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Versions: (draft-yi-manet-olsrv2-multipath) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 RFC 8218

Network Working Group                                              J. Yi
Internet-Draft                                  LIX, Ecole Polytechnique
Intended status: Experimental                                 B. Parrein
Expires: January 3, 2016                            University of Nantes
                                                            July 2, 2015


   Multi-path Extension for the Optimized Link State Routing Protocol
                           version 2 (OLSRv2)
                  draft-ietf-manet-olsrv2-multipath-05

Abstract

   This document specifies a multi-path extension for 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
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   This Internet-Draft will expire on January 3, 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
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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as



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   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Motivation and Experiments to Be Conducted . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Applicability Statement  . . . . . . . . . . . . . . . . . . .  5
   4.  Protocol Overview and Functioning  . . . . . . . . . . . . . .  6
   5.  Parameters and Constants . . . . . . . . . . . . . . . . . . .  7
     5.1.  Router Parameters  . . . . . . . . . . . . . . . . . . . .  7
   6.  Packets and Messages . . . . . . . . . . . . . . . . . . . . .  7
     6.1.  HELLO and TC messages  . . . . . . . . . . . . . . . . . .  8
       6.1.1.  SOURCE_ROUTE TLV . . . . . . . . . . . . . . . . . . .  8
     6.2.  Datagram . . . . . . . . . . . . . . . . . . . . . . . . .  8
       6.2.1.  Source Routing Header in IPv4  . . . . . . . . . . . .  8
       6.2.2.  Source Routing Header in IPv6  . . . . . . . . . . . .  8
   7.  Information Bases  . . . . . . . . . . . . . . . . . . . . . .  9
     7.1.  SR-OLSRv2 Router Set . . . . . . . . . . . . . . . . . . .  9
     7.2.  Multi-path Routing Set . . . . . . . . . . . . . . . . . .  9
   8.  Protocol Details . . . . . . . . . . . . . . . . . . . . . . . 10
     8.1.  HELLO and TC Message Generation  . . . . . . . . . . . . . 10
     8.2.  HELLO and TC Message Processing  . . . . . . . . . . . . . 10
     8.3.  Datagram Processing at the MP-OLSRv2 Originator  . . . . . 10
     8.4.  Multi-path Dijkstra Algorithm  . . . . . . . . . . . . . . 11
     8.5.  Datagram Forwarding  . . . . . . . . . . . . . . . . . . . 12
   9.  Configuration Parameters . . . . . . . . . . . . . . . . . . . 13
   10. Implementation Status  . . . . . . . . . . . . . . . . . . . . 14
     10.1. Multi-path extension based on nOLSRv2  . . . . . . . . . . 14
     10.2. Multi-path extension based on olsrd  . . . . . . . . . . . 14
     10.3. Multi-path extension based on umOLSR . . . . . . . . . . . 15
   11. Security Considerations  . . . . . . . . . . . . . . . . . . . 15
   12. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
     12.1. Expert Review: Evaluation Guidlines  . . . . . . . . . . . 16
     12.2. Message TLV Types  . . . . . . . . . . . . . . . . . . . . 16
   13. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 16
   14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     14.1. Normative References . . . . . . . . . . . . . . . . . . . 17
     14.2. Informative References . . . . . . . . . . . . . . . . . . 17
   Appendix A.  Examples of Multi-path Dijkstra Algorithm . . . . . . 18
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20









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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 a 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 when appropriate 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 forwarding
   reliability and load balancing.

   The Multi-path OLSRv2 (MP-OLSRv2) specified in this document uses
   multi-path Dijkstra algorithm by default to explore multiple disjoint
   paths from a source router to a destination router 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.

1.1.  Motivation and Experiments to Be Conducted

   This document is an experimental extension of OLSRv2 that can
   increase the data forwarding reliability in dynamic and high-load
   MANET scenarios by transmitting datagrams over multiple disjoint
   paths using source routing.  This mechanism is used because:

   o  Disjoint paths can avoid single route failures.

   o  Transmitting datagrams through parallel paths can increase
      aggregated throughput and provide load balancing.

   o  Certain scenarios require some routers must (or must not) be used.

   o  By having control of the paths at the source, the delay can be
      provisioned.

   o  A very important application of this extension is combination with
      Forward Error Correction (FEC) coding.  Because the packet drop is
      normally continuous in a path (for example, due to route failure),
      FEC coding is less effective in single path routing protocols.  By
      providing multiple disjoint paths, the application of FEC coding
      with multi-path protocol is more resilient to routing failures.




