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Network Working Group               Kireeti Kompella (Juniper Networks)
Internet Draft                            Yakov Rekhter (cisco Systems)
Expiration Date:  August 2000                 Daniel O. Awduche (UUNET)
                                          Alan Hannan (Global Crossing)
                                          Gisli Hjalmtysson (AT&T Labs)
                                  Joe Lawrence (Level 3 Communications)
                                                   Satoru Okamoto (NTT)
                                               Debashis Basak (Marconi)
                                     Greg Bernstein (Ciena Corporation)
                                                 John Drake (Chromisys)
                              Near Margalit (New Access Communications)
                                             Ed Stern (Sirocco Systems)

      Extensions to IS-IS/OSPF and RSVP in support of MPL(ambda)S

                    draft-kompella-mpls-optical-00.txt


1. Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as ``work in progress.''

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.













Kompella/Rekhter et al                                          

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2. Abstract

   This document specifies extensions to the IS-IS, OSPF, and RSVP in
   support of Multiprotocol Lambda Switching (MPL(ambda)S). For
   motivations and the overall architecture of MPL(amda)S see [Awduche-
   1].  For the set of required enhancements to IS-IS, OSPF, and RSVP
   see [Basak].


3. IS-IS/OSPF enhancements

   In this section we describe enhancements to IS-IS and OSPF in support
   of MPL(ambda)S. These enhancements are in addition to the extensions
   required to support MPLS Traffic Engineering [Smit], [Katz].


3.1. Link Type TLV

   A network may have links with different characteristics. For example,
   a node may not be able to demultiplex the data it receives on a given
   link on a packet-by-packet basis, but it may be to multiplex or
   demultiplex channels within a SONET payload.

   The Link Type sub-TLV allows to identify a particular type of a link.

   In IS-IS, this TLV is a sub-TLV of the Extended IS Reachability TLV,
   with type 19.  In OSPF, this TLV is a sub-TLV of the Link TLV, with
   type 1 (this sub-TLV currently exists in OSPF; here, we extend the
   range of values, and introduce a further sub-TLV.)

   The length is 1 plus the total length of all sub-TLVs.  The value has
   a fixed length field of one octet, followed by optional sub-TLVs.
   The value is taken from the following list:

       Value         Link Type
           1         Packet-Switch Capable-1 (PSC-1)
           2         Packet-Switch Capable-2 (PSC-2)
           3         Packet-Switch Capable-3 (PSC-3)
           4         Packet-Switch Capable-4 (PSC-4)
         200         Time-Division-Multiplex Capable (TDM)
         210         Lambda-Switch Capable (LSC)
         220         Fiber-Switch Capable (FSC)
         240         Forwarding Adjacency PSC (FA-PSC)
         245         Forwarding Adjacency TDM (FA-TDM)
         250         Forwarding Adjacency LSC (FA-LSC)

   If a link is of type PSC-1 through PSC-4, that means that the node
   receiving data over this link can demultiplex (switch) the received



Kompella/Rekhter et al                                          

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   data on a packet-by-packet basis.  The various levels of PSC
   establish a hierarchy of LSPs tunneled within LSPs.

   If a link is of type TDM, that means that the node receiving data
   over this link can multiplex or demultiplex channels within a SONET
   payload.

   If a link is of type LSC, that means that the node receiving data
   over this link can recognise and switch individual lambdas within the
   link (fiber).

   If a link is of type FSC, that means that the node receiving data
   over this link (fiber) can switch the entire contents to another link
   (fiber) (without distinguishing lambdas, channels or packets).

   If a link is of type FA-PSC, that means that the link is a forwarding
   adjacency (see section 3.5).  Furthermore, the egress node of the
   corresponding FA-LSP is capable of switching the data received over
   the FA-LSP on a packet-by-packet basis.

   If a link is of type FA-TDM, that means that the link is a forwarding
   adjacency.  Furthermore, the egress node of the corresponding FA-LSP
   is capable of multiplexing and demultiplexing the SONET channels
   received over the FA-LSP.

