Network Working Group J. Yi Internet-Draft LIX, Ecole Polytechnique Intended status: Experimental B. Parrein Expires: January 5, 2015 University of Nantes July 4, 2014 Multi-path Extension for the Optimized Link State Routing Protocol version 2 (OLSRv2) draft-yi-manet-olsrv2-multipath-00 Abstract This document specifies a multi-path extension to the Optimized Link State Routing Protocol version 2 (OLSRv2) to discover multiple disjoint paths, so as to improve reliability of the OLSRv2 protocol. The interoperability with OLSRv2 is retained. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as Yi & Parrein Expires January 5, 2015 [Page 1] Internet-Draft Abbreviation July 2014 described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Applicability Statement . . . . . . . . . . . . . . . . . . . 3 4. Protocol Overview and Functioning . . . . . . . . . . . . . . 4 5. Parameters and Constants . . . . . . . . . . . . . . . . . . . 5 5.1. Router Parameters . . . . . . . . . . . . . . . . . . . . 5 6. Packets and Messages . . . . . . . . . . . . . . . . . . . . . 5 6.1. HELLO and TC messages . . . . . . . . . . . . . . . . . . 5 6.1.1. MP_OLSRv2 TLV . . . . . . . . . . . . . . . . . . . . 5 6.2. Datagram . . . . . . . . . . . . . . . . . . . . . . . . . 6 6.2.1. Source Routing Header in IPv4 . . . . . . . . . . . . 6 6.2.2. Source Routing Header in IPv6 . . . . . . . . . . . . 6 7. Information Bases . . . . . . . . . . . . . . . . . . . . . . 6 7.1. MP-OLSRv2 Router Set . . . . . . . . . . . . . . . . . . . 6 7.2. Multi-path Routing Set . . . . . . . . . . . . . . . . . . 7 8. Protocol Details . . . . . . . . . . . . . . . . . . . . . . . 7 8.1. HELLO and TC Message Generation . . . . . . . . . . . . . 7 8.2. HELLO and TC Message Processing . . . . . . . . . . . . . 8 8.3. Datagram Processing at the Originator . . . . . . . . . . 8 8.4. Multi-path Dijkstra Algorithm . . . . . . . . . . . . . . 8 8.5. Datagram Forwarding . . . . . . . . . . . . . . . . . . . 9 9. Configuration Parameters . . . . . . . . . . . . . . . . . . . 10 10. Implementation Status . . . . . . . . . . . . . . . . . . . . 10 10.1. Multi-path extension based on nOLSRv2 . . . . . . . . . . 11 10.2. Multi-path extension based on olsrd . . . . . . . . . . . 11 10.3. Multi-path extension based on umOLSR . . . . . . . . . . . 12 11. Security Considerations . . . . . . . . . . . . . . . . . . . 12 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 12.1. HELLO Message-Type-Specific TLV Type Registries . . . . . 12 12.2. TC Message-Type-Specific TLV Type Registries . . . . . . . 12 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 13.1. Normative References . . . . . . . . . . . . . . . . . . . 13 13.2. Informative References . . . . . . . . . . . . . . . . . . 13 Appendix A. An example of Multi-path Dijkstra Algorithm . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 Yi & Parrein Expires January 5, 2015 [Page 2] Internet-Draft Abbreviation July 2014 1. Introduction The Optimized Link State Routing Protocol version 2 (OLSRv2) [RFC7181] is a proactive link state protocol designed for use in mobile ad hoc networks (MANETs). It generates routing messages periodically to create and maintain a Routing Set, which contains routing information to all the possible destinations in the routing domain. For each destination, there exists an unique Routing Tuple, which indicates the next hop to reach the destination. This document specifies an extension of the OLSRv2 protocol [RFC7181], to provide multiple disjoint paths for a source- destination pair. Because of the characteristics of MANETs [RFC2501], especially the dynamic topology, having multiple paths is helpful for increasing network throughput, improving transmission reliability and load balancing. The Multi-path OLSRv2 (MP-OLSRv2) specified in this document uses multi-path Dijkstra algorithm to explore multiple disjoint paths (or non-disjoint paths if necessary) from source to the destination based on the topology information obtained through OLSRv2, and forward the datagrams in a load-balancing manner using source routing. MP-OLSRv2 is designed to be interoperable with OLSRv2. 