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   While existed deployments, running code and simulations have proven
   the interest of multi-path extension for OLSRv2 in certain networks,
   more experiments and experiences are still needed to understand the
   mechanisms of the protocol.  The multi-path extension for OLSRv2 is
   expected to be revised and improved to the Standard Track, once
   sufficient operational experience is obtained.  Other than general
   experiences including the protocol specification, interoperability
   with original OLSRv2 implementations, the experiences in the
   following aspects are highly appreciated:

   o  Optimal values for the number of multiple paths (NUMBER_OF_PATHS)
      to be used.  This depends on the network topology and router
      density.

   o  Optimal values for the cost functions.  Cost functions are applied
      to punish the costs of used links and nodes so as to obtain
      disjoint paths.  What kind of disjointness is desired (node-
      disjoint or link-disjoint) may depends on the layer 2 protocol
      used, and can be achieved by setting different sets of cost
      functions.

   o  Use of other metrics other than hop-count.  This multi-path
      extension can be used not only for hop-count metric type, but also
      other metric types that meet the requirement of OLSRv2, such as
      [I-D.ietf-manet-olsrv2-dat-metric].  The metric type used has also
      co-relation with the choice of cost functions as indicated in the
      previous bullet.

   o  Optimal choice of "key" routers for loose source routing.  In some
      cases, loose source routing is used to reduce overhead or for
      interoperability with OLSRv2 routers.  Other than the basic rules
      defined in the following of this document, optimal choices of
      routers to put in the loose source routing header can be further
      studied.

   o  Different path-selection schedulers.  By default, Round-Robin
      scheduling is used to select a path to be used for a datagram.  In
      some scenarios, weighted scheduling can be considered: for
      example, the paths with lower costs (higher path quality) can
      transfer more datagrams compared to paths with higher costs.

   o  The impacts of the delay variation due to multi-path routing.
      [RFC2991] brings out some concerns of multi-path routing,
      especially variable latencies.  Although current experiments
      result show that multi-path routing can reduce the jitter in
      dynamic scenarios, some transport protocols or applications may be
      sensitive to the datagram re-ordering.




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   o  The disjoint multi-path protocol has interesting application with
      Forward Error Correction (FEC) Coding, especially for services
      like video/audio streaming.  The combination of FEC coding
      mechanisms and this extension is thus encouraged.  By applying FEC
      coding, the issue of packet re-ordering can be alleviated.

   o  Other algorithms to obtain multiple paths, other than the default
      Multi-path Dijkstra algorithm introduced in this specification.

   o  In addition to IP source routing based approach, it can be
      interesting to try multi-path routing in MANET using label-
      switched flow in the future.

   o  The use of multi-topology information.  By using
      [I-D.ietf-manet-olsrv2-multitopology], multiple topologies using
      different metric types can be obtained.  It is encouraged to
      experiment the use of multiple metrics for building multiple paths
      also.


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
   from a source router to a destination router.

   MP-OLSRv2 is specially designed for networks with dynamic topology
   and low data rate links.  By providing multiple paths, higher
   aggregated throughput can be obtained, and the routing process is



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   more robust to packet loss.

   In a router supporting MP-OLSRv2, MP-OLSRv2 does not necessarily
   replace OLSRv2 completely.  The extension can be applied for certain
   applications that are suitable for multi-path routing (mainly video
   or audio streams), based on the information such as DiifServ Code
   Point [RFC2474].

   Compared to OLSRv2, this extension does not introduce new message
   type in the air.  A new Message TLV type is introduced to identify
   the routers that support forwarding based on source route header.  It
   is interoperable with OLSRv2 implementations that do not have this
   extension.

   MP-OLSRv2 forwards datagrams using the source routing header.
   Depending on the IP version used, the source routing header is
   formatted according to [RFC0791] or [RFC6554].