   If a link is of type FA-LSC, that means that the link is a forwarding
   adjacency.  Furthermore, the egress node of the corresponding FA-LSP
   is capable of recognising and switching the lambdas received over the
   FA-LSP.


3.2. Link Media Type TLV

   A link may support a set of media types, where by media type we mean
   both the bit encoding format as well as the bit transmission rate.
   By support we mean that the link has the ability to carry and switch
   a signal of one or more of these media types depending on the
   resource availability and capacity of the link. The link media type
   should not be confused with the physical link encoding or multiplex
   structure (if any).  These properties are of local significance
   between neighbor nodes.  The types of media a link can support (and
   its associated node switch) are of overall concern to routing as well
   as information on link capacity (bandwidth).

   A typical example of multiple transport methods with the same routing
   representation currently occurs in the optical domain.  Currently
   there are systems  where four OC-48s are switched and transported
   over a single fiber via wavelength division multiplexing (WDM)



Kompella/Rekhter et al                                          

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   technology.  In addition there are systems where four OC-48s are
   transported in a "transparent" OC-192 time division multiplex (TDM)
   structure, i.e., all the overheads of the OC-48's are persevered. In
   both these cases the essential information from a routing perspective
   is that the links can both transport media of type OC-48.

   The Link Media Type TLV is a list of supported media types for a
   link.  In IS-IS, this TLV is a sub-TLV of the Extended IS
   Reachability TLV with type 20.  In OSPF, this TLV is a sub-TLV of the
   Link TLV, with type 10.

   The length is the length of the list of Link Media Types in octets.
   The value is a list of two-tuples of which the first field is a two-
   octet value which defines the media type, and the second field is a
   one-octet value which defines the lowest priority at which that media
   type is available.  Media types values are taken from the following
   list:

         Value   Bit Rate  Encoding
           <n>     OC-<n>     SONET   1 <= <n> <= 3072
    3072 + <n>     OC-<n>       SDH   1 <= <n> <= 3072
    6144 + <n>     OC-<n>     Clear   1 <= <n> <= 3072
          9217        DS0       DS0
          9218        DS1       DS1
          9219         E1        E1
          9220        DS2       DS2
          9221         E2        E2
          9222        DS3       DS3
          9223         E3        E3
          9224         J3        J3
          9225        DS4       DS4
          9226         E4        E4
          9227         J4        J4
          9228      1Gbps      GigE
          9229     10Gbps    10GigE


   Link Media Types (LMTs) present a new constraint for LSP path
   computation. Specifically, when a sequence of links traversed by an
   LSP includes one or more subsequence of links that carry the LMT TLV,
   then for all the links within each such subsequence their bit rate
   (as specified in the LMT TLV) has to be the same and at least the
   LSP's desired bandwidth, and the encoding (as specified in the LMT
   TLV) has to be the same.

   On a bundled link we assume that either the whole link is configured
   with the Link Media Types, or each of its component links are
   configured with the Link Media Types. In the latter case, the Link



Kompella/Rekhter et al                                          

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   Media Type of the bundled link is set to the set union of the Link
   Media Types for all the component links.


3.2.1. Path sub-TLV

   When an LSP advertises a forwarding adjacency into an IGP (IS-IS or
   OSPF), it may be desirable to carry the information about the path
   taken by this adjacency. This information may be used for path
   calculation by other LSRs. This information is carried in the Path
   sub-TLV, which is a sub-TLV of the Link Type TLV.

   In both IS-IS and OSPF, this sub-TLV is encoded as follows: the type
   is 1, the length is 4 times the path length, and the value is a list
   of 4 octet IPv4 addresses identifying the links in the order that
   they form the path of the forwarding adjacency.


3.2.2. Identifying links that can't terminate an LSP

   As discussed in [Basak], some links may not be capable of terminating
   LSPs, and this property of the links needs to be taken into account
   when performing LSP path computation as well as RSVP signalling. Such
   links are identified by using the Link Type sub-TLV.

   Note that the notion of 'Termination Capable' has been generalized to
   'packet-switch capable', 'TDM capable', 'lambda-switch capable', and
   'fiber-switch capable'.


