additional factors that influence what information is
 needed about the TE link.  These arise from existing transport layer
 architecture (e.g., ITU-T Recommendations G.805 and G.806) and
 associated layer services.  Some of these factors are:
 1. The need for LSPs at a specific adaptation, not just a particular
    bandwidth.  Clients of optical networks obtain connection services
    for specific adaptations, for example, a VC-3 circuit.  This not
    only implies a particular bandwidth, but how the payload is
    structured.  Thus the VC-3 client would not be satisfied with any
    LSP that offered other than 48.384 Mbit/s and with the expected

Kompella & Rekhter Standards Track [Page 4] RFC 4202 Routing Extensions for GMPLS October 2005

    structure.  The corollary is that path computation should be able
    to find a route that would give a connection at a specific
    adaptation.
 2. Distinguishing variable adaptation.  A resource between two OXCs
    (specifically a G.805 trail) can sometimes support different
    adaptations at the same time.  An example of this is described in
    section 2.4.8.  In this situation, the fact that two adaptations
    are supported on the same trail is important because the two
    layers are dependent, and it is important to be able to reflect
    this layer relationship in routing, especially in view of the
    relative lack of flexibility of transport layers compared to
    packet layers.
 3. Inheritable attributes.  When a whole multiplexing hierarchy is
    supported by a TE link, a lower layer attribute may be applicable
    to the upper layers.  Protection attributes are a good example of
    this.  If an OC-192 link is 1+1 protected (a duplicate OC-192
    exists for protection), then an STS-3c within that OC-192 (a
    higher layer) would inherit the same protection property.
 4. Extensibility of layers.  In addition to the existing defined
    transport layers, new layers and adaptation relationships could
    come into existence in the future.
 5. Heterogeneous networks whose OXCs do not all support the same set
    of layers.  In a GMPLS network, not all transport layer network
    elements are expected to support the same layers.  For example,
    there may be switches capable of only VC-11, VC-12, and VC-3, and
    there may be others that can only support VC-3 and VC-4.  Even
    though a network element cannot support a specific layer, it
    should be able to know if a network element elsewhere in the
    network can support an adaptation that would enable that
    unsupported layer to be used.  For example, a VC-11 switch could
    use a VC-3 capable switch if it knew that a VC-11 path could be
    constructed over a VC-3 link connection.
 From the factors presented above, development of layer specific GMPLS
 routing documents should use the following principles for TE-link
 attributes.
 1. Separation of attributes.  The attributes in a given layer are
    separated from attributes in another layer.
 2. Support of inter-layer attributes (e.g., adaptation
    relationships).  Between a client and server layer, a general
    mechanism for describing the layer relationship exists.  For

Kompella & Rekhter Standards Track [Page 5] RFC 4202 Routing Extensions for GMPLS October 2005

    example, "4 client links of type X can be supported by this server
    layer link".  Another example is being able to identify when two
    layers share a common server layer.
 3. Support for inheritable attributes.  Attributes which can be
    inherited should be identified.
 4. Layer extensibility.  Attributes should be represented in routing
    such that future layers can be accommodated.  This is much like
    the notion of the generalized label.
 5. Explicit attribute scope.  For example, it should be clear whether
    a given attribute applies to a set of links at the same layer.
 The present document captures general attributes that apply to a
 single layer network, but doesn't capture inter-layer relationships
 of attributes.  This work is left to a future document.

1.2. Excluding Data Traffic from Control Channels

 The control channels between nodes in a GMPLS network, such as OXCs,
 SDH cross-connects and/or routers, are generally meant for control
 and administrative traffic.  These control channels are advertised
 into routing as normal links as mentioned in the previous section;
 this allows the routing of (for example) RSVP messages and telnet
 sessions.  However, if routers on the edge of the optical domain
 attempt to forward data traffic over these channels, the channel
 capacity will quickly be exhausted.
 In order to keep these control channels from being advertised into
 the user data plane a variety of techniques can be used.
 If one assumes that data traffic is sent to BGP destinations, and
 control traffic to IGP destinations, then one can exclude data
 traffic from the control plane by restricting BGP nexthop resolution.
 (It is assumed that OXCs are not BGP speakers.)  Suppose that a
 router R is attempting to install a route to a BGP destination D.  R
 looks up the BGP nexthop for D in its IGP's routing table.  Say R
 finds that the path to the nexthop is over interface I.  R then
 checks if it has an entry in its Link State database associated with
 the interface I.  If it does, and the link is not packet-switch
 capable (see [LSP-HIER]), R installs a discard route for destination
 D.  Otherwise, R installs (as usual) a route for destination D with
 nexthop I.  Note that R need only do this check if it has packet-
 switch incapable links; if all of its links are packet-switch
 capable, then clearly this check is redundant.

Kompella & Rekhter Standards Track [Page 6] RFC 4202 Routing Extensions for GMPLS October 2005

 In other instances it may be desirable to keep the whole address
 space of a GMPLS routing plane disjoint from the endpoint addresses
 in another portion of the GMPLS network.  For example, the addresses
 of a carrier network where the carrier uses GMPLS but does not wish
 to expose the internals of the addressing or topology.  In such a
 network the control channels are never advertised into the end data
 network.  In this instance, independent mechanisms are used to
 advertise the data addresses over the carrier network.
 Other techniques for excluding data traffic from control channels may
 also be needed.