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. This document uses the terminology and notation defined in [RFC5444], [RFC6130], [RFC7181]. Additionally, it defines the following terminology: OLSRv2 Routing Process - The routing process based on [RFC7181], without multi-path extension specified in this document. MP-OLSRv2 Routing Process - The routing process based on this specification as an extension to [RFC7181]. 3. Applicability Statement As an extension of OLSRv2, this specification is applicable to MANETs for which OLSRv2 is applicable (see [RFC7181]). It can operate on single, or multiple interfaces, to discover multiple disjoint paths Yi & Parrein Expires January 5, 2015 [Page 3] Internet-Draft Abbreviation July 2014 from a source router to a destination router. MP-OLSRv2 is specially designed for networks with dynamic topology and slow data rate links. By providing multiple paths, higher aggregated bandwidth can be obtained, and the routing process is more robust to packet loss. Compared to OLSRv2, this extension does not introduce new message type in the air, and is interoperable with OLSRv2 implementations that do not have this extension. As an experimental specification, MP-OLSRv2 is encouraged to be applied to Forward Error Correction (FEC), to provide protection against packet loss and/or advanced scheduler that could consider the quality of each path. 4. Protocol Overview and Functioning This specification requires OLSRv2 [RFC7181] to: o Identify all the reachable routers in the network. o Identify a sufficient subset of links in the networks, so that routes can be calculated to all reachable destinations. o Provide a Routing Set containing shortest routes from this router to all destinations. Based on the above information acquired by OLSRv2, the MP-OLSRv2 Routing Process is able to calculate multiple paths to certain destinations based on multi-path Dijkstra algorithm: the Dijkstra algorithm is performed multiple times . In each iteration, the cost of used links are increased (i.e., punished), so that they can be avoided to be chosen in the next iteration. The multi-path Dijkstra algorithm can generate multiple disjoint paths from a source to a destination , and such information is kept in Multi-path Routing Set. The algorithm is invoked on demand, i.e., only when there is data traffic to be sent from the source to the destination, and there is no available routing tuples in the Multi-path Routing Set. The datagram is forwarded based on source routing. When there is a datagram to be sent to a destination, the source router acquires a path from the Multi-path Routing Set (in Round-Robin fashion here) . The path information is stored in the datagram header as source routing header. All the intermediate routers read the source router header and forward the datagram to the next hop. Yi & Parrein Expires January 5, 2015 [Page 4] Internet-Draft Abbreviation July 2014 5. Parameters and Constants In addition to the parameters and constants defined in [RFC7181], this specification uses the parameters and constants described in this section. 5.1. Router Parameters NUMBER_OF_PATHS The number of paths desired by the router. MAX_SRC_HOPS The maximum number of hops allowed to put in the source routing header. fp Incremental function of multi-path Dijkstra algorithm. It is used to increase costs of links belonging to the previously computed path. fe Incremental function of multi-path Dijkstra algorithm. It is used to increase costs of links who lead to routers of the previous computed path. MR_HOLD_TIME It is the minimal time that a Multi-path Routing Tuple SHOULD be kept in the Multi-path Routing Set. MP_OLSR_HOLD_TIME It is the minimal time that a MP-OLSRv2 Router Tuple SHOULD be kept in the MP-OLSRv2 Router Set. 6. Packets and Messages This extension employs the routing control messages HELLO and TC (Topology Control) as defined in OLSRv2 [RFC7181]. To support source routing, a source routing header is added to each datagram routed by this extension. Depending on the IP version used, the source routing header is defined in following of this section. 6.1. HELLO and TC messages HELLO and TC messages used by MP-OLSRv2 Routing Process share the same format as defined in [RFC7181]. In addition, one Message TLV is defined, to identify the originator of the HELLO or TC message is running MP-OLSRv2. 