3.3. Shared Risk Link Group TLV

   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 TLV
   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 of a path is the union of the SRLGs of the links in the
   path.  If an LSP is required to have multiple diversely routed paths,
   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.

   In IS-IS, the SRLG TLV is a sub-TLV of the Extended IS Reachability
   TLV with type 21.  In OSPF, this TLV is a sub-TLV of the Link TLV,
   with type 11.  The length is the length of the list in octets.  The



Kompella/Rekhter et al                                          

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   value is an unordered list of 32 bit numbers that are the SRLGs that
   the link belongs to.


3.4. Control channels, data channels, and IP links

   A pair of OXCs are neighbors from the MPLS point of view if they are
   connected by both one or more fibers and one or more (logical)
   control channels.  In what follows, we consider only those fibers
   that it is desired to announce into IS-IS/OSPF for LSP establishment.
   (The administrator may decide to reserve some fibers, for example for
   manual provisioning; these fibers are not to be announced into IS-
   IS/OSPF.)

   For a given pair of OXCs connected by a set of fibers and one or more
   (logical) control channels, both of the OXCs must associate the
   fibers in the set with the control channels and form IP links in a
   consistent fashion.  One way to accomplish this is via configuration.
   While other mechanisms to accomplish this may be possible, the
   specification of such mechanisms is outside the scope of this
   document.

   If all the fibers can share the same TE characteristics, then a
   single control channel suffices. From the IS-IS/OSPF point of view
   this control channel, together with all the fibers, forms a single IP
   link.  This IP link could be either unnumbered, or numbered.

   There are cases where all the fibers between a pair of OXCs cannot be
   announced as one IS-IS/OSPF link.  This may be because not all the
   fibers can share the same TE characteristics (for example, some are
   Termination Capable and others are not). Or this may be because it is
   administratively so desired, for example, some fibers have metric 10
   and others metric 20. In such a case, the fibers must be divided into
   sets that share all TE characteristics, Corresponding to each set,
   there must be a logical control channel. Each set of fibers, together
   with the corresponding logical control channel forms an IP link. Each
   such link should be numbered. All the multiple logical control
   channels could be realized via the common control channel.

   When an adjacency is established over a (logical) control channel
   that is part of an IP link formed by the channel and a set of fibers,
   this link is announced into IS-IS/OSPF as a "normal" link; the fiber
   characteristics are represented as TE parameters of that link.  If
   there are more than one fiber in the set, the set is announced using
   the "bundling" technique described in [Kompella].

   Note that while there may be as many adjacencies established as there
   are logical control channels, for flooding purposes, it suffices to



Kompella/Rekhter et al                                          

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   flood over a single logical control channel.


3.4.1. Excluding data traffic from control channels

   The control channels between OXCs, or between an OXC and a router are
   generally meant for low-bandwidth control and administrative traffic.
   These control channels are advertised into IS-IS/OSPF as normal IP
   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.

   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, 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.

   Other techniques for excluding data traffic from control channels may
   also be needed.


3.5. Forwarding adjacencies

   An LSR at the head end of an LSP may advertise this LSP as a link
   into a link-state IGP (e.g., IS-IS, OSPF). When this link is
   advertised into the same instance of the IGP as the one that
   determines the route taken by the LSP, we call such a link a
   "forwarding adjacency". We refer to the LSP as the "forwarding
   adjacency LSP", or just FA-LSP.

   In general, creation/termination of a forwarding adjacency and its
   FA-LSP could be driven either by mechanisms outside of MPLS (e.g.,
   via configuration control on the LSR at the head-end of the
   adjacency), or by mechanisms within MPLS (e.g., as a result of the
   LSR at the head-end of the adjacency receiving LSP setup requests
   originated by some other LSRs).




Kompella/Rekhter et al                                          

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   Forwarding adjacencies are by definition unidirectional.

   Forwarding adjacencies could be represented as unnumbered links. In
   this case the link IP addresses of forwarding adjacencies are the
   router IDs on the two ends of the link. Alternatively, forwarding
   adjacencies could be represented as numbered links. In this case the
   link IP addresses of forwarding adjacencies could be addresses
   assigned to some "virtual" interfaces on a router (it is assumed that
   a router may have multiple virtual interfaces).