2. GMPLS Routing Enhancements

 In this section we define the enhancements to the TE properties of
 GMPLS TE links.  Encoding of this information in IS-IS is specified
 in [GMPLS-ISIS].  Encoding of this information in OSPF is specified
 in [GMPLS-OSPF].

2.1. Support for Unnumbered Links

 An unnumbered link has to be a point-to-point link.  An LSR at each
 end of an unnumbered link assigns an identifier to that link.  This
 identifier is a non-zero 32-bit number that is unique within the
 scope of the LSR that assigns it.
 Consider an (unnumbered) link between LSRs A and B.  LSR A chooses an
 idenfitier for that link.  So does LSR B.  From A's perspective we
 refer to the identifier that A assigned to the link as the "link
 local identifier" (or just "local identifier"), and to the identifier
 that B assigned to the link as the "link remote identifier" (or just
 "remote identifier").  Likewise, from B's perspective the identifier
 that B assigned to the link is the local identifier, and the
 identifier that A assigned to the link is the remote identifier.
 Support for unnumbered links in routing includes carrying information
 about the identifiers of that link.  Specifically, when an LSR
 advertises an unnumbered TE link, the advertisement carries both the
 local and the remote identifiers of the link.  If the LSR doesn't
 know the remote identifier of that link, the LSR should use a value
 of 0 as the remote identifier.

2.2. Link Protection Type

 The Link Protection Type represents the protection capability that
 exists for a link.  It is desirable to carry this information so that
 it may be used by the path computation algorithm to set up LSPs with
 appropriate protection characteristics.  This information is

Kompella & Rekhter Standards Track [Page 7] RFC 4202 Routing Extensions for GMPLS October 2005

 organized in a hierarchy where typically the minimum acceptable
 protection is specified at path instantiation and a path selection
 technique is used to find a path that satisfies at least the minimum
 acceptable protection.  Protection schemes are presented in order
 from lowest to highest protection.
 This document defines the following protection capabilities:
 Extra Traffic
    If the link is of type Extra Traffic, it means that the link is
    protecting another link or links.  The LSPs on a link of this type
    will be lost if any of the links it is protecting fail.
 Unprotected
    If the link is of type Unprotected, it means that there is no
    other link protecting this link.  The LSPs on a link of this type
    will be lost if the link fails.
 Shared
    If the link is of type Shared, it means that there are one or more
    disjoint links of type Extra Traffic that are protecting this
    link.  These Extra Traffic links are shared between one or more
    links of type Shared.
 Dedicated 1:1
    If the link is of type Dedicated 1:1, it means that there is one
    dedicated disjoint link of type Extra Traffic that is protecting
    this link.
 Dedicated 1+1
    If the link is of type Dedicated 1+1, it means that a dedicated
    disjoint link is protecting this link.  However, the protecting
    link is not advertised in the link state database and is therefore
    not available for the routing of LSPs.
 Enhanced
    If the link is of type Enhanced, it means that a protection scheme
    that is more reliable than Dedicated 1+1, e.g., 4 fiber
    BLSR/MS-SPRING, is being used to protect this link.
    The Link Protection Type is optional, and if a Link State
    Advertisement doesn't carry this information, then the Link
    Protection Type is unknown.

Kompella & Rekhter Standards Track [Page 8] RFC 4202 Routing Extensions for GMPLS October 2005

2.3. Shared Risk Link Group Information

 A set of links may constitute a 'shared risk link group' (SRLG) if
 they share a resource whose failure may affect all links in the set.
 For example, two fibers in the same conduit would be in the same
 SRLG.  A link may belong to multiple SRLGs.  Thus the SRLG
 Information describes a list of SRLGs that the link belongs to.  An
 SRLG is identified by a 32 bit number that is unique within an IGP
 domain.  The SRLG Information is an unordered list of SRLGs that the
 link belongs to.
 The SRLG of a LSP is the union of the SRLGs of the links in the LSP.
 The SRLG of a bundled link is the union of the SRLGs of all the
 component links.
 If an LSR is required to have multiple diversely routed LSPs to
 another LSR, the path computation should attempt to route the paths
 so that they do not have any links in common, and such that the path
 SRLGs are disjoint.
 The SRLG Information may start with a configured value, in which case
 it does not change over time, unless reconfigured.
 The SRLG Information is optional and if a Link State Advertisement
 doesn't carry the SRLG Information, then it means that SRLG of that
 link is unknown.

2.4. Interface Switching Capability Descriptor

 In the context of this document we say that a link is connected to a
 node by an interface.  In the context of GMPLS interfaces may have
 different switching capabilities.  For example an interface that
 connects a given link to a node may not be able to switch individual
 packets, but it may be able to switch channels within an SDH payload.
 Interfaces at each end of a link need not have the same switching
 capabilities.  Interfaces on the same node need not have the same
 switching capabilities.
 The Interface Switching Capability Descriptor describes switching
 capability of an interface.  For bi-directional links, the switching
 capabilities of an interface are defined to be the same in either
 direction.  I.e., for data entering the node through that interface
 and for data leaving the node through that interface.
 A Link State Advertisement of a link carries the Interface Switching
 Capability Descriptor(s) only of the near end (the end incumbent on
 the LSR originating the advertisement).

