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Network Working Group                     K. Kompella (Juniper Networks)
Internet Draft                            Y. Rekhter  (Juniper Networks)
Expiration Date: August 2001              A. Banerjee (Calient Networks)
                                          J. Drake    (Calient Networks)
                                          G. Bernstein (Ciena)
                                          D. Fedyk    (Nortel Networks)
                                          E. Mannie   (GTS Network)
                                          D. Saha     (Tellium)
                                          V. Sharma   (Tellabs)

            IS-IS Extensions in Support of Generalized MPLS


                draft-ietf-isis-gmpls-extensions-02.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.















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2. Abstract

   This document specifies extensions to the IS-IS routing protocol in
   support of Generalized Multi-Protocol Label Switching (previously
   known as Multi-Protocol Lambda Switching).


3. Introduction

   This document specifies extensions to the IS-IS routing protocol in
   support of carrying link state information for Generalized Multi-
   Protocol Label Switching (GMPLS, previously known as Multi-Protocol
   Lambda Switching, MPL(ambda)S).  For motivations and overall
   architecture of MPL(ambda)S see [1].  The set of required
   enhancements to IS-IS are outlined in [2].  This document enhances
   the routing extensions [3] required to support MPLS Traffic
   Engineering.  Some of these enhancements also need to be carried in
   the signaling protocols [6].

   The organization of the remainder of the document is as follows.  In
   Section 4, we describe the types of links that may be advertised in
   IS-IS TE LSAs (we call Link State PDUs LSAs to avoid confusion with
   Label Switched Paths).  In Section 5, we define a new set of
   Type/Length/Value (TLV) triplets, as well as extend a proposed TLV,
   and describe their formats.


4. GMPLS TE Links

   Traditionally, a TE link is advertised as an adjunct to a "regular"
   IS-IS link, i.e., an IS-IS adjacency is brought up on the link, and
   when the link is up, both the regular SPF properties of the link
   (basically, the SPF metric) and the TE properties of the link are
   then advertised.

   However, 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, an IS-IS 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 need no longer be between two IS-IS neighbors.
   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 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, some of which may be
   configured on the advertising Label Switching Router (LSR), others



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   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 an
   IS-IS adjacency between these LSRs.  A TE link must also have some
   means by which the advertising LSR can know of its liveness (this
   means may be IS-IS hellos, but is not limited to IS-IS 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) IS-
   IS neighbors using the TE TLVs.  In this document, we call the
   interfaces over which regular IS-IS adjacencies are established
   "control channels".

   [3] defines the canonical TE properties, and says 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).  [5] says how to associate TE
   properties with Label Switched Paths; [4] says how to associate TE
   properties with a "bundle" of links.


4.1. Excluding data traffic from control channels

   The control channels between nodes in a GMPLS network, such as OXCs
   (see [1], [2]), SONET cross-connects and/or routers, are generally
   meant for control and administrative traffic.  These control channels
   are advertised into IS-IS as normal IS 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 (see [5]), 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



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   also be needed.


5. IS-IS Routing Enhancements

   In this section we define the enhancements to the TE properties of
   GMPLS TE links that can be announced in IS-IS TE LSAs.  In this
   document, we enhance the sub-TLVs for the extended IS reachability
   TLV (see [3]) in support of GMPLS.  Specifically, we add sub-TLVs
   for: Outgoing/Incoming Interface Identifier, Maximum LSP Bandwidth
   and Link Protection Type.  This brings the list of sub-TLVs of the
   extended IS reachability TLV to:

      Sub-TLV Type      Length    Name
                 3           4    Administrative group (color)
                 4           4    Outgoing Interface Identifier
                 5           4    Incoming Interface Identifier
                 6           4    IPv4 interface address
                 8           4    IPv4 neighbor address
                 9           4    Maximum link bandwidth
                10           4    Reservable link bandwidth
                11          32    Unreserved bandwidth
                12          32    Maximum LSP Bandwidth
                18           3    TE Default metric
                19           1    Link Mux Capability
                20           2    Link Protection Type
           250-254           -    Reserved for cisco specific extensions
               255           -    Reserved for future expansion


   We further add two new TLVs.