   If there are multiple LSPs that all originate on one LSR, and all
   terminate on another LSR, then at one end of the spectrum all these
   LSPs could be merged (under control of the head-end LSR) into a
   single forwarding adjacency, while at the other end of the spectrum
   each such LSP could be advertised as its own adjacency.

   When a forwarding adjacency is created under administrative control
   (static provisioning), the following parameters can be configured for
   the FA-LSP: the head-end address (if left blank, this will default to
   the head-end LSR's Router ID); the tail-end address (this must be
   configured, and must be either the Router ID of the tail-end LSR of
   the forwarding adjacency, or an interface address on the tail-end
   LSR); bandwidth and resource colors constraints.  The path taken by
   the FA-LSP may be computed by the Constrained SPF (CSPF) mechanism of
   MPLS TE, or by explicit configuration; this choice is determined by
   configuration.

   When a forwarding adjacency is created dynamically, its parameters
   are inherited from the LSP which induced its creation.  Note that the
   bandwidth of the FA-LSP must be at least as big as the LSP that
   induced it, but may be bigger if only discrete bandwidths are
   available for the FA-LSP.

   When the FA-LSP is established, it is advertised as a forwarding
   adjacency into IS-IS/OSPF.  The Link Type associated with the
   forwarding adjacency depends on the link type of the last link in the
   FA-LSP; if this link is packet-switch capable, the Link Type of the
   forwarding adjacency is 'FA-PSC'; if this link is TDM capable, the
   Link Type is 'FA-TDM'; if this link is lambda-switch capable, the
   Link Type is 'FA-LSC'.  Some of the attributes of this link can be
   derived from those of the FA-LSP, but others will need to be
   configured.  Configuration of the attributes of statically
   provisioned forwarding adjacencies is straightforward; for
   dynamically provisioned forwarding adjacencies, a policy-based
   mechanism may be needed to associate attributes to forwarding
   adjacencies. The path taken by the forwarding adjacency may be
   advertised using the Path sub-TLV.




Kompella/Rekhter et al                                          

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   The Link Media Type of the forwarding adjacency is the most
   restrictive of the link media types of the components links of the
   forwarding adjacency.  If none of the components links have a link
   media type, the link associated with the forwarding adjacency doesn't
   have a link media type either.

   This document restricts the priority of the forwarding adjacency to
   0, regardless of how the adjacency is created.

   By default the maximum reservable bandwidth and the maximum LSP
   bandwidth for all priorities of a link associated with a forwarding
   adjacency is set to the bandwidth of the FA-LSP.  These may be
   overridden via configuration at the head-end of the forwarding
   adjacency (note that the maximum LSP bandwidth at any priority should
   be no more than the bandwidth of the FA-LSP).

   By default the TE metric on the forwarding adjacency is set to max(1,
   (the TE metric of the FA-LSP path) - 1) so that it attracts traffic
   in preference to setting up a new LSP.  This may be overridden via
   configuration at the head-end of the forwarding adjacency.

   It is expected that forwarding adjacencies will not be used for
   establishing IGP peering relation between the routers at the ends of
   the adjacency. It is further expected that forwarding adjacencies
   will be used only in CSPF computation.  In IS-IS, this can be
   accomplished by setting the default metric of the extended IS
   reachability TLV the link to infinity (2^24 - 1), and not advertising
   an IS reachability TLV for the link.  In OSPF, this can be
   accomplished by not advertising the link as a regular LSA, but only
   as a TE opaque LSA.

   If forwarding adjacencies are to be established only under
   administrative control, it is important that LSRs would not attempt
   to establish LSPs that have to traverse the optical domain, but for
   which no FA-LSP is established. To accomplish this, all the optical
   links (fibers) within the optical domain have to be excluded from
   CSPF by any LSR outside the domain. This can be achieved by coloring
   optical links with a specific color, and making sure that all LSPs
   originating outside the optical domain exclude this color.


3.6. Two-way connectivity check suppression

   CSPF should not perform two-way connectivity check on the links used
   by CSPF. This is because some of these links may be associated with
   forwarding adjacencies, and therefore are unidirectional.