Kompella & Rekhter Standards Track [Page 9] RFC 4202 Routing Extensions for GMPLS October 2005

 An LSR performing path computation uses the Link State Database to
 determine whether a link is unidirectional or bidirectional.
 For a bidirectional link the LSR uses its Link State Database to
 determine the Interface Switching Capability Descriptor(s) of the
 far-end of the link, as bidirectional links with different Interface
 Switching Capabilities at its two ends are allowed.
 For a unidirectional link it is assumed that the Interface Switching
 Capability Descriptor at the far-end of the link is the same as at
 the near-end.  Thus, an unidirectional link is required to have the
 same interface switching capabilities at both ends.  This seems a
 reasonable assumption given that unidirectional links arise only with
 packet forwarding adjacencies and for these both ends belong to the
 same level of the PSC hierarchy.
 This document defines the following Interface Switching Capabilities:
       Packet-Switch Capable-1         (PSC-1)
       Packet-Switch Capable-2         (PSC-2)
       Packet-Switch Capable-3         (PSC-3)
       Packet-Switch Capable-4         (PSC-4)
       Layer-2 Switch Capable          (L2SC)
       Time-Division-Multiplex Capable (TDM)
       Lambda-Switch Capable           (LSC)
       Fiber-Switch Capable            (FSC)
 If there is no Interface Switching Capability Descriptor for an
 interface, the interface is assumed to be packet-switch capable
 (PSC-1).
 Interface Switching Capability Descriptors present a new constraint
 for LSP path computation.
 Irrespective of a particular Interface Switching Capability, the
 Interface Switching Capability Descriptor always includes information
 about the encoding supported by an interface.  The defined encodings
 are the same as LSP Encoding as defined in [GMPLS-SIG].
 An interface may have more than one Interface Switching Capability
 Descriptor.  This is used to handle interfaces that support multiple
 switching capabilities, for interfaces that have Max LSP Bandwidth
 values that differ by priority level, and for interfaces that support
 discrete bandwidths.
 Depending on a particular Interface Switching Capability, the
 Interface Switching Capability Descriptor may include additional
 information, as specified below.

Kompella & Rekhter Standards Track [Page 10] RFC 4202 Routing Extensions for GMPLS October 2005

2.4.1. Layer-2 Switch Capable

 If an interface is of type L2SC, it means that the node receiving
 data over this interface can switch the received frames based on the
 layer 2 address.  For example, an interface associated with a link
 terminating on an ATM switch would be considered L2SC.

2.4.2. Packet-Switch Capable

 If an interface is of type PSC-1 through PSC-4, it means that the
 node receiving data over this interface can switch the received data
 on a packet-by-packet basis, based on the label carried in the "shim"
 header [RFC3032].  The various levels of PSC establish a hierarchy of
 LSPs tunneled within LSPs.
 For Packet-Switch Capable interfaces the additional information
 includes Maximum LSP Bandwidth, Minimum LSP Bandwidth, and interface
 MTU.
 For a simple (unbundled) link, the Maximum LSP Bandwidth at priority
 p is defined to be the smaller of the unreserved bandwidth at
 priority p and a "Maximum LSP Size" parameter which is locally
 configured on the link, and whose default value is equal to the Max
 Link Bandwidth.  Maximum LSP Bandwidth for a bundled link is defined
 in [LINK-BUNDLE].
 The Maximum LSP Bandwidth takes the place of the Maximum Link
 Bandwidth ([ISIS-TE], [OSPF-TE]).  However, while Maximum Link
 Bandwidth is a single fixed value (usually simply the link capacity),
 Maximum LSP Bandwidth is carried per priority, and may vary as LSPs
 are set up and torn down.
 Although Maximum Link Bandwidth is to be deprecated, for backward
 compatibility, one MAY set the Maximum Link Bandwidth to the Maximum
 LSP Bandwidth at priority 7.
 The Minimum LSP Bandwidth specifies the minimum bandwidth an LSP
 could reserve.
 Typical values for the Minimum LSP Bandwidth and for the Maximum LSP
 Bandwidth are enumerated in [GMPLS-SIG].
 On a PSC interface that supports Standard SDH encoding, an LSP at
 priority p could reserve any bandwidth allowed by the branch of the
 SDH hierarchy, with the leaf and the root of the branch being defined
 by the Minimum LSP Bandwidth and the Maximum LSP Bandwidth at
 priority p.

Kompella & Rekhter Standards Track [Page 11] RFC 4202 Routing Extensions for GMPLS October 2005

 On a PSC interface that supports Arbitrary SDH encoding, an LSP at
 priority p could reserve any bandwidth between the Minimum LSP
 Bandwidth and the Maximum LSP Bandwidth at priority p, provided that
 the bandwidth reserved by the LSP is a multiple of the Minimum LSP
 Bandwidth.
 The Interface MTU is the maximum size of a packet that can be
 transmitted on this interface without being fragmented.