          TLV Type      Length    Name
         136 (TBD)    variable    Link Descriptor
         138 (TBD)    variable    Shared Risk Link Group


5.1. Outgoing Interface Identifier

   A link from LSR A to LSR B may be assigned an "outgoing interface
   identifier".  This identifier is a non-zero 32-but number that is
   assigned by LSR A.  This identifier must be unique within the scope
   of A.  If such an identifier has been assigned, A can advertise it as
   a sub-TLV of the extended IS reachability TLV with type 4, length 4
   and value equal to the assigned identifier.






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5.2. Incoming Interface Identifier

   Suppose there is a link L from A to B.  Suppose further that the link
   L' from B to A that corresponds to the same interface as L has been
   assigned an outgoing interface identifier by B.  The "incoming
   interface identifier" for L (from A's point of view) is defined as
   the outgoing interface identifier for L' (from B's point of view).
   If A knows this value (by means beyond the scope of this document), A
   can advertise it as a sub-TLV of the extended IS reachability TLV
   with type 5, length 4 and value equal to L's incoming interface
   identifier.


5.3. Maximum LSP Bandwidth sub-TLV

   The Maximum LSP Bandwidth takes the place of the Maximum Link
   Bandwidth.  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.

   The Maximum LSP Bandwidth of a bundled link at priority p is defined
   to be the maximum of the Maximum LSP Bandwidth at priority p of each
   component link.

   If a component link is a simple (unbundled) link, define its Maximum
   LSP Bandwidth at priority p to be the smaller of its unreserved
   bandwidth at priority p and its maximum link bandwidth.

   The Maximum LSP Bandwidth TLV has type 12 and length 32 octets.  The
   value is a list of eight 4 octet fields in IEEE floating point format
   of the Maximum LSP Bandwidth of the link, with priority 0 first and
   priority 7 last.

   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 of the link.


5.4. Link Protection Type sub-TLV

   The Link Protection Type sub-TLV represents the protection capability
   that exists on 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 is a sub-TLV (of
   type 20) of the extended IS reachability TLV, with length two octets,
   the first of which is a bit vector describing the protection
   capabilities of the link. They are:




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   0x01  Extra Traffic
      If the link is Extra Traffic, it indicates that these links are
      protecting other (primary) links.  The LSPs on a link of this
      type will be lost if the primary links being protected fail.

   0x02  Unprotected
      If the link is Unprotected, it means that there is no backup link
      for traffic being carried on the link.

   0x04  Shared
      If the link has Shared protection, it means that for the N > 1
      primary data-bearing channels, there are M disjoint backup data-
      bearing channels reserved to carry the traffic.  Additionally, the
      protection data-bearing channel MAY carry low-priority preemptable
      traffic.  The bandwidth of backup data-bearing channels will be
      announced in the unreserved bandwidth sub-TLV at the appropriate
      priority.

   0x08  Dedicated 1:1
      If the link has Dedicated 1:1 protection, it means that for each
      primary data-bearing channel, there is one disjoint backup data-
      bearing channel reserved to carry the traffic.  Additionally, the
      protection data-bearing channel MAY carry low-priority preemptable
      traffic.  The bandwidth of backup data-bearing channels will be
      announced in the unreserved bandwidth sub-TLV at the appropriate
      priority.

   0x10  Dedicated 1+1
      If the link has Dedicated 1+1 protection, it means that a disjoint
      backup data-bearing channel is reserved and dedicated for
      protecting the primary data-bearing channel.  This backup data-
      bearing channel is not shared by any other connection, and traffic
      is duplicated and carried simultaneously over both channels.

   0x20 Enhanced
      If the link has Enhanced protection, it indicates that a protection
      scheme that is more reliable than Dedicated 1+1 is being used,
      e.g., 4 fiber BLSR/MS-SPRING to protect this link.

   0x40 Reserved
   0x80 Reserved

   The second octet gives a priority value such that a new connection
   with a higher priority (i.e., numerically lower than this value) is
   guaranteed to be setup on a primary (or working) channel, and not on
   a secondary (or protect) channel.

