Internet Draft Network Working Group Senthil Venkatachalam Internet Draft Alcatel. Expiration Date: November 2000 Ben Abarbanel Alcatel. OSPF Extensions to Support Inter-Area Traffic Engineering draft-venkatachalam-ospf-traffic-00.txt Status 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. Abstract This document describes the OSPF "Traffic Engineering Summary LSA" and its support to enable traffic engineering across area boundaries. 1. Introduction Currently, there is no way to support traffic engineering across areas using the OSPF protocol [1]. Previous work on traffic engineering support [2] using the OSPF protocol has restricted the focus to within an OSPF area. This draft proposes a new opaque LSA [3] called the "Traffic Engineering Summary LSA" that helps propagate the traffic engineering metric information across areas. Senthil Venkatachalam, B. Abarbanel Expires November 2000 [Page 1] Internet Draft draft-venkatachalam-ospf-traffic-00.txt May 2000 2. Traffic Engineering Summary LSA The traffic engineering (TE) summary LSA will be originated by the Area Border Router (ABR) into an area. This summary LSA is a type-10 opaque LSA, that will be flooded within the area. The functionality of the TE summary LSA is similar to that of the summary LSA of standard OSPF, but in addition it carries the traffic engineering metrics to the remote destination (IP network or ASBR). 3. Traffic Engineering Attributes The various traffic engineering attributes that are used to describe the destination (either a network or an ASBR) in the TE summary LSA are: 1 - Traffic engineering metric 2 - Hops 3 - Maximum bandwidth 4 - Unreserved bandwidth 5 - Delay 6 - Color One or more of these attributes need to be used in the metrics portion of the TE summary LSA. The traffic engineering and hop metrics are additive metrics similar to the ospf metric, but need not be the same. The traffic engineering and hop metrics advertised by the router for the given summary destination will have been computed in a manner similar to the dijkstra computation for the ospf metric. The maximum bandwidth to the summary destination is the largest of all path-capacities, each associated with a possible path to the destination. The path-capacity is the smallest link capacity of all the links in the path. Hence, the maximum bandwidth is the maximum amount of traffic that can be sent to that destination, when there is no other traffic on the links. The unreserved bandwidth to the summary destination is the largest of all path-unreserved bandwidths, each associated with a possible path to the destination. The path-unreserved bandwidth is the smallest unreserved bandwidth of all the links in the path. Hence, the unreserved bandwidth is the maximum amount of traffic that can currently be sent to that destination, the other traffic on the links being steady. Senthil Venkatachalam, B. Abarbanel Expires November 2000 [Page 2] Internet Draft draft-venkatachalam-ospf-traffic-00.txt May 2000 The delay is an additive metric. The value of the delay attribute for a summary destination will have been determined through a dijkstra computation based on the delay. The value of the color attribute to the summary destination is some combination of the path-colors, each associated with a possible path to the destination. The path-color is a combination of the colors of the links in the path. Usually, this combination is a "logical and" of the colors. Once these attributes are determined for the destination networks and ASBRs, the advertising ABR then creates the TE summary LSA to be flooded out of its interfaces into the area. The ABR should generate a new TE summary LSA when the attributes change, or other normal OSPF behavior require it. 4. The TE Summary LSA Format The TE summary LSA has the basic LSA structure with a modified opaque LSA header called the TE summary LSA header. The TE summary LSA contents include a destination field, network mask, and TLV-tuples describing the traffic engineering attributes. 4.1 TE Summary LSA Header The TE summary LSA's header is derived from the standard and opaque LSA headers. The LS type field is assigned the value 10 to denote that this is an opaque LSA of type-10 or area-local scope. The Link State ID field of the standard LSA header is replaced by the Opaque Type (1 octet), TE-LS Type (1 octet) and the TE-summary LSA ID (2 octets). The value of the opaque type field for the TE-summary LSA is TBD. The TE-LS Type can take values 3 or 4, depending on whether the destination being described in the LSA is an IP network or an ASBR respectively. The TE-summary LSA ID is a unique 16-bit number that helps identify the TE Summary LSA. A total of 65536 TE summary LSAs can be originated by an ABR. Senthil Venkatachalam, B. Abarbanel Expires November 2000 [Page 3] Internet Draft draft-venkatachalam-ospf-traffic-00.txt May 2000 The format of the TE summary LSA header is as follows: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS age | Options | 10 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Opaq. Type(TBD)|TE LS Type=3/4 | TE Summary LSA ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Advertising Router | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS checksum | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 4.2 TE Summary LSA Contents The summary LSA consists of: o The Destination ID, which is: o The IP address of the described network (if TE LS Type = 3), or o The Router ID of the described ASBR (if TE LS Type = 4). (The functionality of the destination ID field is the same as the LS ID field in the standard summary LSA header). This field is 4 octets in length. o The Network Mask, which holds the mask of the network described in the summary. If the summary is for an ASBR, this field is set to 0. (The functionality is the same as in the standard summary LSA). This field is 4 octets in length. It is followed by: o One or more TLV-tuples that describe the traffic engineering metrics to reach the network or the ASBR defined in the TE summary LSA. These TLV-tuples have a constant "type" and "length" field-lengths of 2 octets each, and a variable length "value" field. The length field specifies the length of the value field in bytes. The TLV is padded to the standard 4-byte alignment. Senthil Venkatachalam, B. Abarbanel Expires