Multi-path Extension for the Optimized Link State Routing Protocol version 2 (OLSRv2)
draft-ietf-manet-olsrv2-multipath-07
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (manet WG) | |
|---|---|---|---|
| Authors | Jiazi Yi , Benoit Parrein | ||
| Last updated | 2016-01-20 | ||
| Replaces | draft-yi-manet-olsrv2-multipath | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | plain text htmlized pdfized bibtex | ||
| Reviews |
INTDIR Telechat review
(of
-12)
Ready with Issues
GENART Last Call review
(of
-12)
Ready with Nits
RTGDIR Telechat review
(of
-12)
Has Nits
|
||
| Stream | WG state | WG Document | |
| Document shepherd | (None) | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ietf-manet-olsrv2-multipath-07
Network Working Group J. Yi
Internet-Draft LIX, Ecole Polytechnique
Intended status: Experimental B. Parrein
Expires: July 23, 2016 University of Nantes
January 20, 2016
Multi-path Extension for the Optimized Link State Routing Protocol
version 2 (OLSRv2)
draft-ietf-manet-olsrv2-multipath-07
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
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/.
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."
This Internet-Draft will expire on July 23, 2016.
Copyright Notice
Copyright (c) 2016 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. 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 July 23, 2016 [Page 1]
Internet-Draft Multi-Path OLSRv2 January 2016
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 . . . . . . . . . . . . . . . . . . 7
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 . . . . . . . . . . . . . . . . . . . . . . 8
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. MPR Selection . . . . . . . . . . . . . . . . . . . . . . 10
8.4. Datagram Processing at the MP-OLSRv2 Originator . . . . . 11
8.5. Multi-path Calculation . . . . . . . . . . . . . . . . . . 11
8.5.1. Requirements of Multi-path Calculation . . . . . . . . 11
8.5.2. Multi-path Dijkstra Algorithm . . . . . . . . . . . . 12
8.6. Datagram Forwarding . . . . . . . . . . . . . . . . . . . 13
9. Configuration Parameters . . . . . . . . . . . . . . . . . . . 13
10. Implementation Status . . . . . . . . . . . . . . . . . . . . 14
10.1. Multi-path extension based on nOLSRv2 . . . . . . . . . . 15
10.2. Multi-path extension based on olsrd . . . . . . . . . . . 15
10.3. Multi-path extension based on umOLSR . . . . . . . . . . . 15
11. Security Considerations . . . . . . . . . . . . . . . . . . . 16
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
12.1. Expert Review: Evaluation Guidlines . . . . . . . . . . . 16
12.2. Message TLV Types . . . . . . . . . . . . . . . . . . . . 17
13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17
14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
14.1. Normative References . . . . . . . . . . . . . . . . . . . 17
14.2. Informative References . . . . . . . . . . . . . . . . . . 18
Appendix A. Examples of Multi-path Dijkstra Algorithm . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
Yi & Parrein Expires July 23, 2016 [Page 2]
Internet-Draft Multi-Path OLSRv2 January 2016
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 to 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 in combination
with Forward Error Correction (FEC) coding. Because the packet
drop is normally bursty 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.
Yi & Parrein Expires July 23, 2016 [Page 3]
Internet-Draft Multi-Path OLSRv2 January 2016
While in existing 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 effects 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 used in the metric functions. Metric functions are
applied to increase the metric of used links and nodes so as to
obtain disjoint paths. What kind of disjointness is desired
(node-disjoint or link-disjoint) may depend on the layer 2
protocol used, and can be achieved by setting different sets of
metric functions.
o Use of other metric types. 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 metric functions as indicated in
the previous bullet point.
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 datagrams. In
some scenarios, weighted scheduling can be considered: for
example, the paths with lower metrics (i.e., higher quality) can
transfer more datagrams compared to paths with higher metrics.
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 experiment
results 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.
Yi & Parrein Expires July 23, 2016 [Page 4]
Internet-Draft Multi-Path OLSRv2 January 2016
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 Different algorithms to obtain multiple paths, other than the
default Multi-path Dijkstra algorithm introduced in this
specification.
o The use of multi-topology information. By using [RFC7722],
multiple topologies using different metric types can be obtained.