   The Link Protection Type sub-TLV is optional and if an LSA does not



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   carry the TLV, then the Link Protection Type is unknown.  The
   protection capability of a link is typically pre-configured and does
   not change dynamically over time.  The working priority value is pre-
   configured and does not depend on the traffic characteristics on the
   primary data-bearing channel.


5.5. Link Descriptor TLV

   The Link Descriptor TLV represents the characteristics of the link,
   in particular the link type and the bit transmission rate.  These
   characteristics represent one of the constraints on the type of LSPs
   that could be carried over a link.

   These characteristics should not be confused with the physical link
   encoding or multiplex structure (if any).  For example there are
   systems where four OC-48s are switched and transported over a single
   fiber via wavelength division multiplexing (WDM) technology.  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 both of the links can
   transport media of type OC-48.

   The proposed Link Descriptor TLV (of type 136 TBD) contains a new
   data structure consisting of:
       7 octets of System ID and Pseudonode Number
       4 octets of IPv4 interface address
       4 octets of IPv4 neighbor address
   and a list of Link Descriptors, where each element in the list has 10
   octets.  The length of the TLV is thus 15+10*n octets, where n is the
   number of elements in the list.

   Each Link descriptor element consists of the following fields: the
   first field is a one-octet value which defines the link encoding
   type, the second field is a one-octet value which defines the lowest
   priority at which that link encoding type is available, the third
   field is four-octets and specifies the minimum reservable bandwidth
   (in IEEE floating point format, the units being bytes per second) for
   this link encoding type, and the last field is four-octets and
   specifies the maximum reservable bandwidth (in IEEE floating point
   format, the units being bytes per second) for this link encoding
   type.  Link encoding type values are taken from the following list:

      Value        Link Encoding Type
          1        Standard SONET
          2        Arbitrary SONET
          3        Standard SDH



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          4        Arbitrary SDH
          5        Clear
          6        GigE
          7        10GigE

   A link having Standard SONET (or Standard SDH) link encoding type can
   switch data at a minimum rate, which is given by the Minimum
   Reservable Bandwidth on that link, and the maximum rate is given by
   the Maximum Reservable Bandwidth on that link.  Typical values of
   these are enumerated in the GMPLS signaling draft [6].  In other
   words, the Minimum and Maximum Reservable Bandwidth represents the
   leaf and the root of one branch within the structure of the SONET (or
   SDH) hierarchy.  An LSP on that link may reserve any bit transmission
   rate that is allowed by the SONET (or SDH) hierarchy between the
   minimum and maximum reservable values (the spectrum is discrete).
   For example, consider a branch of SONET multiplexing tree : VT-1.5,
   STS-1, STS-3c, STS-12c, STS-48c, STS-192c.  If it is possible to
   establish all these connections on a OC-192 link, it can be
   advertised as follows: Minimum Reservable Bandwidth VT-1.5 and
   Maximum Reservable Bandwidth STS-192.

   A link having Arbitrary SONET (or Arbitrary SDH) link encoding type
   can switch data at a minimum rate, which is given by the Minimum
   Reservable Bandwidth on that link, and the maximum rate is given by
   the Maximum Reservable Bandwidth on that link.  Typical values of
   these are enumerated in the GMPLS signaling draft [6].  An LSP on
   that link may reserve any bit transmission rate that is a multiple of
   the Minimum Reservable Bandwidth between the minimum and maximum
   reservable values (the spectrum is discrete).

   To handle the case where a link could support multiple branches of
   the SONET (or SDH) multiplexing hierarchy, one could use multiple LSP
   descriptors.  For example, if a link supports VT-1.5 and VT-2 (which
   are not part of same branch of SONET multiplexing tree), then it
   could advertise two LSP descriptors, one for each one.

   For a link with Clear encoding, the minimum and maximum reservable
   bandwidth will imply that the optical path is tuned to carry traffic
   within those range of values.  (Note that it should be possible to
   carry OC-x as well as GigE or any other encoding format, as long as
   the bit transmission rate of the data to be carried is within this
   range.)

