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>Linux Optimized Link State Routing Protocol (OLSR) IPv6
HOWTO</TH
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><H1
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><A
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></A
>1. Introduction</H1
><P
> This document describes the software and procedures to set up
and use Optimized Link State Routing Protocol (OLSR) with IPv6
for Linux.
</P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="WhyAdHoc"
></A
>1.1. Why Ad-Hoc network?</H2
><P
> An English translation of <EM
>ad-hoc</EM
> is <SPAN
CLASS="QUOTE"
>"For a
particular purpose (improvised, made up in an instant)"</SPAN
>
(source: <A
HREF="http://en.wikipedia.org/wiki/List_of_Latin_phrases#A"
TARGET="_top"
>Wikipedia</A
>).
An Ad-hoc network, or <SPAN
CLASS="QUOTE"
>"spontaneous network"</SPAN
>, is
especially useful when dealing with wireless devices in which some
of the devices are part of the network only for the duration of a
communications session and the need for a dynamic network topology
is eminent. A <SPAN
CLASS="QUOTE"
>"Mobile Ad hoc Network"</SPAN
> is usually
called a <EM
>MANET</EM
>.
</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="WhatMANET"
></A
>1.2. What is a MANET?</H2
><P
><SPAN
CLASS="QUOTE"
>"
A MANET consists of mobile platforms (e.g., a router with multiple
hosts and wireless communications devices)--herein simply referred to
as <SPAN
CLASS="QUOTE"
>'nodes'</SPAN
>--which are free to move about
arbitrarily. The nodes may be located in or on airplanes, ships,
trucks, cars, perhaps even on people or very small devices, and
there may be multiple hosts per router. A MANET is an autonomous
system of mobile nodes. The system may operate in isolation, or
may have gateways to and interface with a fixed network."</SPAN
>
--- <A
HREF="http://www.ietf.org/rfc/rfc2501.txt"
TARGET="_top"
>RFC2501:
Mobile Ad hoc Networking (MANET), section 3 (page 3).</A
>
</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="WhatOLSR"
></A
>1.3. What is Optimized Link State Routing (OLSR)?</H2
><P
> <SPAN
CLASS="QUOTE"
>"OLSR is a proactive routing protocol for mobile ad hoc
networks. The protocol inherits the stability of a link state
algorithm and has the advantage of having routes immediately
available when needed due to its proactive nature. OLSR is an
optimization over the classical link state protocol, tailored for
mobile ad hoc networks."</SPAN
>
</P
><P
> <SPAN
CLASS="QUOTE"
>"OLSR is designed to work in a completely distributed manner
and does not depend on any central entity. The protocol does NOT
REQUIRE reliable transmission of control messages: each node sends
control messages periodically, and can therefore sustain a
reasonable loss of some such messages. Such losses occur
frequently in radio networks due to collisions or other
transmission problems."</SPAN
> --- <A
HREF="http://www.ietf.org/rfc/rfc3626.txt"
TARGET="_top"
>RFC3626: OLSR, section
1.3 (page 8)</A
>
</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="HowOLSR"
></A
>1.4. How does OLSR work?</H2
><P
>
<SPAN
CLASS="QUOTE"
>"The Optimized Link State Routing Protocol (OLSR) is
developed for mobile ad hoc networks. It operates as a table
driven, proactive protocol, i.e., exchanges topology information
with other nodes of the network regularly. Each node selects a
set of its neighbor nodes as <SPAN
CLASS="QUOTE"
>'multi-point relays'</SPAN
>
(MPR). In OLSR, only nodes, selected as such MPRs, are
responsible for forwarding control traffic, intended for diffusion
into the entire network. MPRs provide an efficient mechanism for
flooding control traffic by reducing the number of transmissions
required."</SPAN
> --- <A
HREF="http://www.ietf.org/rfc/rfc3626.txt"
TARGET="_top"
>RFC3626: OLSR, section
1 (page 4)</A
>
</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="IBSS"
></A
>1.5. What about IBSS (IEEE ad-hoc mode)?</H2
><P
>The IEEE 802.11 standard defines two modes: </P
><DIV
CLASS="mediaobject"
><P
><IMG
SRC="images/802-11.png"
ALIGN="center"
WIDTH="550"><DIV
CLASS="caption"
><P
>IEEE 802.11 standard</P
></DIV
></P
></DIV
><P
></P
><OL
TYPE="1"
><LI
><P
><EM
>Infrastructure mode:</EM
> The
wireless network consist of at least one access point (AP)
connected to the wired network and a set of wireless
nodes (WN). This configuration is called a <EM
>Basic Service Set
(BSS)</EM
>. Extended Service Set (ESS) is a set of two or
more BSSs (multiple cells).</P
></LI
><LI
><P
><EM
>Ad hoc mode:</EM
> Also called
<SPAN
CLASS="QUOTE"
>"IEEE ad-hoc mode"</SPAN
> or <SPAN
CLASS="QUOTE"
>"peer-to-peer
mode"</SPAN
>. This configuration is called
<EM
>Independent Basic Service Set
(IBSS)</EM
> and is useful for establishing a
network where wireless infrastructure does not exist or where
services are not required.</P
></LI
></OL
><P
> So why use OLSR when we can use <SPAN
CLASS="QUOTE"
>"IEEE ad-hoc
mode"</SPAN
>? <EM
>IEEE ad-hoc mode does NOT support
multi-hop.</EM
> See <A
HREF="intro.html#multihop"
>figure
below</A
>
</P
><DIV
CLASS="mediaobject"
><P
><IMG
SRC="images/multihop.png"
ALIGN="center"
WIDTH="550"><DIV
CLASS="caption"
><P
><SPAN
CLASS="QUOTE"
>"IEEE 8102.11 Ad hoc"</SPAN
> mode has
<EM
>no</EM
> support for multihop, something OLSR
does have.</P
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