2.4.3. Time-Division Multiplex Capable

 If an interface is of type TDM, it means that the node receiving data
 over this interface can multiplex or demultiplex channels within an
 SDH payload.
 For Time-Division Multiplex Capable interfaces the additional
 information includes Maximum LSP Bandwidth, the information on
 whether the interface supports Standard or Arbitrary SDH, and Minimum
 LSP Bandwidth.
 For a simple (unbundled) link the Maximum LSP Bandwidth at priority p
 is defined as the maximum bandwidth an LSP at priority p could
 reserve.  Maximum LSP Bandwidth for a bundled link is defined in
 [LINK-BUNDLE].
 The Minimum LSP Bandwidth specifies the minimum bandwidth an LSP
 could reserve.
 Typical values for the Minimum LSP Bandwidth and for the Maximum LSP
 Bandwidth are enumerated in [GMPLS-SIG].
 On an interface having Standard SDH multiplexing, an LSP at priority
 p could reserve any bandwidth allowed by the branch of the SDH
 hierarchy, with the leaf and the root of the branch being defined by
 the Minimum LSP Bandwidth and the Maximum LSP Bandwidth at priority
 p.
 On an interface having Arbitrary SDH multiplexing, an LSP at priority
 p could reserve any bandwidth between the Minimum LSP Bandwidth and
 the Maximum LSP Bandwidth at priority p, provided that the bandwidth
 reserved by the LSP is a multiple of the Minimum LSP Bandwidth.
 Interface Switching Capability Descriptor for the interfaces that
 support sub VC-3 may include additional information.  The nature and
 the encoding of such information is outside the scope of this
 document.

Kompella & Rekhter Standards Track [Page 12] RFC 4202 Routing Extensions for GMPLS October 2005

 A way to handle the case where an interface supports multiple
 branches of the SDH multiplexing hierarchy, multiple Interface
 Switching Capability Descriptors would be advertised, one per branch.
 For example, if an interface supports VC-11 and VC-12 (which are not
 part of same branch of SDH multiplexing tree), then it could
 advertise two descriptors, one for each one.

2.4.4. Lambda-Switch Capable

 If an interface is of type LSC, it means that the node receiving data
 over this interface can recognize and switch individual lambdas
 within the interface.  An interface that allows only one lambda per
 interface, and switches just that lambda is of type LSC.
 The additional information includes Reservable Bandwidth per
 priority, which specifies the bandwidth of an LSP that could be
 supported by the interface at a given priority number.
 A way to handle the case of multiple data rates or multiple encodings
 within a single TE Link, multiple Interface Switching Capability
 Descriptors would be advertised, one per supported data rate and
 encoding combination.  For example, an LSC interface could support
 the establishment of LSC LSPs at both STM-16 and STM-64 data rates.

2.4.5. Fiber-Switch Capable

 If an interface is of type FSC, it means that the node receiving data
 over this interface can switch the entire contents to another
 interface (without distinguishing lambdas, channels or packets).
 I.e., an interface of type FSC switches at the granularity of an
 entire interface, and can not extract individual lambdas within the
 interface.  An interface of type FSC can not restrict itself to just
 one lambda.

2.4.6. Multiple Switching Capabilities per Interface

 An interface that connects a link to an LSR may support not one, but
 several Interface Switching Capabilities.  For example, consider a
 fiber link carrying a set of lambdas that terminates on an LSR
 interface that could either cross-connect one of these lambdas to
 some other outgoing optical channel, or could terminate the lambda,
 and extract (demultiplex) data from that lambda using TDM, and then
 cross-connect these TDM channels to some outgoing TDM channels.  To
 support this a Link State Advertisement may carry a list of Interface
 Switching Capabilities Descriptors.

Kompella & Rekhter Standards Track [Page 13] RFC 4202 Routing Extensions for GMPLS October 2005

2.4.7. Interface Switching Capabilities and Labels

 Depicting a TE link as a tuple that contains Interface Switching
 Capabilities at both ends of the link, some examples links may be:
    [PSC, PSC] - a link between two packet LSRs
    [TDM, TDM] - a link between two Digital Cross Connects
    [LSC, LSC] - a link between two OXCs
    [PSC, TDM] - a link between a packet LSR and Digital Cross Connect
    [PSC, LSC] - a link between a packet LSR and an OXC
    [TDM, LSC] - a link between a Digital Cross Connect and an OXC
 Both ends of a given TE link has to use the same way of carrying
 label information over that link.  Carrying label information on a
 given TE link depends on the Interface Switching Capability at both
 ends of the link, and is determined as follows:
    [PSC, PSC] - label is carried in the "shim" header [RFC3032]
    [TDM, TDM] - label represents a TDM time slot [GMPLS-SONET-SDH]
    [LSC, LSC] - label represents a lambda
    [FSC, FSC] - label represents a port on an OXC
    [PSC, TDM] - label represents a TDM time slot [GMPLS-SONET-SDH]
    [PSC, LSC] - label represents a lambda
    [PSC, FSC] - label represents a port
    [TDM, LSC] - label represents a lambda
    [TDM, FSC] - label represents a port
    [LSC, FSC] - label represents a port