6.1.1. MP_OLSRv2 TLV An MP_OLSRv2 TLV is a Message TLV that signals the message is generated by an MP-OLSRv2 Routing Process. It does not include any value. Yi & Parrein Expires January 5, 2015 [Page 5] Internet-Draft Abbreviation July 2014 Every HELLO or TC message generated by MP-OLSRv2 Routing Process MUST has one MP_OLSRv2 TLV. 6.2. Datagram 6.2.1. Source Routing Header in IPv4 In IPv4 [RFC0791] networks, the MP-OLSRv2 routing process employs loose source routing, as defined in [RFC0791]. It exists as an option header, with option class 0, and option number 3. The source route information is kept in the "route data" field of the loss source route header. 6.2.2. Source Routing Header in IPv6 In IPv6 [RFC2460] networks, the MP-OLSRv2 routing process employs the source routing header as defined in [RFC6554], with IPv6 Routing Type 3. The source route information is kept in the "Addresses" field of the routing header. 7. Information Bases Each MP-OLSRv2 routing process maintains the information bases as defined in [RFC7181]. Additionally, two more information bases are defined for this specification. 7.1. MP-OLSRv2 Router Set The MP-OLSRv2 Router Set recordes the routers running the MP-OLSRv2 Routing Process. It consists of MP-OLSRv2 Router Tuples: (MP_OLSR_addr, MP_OLSR_valid_time) where: MP_OLSR_addr - it is the network address of the router that runs MP-OLSRv2 Routing Process; MP_OLSR_valid_time - it is the time until which the MP-OLSRv2 Router Tuples is considered valid. Yi & Parrein Expires January 5, 2015 [Page 6] Internet-Draft Abbreviation July 2014 7.2. Multi-path Routing Set The Multi-path Routing Set records the full path information of different paths to the destination. It consists of Multi-path Routing Tuples: (MR_dest_addr, MR_valid_time, MR_path_set) where: MR_dest_addr - it is the network address of the destination, either the network address of an interface of a destination router or the network address of an attached network; MR_valid_time - it is the time until which the Multi-path Routing Tuples is considered valid; MP_path_set - it contains the multiple paths to the destination. It consists of Path Tuples. Each Path Tuple is defined as: (PT_cost, PT_address[1], PT_address[2], ..., PT_address[n]) where: PT_cost - the cost of the path to the destination; PT_address[1...n] - the addresses of intermediate router to be visited numbered from 1 to n. 8. Protocol Details This protocol is based on OLSRv2, and extended to discover multiple disjoint paths from the source to the destination router. It retains the basic routing control packets formats and processing of OLSRv2 to obtain topology information of the network. The main differences between OLSRv2 routing process is the datagram processing at the source router and datagram forwarding. 8.1. HELLO and TC Message Generation HELLO and TC messages are generated according to the section 15.1 or section 16.1 of [RFC7181]. A single Message-Type-Specific TLV with Type := MP_OLSRv2 is added to the message. Yi & Parrein Expires January 5, 2015 [Page 7] Internet-Draft Abbreviation July 2014 8.2. HELLO and TC Message Processing HELLO and TC messages are processed according to the section 15.3 and 16.3 of [RFC7181]. For every HELLO or TC message received, if there exists a TLV with Type := MP_OLSRv2, create or update (if the tuple exists already) the MP-OLSR Router Tuple with o MP_OLSR_addr = originator of the HELLO or TC message and set the MP_OLSR_valid_time := current_time + MP_OLSR_HOLD_TIME. 8.3. Datagram Processing at the Originator When the MP-OLSRv2 routing process receives a datagram from upper layers, find the Multi-path Routing Tuple where: o MR_dest_addr = destination of the datagram, and o MR_valid_time < current_time. If a matching Multi-path Routing Tuple is found, a Path Tuple is chosen from the MR_path_set in Round-robin fashion (if there are multiple datagrams to be sent). Or else, the Multi-path Dijkstra Algorithm defined in Section 8.4 is invoked, to generate the desired Multi-path Routing Tuple. The addresses in PT_address[1...n] of the chosen Path Tuple are thus added to the datagram header in order as source routing header, following the rules: o Only the addresses exist in MP-OLSR Router Set can be added to the source routing header. o If the length of the path (n) is greater than MAX_SRC_HOPS, only the key routers in the path are kept. By default, the key routers are uniformly chosen in the path. 8.4. Multi-path Dijkstra Algorithm The Multi-path