Internet Draft Kaouthar Sethom INT-France Document: draft-sethom-dynamic-router- Sidi-Mohammed selection-00.txt Senouci FRANCE TELECOM Expires: January 2006 Hossam Afifi INT-France July 2005 Dynamic router selection Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. This document is an Internet-Draft and is NOT offered in accordance with Section 10 of RFC2026, and the author does not provide the IETF with any rights other than to publish as an Internet-Draft. 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 Sethom Expires - January 2006 [Page 1] Dynamic router selection July 2005 In a network topology where the host has multiple routers on its Default Router List, it is important to select the most suitable one according to nodeÆs application requirements. This document describes an extension to router advertisement message [RFC 1256, RFC 2461] for dynamic router selection. This new functionality is implemented in routers with additional capabilities. 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 [i]. Table of Contents 1. Introduction...................................................2 2. Terminology....................................................2 3. Protocol Overview..............................................3 3.1 Message Formats............................................4 3.1.1 ICMP Router Advertisement Message 4 3.1.2 IPv6 Router Advertisement Message 6 Security Considerations...........................................8 References........................................................8 Author's Addresses................................................9 1. Introduction The core of the next generation infrastructure is expected to be the IP based multi-service network that provides connectivity and transport via any access technology, including optical fibre, wireless local area networks (WLAN), 3G systems and future access technologies. Since each system may be different in terms of QoS capabilities, availability (coverage), capacity and price; a node with a list of default routers must be able to choose the most suitable one in terms of offered QoS. As current router discovery protocols do not offer such opportunity, we describe here an optional extension to router discovery process to support dynamic gateway selection. Each router will be able to broadcast ôfreshö informations about its offered QoS. This improves the ability of nodes to choose an appropriate router for a destination. 2. Terminology Sethom Expires - January 2006 [Page 2] Dynamic router selection July 2005 - Router Egress interface: One of the routerÆs interfaces used to forward packets upstream to the rest of the Internet. - Router Ingress interface: one of the routerÆs interfaces used to forward packets downstream to the nodes inside a subnet. 3. Protocol Overview In this section, we describe the dynamic gateway selection process that is designed to work in the case of IPv4 as well as in the case of IPv6 addressing system. Traditionally, nodes on a LAN learn about default routers by receiving Router Advertisements [1,2]. Each router periodically multicasts a Router Advertisement from each of its multicast interfaces, announcing the IP address(es) of that interface. Delivery of a packet to another subnetwork requires that the packet be sent to a router on the same subnetwork as the sender for forwarding to the ultimate destination. Since the only router known to the end system is the default gateway, this would be the router used. Routers, on the other hand, learn through their router-to- router routing protocols of all other routers that they can reach and that provide the best path to each possible destination. If another router on the same subnetwork as the sender has a better route to the desired destination, the router initially receiving the packet would forward the original packet along the best path available. It would also send a re-direct packet back to the sending end system, informing it of the better router available for that destination. Depending upon the sophistication of the protocol implementation on the sending end system, that new router information might be remembered for future use with packets destined to the same destination, or it might be ignored. Either way, the off-network packets would be delivered correctly. A Router Advertisement can includes a "preference field" [1,3] for each advertised router address. When a node must choose a default router, it is expected to choose from those router addresses that have the highest preference level. These preference values are not automatically derived from routing table, they are generally pre-configured by the network administrator to encourage or discourage the use of particular routers as default routers. Changes in the availability or characteristics of some links - such as congestion - can result in a situation, where the user wants to move already established traffic flows from one path to another. ôFreshö information on the routersÆ egress interfaces characteristics should then always be available to the application Sethom Expires - January 2006 [Page 3] Dynamic router selection July 2005 layers, so that they can dynamically adapt to such changes and choose the best available router. To thatÆs end, we propose to add a new option field ôDynamic router selection (DRS)ö to the router advertisement message that will contain information about routerÆs interfaces characteristics such as throughput, type... At each node in the network, all received router advertisement packets (with DRS field) are registered in what we called the gateway table. This information repository is re-freshed periodically. This means that entries are deleted as soon as their validity time expires. Each time a host wants to send IP data datagrams, it uses the information on its local gateway table to choose among available router the best one to destination according to its applications requirements or needs. Note that, for nodes that do not support dynamic router selection processing, they simply ignore the DRS field and continue to choose a default router in the traditional way. When a new router advertisement message is received, the host updates its gateway table either by updating an existing entry, or if no entry exists for the gateway address, creating a new entry. 