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.

   In addition, the MP-OLSRv2 Routing Process identifies the routers
   that support source routing by adding a new Message TLV in HELLO and
   TC messages.  Based on the above information acquired, every MP-
   OLSRv2 Routing Process is aware of a reduced topology map of the
   network and the routers supporting source routing.

   A multi-path algorithm is invoked on demand, i.e., only when there is
   datagram to be sent from the source to the destination, and there is
   no available routing tuple in the Multi-path Routing Set. 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 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 (MAY be Round-Robin, or other
   scheduling algorithms).  The path information is stored in the



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   datagram header as source routing header.

   All the intermediate routers are listed in the source routing header
   (SRH), unless there are routers that do not support source-route
   forwarding in the paths, or the paths are too long to be fully stored
   in the SRH -- in which case, loose source routing is used.  The
   intermediate routers listed in the SRH read the SRH and forward the
   datagram to the next hop as indicated in the SRH.


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 be 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 that 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.

   SR_OLSR_HOLD_TIME  It is the minimal time that a SR-OLSRv2 Router
      Tuple SHOULD be kept in the SR-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.






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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, a new Message TLV
   type is defined, to identify the originator of the HELLO or TC
   message that supports source route forwarding.  The new Message TLV
   type is introduced for the interoperability between OLSRv2 and MP-
   OLSRv2: only the routers supporting source-route forwarding can be
   used in the source routing header of a datagram, because adding an
   router that does not understand the source routing header will cause
   routing failure.

6.1.1.  SOURCE_ROUTE TLV

   SOURCE_ROUTE TLV is a Message TLV that signals the message is
   generated by a router that supports source-route forwarding.  It can
   be an MP-OLSRv2 Routing Process, or an OLSRv2 Routing Process that
   support source-route forwarding.  The SOURCE_ROUTE TLV does not
   include any value.

   Every HELLO or TC message generated by a MP-OLSRv2 Routing Process
   MUST have one SOURCE_ROUTE TLV.

   Every HELLO or TC message generate by a OLSRv2 Routing Process MAY
   have one SOURCE_ROUTE TLV, if the OLSRv2 Routing Process supports
   source-route forwarding, and is willing to join the source route
   generated by other MP-OLSRv2 Routing Processes.  The existence of
   SOURCE_ROUTE TLV MUST be consistent for a specific OLSRv2 Routing
   Process, i.e., either it adds SOURCE_ROUTE TLV to all its HELLO/TC
   messages, or it does not add SOURCE_ROUTE TLV to any HELLO/TC
   message.

6.2.  Datagram

6.2.1.  Source Routing Header in IPv4

   In IPv4 [RFC0791] networks, the MP-OLSRv2 routing process employs
   loose source routing header, 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.



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   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.  SR-OLSRv2 Router Set

   The SR-OLSRv2 Router Set records the routers that supports source-
   route forwarding.  It can be routers that run MP-OLSRv2 Routing
   Process, or OLSRv2 Routing Process with source-route forwarding
   support.  It consists of SR-OLSRv2 Router Tuples:

   (SR_OLSR_addr, SR_OLSR_valid_time)

   where:

   SR_OLSR_addr -   it is the network address of the router that
      supports source-route forwarding;

   SR_OLSR_valid_time -   it is the time until which the SR-OLSRv2
      Router Tuples is considered valid.

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:



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   (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 routers 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 a source router to a 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 are 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 TLV with Type := SOURCE_ROUTE MUST be added to the
   message.

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 Message TLV
   with Type := SOURCE_ROUTE, create or update (if the tuple exists
   already) the SR-OLSR Router Tuple with

   o  SR_OLSR_addr = originator of the HELLO or TC message

   and set the SR_OLSR_valid_time := current_time + SR_OLSR_HOLD_TIME.

