Internet Engineering Task Force C. Jacquenet INTERNET-DRAFT France Telecom R & D Document: draft-jacquenet-qos-nlri-00.txt Category: informational Expires: January 2001 Providing Quality of Service Indication by the BGP-4 Protocol: the QOS_NLRI attribute <draft-jacquenet-qos-nlri-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 RFC 2026 ([RFC-2026]). 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. 2. Abstract For almost the last decade, value-added IP service offerings have been massively deployed over the Internet, thus yielding a dramatic development of the specification effort, as far as quality of service (QOS) in IP networks is concerned. Nevertheless, providing end-to-end quality of service by crossing administrative domains still remains an issue, mainly because: - quality of service policies may dramatically differ from one service provider to another; - the enforcement of a specific quality of service policy may also differ from one domain to another, although the definition of a set of basic and common quality of service indicators may be shared between the service providers. As far as IP routing is concerned, the BGP-4 protocol (Border Gateway Protocol, version 4,[RFC-1771]) has been systematically activated between autonomous systems for the purpose of exchanging routing information related to the reachability of IP destination prefixes. From this standpoint, the BGP-4 protocol appears to be one of the key components for the enforcement of a global quality of service policy, by allowing BGP peers to indicate each other if (1) The QOS_NLRI attribute July 2000 they have the ability to announce QOS-related information when transmitting UPDATE messages and (2) they have the ability to process such a QOS-related information when conveyed in an UPDATE message. The purpose of this draft consists in proposing an additional BGP4 attribute, named the QOS_NLRI attribute, which aims at providing QOS-related information related to the NLRI information conveyed in a BGP UPDATE message. 3. Conventions used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 ([RFC- 2119]). 4. Introduction Providing end-to-end quality of service is probably one of the most important challenges of the Internet, not only because of the massive development of value-added IP service offerings, but also because of the various QOS policies that are currently deployed and enforced within an autonomous system, and which may well differ from one AS to another. Activate the BGP-4 protocol for exchanging reachability information between autonomous systems has been a must for many years, and, from this standpoint, the BGP-4 protocol appears to be a key component in the deployment of end-to-end QOS policies. Exchanging QOS-related information as well as reachability information in a given BGP UPDATE message might be helpful in enforcing an end-to-end QOS policy. This draft aims at specifying a new BGP-4 attribute, the QOS_NLRI attribute which will convey QOS-related information associated to the (possibly withdrawn) routes described in the NLRI (Network Layer Reachability Information) field of a BGP UPDATE message. 5. The QOS_NLRI attribute (Type Code XY*) *: "XY" is subject to the IANA considerations section of this draft. This is an optional transitive attribute which can be used for the following purposes: (a) to advertise a QOS route to a peer. A QOS route is a route which meets one or a set of QOS requirements to reach a given (set of) destination prefixes. Such QOS requirements can be expressed in terms of minimum transit delay to reach a destination, maximum available bandwidth along the path to reach a destination, the identification of the traffic which is expected to use this specific route (identification means for such traffic include DSCP (DiffServ Code Point, [RFC-2475]) marking), etc., and they can be provided as The QOS_NLRI attribute July 2000 an input for the route calculation process embedded in the BGP peers thanks to the activation of a signaling protocol, such as RSVP (Resource ReSerVation Protocol, [RFC-2205]); (b) to provide QOS information along with the NLRI information in a single BGP UPDATE message. It is assumed that this QOS information will be related to the route (or set of routes) described in the NLRI field of the BGP UPDATE message. The QOS_NLRI attribute is encoded as follows: +---------------------------------------------------------+ | QOS Information Code (1 octet) | +---------------------------------------------------------+ | QOS Information Sub-code (1 octet) | +---------------------------------------------------------+ | QOS Information Value (2 octets) | +---------------------------------------------------------+ | QOS Information Origin (1 octet) | +---------------------------------------------------------+ | Network Address of Next Hop (1 octet) | +---------------------------------------------------------+ | Network Layer Reachability Information (variable) | +---------------------------------------------------------+ The use and meaning of these fields are as follows: - QOS Information Code: This field carries the type of the QOS information. The following types have been identified so far: (0) Reserved (1) Bandwidth (2) Delay (3) Jitter (4) DSCP - QOS Information Sub-code: This field carries the sub-type of the QOS information. The following sub-types have been identified so far: (0) None (i.e. no sub-type, or sub-type unavailable, or unknown sub- type) (1) Reserved bandwidth (2) Available bandwidth (3) Minimum transit delay (4) Maximum transit delay (5) Average transit delay (6) AF (Assured Forwarding, [RFC-2597]) type The instantiation of this sub-code field MUST be compatible with the value conveyed in the QOS Information code field, as stated in the The QOS_NLRI attribute July 2000 following table (the rows represent the QOS Information Code possible values, the columns represent the QOS Information Sub-code values identified so far, while the "X" sign indicates incompatibility). +----------------------------------------+ | | 0 | 1 | 2 | 3 | 4 | 5 | 6 | +---------------------------------------+ | 0 | | | | | | | | +---------------------------------------+ | 1 | | | | X | X | X | X | +---------------------------------------+ | 2 | | X | X | | | | X | +---------------------------------------+ | 3 | | X | X | X | X | X | X | +---------------------------------------+ | 4 | | X | X | X | X | X | | +---------------------------------------+ - QOS Information value: This field indicates the value of the QOS information. The corresponding units obviously depend on the instantiation of the QOS Information Code. Namely, if: (a) QOS Information Code field is "0", no unit specified, (b) QOS Information Code field is "1", unit is bits per second (bps), (c) QOS Information Code field is "2", unit is milliseconds, (d) QOS Information Code field is "3", unit is milliseconds, (e) QOS Information Code field is "4", no unit specified. - Network Address of Next Hop: A variable length field that contains the Network Address of the next router on the path to the destination prefix. - Network Layer Reachability Information: A variable length field that lists NLRI for the feasible routes that are being advertised in this attribute. The next hop information carried in the QOS_NLRI path attribute defines the Network Layer address of the border router that should be used as the next hop to the destinations listed in the QOS_NLRI attribute in the UPDATE message. When advertising a QOS_NLRI attribute to an external peer, a router may use one of its own interface addresses in the next hop component of the attribute, provided the external peer to which the route is being advertised shares a common subnet with the next hop address. This is known as a "first party" next hop. A BGP speaker can advertise to an external peer an interface of any internal peer router in the next hop component, provided the external peer to which the route is being advertised shares a common The QOS_NLRI attribute July 2000 subnet with the next hop address. This is known as a "third party" next hop information. A BGP speaker can advertise any external peer router in the next hop component, provided that the Network Layer address of this border router was learned from an external peer, and the external peer to which the route is being advertised shares a common subnet with the next hop address. This is a second form of "third party" next hop information. Normally the next hop information is chosen such that the shortest available path will be taken. A BGP speaker must be able to support disabling advertisement of third party next hop information to handle imperfectly bridged media or for reasons of policy. A BGP speaker must never advertise an address of a peer to that peer as a next hop, for a route that the speaker is originating. A BGP speaker must never install a route with itself as the next hop. When a BGP speaker advertises the route to an internal peer, the advertising speaker should not modify the next hop information associated with the route. When a BGP speaker receives the route via an internal link, it may forward packets to the next hop address if the address contained in the attribute is on a common subnet with the local and remote BGP speakers. A BGP UPDATE message that carries the QOS_NLRI MUST also carry the ORIGIN and the AS_PATH attributes (both in EBGP and in IBGP exchanges). Moreover, in IBGP exchanges such a message MUST also carry the LOCAL_PREF attribute. If such a message is received from an external peer, the local system shall check whether the leftmost AS in the AS_PATH attribute is equal to the autonomous system number of the peer than sent the message. If that is not the case, the local system shall send the NOTIFICATION message with Error Code UPDATE Message Error, and the Error Subcode set to Malformed AS_PATH. An UPDATE message that carries no NLRI, other than the one encoded in the QOS_NLRI attribute, should not carry the NEXT_HOP attribute. If such a message contains the NEXT_HOP attribute, the BGP speaker that receives the message should ignore this attribute. 6. Use of Capabilities Advertisement with BGP-4 A BGP speaker that uses the QOS_NLRI attribute SHOULD use the Capabilities Advertisement procedures, as defined in [RFC-2842], so that it might be able to determine if it can use such an attribute with a particular peer. The fields in the Capabilities Optional Parameter are defined as follows: - The Capability Code field is set to N (127 < N < 256, when considering the "Private Use" range, as specified in [RFC-2434]), while the Capability Length field is set to "1". The QOS_NLRI attribute July 2000 - The Capability Value field is a one-octet field, encoded the same way as the QOS Information Code field of the QOS_NLRI attribute. 7. IANA Considerations Section 5 of this draft documents an optional transitive BGP-4 attribute named "QOS_NLRI" whose type value will be assigned by IANA. To be completed. 8. Security considerations This additional BGP-4 attribute specification does not change the underlying security issues inherent in the existing BGP-4 protocol specification [RFC-2385]. 9. References [RFC-1771] Y. Rekhter, T. Li, "A Border Gateway Protocol 4 (BGP-4)", RFC 1771, March 1995. [RFC-2026] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996. [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997 [RFC-2205] R. braden et al., "Resource ReSerVation Protocol (RSVP) - Version 1 Functional Specification", RFC 2205, September 1997. [RFC-2385] A. Heffernan, "Protection of BGP sessions via the TCP MD5 Signature Option", RFC 2385, August 1998. [RFC-2434] T. Narten, H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", RFC 2434, October 1998. [RFC-2475] S. Blake et al., "An Architecture for Differentiated Services", RFC 2475, December 1998. [RFC-2597] J. Heinanen et al., " Assured Forwarding PHB Group", RFC 2597, June 1999. [RFC-2842] R. Chandra, J. Scudder, "Capabilities Advertisement with BGP-4", RFC 2842, May 2000. 10. Author's address Christian Jacquenet France Telecom R & D 42, rue des Coutures BP 6243 14066 Caen cedex 04 France Phone : + 33 2 31 75 94 28 Fax : + 33 2 31 73 56 26 Email : christian.jacquenet@francetelecom.fr 11. Full copyright statement Copyright (C) The Internet Society (2000). All Rights Reserved. The QOS_NLRI attribute July 2000 This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.