Building An improved OLSR routing protocol on IEEE 802'11based MANET

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Building An improved OLSR routing protocol on
IEEE 802.11-based MANET
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• Team 8
• 9317525??? 9317551???
• 9317561??? 9317597???
• 9317612???

yrchiang, chhan, chiahung, zhihao,
cjhung_at_csie.nctu.edu.tw
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Classification
proactive
reactive
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Optimized Link State Routing Protocol

• Proactive Table-driven
• Link State Routing
• Each node expands a spanning tree
• Each node can obtain the whole network topology
• Utilizes a technique to reduce message flooding
• Multipoint relaying (MPR)

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Optimized Link State Routing Protocol

• Three main modules
• Neighbor/link sensing
• Provide topology information up to two hops
• MPR selector information notification
• (A select B as As MPR in HELLO message to B)
• Optimized flooding/forwarding
• MPR set to cover all the two hop neighbors
• MPR selector set set of nodes that select me as
  one of their MPR set
• OLSR-Messages from MPR selector set are to be
  forwarded
• Link-State messaging and route calculation
• Each node with non-empty MPR selector set floods
  the network with topology control (TC) messages
  to advertise link state

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Example
D is Bs MPR and only MPR nodes forward TC
messages
A selects B as its MPR
B
G
A
D
D
B
H
B
MPR selector set(B) A, D
A
E
D selects B as its MPR
C
C is As MPR and only MPR nodes forward TC
messages
A is Bs MPR and only MPR nodes forward TC
messages
F
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All nodes have the same LSDB
A
A select B as its MPR
B

• Each node uses Dijkstras SPF to construct the
  routes to all known destinations
• Routing table is calculated from Topology table
• Routing Table

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What we want to do to improve OLSR

• Aggregated and Differential topology change route
  maintenance messages
• Instead of forwarding TC only, MPR nodes also
  cache its known topology information
  intelligently
• The aggregated topology changes messages is
  numbered and could be queried from other nodes
• The fully aggregated TCs are transmitted if
  needed, and the differential ones are transmitted
  periodically or at the time the topology is
  changed
• Fast re-route mechanism
• To be elaborated in the next page
• Support ZRP hybrid routing
• Limit the flooding range up to specified hop
  count
• Bordercasting Support route query and response
  procedure

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Fast re-route Mechanism

• MPRs can result in delayed recovery from link
  failures, as the following example shows.
• Node i was not allowed to reroute through node j
  until it knows j is an MPR of node k. This
  requires messages to travel around the loop from
  i to j to k to j and back to i. This will
  either cause a delay or add overhead (if
  additional messages are sent).
• Our Mechanism
• Node i could route packet to j immediately by
  its two-hop information
• Besides, it could intelligently generate the TC
  as k chooses j as ks MPR

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Related work

• Optimized Link State Routing (OLSR) is an
  optimization of the classical link state
  algorithm
• RFC3226
• Many version of implementation with/without
  additional feature for IPv4/IPv6 in different
  programming languages
• QOLSR QoS OLSR, http//qolsr.lri.fr/
• Topology Dissemination Based on Reverse-Path
  Forwarding (TBRPF)
• RFC3684
• Similar to OLSR, but each node
• computes a source tree based on partial topology
  information stored in its topology table
• reports only part of its source tree to neighbors
• Implementation SRI Inernational
• http//www.sri.com/esd/projects/tbrpf/
• approved commercial licensing only