8.3.  Datagram Processing at the MP-OLSRv2 Originator

   When the MP-OLSRv2 routing process receives a datagram from upper
   layers or interfaces connecting other routing domains, find the
   Multi-path Routing Tuple where:

   o  MR_dest_addr = destination of the datagram, and




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   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 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 as source routing header, following the
   rules:

   o  Only the addresses exist in SR-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.

   o  The routers with higher priority (such as higher routing
      willingness) are preferred.

   o  The routers that are considered not appropriate for forwarding
      indicated by external policies should be avoided.

8.4.  Multi-path Dijkstra Algorithm

   A multi-path algorithm is invoked when there is no available Multi-
   path Routing Tuple to a desired destination d to obtain the multiple
   paths.  This section introduces Multi-path Dijkstra Algorithm as a
   default mechanism.  It tries to obtain disjoint paths when
   appropriate, but does not guarantee strict disjoint paths.  The
   rationale is explained in Appendix A.

   The use of other algorithms is not prohibited, as long as they can
   provide a full path from the source to the destination router.  Using
   different multi-path algorithms will not impact the interoperability.

   The general principle of the Multi-path Dijkstra 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 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



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   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 are 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 Destination
   Address field of the IP header is first compared to the addresses of
   the local interfaces.  If a matching local address if found, the
   datagram is processed from Step 1 to Step 4 as follows.  Or else, the
   datagram is processed from Step 3 to Step 4.

   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.  If no next source address is
       found, the forwarding process is finished.

   2.  Swap Address[i] and destination address in the IP header.





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   3.  If the Destination Address of the IP header belongs to one of the
       router's 1-hop symmetric neighbors, the datagram is forwarded to
       the neighbor router.  Or else:

   4.  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  MP_OLSR_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=fe<fp: paths tend to be link disjoint;

   o  if id<fe=fp: paths tend to be node-disjoint;

   o  if id<fe<fp: paths also tend to be node-disjoint, but when is not
      possible they tend to be arc disjoint.






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10.  Implementation Status

   This section records the status of known implementations of the
   protocol defined by this specification at the time of posting of this
   Internet-Draft, and based on a proposal described in [RFC6982].  The
   description of implementations in this section is intended to assist
   the IETF in its decision processes in progressing drafts to RFCs.
   Please note that the listing of any individual implementation here
   does not imply endorsement by the IETF.  Furthermore, no effort has
   been spent to verify the information presented here that was supplied
   by IETF contributors.  This is not intended as, and must not be
   construed to be, a catalog of available implementations or their
   features.  Readers are advised to note that other implementations may
   exist.

   According to [RFC6982], "this will allow reviewers and working groups
   to assign due consideration to documents that have the benefit of
   running code, which may serve as evidence of valuable experimentation
   and feedback that have made the implemented protocols more mature.
   It is up to the individual working groups to use this information as
   they see fit".

   Until April 2014, there are 3 open source implementations of the
   protocol specified in this document, for both testbed and simulation
   use.

10.1.  Multi-path extension based on nOLSRv2

   The implementation is conducted by University of Nantes, France, and
   is based on Niigata University's nOLSRv2 implementation.  It is an
   open source implementation.  The code is available at
   https://github.com/yijiazi/mpolsr_qualnet and
   http://jiaziyi.com/index.php/research-projects/mp-olsr .

   It can be used for Qualnet simulations, and be exported to run in
   testbed.  All the specification is implemented in this
   implementation.

   Implementation experience and test data can be found at [ADHOC11].

10.2.  Multi-path extension based on olsrd

   The implementation is conducted under SEREADMO (Securite des Reseaux
   Ad Hoc & Mojette) project, and supported by French research agency
   (RNRT2803).  It is based on olsrd (http://www.olsr.org/)
   implementation, and is open sourced.  The code is available at
   https://github.com/yijiazi/mpolsr_testbed and
   http://jiaziyi.com/index.php/research-projects/sereadmo .



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   The implementation is for testing the specification in the field.
   All the specification is implemented in this implementation.

   Implementation experience and test data can be found at [ADHOC11].

10.3.  Multi-path extension based on umOLSR

   The implementation is conducted by University of Nantes, France, and
   is based on um-olsr implementation
   (http://masimum.inf.um.es/fjrm/development/um-olsr/).  The code is
   available at https://github.com/yijiazi/mpolsr_ns2 and
   http://jiaziyi.com/index.php/research-projects/mp-olsr under GNU GPL
   license.