It is also encouraged to experiment the use of multiple metrics
for building multiple paths.
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 multi-path 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
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
Yi & Parrein Expires July 23, 2016 [Page 5]
Internet-Draft Multi-Path OLSRv2 January 2016
applications that are suitable for multi-path routing (mainly video
or audio streams), based on the information such as DiffServ 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. For
IPv4 networks, implementation of loose source routing is required
following [RFC0791]. For IPv6 networks, implementation of strict
source routing is required following [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
a 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 (defined in Section 8.5) can generate
multiple disjoint paths from a source to a destination, and such
information is kept 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 (MAY be Round-Robin, or other
scheduling algorithms). The path information is stored in the
datagram header as source routing header.
Yi & Parrein Expires July 23, 2016 [Page 6]
Internet-Draft Multi-Path OLSRv2 January 2016
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. A value set zero means there is no
limitation on the maximum number of hops. In an IPv6 network, it
MUST be set to 0. In an IPv4 network, it MUST be strictly less
than 11.
CUTOFF_RATIO The ratio that defines the maximum metric of a path
compared to the shortest path kept in the OLSRv2 Routing Set. For
example, the metric to a destination is R_metric based on the
Routing Set. Then the maximum metric allowed for a path is
CUTOFF_RATIO * R_metric. CUTOFF_RATIO MUST be strictly greater
than 1.
SR_TC_INTERVAL The maximum time between the transmission of two
successive TC messages by a MP-OLSRv2 Routing Process.
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 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, 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 enabling MP-OLSRv2 as an extension of OLSRv2:
only the routers supporting source-route forwarding can be used in
the source routing header of a datagram, because adding a router that
does not understand the source routing header will cause routing
Yi & Parrein Expires July 23, 2016 [Page 7]
Internet-Draft Multi-Path OLSRv2 January 2016
failure.
6.1.1. SOURCE_ROUTE TLV
SOURCE_ROUTE TLV is a Message TLV signalling that 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
supports 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 exactly one SOURCE_ROUTE TLV.
Every HELLO or TC message generated by an 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
loose 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.
Yi & Parrein Expires July 23, 2016 [Page 8]
Internet-Draft Multi-Path OLSRv2 January 2016
7.1. SR-OLSRv2 Router Set
The SR-OLSRv2 Router Set records the routers that support source-
route forwarding. This includes routers that run MP-OLSRv2 Routing
Process, or OLSRv2 Routing Process with source-route forwarding
support. The set 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_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;
MP_path_set - it contains the multiple paths to the destination.
It consists of a set of Path Tuples.
Each Path Tuple is defined as:
(PT_metric, PT_address[1], PT_address[2], ..., PT_address[n])
where:
PT_metric - the metric of the path to the destination, measured in
LINK_METRIC_TYPE defined in [RFC7181];
PT_address[1...n] - the addresses of intermediate routers to be
visited numbered from 1 to n.
Yi & Parrein Expires July 23, 2016 [Page 9]
Internet-Draft Multi-Path OLSRv2 January 2016
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 messages are generated according to the Section 15.1 of
[RFC7181].
TC message are generated according to the Section 16.1 of [RFC7181].
As least one TC message MUST be generated by an MP-OLSRv2 Routing
Process during SR_TC_INTERVAL.
For both TC and HELLO messages, 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 is 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
o SR_OLSR_valid_time := current_time + SR_OLSR_HOLD_TIME.
8.3. MPR Selection
Each MP-OLSRv2 Routing Process selects routing MPRs and flooding MPRs
following Section 18 of [RFC7181]. In a mixed network with OLSRv2-
only routers, the following considerations apply when calculating
MPRs:
o MP-OLSR routers SHOULD be preferred as routing MPRs.
o The number of routing MPRs that run MP-OLSR Routing Process MUST
be equal or greater than NUMBER_OF_PATHS if there are enough MP-
OLSR symmetric neighbors. Or else, all the MP-OLSR routers are
selected as routing MPRs.
