2. Outline of Presentation
Ad Hoc Networks in general
AODV in particular
Recent results from MANET
Internet Gateways for ad hoc networks
Address auto configuration
2
Ashok Panwar
Technical Officer in ECIL
3. Ad Hoc Network characteristics
peer-to-peer
Multi hop
dynamic
zero-administration
low power
autonomous
Auto configured
But, most of these have exceptions!
Idea: let (?almost?) every node be a router
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Ashok Panwar
Technical Officer in ECIL
4. Commercial (or not!) Opportunities
Conferencing
Home networking
Range extension for cellular base stations
Emergency services
◦ Ambulance
◦ Police
Hospitals
Embedded computing applications
◦ Ubiquitous computers with short-range interactions
◦ Automotive/PC interaction
Enable computing where subnets do not exist
Jungle telemetry
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Ashok Panwar
Technical Officer in ECIL
5. Technical/Market/Political hurdles
Scalability (memory search time, bandwidth, processing)
Power budget vs. latency
Protocol deployment, incompatible standards
Why should one node “waste power'' to help a neighbor ?
Wireless data rates
Obsoletes the client/server model... breaks a lot of
protocols
User education, acculturation
Antenna inconvenience (not anymore, really)
Higher bit-error-rate (BER)
Additional security exposure
Non-ubiquitous coverage
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Ashok Panwar
Technical Officer in ECIL
6. On-Demand Routing Protocols
Eliminate route table updates for routes that are not used
Fewer control packets:
◦ better scalability, reduced congestion, better robustness
◦ reduced processing requirement
Even more localization for topology changes if distance
vector
Also can be made to work for (partial) link state
◦ or, better, hybridized distance vector and link state
Downsides:
◦ Latency
◦ Route Discovery broadcasts
◦ ICMP Unreachable only after Route Discovery attempt
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Ashok Panwar
Technical Officer in ECIL
7. Mobile Ad Hoc Networking (MANET) / AODV
AODV: on-demand, and distance vector
◦ Route caching & timeout offers improvement over others
◦ Proved “correct”
◦ Interoperability testing, and (soon?!) Experimental RFC status
AODV uses network-wide RREQ, unicast RREP along
reverse path to source of the request.
DSR uses similar route discovery, maintains source routes
OLSR and TBRPF are link state, proactive protocols
Active discussion about Internet Gateways
Address Auto configuration
Reducing retransmissions for system-wide flooding
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Ashok Panwar
Technical Officer in ECIL
8. AODV Features
Reactive routing protocol; route discovery cycle for
route finding
Route repairs and TTL restrictions reduce network-
wide flooding
Maintenance of active routes
Loop freedom achieved through sequence numbers
No overhead on data packets
Scalability shown to 10,000 nodes
◦ performance suffers
Integrated multicast protocol (MAODV) specified
◦ multiple next hops
◦ group leader maintains sequence number
QoS extension specified (undergoing revision)
AODV for IPv6 is specified, built, and works
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Ashok Panwar
Technical Officer in ECIL
11. Internet Gateways for Ad Hoc Networks
Our model: do not inject per-host routes into Internet
Good start: ad hoc nodes use gateway as default router
◦ but it could be multiple hops away
◦ plus, the ad hoc nodes need to know its IP address
◦ router solicitation/advertisement “work”, with changes
Gateway should be “protocol-agnostic” (for any MANET
protocol)
Gateway needs a host route for each MANET node
Gateway
Entry node
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Ashok Panwar
Technical Officer in ECIL
12. Address Auto configuration
Node discovers Internet-routable prefix from Internet Gateway, if any
Otherwise, use canonical site-local address
Required: some variety of Duplicate Address Detection (DAD)
For connected networks, RREQ/RREP does the job
◦ tricky part: what is the source address?
◦ have specified AREQ and AREP for “general” case (should work with protocols other
than AODV)
The hard part: dealing with network merge or healing
Gateway
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Ashok Panwar
Technical Officer in ECIL
13. Ad Hoc Networking Research
MobiHoc (ACM SIGMOBILE) (plus quite a few others!)
◦ Third conference held in June – 150 papers submitted
Active research areas (a few among many!)
◦ Inherent capacity bounds?
◦ Better Routing
◦ Automotive (“parallel” one-dimensional networks?)
◦ Backbones, Clustering
◦ Power control
◦ Simulations seem quite untrusted
AODVng
◦ Gray zones (interference range vs. signal range; HELLO nonworking)
◦ QoS/Diffserv/”no free lunch”
◦ Security (!!)
◦ Implementer’s mailing list
◦ Multipath
◦ AODVjr.
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Ashok Panwar
Technical Officer in ECIL
14. Summary and Conclusions
Ad Hoc Networking is well-established as a viable
research area
Infrastructureless operation has many applications
On-demand protocols offer many advantages
AODV makes use of advantages from both Distance-
Vector and On-demand
AODV has good chances for standardization
Ad hoc networks can be glued to the Internet and then
provide wireless extension domains
Address autoconfiguration techniques have been
adapted
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Ashok Panwar
Technical Officer in ECIL
