Network Working Group K. Kompella (Juniper Networks) Internet Draft Y. Rekhter (Cisco Systems) Expiration Date: May 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-01.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. draft-ietf-isis-gmpls-extensions-01.txt [Page 1] Internet Draft draft-ietf-isis-gmpls-extensions-01.txt November 2000 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 draft-ietf-isis-gmpls-extensions-01.txt [Page 2] Internet Draft draft-ietf-isis-gmpls-extensions-01.txt November 2000 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 draft-ietf-isis-gmpls-extensions-01.txt [Page 3] Internet Draft draft-ietf-isis-gmpls-extensions-01.txt November 2000 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. draft-ietf-isis-gmpls-extensions-01.txt [Page 4] Internet Draft draft-ietf-isis-gmpls-extensions-01.txt November 2000 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 can take one of the following values: Value Link Protection Type draft-ietf-isis-gmpls-extensions-01.txt [Page 5] Internet Draft draft-ietf-isis-gmpls-extensions-01.txt November 2000 0 Unprotected 1 Shared 2 Dedicated 1:1 3 Dedicated 1+1 4 Enhanced If the link is Unprotected, it means that there is no backup link for traffic being carried on the link. 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. 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. 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. If the link has Enhanced protection, it indicates that the protection scheme for the link is more reliable than the Dedicated 1+1, e.g., 4 fiber BLSR/MS-SPRING. 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 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. draft-ietf-isis-gmpls-extensions-01.txt [Page 6] Internet Draft draft-ietf-isis-gmpls-extensions-01.txt November 2000 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 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 draft-ietf-isis-gmpls-extensions-01.txt [Page 7] Internet Draft draft-ietf-isis-gmpls-extensions-01.txt November 2000 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. 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, draft-ietf-isis-gmpls-extensions-01.txt [Page 8] Internet Draft draft-ietf-isis-gmpls-extensions-01.txt November 2000 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. 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 draft-ietf-isis-gmpls-extensions-01.txt [Page 9] Internet Draft draft-ietf-isis-gmpls-extensions-01.txt November 2000 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-04.txt (work in progress) [5] Kompella, K., Rekhter, Y., "LSP Hierarchy with MPLS TE", draft-ietf-mpls-lsp-hierarchy-00.txt (work in progress) [6] Generalized MPLS Group, "Generalized MPLS - Signaling Functional Description", draft-ietf-mpls-generalized-signaling-01.txt (work in progress) [7] Lang J., Mitra K., Drake J., Kompella K., Rekhter Y., Berger L., draft-ietf-isis-gmpls-extensions-01.txt [Page 10] Internet Draft draft-ietf-isis-gmpls-extensions-01.txt November 2000 Saha, D., Sandick, H., and Basak D., "Link Management Protocol", draft-ietf-mpls-lmp-01.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 Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA 95134 Email: yakov@cisco.com 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 draft-ietf-isis-gmpls-extensions-01.txt [Page 11] Internet Draft draft-ietf-isis-gmpls-extensions-01.txt November 2000 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 Tellabs Research Center One Kendall Square Bldg. 100, Ste. 121 Cambridge, MA 02139-1562 Phone: (617) 577-8760 Email: Vishal.Sharma@tellabs.com draft-ietf-isis-gmpls-extensions-01.txt [Page 12]