Kompella/Rekhter et al                                          

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4. RSVP changes

   In this section we describe enhancements to RSVP in support of
   MPL(ambda)S. These enhancements are in addition to the extensions
   required to support MPLS Traffic Engineering [Awduche-2].


4.1. Label request object modification

   The first field in the Label Request object is changed to contain the
   Link Media Type.  When an LSR receives a Path message, it must
   allocate a label, lambda or channel that is compatible with the Link
   Media Type.  The values for Link Media type as the same as for the
   two-octet media type values in IS-IS/OSPF Link Media Type TLV.

   If the choice of label, lambda or channel is not to be restricted, a
   Link Media Type of 0 is to be used.

         0                   1                   2                   3
         0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |        Link Media Type        |             L3PID             |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


4.2. Label object modification

   The information carried in the Label Object should be sufficient to
   control the connectivity matrix on an OXC, even when there are
   multiple fibers  between a pair of OXCs, and (at least some, or even
   all of) these fibers can't be used for exchanging MPLS control
   information between these two OXCs, and these fibers are combined
   into bundled links.

   That is, the Label Object should identify both a specific fiber
   (e.g., as an Interface Index), and a specific wavelength within that
   fiber, or a specific channel within that fiber.  Which of the two is
   intended should be obvious to the receiver of the Resv message.  The
   special value of 0xffff for the lambda or channel means the whole
   fiber.

         0                   1                   2                   3
         0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |        Fiber (16 bits)        |        Lambda (16 bits)       |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         0                   1                   2                   3



Kompella/Rekhter et al                                         

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         0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |        Fiber (16 bits)        |        Channel (16 bits)      |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


4.3. LSP aggregation via nesting


4.3.1. Domains

   Define an ordering among link types as follows: PSC-1 < PSC-2 < PSC-3
   < PSC-4 < TDM < LSC < FSC.  Say that a link type x is compatible with
   link type y iff x equals y, or x and y are both packet-switch
   capable.

   Suppose an LSP's path is as follows: node-0, link-1, node-1, link-2,
   node-2, ..., link-n, node-n; let the link type of link-i be lt-i.  If
   lt-i < lt-(i+1), we say that the LSP has crossed a domain boundary at
   node-i; with respect to that LSP path, the LSR at node-i is an edge
   LSR.  The 'other edge' of the domain with respect to the LSP path is
   node-k, where k is the smallest number greater than i+1 such that
   lt-k is compatible with lt-i.

   Note that the concept of 'domain' introduced above has to do with
   link types, but has nothing to do with routing domains.


4.3.2. LSP aggregation

   LSP aggregation is controlled by the LSRs at the edges of a domain.
   The aggregation is accomplished by establishing LSPs that span the
   domain, and start and end at the edges of that domain. The edge LSRs
   then use these LSPs for (a) creating forwarding adjacencies, and for
   (b) nesting of other LSPs that are established and terminated at LSRs
   beyond the domain and its edges.

   Note that a 'normal' packet-switched LSP may only be nested in an
   FA-LSP of type FA-PSC; a SONET trail may only be nested in an FA-LSP
   of type FA-TDM; and an optical trail may only be nested in an FA-LSP
   of type FA-LSC.

   Establishment/termination of the LSPs that span a domain could be
   triggered either by mechanisms outside of MPLS (e.g., via
   administrative control), or by mechanisms within MPLS (e.g., as a
   result of the LSR at the edge of a domain domain receiving LSP setup
   requests originated by some other LSRs beyond the domain and its
   edges. Procedures described in Section 4.3.3 applied to both cases.



Kompella/Rekhter et al                                         

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   Procedures described in Section 4.3.4 apply only to the latter case.


4.3.3. Common procedures

   For the purpose of processing the ERO in a Path message of an LSP
   that is to be tunneled over a forwarding adjacency, an LSR at the
   head-end of the FA-LSP views the LSR at the tail of that FA-LSP as
   adjacent (one IP hop away).