Yi & Parrein Expires July 23, 2016 [Page 10]
Internet-Draft Multi-Path OLSRv2 January 2016
8.4. Datagram Processing at the MP-OLSRv2 Originator
If datagrams without source routing header need to be forwarded using
multiple paths (for example, based on the information of DiffServ
Code Point [RFC2474]), the MP-OLSRv2 routing process will try to find
the Multi-path Routing Tuple where:
o MR_dest_addr = destination of the datagram
If no matching Multi-path Routing Tuple is found, the multi-path
algorithm defined in Section 8.5 is invoked, to calculate the Multi-
path Routing Tuple to the destination. If the calculation does not
return any Multi-path Routing Tuple, the following steps are aborted
and the datagram is forwarded following OLSRv2 routing process.
The Path Tuples of the Multi-path Routing Tuple obtained are applied
to the datagrams using Round-robin scheduling. For example, they are
2 path tuples (Path-1, Path-2) for destination router D. A series of
datagrams (Packet-1, Packet-2, Packet-3, ... etc.) are to be sent
router D. Path-1 is then chosen for Packet-1, Path-2 for Packet-2,
Path-1 for Packet 3, etc.
The addresses in PT_address[1...n] of the chosen Path Tuple are thus
added to the datagram header as the source routing header. For IPv6
networks, strict source routing is used, thus all the intermediate
routers in the path are stored in the source routing header following
[RFC6554]. For IPv4 networks, loose source routing is used, with
following rules:
o Only the addresses that 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. The key routers can be
chosen based on the capacity of the routers (e.g., battery life)
or the router's willingness in forwarding data. If no such
information is available, the key routers are uniformly chosen in
the path.
o The routers that are considered not appropriate for forwarding
indicated by external policies should be avoided.
8.5. Multi-path Calculation
8.5.1. Requirements of Multi-path Calculation
The Multi-path Routing Set maintains the information of multiple
paths the the destination. The tuples are generated based on a
Yi & Parrein Expires July 23, 2016 [Page 11]
Internet-Draft Multi-Path OLSRv2 January 2016
multi-path algorithm.
A multi-path algorithm is invoked when there is no available Multi-
path Routing Tuple to a desired destination to obtain the multiple
paths. For each path to a destination, the algorithm must provide:
o The metric of the path to the destination,
o The list of intermediate routers on the path.
For IPv6 networks, as strict source routing is used, only the routers
that exist in SR-OLSRv2 Router Set are considered in the path
calculation, i.e., only the source-routing supported routers can
exist in the path. After the calculation of multiple paths, the
metric of the shortest path (denoted c) to the destination is
compared to the R_metric of the OLSRv2 Routing Tuple ([RFC7181]) to
the same destination. If the metric c is greater than R_metric *
CUTOFF_RATIO, the multipath routing SHOULD NOT be used, and the
router SHOULD fall back to OLSRv2 Routing Process. This can happen
if there are too much OLSRv2-only routers in the network, and
requiring multipath routing brutally may result in inferior paths.
By invoking the multi-path algorithm, NUMBER_OF_PATHS paths are
obtained and added to the Multi-path Routing Set, by creating a
Multi-path Routing Tuple with:
o MR_dest_addr := destination of the datagram
o A MP_path_set with calculated Path Tuples. Each Path Tuple
corresponds to a path obtained in Multi-path Dijkstra algorithm,
with PT_metric := metric of the calculated path and
PT_address[1...n] := list of intermediate routers.
8.5.2. Multi-path Dijkstra Algorithm
This section introduces Multi-path Dijkstra Algorithm as a default
algorithm. It tries to obtain disjoint paths when appropriate, but
does not guarantee strict disjoint paths. The use of other
algorithms is not prohibited, as long as the requirements described
in Section 8.5.1 are met. 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 P[i] to the destination d. Compared
to the original Dijkstra algorithm, the main modification consists in
adding two incremental functions named metric functions fp and fe in
order to prevent the next steps resulting in similar paths:
Yi & Parrein Expires July 23, 2016 [Page 12]
Internet-Draft Multi-Path OLSRv2 January 2016
o fp(c) is used to increase metrics of arcs belonging to the
previous path P[i-1] (with i>1), where c is the value of the
previous metric. This encourages future paths to use different
arcs but not different vertices.
o fe(c) is used to increase metrics of the arcs who lead to
intermediate vertices (i.e., the source and destination are not
considered) of the previous path P[i-1] (with i>1), where c is the
value of the previous metric.
