A Review of Current Routing
Protocols for Ad-Hoc Mobile
Wireless Networks
By Lei Chen
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What is Ad Hoc Wireless
Network?
• A collection of mobile nodes that are
dynamically and aribitrarily located
• Infrastructureless mobile network
• Each node must act as a router
• Most nodes will not wish to perform any
administrative actions to set up such a network.
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Routing Protocols
Ad-Hoc Routing
Protocols
Table Driven
DSDV
CGSR
WRP
Source-initiated
On-Demand
Driven
AODV DSR
TORA
ABR
SSR
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Table Driven Routing Protocol
• Attempt to maintain consistent, up-to-date
routing information from each node to every
other node in the network
• The number of necessary routing-related
tables and methods of broadcasting are
different
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Destination-Sequenced DistanceVector Routing (DSDV)
• A table based protocol
• Every node maintains a complete table
listed all possible destination
• Each entry of the table marked with a
sequence number assigned by the
destination node
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DSDV (continue)
Every node keep a route table <Destination-address,
Metric, Sequence-number> for every possible
destination
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Source-initiated On-demand
Routing Protocol
• Initiates a route discovery process within
the network, when a node requires a route to
a destination
• Maintain by some form of route
maintenance procedure until either the
destination becomes inaccessible or the
route is not desired
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Ad-hoc On-demand Distance
Vector Routing (AODV)
• An on demand routing protocol
• Description
AODV uses a broadcast route discovery
mechanism as is also used in DSR. Instead
of source routing, however, AODV relies on
dynamically establishing route table entries
at intermediate nodes
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AODV (continue)
•
A mobile node maintains a table entry for
each destination of interest. Route table entry
contains the following information:
• Destination
• Next Hop
• Number of hops (metric)
• Sequence number for the destination
• Active neighbors for this route
• Expiration time for the route table entry
•
•
•
Source node sends a RREQ packet
Intermediate nodes forward it to destination
Destination node distinguish the RREQ by
<broadcastID, source-address>, and sends
back RREP when receives the first RREQ
packet.
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Dynamic Source Routing (DSR)
• An on-demand routing protocol
• Description
– A source flood REQUEST if it has data to send
but no route to its destination is know
– When the destination get the REQUEST, it
sends a REPLY to the source via the recorded
route
– Use source routing instead of hop-to-hop
routing
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DSR continue
•
•
•
•
Every node has a cache which contain the
complete path information to the
destination node
If the source node can’t find the
destination node in its cache, it will initial
a route discovery
The source node sends the RREQ packet
which is <source-address, destinationaddress, route-record, request-id>
Intermediate node
–
–
–
If it is the destination copy the head and
send RREP
If it is already listed in the route-record,
discard it
Else, it forward the RREQ, and add itself
in the route-record
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Table-Driven vs On-Demand
Routing
• Table-Driven
– is similar to the connectionless approach of
forwarding packets, with no regard to when and
how frequent such routes are desired
– A routing is always available, regardless
whether or not it is needed
• On-Demand
– Has to wait until a desired route is discovered.
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