2.4.8. Other Issues

 It is possible that Interface Switching Capability Descriptor will
 change over time, reflecting the allocation/deallocation of LSPs.
 For example, assume that VC-3, VC-4, VC-4-4c, VC-4-16c and VC-4-64c
 LSPs can be established on a STM-64 interface whose Encoding Type is
 SDH.  Thus, initially in the Interface Switching Capability
 Descriptor the Minimum LSP Bandwidth is set to VC-3, and Maximum LSP
 Bandwidth is set to STM-64 for all priorities.  As soon as an LSP of
 VC-3 size at priority 1 is established on the interface, it is no
 longer capable of VC-4-64c for all but LSPs at priority 0.
 Therefore, the node advertises a modified Interface Switching
 Capability Descriptor indicating that the Maximum LSP Bandwidth is no
 longer STM-64, but STM-16 for all but priority 0 (at priority 0 the
 Maximum LSP Bandwidth is still STM-64).  If subsequently there is
 another VC-3 LSP, there is no change in the Interface Switching
 Capability Descriptor.  The Descriptor remains the same until the
 node can no longer establish a VC-4-16c LSP over the interface (which

Kompella & Rekhter Standards Track [Page 14] RFC 4202 Routing Extensions for GMPLS October 2005

 means that at this point more than 144 time slots are taken by LSPs
 on the interface).  Once this happened, the Descriptor is modified
 again, and the modified Descriptor is advertised to other nodes.

2.5. Bandwidth Encoding

 Encoding in IEEE floating point format [IEEE] of the discrete values
 that could be used to identify Unreserved bandwidth, Maximum LSP
 bandwidth and Minimum LSP bandwidth is described in Section 3.1.2 of
 [GMPLS-SIG].

3. Examples of Interface Switching Capability Descriptor

3.1. STM-16 POS Interface on a LSR

    Interface Switching Capability Descriptor:
       Interface Switching Capability = PSC-1
       Encoding = SDH
       Max LSP Bandwidth[p] = 2.5 Gbps, for all p
 If multiple links with such interfaces at both ends were to be
 advertised as one TE link, link bundling techniques should be used.

3.2. GigE Packet Interface on a LSR

    Interface Switching Capability Descriptor:
       Interface Switching Capability = PSC-1
       Encoding = Ethernet 802.3
       Max LSP Bandwidth[p] = 1.0 Gbps, for all p
 If multiple links with such interfaces at both ends were to be
 advertised as one TE link, link bundling techniques should be used.

3.3. STM-64 SDH Interface on a Digital Cross Connect with Standard SDH

 Consider a branch of SDH multiplexing tree : VC-3, VC-4, VC-4-4c,
 VC-4-16c, VC-4-64c.  If it is possible to establish all these
 connections on a STM-64 interface, the Interface Switching Capability
 Descriptor of that interface can be advertised as follows:
    Interface Switching Capability Descriptor:
       Interface Switching Capability = TDM [Standard SDH]
       Encoding = SDH
       Min LSP Bandwidth = VC-3
       Max LSP Bandwidth[p] = STM-64, for all p
 If multiple links with such interfaces at both ends were to be
 advertised as one TE link, link bundling techniques should be used.

Kompella & Rekhter Standards Track [Page 15] RFC 4202 Routing Extensions for GMPLS October 2005

3.4. STM-64 SDH Interface on a Digital Cross Connect with Two Types of

    SDH Multiplexing Hierarchy Supported
    Interface Switching Capability Descriptor 1:
       Interface Switching Capability = TDM [Standard SDH]
       Encoding = SDH
       Min LSP Bandwidth = VC-3
       Max LSP Bandwidth[p] = STM-64, for all p
    Interface Switching Capability Descriptor 2:
       Interface Switching Capability = TDM [Arbitrary SDH]
       Encoding = SDH
       Min LSP Bandwidth = VC-4
       Max LSP Bandwidth[p] = STM-64, for all p
 If multiple links with such interfaces at both ends were to be
 advertised as one TE link, link bundling techniques should be used.

3.5. Interface on an Opaque OXC (SDH Framed) with Support for One

    Lambda per Port/Interface
 An "opaque OXC" is considered operationally an OXC, as the whole
 lambda (carrying the SDH line) is switched transparently without
 further multiplexing/demultiplexing, and either none of the SDH
 overhead bytes, or at least the important ones are not changed.
 An interface on an opaque OXC handles a single wavelength, and cannot
 switch multiple wavelengths as a whole.  Thus, an interface on an
 opaque OXC is always LSC, and not FSC, irrespective of whether there
 is DWDM external to it.
 Note that if there is external DWDM, then the framing understood by
 the DWDM must be same as that understood by the OXC.
 A TE link is a group of one or more interfaces on an OXC.  All
 interfaces on a given OXC are required to have identifiers unique to
 that OXC, and these identifiers are used as labels (see 3.2.1.1 of
 [GMPLS-SIG]).
 The following is an example of an interface switching capability
 descriptor on an SDH framed opaque OXC:
    Interface Switching Capability Descriptor:
       Interface Switching Capability = LSC
       Encoding = SDH
       Reservable Bandwidth = Determined by SDH Framer (say STM-64)