   The implementation is just for network simulation for NS2 network
   simulator.  All the specification is implemented in this
   implementation.

   Implementation experience and test data can be found at [WCNC08].


11.  Security Considerations

   As an extension of [RFC7181], the security considerations and
   security architecture illustrated in [RFC7181] are applicable to this
   MP-OLSRv2 specification.

   The implementations without security mechanisms are vulnerable to
   threats discussed in [I-D.ietf-manet-olsrv2-sec-threats].  As
   [RFC7181], a conformant implementation of MP-OLSRv2 MUST, at minimum,
   implement the security mechanisms specified in [RFC7183] to provide
   integrity and replay protection of routing control messages.

   Compared to OLSRv2, the use of source routing header in this
   specification introduces vulnerabilities related to source routing
   attacks, which include bypassing filtering devices, bandwidth
   exhaustion of certain routers, etc.  Those attacks are discussed in
   Section 5.1 of [RFC6554] and [RFC5095].  To make sure that the
   influence is limited to the OLSRv2/MP-OLSRv2 routing domain, the
   source routing header MUST be used only in the current routing
   domain.


12.  IANA Considerations

   This section adds one new Message TLV, allocated as a new Type
   Extension to an existing Message TLV.




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   This specification assumes that the TLV renaming specified in
   [I-D.ietf-manet-tlv-naming] has been carried out.

12.1.  Expert Review: Evaluation Guidlines

   For the registry where an Expert Review is required, the designated
   expert SHOULD take the same general recommendations into
   consideration as are specified by [RFC5444] and
   [I-D.ietf-manet-tlv-naming].

12.2.  Message TLV Types

   This specification updates the Message Type 7 by adding the new Type
   Extension SOURCE_ROUTE, as illustrated in Table 1.

   +-----------+--------------+------------------------+---------------+
   |    Type   |     Name     |       Description      | Reference     |
   | Extension |              |                        |               |
   +-----------+--------------+------------------------+---------------+
   |    TBD    | SOURCE_ROUTE |      Indicates the     | This          |
   |           |              |    originator of the   | specification |
   |           |              |    message supports    |               |
   |           |              |      source route      |               |
   |           |              | forwarding.  No value. |               |
   |  TBD-223  |              |       Unassigned       |               |
   |  224-255  |              |      Reserved for      |               |
   |           |              |    Experimental Use    |               |
   +-----------+--------------+------------------------+---------------+

      Table 1: SOURCE_ROUTE type for RFC 5444 Type 7 Message TLV Type
                                Extensions


13.  Acknowledgments

   The authors would like to thank Sylvain David, Asmaa Adnane, Eddy
   Cizeron, Salima Hamma, Pascal Lesage and Xavier Lecourtier for their
   efforts in developing, implementing and testing the specification.
   The authors also appreciate valuable comments and discussions from
   Thomas Clausen, Ulrich Herberg, Justin Dean, Geoff Ladwig, Henning
   Rogge and Christopher Dearlove.


14.  References







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14.1.  Normative References

   [I-D.ietf-manet-tlv-naming]
              Dearlove, C. and T. Clausen, "TLV Naming in the MANET
              Generalized Packet/Message Format",
              draft-ietf-manet-tlv-naming-05 (work in progress),
              June 2015.

   [RFC0791]  Postel, J., "Internet Protocol", STD 5, RFC 791,
              September 1981.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5444]  Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
              "Generalized Mobile Ad Hoc Network (MANET) Packet/Message
              Format", RFC 5444, February 2009.

   [RFC6130]  Clausen, T., Dearlove, C., and J. Dean, "Mobile Ad Hoc
              Network (MANET) Neighborhood Discovery Protocol (NHDP)",
              RFC 6130, April 2011.

   [RFC6554]  Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6
              Routing Header for Source Routes with the Routing Protocol
              for Low-Power and Lossy Networks (RPL)", RFC 6554,
              March 2012.

   [RFC7181]  Clausen, T., Dearlove, C., Jacquet, P., and U. Herberg,
              "The Optimized Link State Routing Protocol Version 2",
              RFC 7181, April 2014.