   If the LSR at the tail of the FA-LSP is capable of packet switching,
   the Path message for the tunneled LSP can itself be tunneled over the
   FA-LSP.  If the encapsulation on the carrier LSP can distinguish IP
   from MPLS, the Path message is sent as a plain IP packet.  Otherwise,
   the Path message is sent with a label of 0, meaning "pop the label
   and treat as IP".

   If the LSR at the tail of the FA-LSP is not capable of packet
   switching, the Path message is unicast over the control plane to the
   tail of the carrier LSP, without the Router Alert option.

   The Resv message back to the head-end of the FA-LSP (PHOP) cannot be
   sent over the same FA-LSP as it is unidirectional.  The Resv message
   can either take any LSP whose end-point is the head-end of the FA-
   LSP, or be unicast over the control plane to the head-end.

   When an LSP is tunneled through an FA-LSP, the LSR at the head-end of
   the FA-LSP subtracts the LSP's bandwidth from the unreserved
   bandwidth of the forwarding adjacency.



4.3.4. Specific procedures

   When an LSR receives a Path message, the LSR determines whether it is
   at the edge of a domain with respect to the ERO carried in the
   message.  The LSR does this by looking up the link types of the
   previous hop and the next hop in its IGP database, and comparing them
   using the relation defined in section 4.3.1.  If the LSR is not at
   the edge of a domain, the procedures in this section do not apply.

   If the LSR is at the edge of a domain, it must then determine the
   other edge of the domain with respect to the ERO, again using the IGP
   database.  The LSR then extracts the strict hop subsequence from
   itself to the other end of the domain.

   The LSR then compares the strict hop subsequence with all existing
   FA-LSPs originated by the LSR; if a match is found, and that FA-LSP



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   has enough unreserved bandwidth for the LSP being signaled, the LSR
   uses that FA-LSP as follows. The Path message for the original LSP is
   sent to the egress of the FA-LSP, not to the next hop along the FA-
   LSP's path. The PHOP in the message is the address of the LSR at the
   head-end of the FA-LSP. Before sending the Path message, the ERO in
   that message is adjusted by removing the subsequence of the ERO that
   lies in the FA-LSP, and replacing it with just the end point of the
   FA-LSP.

   Otherwise (if no existing FA-LSP is found), the LSR sets up a new
   FA-LSP.  That is, it initiates (using RSVP) a new LSP setup just for
   the FA-LSP.

   After the LSR establishes the new FA-LSP, the LSR announces this LSP
   into IS-IS/OSPF as a forwarding adjacency.

   The unreserved bandwidth of the forwarding adjacency is computed by
   subtracting the bandwidth of sessions pending the establishment of
   the FA-LSP associated from the bandwidth of the FA-LSP.

   An FA-LSP could be torn down by the LSR at the head-end of the FA-LSP
   as a matter of policy local to the LSR. It is expected that the FA-
   LSP would be torn down once there are no more LSPs carried by the
   FA-LSP.  When the FA-LSP is torn down, the forwarding adjacency
   associated with the FA-LSP is no longer advertised into IS-IS/OSPF.



5. Bandwidth accounting on OXCs

   As mentioned above, an IP link consists of a control channel and a
   set of fibers.  Initially, for each fiber the administrator sets up
   how many lambdas could be reserved at each priority on that fiber,
   and the Link Media type(s) supported by the fiber.  For an IP link,
   the unreserved bandwidth at each priority level is determined by
   adding up the bandwidths of all the lambdas of all the fibers in the
   IP link at that priority level.  The Link Media Type of the IP link
   is the set union of the Link Media Types of each fiber in the link.
   Note that while the IP link contains the aggregated information, RSVP
   needs to track the unaggregated information, i.e., the available
   lambdas for each fiber.

   Suppose, in response to a previously sent Path message, a Resv
   message is received at an ingress or intermediate OXC of an optical
   trail, along with the lambda and fiber to use, say <L, F>.  Say
   lambda L has bandwidth B and Link Media Type M.  RSVP must remove L
   from the list of available lambdas for fiber F.  Furthermore, the
   unreserved bandwidth at the holding priority of the optical trail is



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   reduced by B.  Also, if after lambda L is removed, there are no more
   available lambdas with Link Media Type M in the fiber set that F
   belongs to, M is removed from the list of Link Media Types for the
   link containing F.  Finally, the bandwidth accounting procedures for
   link bundles [Kompella] may also apply.