November 2000 [Page 4] Internet Draft draft-venkatachalam-ospf-traffic-00.txt May 2000 The contents of the TE summary LSA is then of the following format: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Destination ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Network Mask | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value (4x octets, x >= 0) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 4.3 The Traffic Engineering Attributes The following traffic engineering attributes are defined: 1 - Traffic engineering metric (4 octets) 2 - Hops (4 octets) 3 - Maximum bandwidth (4 octets) 4 - Unreserved bandwidth (4 octets) 5 - Delay (4 octets) 6 - Resource class/color (4 octets) Some of these traffic engineering attributes have sizes the same as in [2] but others (notably the bandwidths) are not. The bandwidths have been kept to just 4 octets to restrict the size of the TLV. Each of these attributes (and the value associated with it) is represented as a TLV-tuple. Each such attribute may occur at most once (none or once) in an LSA. In addition, new traffic engineering attributes may be defined in the future. The TLV attributes are as follows (see Section 3 for the definition): 4.3.1 Traffic Engineering Metric The traffic engineering metric represents the traffic engineering cost of reaching the destination network or ASBR from the advertising ABR. The TLV-type is 1, and the length of this attribute is 4 octets. Senthil Venkatachalam, B. Abarbanel Expires November 2000 [Page 5] Internet Draft draft-venkatachalam-ospf-traffic-00.txt May 2000 4.3.2 Hops The hops TLV is the cost in hops, of reaching the destination network or ASBR from the advertising ABR. The TLV-type is 2, and the length is 4 octets. 4.3.3 Maximum Bandwidth The maximum bandwidth to the destination is described in bytes/second as an IEEE floating point number. The TLV-type is 3, and the length is 4 octets. 4.3.4 Unreserved Bandwidth The unreserved bandwidth to the destination is described in bytes/second as an IEEE floating point number. The TLV-type is 4, and the length is 4 octets. 4.3.5 Delay The delay attribute is the delay cost to reach the destination network (or ASBR), in milliseconds, represented as an unsigned (4-byte) long integer. The TLV-type is 5, and the length is 4 octets. 4.3.6 Resource Class/Color The resource class or color of the destination network (or ASBR) is a combination of the colors for the various paths to the network (or ASBR). The TLV-type of the resource class/color attribute is 6, and the length is 4 octets. 5. Use of the Traffic Engineering Summary LSA The TE summary LSA provides the traffic engineering information regarding remote destinations (networks or ASBRs) in other areas. This information is valuable in order to make accurate routing decisions based on attributes such as bandwidth, delay, metrics and colors. The TE summary LSAs along with the TE LSAs [2] provide a comprehensive traffic topology of the OSPF domain. Using this traffic topology database, routing calculations can be performed based on a variety of criteria which could be combinations of constraints [4] on one or more traffic engineering attributes. Senthil Venkatachalam, B. Abarbanel Expires November 2000 [Page 6] Internet Draft draft-venkatachalam-ospf-traffic-00.txt May 2000 Such a traffic topology database can be used: 1. to effect QoS routing, by precomputing routes to remote destinations based on a fixed combination of traffic engineering constraints, 2. to calculate a route to a remote destination based on traffic engineering constraints, on an as-needed basis, 3. to determine the traffic engineering "distance" from an ASBR to the various networks and other ASBRs in the domain, so that this information can be redistributed into BGP, and be propagated outside of the domain[5]. This setup can help in the distribution of traffic engineering information across ASs. 6. Compatibility Issues Three different cases are possible with respect to an ABR's support of the TE summary LSA: 1. The ABR doesn't support opaque LSAs, in which case the opaque LSAs received by it are simply ignored, and none are generated or forwarded. 2. The ABR supports opaque LSAs, but not the TE summary LSA, in which case it floods out any TE summary LSA received from one of its interfaces out of other interfaces in the same area. However, no TE summary LSAs are generated into an area. 3. The ABR supports the TE summary LSA. In this case, the TE summary LSA is generated for each area and flooded out the interfaces of that area. If a router interior to an area doesn't support TE summary LSAs, it will not be able to take advantage of the traffic engineering attributes of remote destinations outside the area, and hence will not be able to calculate remote routes based on these attributes. If a router interior to an area doesn't support TE LSAs from [2], the TE summary LSAs generated by the ABR of the area will describe a traffic topology that is smaller than the underlying network topology. Hence if all the routes of the underlying network topology need to be represented in the traffic topology, all routers in the area must support the TE LSAs. Senthil Venkatachalam, B. Abarbanel Expires November 2000 [Page 7] Internet Draft draft-venkatachalam-ospf-traffic-00.txt May 2000 7. Security Considerations There are no new security considerations necessary beyond that of[1]. 8. References [1] Moy, J., "OSPF Version 2", RFC 2328, April 1998. [2] Katz, D. and Yeung D., "Traffic Engineering Extensions to OSPF", Internet Draft <draft-katz-yeung-ospf-traffic-00.txt> [3] Coltun, R., "The OSPF Opaque LSA Option," RFC 2370, July 1998. [4] Awduche, D. et al "Extensions to RSVP for LSP Tunnels", Work in Progress, Internet Draft <draft-ietf-mpls-rsvp-lsp-tunnel-04.txt, September 1999. [5] Abarbanel, B. and Venkatachalam, Senthil, "BGP-4 support for Traffic Engineering", Internet Draft <draft-abarbanel-idr-bgp4-te-00.txt> 9. Authors' Addresses Senthil Venkatachalam Alcatel USA 45195 Business Court, Suite 400 Dulles, VA 20166 email: senthil.venkatachalam@usa.alcatel.com Phone: (703)654-8635 Ben Abarbanel Alcatel USA 45195 Business Court, Suite 400 Dulles, VA 20166 email: benjamin.abarbanel@usa.alcatel.com home email: ben@baces.com Senthil Venkatachalam, B. Abarbanel Expires November 2000 [Page 7]