   [RFC7183]  Herberg, U., Dearlove, C., and T. Clausen, "Integrity
              Protection for the Neighborhood Discovery Protocol (NHDP)
              and Optimized Link State Routing Protocol Version 2
              (OLSRv2)", RFC 7183, April 2014.

14.2.  Informative References

   [ADHOC11]  Yi, J., Adnane, A-H., David, S., and B. Parrein,
              "Multipath optimized link state routing for mobile ad hoc
              networks", In Elsevier Ad Hoc Journal, vol.9, n. 1, 28-47,
              January, 2011.

   [I-D.ietf-manet-olsrv2-dat-metric]
              Rogge, H. and E. Baccelli, "Packet Sequence Number based
              directional airtime metric for OLSRv2",
              draft-ietf-manet-olsrv2-dat-metric-05 (work in progress),
              April 2015.



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   [I-D.ietf-manet-olsrv2-multitopology]
              Dearlove, C. and T. Clausen, "Multi-Topology Extension for
              the Optimized Link State Routing Protocol version 2
              (OLSRv2)", draft-ietf-manet-olsrv2-multitopology-05 (work
              in progress), February 2015.

   [I-D.ietf-manet-olsrv2-sec-threats]
              Clausen, T., Herberg, U., and J. Yi, "Security Threats for
              the Optimized Link State Routing Protocol version 2
              (OLSRv2)", draft-ietf-manet-olsrv2-sec-threats-00 (work in
              progress), February 2015.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

   [RFC2474]  Nichols, K., Blake, S., Baker, F., and D. Black,
              "Definition of the Differentiated Services Field (DS
              Field) in the IPv4 and IPv6 Headers", RFC 2474,
              December 1998.

   [RFC2501]  Corson, M. and J. Macker, "Mobile Ad hoc Networking
              (MANET): Routing Protocol Performance Issues and
              Evaluation Considerations", RFC 2501, January 1999.

   [RFC2991]  Thaler, D. and C. Hopps, "Multipath Issues in Unicast and
              Multicast Next-Hop Selection", RFC 2991, November 2000.

   [RFC5095]  Abley, J., Savola, P., and G. Neville-Neil, "Deprecation
              of Type 0 Routing Headers in IPv6", RFC 5095,
              December 2007.

   [RFC6982]  Sheffer, Y. and A. Farrel, "Improving Awareness of Running
              Code: The Implementation Status Section", RFC 6982,
              July 2013.

   [WCNC08]   Yi, J., Cizeron, E., Hamma, S., and B. Parrein,
              "Simulation and performance analysis of MP-OLSR for mobile
              ad hoc networks", In Proceeding of IEEE Wireless
              Communications and Networking Conference, 2008.


Appendix A.  Examples of Multi-path Dijkstra Algorithm

   This appendix gives two examples of multi-path Dijkstra algorithm.

   A network topology is depicted in Figure 1.





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                               .-----2-----.
                              /     / \     \
                             /     /   \     \
                            1     /     \     5
                             \   /       \   /
                              \ /         \ /
                               3-----------4


                                 Figure 1

   The initial cost of all the links is set to 1.  The incremental
   functions fp and fe are defined as fp(c)=4c and fe(c)=2c in this
   example.  Two paths from node 1 to node 5 are demanded.

   On the first run of the Dijkstra algorithm, the shortest path 1->2->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.

   As mentioned in Section 8.4, the Multi-path Dijkstra Algorithm does
   not guarantee strict disjoint path to avoid choosing inferior paths.
   For example, given the topology in Figure 2, two paths from node S to
   D are desired.

   If a algorithm tries to obtain strict disjoint paths, the two paths
   obtained will be S--B--D and S--50 hops--D, which are extremely
   unbalanced.  It is undesired because it will cause huge delay
   variance between the paths.  By using the Multi-path Dijkstra
   algorithm, which is based on the punishing scheme, S--B--D and
   S--B--C--D will be obtained.

                             ---50 hops-------
                            /                 \
                           /                   \
                           S----B--------------D
                                 \           /
                                  \---C-----/




                                 Figure 2



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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





























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