MANET Working Group Sanghyun Ahn Internet Draft University of Seoul Expires: June 13, 2016 December 22, 2015 DSR Extensions for Multipath Routing draft-ahn-manet-multipath-dsr-00.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. This document may not be modified, and derivative works of it may not be created, except to format it for publication as an RFC or to translate it into languages other than English. 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. This Internet-Draft will expire on June 13, 2016. Copyright Notice Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Ahn Expires June 13, 2016 [Page 1] Internet-Draft DSR Extensions for Multipath Routing December 2015 Abstract This document describes how DSR [1] can be extended for the support of MANET multipath routing. Since DSR uses the source routing approach, it can be appropriate for multipath routing. Therefore, in this draft, we describe how we can extend DSR for finding multiple routes from the source to the destination. Table of Contents 1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Extensions on DSR Options Header . . . . . . . . . . . . . . . 3 3.1 Extensions on DSR Route Request Option . . . . . . . . . . . . 4 4. Other Considerations . . . . . . . . . . . . . . . . . . . . . 5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 5 Ahn Expires June 13, 2016 [Page 2] Internet-Draft DSR Extensions for Multipath Routing December 2015 1. Requirements notation 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 [RFC2119]. 2. Introduction The mobile ad hoc network (MANET) is composed of a number of mobile nodes which can communicate with each other through multiple wireless links without the help of a wired infrastructure. Therefore, in the MANET, the route connectivity tends to be very unstable. This route unstability can be mitigated by providing more than one route to a source and destination node pair. In recent years, there have been intensive studies done on multipath routing protocols for the MANET [1]. Also, multipath routing protocols may have the advantage of providing load balancing by distributing data traffic to a number of routes. On the other hand, it may incur more control message overhead to set up multiple routes. The DSR protocol [2] works based on the source routing mechanism and support multiple routes between a pair of the source and the destination nodes by maintaining several routes in the route cache of the source node. That is, DSR basically support multipath routing and the source routing capability makes the support of multipath routing easier. However, in DSR, a route reply (RREP) message with a route information is sent back to the source by an intermediate node with a fresh route to the destination or by the destination itself. By doing this way, the source can collect a random number of the routes to the destination. And this may cause higher route discovery overhead. The route discovery overhead can be reduced by allowing the source to specify the maximum number of routes between the source and the destination and by making the destination to select that number of routes from the routes obtained from the route request (RREQ) messages received at the destination. This type of route selection can be achieved by disabling the C bit in the DSR Route Request option [3] (i.e., the cached route reply capability is disabled) and specifying the number of routes as defined in this document. In this draft, we describe how the DSR Options header has to be extended to support the source to specify the number of routes it needs. 3. Extensions on DSR Options Header Ahn Expires June 13, 2016 [Page 3] Internet-Draft DSR Extensions for Multipath Routing December 2015 3.1 Extensions on DSR Route Request Option The Route Request option in the DSR Options header is extended 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option Type | Opt Data Len | Identification |C| Pt|R| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Target Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Address[1] | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Address[2] | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Address[n] | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ IP fields: the same as described in [2] Route Request fields: the same as described in [3] except for the R bit and the Pt field Pt The maximum allowable number of paths (routes) between the source and the destination which is specified in the Target Address field. The source specifies the value of the Pt field. The number of routes is the value of the Pt field plus 1 (i.e., the value 0 in the Pt field is the default value and implies a single route between the source and the destination). Thus, the maximum allowable number of routes between a pair of source and destination nodes is 4 and this is usually expected to be enough. When the C bit is 1, the value in the Pt field has to be ignored. In other words, the value in the Pt field is meaningful only when the C bit value is 0. When the destination receives an RREQ message with the C bit value of 0 in its Route Request option, it has to send back upto that number of RREP messages to the source. The mechanism to select those routes sent back to the source is out of the scope of this draft. R R bit is a reserved bit for further extension of DSR Route Request option. Ahn Expires June 13, 2016 [Page 4] Internet-Draft DSR Extensions for Multipath Routing December 2015 4. Other Considerations TBD. References [1] M. Tarique, K. E. Tepe, S. Abidi and S. Erfani, "Survey of Multipath Routing Protocols for Mobile Ad Hoc Networks," Journal of Network and Computer Applications, November 2009. [2] D. Johnson, Y. Hu and D. Maltz, "The Dynamic Source Routing Protocol," RFC 4728, February 2007. [3] S. Ahn, "DSR Extensions for the Resolution of Cached Route Reply Implosion," IETF draft-ahn-manet-dsr-crri-00.txt, December 2015. Author's Address Sanghyun Ahn University of Seoul 90, Cheonnong-dong, Tongdaemun-gu Seoul 130-743 Korea Email: ahn@uos.ac.kr Ahn Expires June 13, 2015 [Page 5]