Kompella & Rekhter Standards Track [Page 16] RFC 4202 Routing Extensions for GMPLS October 2005

3.6. Interface on a Transparent OXC (PXC) with External DWDM That

    Understands SDH Framing
 This example assumes that DWDM and PXC are connected in such a way
 that each interface (port) on the PXC handles just a single
 wavelength.  Thus, even if in principle an interface on the PXC could
 switch multiple wavelengths as a whole, in this particular case an
 interface on the PXC is considered LSC, and not FSC.
                   _______
                  |       |
             /|___|       |
            | |___|  PXC  |
    ========| |___|       |
            | |___|       |
             \|   |_______|
           DWDM
       (SDH framed)
 A TE link is a group of one or more interfaces on the PXC.  All
 interfaces on a given PXC are required to have identifiers unique to
 that PXC, and these identifiers are used as labels (see 3.2.1.1 of
 [GMPLS-SIG]).
 The following is an example of an interface switching capability
 descriptor on a transparent OXC (PXC) with external DWDM that
 understands SDH framing:
    Interface Switching Capability Descriptor:
       Interface Switching Capability = LSC
       Encoding = SDH (comes from DWDM)
       Reservable Bandwidth = Determined by DWDM (say STM-64)

3.7. Interface on a Transparent OXC (PXC) with External DWDM That Is

    Transparent to Bit-Rate and Framing
 This example assumes that DWDM and PXC are connected in such a way
 that each interface (port) on the PXC handles just a single
 wavelength.  Thus, even if in principle an interface on the PXC could
 switch multiple wavelengths as a whole, in this particular case an
 interface on the PXC is considered LSC, and not FSC.

Kompella & Rekhter Standards Track [Page 17] RFC 4202 Routing Extensions for GMPLS October 2005

                      _______
                     |       |
                /|___|       |
               | |___|  PXC  |
       ========| |___|       |
               | |___|       |
                \|   |_______|
              DWDM (transparent to bit-rate and framing)
 A TE link is a group of one or more interfaces on the PXC.  All
 interfaces on a given PXC are required to have identifiers unique to
 that PXC, and these identifiers are used as labels (see 3.2.1.1 of
 [GMPLS-SIG]).
 The following is an example of an interface switching capability
 descriptor on a transparent OXC (PXC) with external DWDM that is
 transparent to bit-rate and framing:
    Interface Switching Capability Descriptor:
       Interface Switching Capability = LSC
       Encoding = Lambda (photonic)
       Reservable Bandwidth = Determined by optical technology limits

3.8. Interface on a PXC with No External DWDM

 The absence of DWDM in between two PXCs, implies that an interface is
 not limited to one wavelength.  Thus, the interface is advertised as
 FSC.
 A TE link is a group of one or more interfaces on the PXC.  All
 interfaces on a given PXC are required to have identifiers unique to
 that PXC, and these identifiers are used as port labels (see 3.2.1.1
 of [GMPLS-SIG]).
    Interface Switching Capability Descriptor:
       Interface Switching Capability = FSC
       Encoding = Lambda (photonic)
       Reservable Bandwidth = Determined by optical technology limits
 Note that this example assumes that the PXC does not restrict each
 port to carry only one wavelength.

3.9. Interface on a OXC with Internal DWDM That Understands SDH Framing

 This example assumes that DWDM and OXC are connected in such a way
 that each interface on the OXC handles multiple wavelengths
 individually.  In this case an interface on the OXC is considered
 LSC, and not FSC.

Kompella & Rekhter Standards Track [Page 18] RFC 4202 Routing Extensions for GMPLS October 2005

                _______
               |       |
             /||       ||\
            | ||  OXC  || |
    ========| ||       || |====
            | ||       || |
             \||_______||/
           DWDM
       (SDH framed)
 A TE link is a group of one or more of the interfaces on the OXC.
 All lambdas associated with a particular interface are required to
 have identifiers unique to that interface, and these identifiers are
 used as labels (see 3.2.1.1 of [GMPLS-SIG]).
 The following is an example of an interface switching capability
 descriptor on an OXC with internal DWDM that understands SDH framing
 and supports discrete bandwidths:
    Interface Switching Capability Descriptor:
       Interface Switching Capability = LSC
       Encoding = SDH (comes from DWDM)
       Max LSP Bandwidth = Determined by DWDM (say STM-16)
       Interface Switching Capability = LSC
       Encoding = SDH (comes from DWDM)
       Max LSP Bandwidth = Determined by DWDM (say STM-64)

3.10. Interface on a OXC with Internal DWDM That Is Transparent to

     Bit-Rate and Framing
 This example assumes that DWDM and OXC are connected in such a way
 that each interface on the OXC handles multiple wavelengths
 individually.  In this case an interface on the OXC is considered
 LSC, and not FSC.
                       _______
                      |       |
                    /||       ||\
                   | ||  OXC  || |
           ========| ||       || |====
                   | ||       || |
                    \||_______||/
                  DWDM (transparent to bit-rate and framing)