3.1 Message Formats 3.1.1 ICMP Router Advertisement Message Changes to ICMP Router Advertisement Message [RFC 1256] section 3 are 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Num Addrs |Addr Entry Size| Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Router Address[1] | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | DRS option[1] | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Router Address[2] | Sethom Expires - January 2006 [Page 4] Dynamic router selection July 2005 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | DRS option[2] | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | . | | . | ICMP Fields: Type 9 Code 1 to indicate that the IP addresses in the Router address fields refer to reachable networks through this router and is not on-link router interfaces addresses. Num Addrs the number of router addresses advertised in this message. Router Address[i], the address of a network reachable through i = 1..Num Addrs the engress interface i of this router. DRS option [i] characteristics of the routerÆs egress interface i associated with the Address[i]. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Interface Type | Cost | Throughput | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Interface Type This field indicates the technology used by the router Egress interface. Example Bluetooth, 802.11, Ethernet, UMTS... Sethom Expires - January 2006 [Page 5] Dynamic router selection July 2005 Type values can be encoded as follows: 0x00 Ethernet (default) 0x01 Bluetooth 0x10 UMTS 0x11 802.16 à Cost This field indicates the communication cost associated with the use of this interface: high, medium, low. This parameter can be a combination of different metrics such as offered QoS, security issues, price and possibly other preferences. Throughput This field indicates the throughput associated with the router egress interface. 3.1.2 IPv6 Router Advertisement Message Changes to Router Advertisement Message [RFC 2461] section 4.6.2 are 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Prefix Length |L|A|O|Reserved1| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Valid Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Preferred Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | DRS option | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Prefix | Sethom Expires - January 2006 [Page 6] Dynamic router selection July 2005 + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Fields: L 1-bit link flag. When set to 1, indicates that this prefix can be used for on-link determination. When set to zero, indicates that if the field O is set to 1 this prefix can be used for off-link determination. A 1-bit autonomous address-configuration flag. When set indicates that this prefix can be used for autonomous address configuration as specified in [ADDRCONF]. O 1-bit off-link flag. When set, indicates that the router has an egress-interface with this prefix and can be used for off-link determination. DRS option characteristics of the routerÆs egress interface i associated with the prefix announced in the next field. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Interface Type | Cost | Throughput | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Interface Type This field indicates the technology used by the router Egress interface. Example Bluetooth, 802.11, Ethernet, UMTS ... Type values can be encoded as follows: 0x00 Ethernet (default) Sethom Expires - January 2006 [Page 7] Dynamic router selection July 2005 0x01 Bluetooth 0x10 UMTS 0x11 802.16 à Cost This field indicates the communication cost associated with the use of this interface: high, medium, low. This parameter can be a combination of different metrics such as offered QoS, security issues, price and possibly other preferences. Throughput This field indicates the throughput associated with the router egress interface. Prefix An IP address or a prefix of an IP address. The Prefix Length field contains the number of valid leading bits in the prefix. When the bit L is set to zero and O to 1, it indicates the IP address of a network reachable through this router. The Prefix Length field contains the number of valid leading bits in the prefix. The bits in the prefix after the prefix length are reserved and MUST be initialized to zero by the sender and ignored by the receiver. Security Considerations This memo does not specify any security considerations. References Sethom Expires - January 2006 [Page 8] Dynamic router selection July 2005 [1] Stephen E. Deering. ôICMP router discovery messagesö. Internet RFC 1256, September 1991 [2] Narten, T., E. Nordmark, W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)", RFC2461, December 1998. [3] R. Draves, D. Thaler, "Default Router Preferences and More-Specific Routes", draft-ietf-ipv6-router-selection- 07.txt, January 2005 Author's Addresses Kaouthar Sethom INT-France 9 rue charles fourrier 91011 evry cedex France Email: kaouthar.sethom@int-evry.fr Sidi-Mohammed Senouci France T‰l‰com R&D 2, Avenue Pierre Marzin 22307 Lannion Cedex France Email : sidimohammed.senouci@francetelecom.com Hossam Afifi INT-France 9 rue charles fourrier 91011 evry cedex France Email: hassam.afifi@int-evry.fr Copyright (C) The Internet Society (2005) This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET Sethom Expires - January 2006 [Page 9] Dynamic router selection July 2005 ENGINEERING TASK FORCE DISCLAIM 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. Sethom Expires - January 2006 [Page 10]