   When an optical trail that was using lambda L of fiber F at an
   ingress or intermediate OXC is torn down, that OXC needs to mark L as
   available.  The unreserved bandwidth (at the holding priority of the
   optical trail) of the IP link to which fiber F belongs is increased
   by the bandwidth of lambda L, and the Link Media Type of lambda L is
   added to the list of Link Media Types for the IP link if not already
   present.  Finally, the accounting procedures for link bundles may
   also apply.


6. Security Considerations

   This document raises no new security issues for IS-IS, OSPF or RSVP.


7. Acknowledgements

   We would like to thank Der-Hwa Gan, Jim Gibson, Robert Goguen, George
   Swallow, and Quaizar Vohra for their review and comments.


8. References

   [Awduche-1] Awduche, D., Rekhter, Y., Drake, J., Coltun, R., "Multi-
   Protocol Lambda Switching: Combining MPLS Traffic Engineering Control
   With Optical Crossconnects", draft-awduche-mpls-te-optical-01.txt

   [Awduche-2] Awduche, D., Berger, L., Gan, D-H., Li, T., Swallow, G.,
   Srinivasan, V., "Extensions to RSVP for LSP Tunnels", draft-ietf-
   mpls-rsvp-lsp-tunnel-04.txt

   [Basak] Basak, D., Awduche, D., Drake, J., Rekhter, Y., "Multi-
   protocol Lambda Switching: Issues in Combining MPLS Traffic
   Engineering Control With Optical Crossconnects", draft-basak-mpls-
   oxc-issues-00.txt

   [Smit] Smit, H., Li, T., "IS-IS extensions for Traffic Engineering",
   draft-ietf-isis-traffic-01.txt

   [Katz] Katz, D., Yeung, D., "Traffic Engineering Extensions to OSPF",
   draft-katz-yeung-ospf-traffic-01.txt




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   [Kompella] Kompella, K., Rekhter, Y., "Link Bundling in MPLS Traffic
   Engineering", draft-kompella-mpls-bundle-00.txt


9. Author Information


   Kireeti Kompella                            Yakov Rekhter
   Juniper Networks, Inc.                      Cisco Systems, Inc.
   385 Ravendale Drive                         170 West Tasman Drive
   Mountain View, CA 94043                     San Jose, CA 95134
   email: kireeti@juniper.net                  email: yakov@cisco.com

   Daniel O. Awduche                           Alan Hannan
   UUNET (MCI Worldcom)                        Global Crossing
   22001 Loudoun County Parkway                141 Caspian Court
   Ashburn, VA 20147                           Sunnyvale, CA 94087
   email: awduche@uu.net                       email: alan@gblx.net

   Gisli Hjalmtysson                           Joe Lawrence
   AT&T Labs - Research                        Level 3 Communications
   180 Park Avenue                             1025 Eldorado Boulevard
   Florham Park, NJ 07932                      Broomfied CO, 80021
   email: gisli@research.att.com               email: joe.lawrence@level3.com

   Satoru Okamoto                              Debashis Basak
   NTT Network Innovation Laboratories         Marconi
   Room 807A, 1-1 Hikari-no-oka,               1000 FORE Drive
   Yokosuka-shi, Kanagawa 239-0847 Japan       Warrendale, PA  15086-7502
   email: okamoto@exa.onlab.ntt.co.jp          email:  dbasak@fore.com

   Greg Bernstein                              John Drake
   Ciena Corporation                           Chromisys
   10201 Bubb Road                             1012 Stuart Drive
   Cupertino, CA 95014                         Sunnyvale, CA 94086
   email: GregB@ciena.com                      email:jdrake@chromisys.com

   Near Margalit                               Ed Stern
   New Access Communications                   Sirocco Systems
   71 Vista Montana                            95 Barnes Rd.
   San Jose CA 95134                           Wallingford, CT 06492
   email: margalit@new-access.com              email:ed.stern@siroccosystems.com









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