Kompella & Rekhter Standards Track [Page 19] RFC 4202 Routing Extensions for GMPLS October 2005

 A TE link is a group of one or more of the interfaces on the OXC.
 All lambdas associated with a particular interface are required to
 have identifiers unique to that interface, and these identifiers are
 used as labels (see 3.2.1.1 of [GMPLS-SIG]).
 The following is an example of an interface switching capability
 descriptor on an OXC with internal DWDM that is transparent to bit-
 rate and framing:
    Interface Switching Capability Descriptor:
       Interface Switching Capability = LSC
       Encoding = Lambda (photonic)
       Max LSP Bandwidth = Determined by optical technology limits

4. Example of Interfaces That Support Multiple Switching Capabilities

 There can be many combinations possible, some are described below.

4.1. Interface on a PXC+TDM Device with External DWDM

 As discussed earlier, the presence of the external DWDM limits that
 only one wavelength be on a port of the PXC.  On such a port, the
 attached PXC+TDM device can do one of the following.  The wavelength
 may be cross-connected by the PXC element to other out-bound optical
 channel, or the wavelength may be terminated as an SDH interface and
 SDH channels switched.
 From a GMPLS perspective the PXC+TDM functionality is treated as a
 single interface.  The interface is described using two Interface
 descriptors, one for the LSC and another for the TDM, with
 appropriate parameters.  For example,
    Interface Switching Capability Descriptor:
       Interface Switching Capability = LSC
       Encoding = SDH (comes from WDM)
       Reservable Bandwidth = STM-64
    and
    Interface Switching Capability Descriptor:
       Interface Switching Capability = TDM [Standard SDH]
       Encoding = SDH
       Min LSP Bandwidth = VC-3
       Max LSP Bandwidth[p] = STM-64, for all p

Kompella & Rekhter Standards Track [Page 20] RFC 4202 Routing Extensions for GMPLS October 2005

4.2. Interface on an Opaque OXC+TDM Device with External DWDM

 An interface on an "opaque OXC+TDM" device would also be advertised
 as LSC+TDM much the same way as the previous case.

4.3. Interface on a PXC+LSR Device with External DWDM

 As discussed earlier, the presence of the external DWDM limits that
 only one wavelength be on a port of the PXC.  On such a port, the
 attached PXC+LSR device can do one of the following.  The wavelength
 may be cross-connected by the PXC element to other out-bound optical
 channel, or the wavelength may be terminated as a Packet interface
 and packets switched.
 From a GMPLS perspective the PXC+LSR functionality is treated as a
 single interface.  The interface is described using two Interface
 descriptors, one for the LSC and another for the PSC, with
 appropriate parameters.  For example,
    Interface Switching Capability Descriptor:
       Interface Switching Capability = LSC
       Encoding = SDH (comes from WDM)
       Reservable Bandwidth = STM-64
    and
    Interface Switching Capability Descriptor:
       Interface Switching Capability = PSC-1
       Encoding = SDH
       Max LSP Bandwidth[p] = 10 Gbps, for all p

4.4. Interface on a TDM+LSR Device

 On a TDM+LSR device that offers a channelized SDH interface the
 following may be possible:
  1. A subset of the SDH channels may be uncommitted. That is, they

are not currently in use and hence are available for allocation.

  1. A second subset of channels may already be committed for transit

purposes. That is, they are already cross-connected by the SDH

    cross connect function to other out-bound channels and thus are
    not immediately available for allocation.
  1. Another subset of channels could be in use as terminal channels.

That is, they are already allocated by terminate on a packet

    interface and packets switched.

Kompella & Rekhter Standards Track [Page 21] RFC 4202 Routing Extensions for GMPLS October 2005

 From a GMPLS perspective the TDM+PSC functionality is treated as a
 single interface.  The interface is described using two Interface
 descriptors, one for the TDM and another for the PSC, with
 appropriate parameters.  For example,
    Interface Switching Capability Descriptor:
       Interface Switching Capability = TDM [Standard SDH]
       Encoding = SDH
       Min LSP Bandwidth = VC-3
       Max LSP Bandwidth[p] = STM-64, for all p
    and
    Interface Switching Capability Descriptor:
       Interface Switching Capability = PSC-1
       Encoding = SDH
       Max LSP Bandwidth[p] = 10 Gbps, for all p

5. Acknowledgements

 The authors would like to thank Suresh Katukam, Jonathan Lang, Zhi-
 Wei Lin, and Quaizar Vohra for their comments and contributions to
 the document.  Thanks too to Stephen Shew for the text regarding
 "Representing TE Link Capabilities".

6. Security Considerations

 There are a number of security concerns in implementing the
 extensions proposed here, particularly since these extensions will
 potentially be used to control the underlying transport
 infrastructure.  It is vital that there be secure and/or
 authenticated means of transferring this information among the
 entities that require its use.
 While this document proposes extensions, it does not state how these
 extensions are implemented in routing protocols such as OSPF or
 IS-IS.  The documents that do state how routing protocols implement
 these extensions [GMPLS-OSPF, GMPLS-ISIS] must also state how the
 information is to be secured.