   For other encoding types, the minimum and maximum reservable
   bandwidth should be set to have the same values.

   Link Descriptors present a new constraint for LSP path computation.




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   On a bundled link we assume that either the whole link is configured
   with the Link Descriptor Types, or each of its component links are
   configured with the Link Descriptor Types.  In the latter case, the
   Link Descriptor Type of the bundled link is set to the set union of
   the Link Descriptor Types for all the component links.

   It is possible that Link Descriptor TLV will change over time,
   reflecting the allocation/deallocation of component links.  In
   general, creation/deletion of an LSP on a link doesn't necessarily
   result in changing the Link Descriptor of that link.  For example,
   assume that STS-1, STS-3c, STS-12c, STS-48c and STS-192c LSPs can be
   established on a OC-192 link whose Link Type is SONET.  Thus,
   initially in the Link Descriptor the minimum reservable bandwidth is
   set to STS-1, and the maximum reservable bandwidth is set of STS-192.
   As soon as an LSP of STS-1 size is established on the link, it is no
   longer capable of STS-192c.  Therefore, the node advertises a
   modified Link Descriptor indicating that the maximum reservable
   bandwidth is no longer STS-192, but STS-48.  If subsequently there is
   another STS-1 LSP, there is no change in the Link Descriptor.  The
   Link Descriptor remains the same until the node can no longer
   establish a STS-48c LSP over the link (which means that at this point
   more than 144 time slots are taken by LSPs on the link).  Once this
   happened, the Link Descriptor is modified again, and the modified
   Link Descriptor is advertised to other nodes.

   Note that changes to the Link Descriptor TLV will also affect the
   Unreserved Bandwidth sub-TLV with respect to bandwidth available on
   the link.


5.6. 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 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.  The SRLG values are an unordered list of 4 octet
   numbers that the link belongs to.

   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.



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   The proposed SRLG (of type 138 TBD) contains a new data structure
   consisting of:
       7 octets of System ID and Pseudonode Number
       4 octets of IPv4 interface address
       4 octets of IPv4 neighbor address
   and a list of SRLG values, where each element in the list has 4
   octets.  The length of the TLV is thus 15+4*n octets, where n is the
   number of elements in the list.

   The SRLG TLV starts with a configured value and does not change over
   time, unless manually reconfigured.  The SRLG TLV is optional and if
   an LSA doesn't carry the SRLG TLV, then it means that SRLG of that
   link is unknown.


6. Security Considerations

   The sub-TLVs proposed in this document does not raise any new
   security concerns.


7. Acknowledgements

   The authors would like to thank Suresh Katukam, Jonathan Lang and
   Quaizar Vohra for their comments on the draft.


8. References

   [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-02.txt (work in progress)

   [2] 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-01.txt (work in progress)

   [3] Smit, H., Li, T., "IS-IS Extensions for Traffic Engineering",
       draft-ietf-isis-traffic-02.txt (work in progress)

   [4] Kompella, K., Rekhter, Y., Berger, L., "Link Bundling in MPLS
       Traffic Engineering", draft-kompella-mpls-bundle-05.txt (work
       in progress)

   [5] Kompella, K., Rekhter, Y., "LSP Hierarchy with MPLS TE",
       draft-ietf-mpls-lsp-hierarchy-01.txt (work in progress)



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   [6] Generalized MPLS Group, "Generalized MPLS - Signaling Functional
       Description", draft-ietf-mpls-generalized-signaling-02.txt (work
       in progress)

   [7] Lang J., Mitra K., Drake J., Kompella K., Rekhter Y., Berger L.,
       Saha, D., Sandick, H., and Basak D., "Link Management Protocol",
       draft-ietf-mpls-lmp-02.txt (work in progress)


9. Authors' Information


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



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








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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


Eric Mannie
GTS Network Services
RDI Department, Core Network Technology Group
Terhulpsesteenweg, 6A
1560 Hoeilaart, Belgium
Phone: +32-2-658.56.52
E-mail: eric.mannie@gtsgroup.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
Jasmine Networks, Inc.
3061 Zanker Rd, Suite B
San Jose, CA 95134
Phone: (408) 895-5000











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