It is possible to choose different fp and fe to get link-disjoint
paths or node-disjoint paths as desired. A recommendation of
configuration of fp and fe is given in Section 9.
To get NUMBER_OF_PATHS different paths, for each path P[i] (i = 1,
..., NUMBER_OF_PATHS) do:
1. Run Dijkstra algorithm to get the shortest path P[i] for the
destination d.
2. Apply metric function fp to the metric of links (in both
directions) in P[i].
3. Apply metric function fe to the metric of links (in both
directions) that lead to routers used in P[i].
A simple example of Multi-path Dijkstra Algorithm is illustrated in
Appendix A.
8.6. Datagram Forwarding
In IPv4 networks, datagrams are forwarded using loose source routing
as specified in Section 3.1 of [RFC0791].
In IPv6 networks, datagrams are forwarded using strict source routing
as specified in Section 4.2 of [RFC6554].
9. Configuration Parameters
This section gives default values and guideline for setting
parameters defined in Section 5. Network administrators 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.
Yi & Parrein Expires July 23, 2016 [Page 13]
Internet-Draft Multi-Path OLSRv2 January 2016
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
large values may lead to unnecessary computational overhead and
inferior paths.
o MAX_SRC_HOPS := 10, for IPv4 networks. For IPv6 networks, it MUST
be set to 0, i.e., no constraint on maximum number of hops.
o CUTOFF_RATIO := 1.5. It MUST be strictly greater than 1.
o SR_TC_INTERVAL := 10 x TC_INTERVAL. It SHOULD be significantly
greater than TC_INTERVAL to reduce unnecessary TC message
generations.
o SR_OLSR_HOLD_TIME := 3 x SR_TC_INTERVAL
If Multi-path Dijkstra Algorithm is applied:
o fp(c) := 4*c, where c is the original metric of the link.
o fe(c) := 2*c, where c is the original metric of the link.
The setting of metric functions fp and fc defines the preference of
obtained multiple disjoint paths. If id is the identity function,
i.e., fp(c)=c, 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.
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
Yi & Parrein Expires July 23, 2016 [Page 14]
Internet-Draft Multi-Path OLSRv2 January 2016
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 2015, 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 a
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 .
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] and
[GIIS14].
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
Yi & Parrein Expires July 23, 2016 [Page 15]
Internet-Draft Multi-Path OLSRv2 January 2016
http://jiaziyi.com/index.php/research-projects/mp-olsr under GNU GPL
license.
The implementation is 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].
In a mixed network with OLSRv2-only routers, a compromised router can
add SOURCE_ROUTE TLVs in its TC and HELLO messages, which will make
other MP-OLSR Routing Process believes that it supports source
routing. This will increase the the possibility of being chosen as
MPRs and be put into the source routing header. The former will make
it possible to manipulate the flooding of TC messages and the latter
will make the datagram pass through the compromised router.
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].
12. IANA Considerations
This section adds one new Message TLV, allocated as a new Type
Extension to an existing Message TLV.
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].
Yi & Parrein Expires July 23, 2016 [Page 16]
Internet-Draft Multi-Path OLSRv2 January 2016
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. | |
+-----------+--------------+------------------------+---------------+
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, Christopher Dearlove and Marcus Barkowsky.
14. References
14.1. Normative References
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<http://www.rfc-editor.org/info/rfc791>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC5444] Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
"Generalized Mobile Ad Hoc Network (MANET) Packet/Message
Format", RFC 5444, DOI 10.17487/RFC5444, February 2009,
<http://www.rfc-editor.org/info/rfc5444>.
Yi & Parrein Expires July 23, 2016 [Page 17]
Internet-Draft Multi-Path OLSRv2 January 2016
[RFC6130] Clausen, T., Dearlove, C., and J. Dean, "Mobile Ad Hoc
Network (MANET) Neighborhood Discovery Protocol (NHDP)",
RFC 6130, DOI 10.17487/RFC6130, April 2011,
<http://www.rfc-editor.org/info/rfc6130>.
[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,
DOI 10.17487/RFC6554, March 2012,
<http://www.rfc-editor.org/info/rfc6554>.