Kompella & Rekhter Standards Track [Page 22] RFC 4202 Routing Extensions for GMPLS October 2005

7. References

7.1. Normative References

 [GMPLS-OSPF]      Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF
                   Extensions in Support of Generalized Multi-Protocol
                   Label Switching (GMPLS)", RFC 4203, October 2005.
 [GMPLS-SIG]       Berger, L., "Generalized Multi-Protocol Label
                   Switching (GMPLS) Signaling Functional
                   Description", RFC 3471, January 2003.
 [GMPLS-SONET-SDH] Mannie, E. and D. Papadimitriou, "Generalized
                   Multi-Protocol Label Switching (GMPLS) Extensions
                   for Synchronous Optical Network (SONET) and
                   Synchronous Digital Hierarchy (SDH) Control", RFC
                   3946, October 2004.
 [IEEE]            IEEE, "IEEE Standard for Binary Floating-Point
                   Arithmetic", Standard 754-1985, 1985 (ISBN 1-5593-
                   7653-8).
 [LINK-BUNDLE]     Kompella, K., Rekhter, Y., and L. Berger, "Link
                   Bundling in MPLS Traffic Engineering (TE)", RFC
                   4201, October 2005.
 [LMP]             Lang, J., Ed., "Link Management Protocol (LMP)",
                   RFC 4204, October 2005.
 [LSP-HIER]        Kompella, K. and Y. Rekhter, "Label Switched Paths
                   (LSP) Hierarchy with Generalized Multi-Protocol
                   Label Switching (GMPLS) Traffic Engineering (TE))",
                   RFC 4206, October 2005.
 [OSPF-TE]         Katz, D., Kompella, K., and D. Yeung, "Traffic
                   Engineering (TE) Extensions to OSPF Version 2", RFC
                   3630, September 2003.
 [RFC2119]         Bradner, S., "Key words for use in RFCs to Indicate
                   Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC3032]         Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
                   Farinacci, D., Li, T., and A. Conta, "MPLS Label
                   Stack Encoding", RFC 3032, January 2001.

Kompella & Rekhter Standards Track [Page 23] RFC 4202 Routing Extensions for GMPLS October 2005

7.2. Informative References

 [GMPLS-ISIS]      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.
 [ISIS-TE]         Smit, H. and T. Li, "Intermediate System to
                   Intermediate System (IS-IS) Extensions for Traffic
                   Engineering (TE)", RFC 3784, June 2004.

8. Contributors

 Ayan Banerjee
 Calient Networks
 5853 Rue Ferrari
 San Jose, CA 95138
 Phone: +1.408.972.3645
 EMail: abanerjee@calient.net
 John Drake
 Calient Networks
 5853 Rue Ferrari
 San Jose, CA 95138
 Phone: (408) 972-3720
 EMail: jdrake@calient.net
 Greg Bernstein
 Ciena Corporation
 10480 Ridgeview Court
 Cupertino, CA 94014
 Phone: (408) 366-4713
 EMail: greg@ciena.com
 Don Fedyk
 Nortel Networks Corp.
 600 Technology Park Drive
 Billerica, MA 01821
 Phone: +1-978-288-4506
 EMail: dwfedyk@nortelnetworks.com

Kompella & Rekhter Standards Track [Page 24] RFC 4202 Routing Extensions for GMPLS October 2005

 Eric Mannie
 Libre Exaministe
 EMail: eric_mannie@hotmail.com
 Debanjan Saha
 Tellium Optical Systems
 2 Crescent Place
 P.O. Box 901
 Ocean Port, NJ 07757
 Phone: (732) 923-4264
 EMail: dsaha@tellium.com
 Vishal Sharma
 Metanoia, Inc.
 335 Elan Village Lane, Unit 203
 San Jose, CA 95134-2539
 Phone: +1 408-943-1794
 EMail: v.sharma@ieee.org
 Debashis Basak
 AcceLight Networks,
 70 Abele Rd, Bldg 1200
 Bridgeville PA 15017
 EMail: dbasak@accelight.com
 Lou Berger
 Movaz Networks, Inc.
 7926 Jones Branch Drive
 Suite 615
 McLean VA, 22102
 EMail: lberger@movaz.com

Kompella & Rekhter Standards Track [Page 25] RFC 4202 Routing Extensions for GMPLS October 2005

Authors' Addresses

 Kireeti Kompella
 Juniper Networks, Inc.
 1194 N. Mathilda Ave
 Sunnyvale, CA 94089
 EMail: kireeti@juniper.net
 Yakov Rekhter
 Juniper Networks, Inc.
 1194 N. Mathilda Ave
 Sunnyvale, CA 94089
 EMail: yakov@juniper.net

Kompella & Rekhter Standards Track [Page 26] RFC 4202 Routing Extensions for GMPLS October 2005

Full Copyright Statement

 Copyright (C) The Internet Society (2005).
 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.
 This document and the information contained herein are provided on an
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Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Kompella & Rekhter Standards Track [Page 27]

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