Dijkstra Algorithm is invoked when there is no available Multi-path Routing Tuple to a desired destination d. The general principle of the algorithm is at step i to look for the shortest path Pi to the destination d. Based on Dijkstra algorithm, the main modification consists in adding two cost functions namely incremental functions fp and fe in order to prevent the next steps to use similar path. fp is used to increase costs of arcs belonging to Yi & Parrein Expires January 5, 2015 [Page 8] Internet-Draft Abbreviation July 2014 the previously path Pi (or which opposite arcs belong to it). This encourages future paths to use different arcs but not different vertices. fe is used to increase costs of the arcs who lead to vertices of the previous path Pi. It is possible to choose different fp and fe to get link-disjoint path or node-disjoint routes as necessary. A recommendation of configuration of fp and fe is given in Section 5. To get NUMBER_OF_PATHS distinct paths, for each path Pi (i = 1, ..., NUMBER_OF_PATHS) do: 1. Run Dijkstra algorithm to get the shortest path Pi for the destination d. 2. Apply cost function fp to the links in Pi. 3. Apply cost function fe to the links who lead to routers used in P. A simple example of Multi-path Dijkstra Algorithm is illustrated in Appendix A. By invoking the algorithm depicted above, NUMBER_OF_PATHS distinct paths is obtained, and added to the Multi-path Routing Set, by creating a Multi-path Routing Tuple with: o MR_dest_addr := destination d o MR_valid_time := current time + MR_HOLD_TIME o Each Path Tuple in the MP_path_set corresponds to a path obtained in multi-path Dijkstra algorithm, with PT_cost := cost of the path to the destination d. 8.5. Datagram Forwarding On receiving a datagram with source routing header, the datagram is processed as follows: 1. Obtain the next source address Address[i] in the source route header. How to obtain the next source address depends on the IP version used. In IPv4, the position of the next source address is indicated by the "pointer" field of the source routing header [RFC0791]. In IPv6, the position is indicated by "Segments Left" field of the source routing header. 2. Swap Address[i] and destination address in the IP header. Yi & Parrein Expires January 5, 2015 [Page 9] Internet-Draft Abbreviation July 2014 3. Forward the datagram to the destination address according to the OLSRv2 Routing Tuple information through R_local_iface_addr where * R_dest_addr = destination address in the IP header 9. Configuration Parameters This section gives default values and guideline for setting parameters defined in Section 5. Network administrator may wish to change certain, or all the parameters for different network scenarios. As an experimental track protocol, the users of this protocol are also encouraged to explore different parameter setting in various network environments, and provide feedback. o NUMBER_OF_PATHS = 3. This parameter defines the number of parallel paths used in datagram forwarding. Setting it to one makes the specification identical to OLSRv2. Setting it to too big value can lead to unnecessary computational overhead and inferior paths. o MAX_SRC_HOPS = 10. o MR_HOLD_TIME = 10 seconds. o fp(c) = 4*c, where c is the original cost of the link. o fe(c) = 2*c, where c is the original cost of the link. The setting of cost functions fp and fc defines the preference of obtained multiple disjoint paths. If id is the identity functions, 3 cases are possible: o if id=fe2->5 with cost 2 is obtained. The incremental function fp is applied to increase the cost of the link 1-2 and 2-5, from 1 to 4. fe is applied to increase the cost of the link 1-3, 2-3, 2-4, 4-5, from 1 to 2. On the second run of the Dijkstra algorithm, the second path 1->3->4->5 with cost 5 is obtained. Yi & Parrein Expires January 5, 2015 [Page 14] Internet-Draft Abbreviation July 2014 Authors' Addresses Jiazi Yi LIX, Ecole Polytechnique 91128 Palaiseau Cedex, France Phone: +33 1 77 57 80 85 Email: jiazi@jiaziyi.com URI: http://www.jiaziyi.com/ Benoit Parrein University of Nantes IRCCyN lab - IVC team Polytech Nantes, rue Christian Pauc, BP50609 44306 Nantes cedex 3 France Phone: +33 (0) 240 683 050 Email: Benoit.Parrein@polytech.univ-nantes.fr URI: http://www.irccyn.ec-nantes.fr/~parrein Yi & Parrein Expires January 5, 2015 [Page 15]