[RFC7181] Clausen, T., Dearlove, C., Jacquet, P., and U. Herberg,
"The Optimized Link State Routing Protocol Version 2",
RFC 7181, DOI 10.17487/RFC7181, April 2014,
<http://www.rfc-editor.org/info/rfc7181>.
[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, DOI 10.17487/RFC7183, April 2014,
<http://www.rfc-editor.org/info/rfc7183>.
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.
[GIIS14] Macedo, R., Melo, R., Santos, A., and M. Nogueria,
"Experimental performance comparison of single-path and
multipath routing in VANETs", In Global Information
Infrastructure and Networking Symposium (GIIS), 2014 ,
vol. 1, no. 6, pp. 15-19, 2014.
[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-12 (work in progress),
December 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-01 (work in
progress), November 2015.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
Yi & Parrein Expires July 23, 2016 [Page 18]
Internet-Draft Multi-Path OLSRv2 January 2016
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>.
[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,
DOI 10.17487/RFC2474, December 1998,
<http://www.rfc-editor.org/info/rfc2474>.
[RFC2501] Corson, S. and J. Macker, "Mobile Ad hoc Networking
(MANET): Routing Protocol Performance Issues and
Evaluation Considerations", RFC 2501, DOI 10.17487/
RFC2501, January 1999,
<http://www.rfc-editor.org/info/rfc2501>.
[RFC2991] Thaler, D. and C. Hopps, "Multipath Issues in Unicast and
Multicast Next-Hop Selection", RFC 2991, DOI 10.17487/
RFC2991, November 2000,
<http://www.rfc-editor.org/info/rfc2991>.
[RFC5095] Abley, J., Savola, P., and G. Neville-Neil, "Deprecation
of Type 0 Routing Headers in IPv6", RFC 5095,
DOI 10.17487/RFC5095, December 2007,
<http://www.rfc-editor.org/info/rfc5095>.
[RFC6982] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", RFC 6982,
DOI 10.17487/RFC6982, July 2013,
<http://www.rfc-editor.org/info/rfc6982>.
[RFC7722] Dearlove, C. and T. Clausen, "Multi-Topology Extension for
the Optimized Link State Routing Protocol Version 2
(OLSRv2)", RFC 7722, DOI 10.17487/RFC7722, December 2015,
<http://www.rfc-editor.org/info/rfc7722>.
[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.
Yi & Parrein Expires July 23, 2016 [Page 19]
Internet-Draft Multi-Path OLSRv2 January 2016
.-----A-----(2)
(1) / \ \
/ / \ \
S (2) (1) D
\ / \ /
(1) / \ / (2)
B----(3)----C
Figure 1
The capital letters are name of routers. An arbitrary metric with
value between 1 and 3 is used. The initial metrics of all the links
are indicated in the parenthesis. The incremental functions fp and
fe are defined as fp(c)=4c and fe(c)=2c in this example. Two paths
from router S to router D are demanded.
On the first run of the Dijkstra algorithm, the shortest path S->A->D
with metric 3 is obtained.
The incremental function fp is applied to increase the metric of the
link S-A and A-D. fe is applied to increase the metric of the link
A-B and A-C. Figure 2 shows the link metrics after the punishment.
.-----A-----(8)
(4) / \ \
/ / \ \
S (4) (2) D
\ / \ /
(1) / \ / (2)
B----(3)----C
Figure 2
On the second run of the Dijkstra algorithm, the second path
S->B->C->D with metric 6 is obtained.
As mentioned in Section 8.5, the Multi-path Dijkstra Algorithm does
not guarantee strict disjoint path to avoid choosing inferior paths.
For example, given the topology in Figure 3, two paths from node S to
D are desired. On the top of the figure, there is a high cost path
between S and D.
If a algorithm tries to obtain strict disjoint paths, the two paths
obtained will be S--B--D and S--(high cost path)--D, which are
extremely unbalanced. It is undesired because it will cause huge
delay variance between the paths. By using the Multi-path Dijkstra
Yi & Parrein Expires July 23, 2016 [Page 20]
Internet-Draft Multi-Path OLSRv2 January 2016
algorithm, which is based on the punishing scheme, S--B--D and
S--B--C--D will be obtained.
--high cost path-
/ \
/ \
S----B--------------D
\ /
\---C-----/
Figure 3
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 July 23, 2016 [Page 21]