1 © NOKIA FILENAMs.PPT/ DATE / NN

Ad Hoc Networking with AODV

Charles E. Perkins

Nokia Research Center

Mountain View, CA USA

http://people.nokia.net/charliep

charliep@iprg.nokia.com

2 © NOKIA FILENAMs.PPT/ DATE / NN

Outline of Presentation

• Ad Hoc Networks in general

• AODV in particular

• Recent results from manet

• Internet Gateways for ad hoc networks

• Address autoconfiguration

3 © NOKIA FILENAMs.PPT/ DATE / NN

Ad Hoc Network characteristics

• peer-to-peer

• multihop

• dynamic

• zero-administration

• low power

• autonomous

• autoconfigured

But, most of these have exceptions!Idea: let (?almost?) every node be a router

4 © NOKIA FILENAMs.PPT/ DATE / NN

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

5 © NOKIA FILENAMs.PPT/ DATE / NN

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

6 © NOKIA FILENAMs.PPT/ DATE / NN

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

7 © NOKIA FILENAMs.PPT/ DATE / NN

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 Autoconfiguration

• Reducing retransmissions for system-wide flooding

8 © NOKIA FILENAMs.PPT/ DATE / NN

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

9 © NOKIA FILENAMs.PPT/ DATE / NN

AODV Unicast Route Discovery Initiation

Route Request (RREQ) broadcast flood

Source

Destination

10 © NOKIA FILENAMs.PPT/ DATE / NN

AODV Unicast Route Discovery Completion

Route Reply (RREP) propagation

Destination

Source

11 © NOKIA FILENAMs.PPT/ DATE / NN

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

12 © NOKIA FILENAMs.PPT/ DATE / NN

Address Autoconfiguration

• 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

13 © NOKIA FILENAMs.PPT/ DATE / NN

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.

14 © NOKIA FILENAMs.PPT/ DATE / NN

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

15 © NOKIA FILENAMs.PPT/ DATE / NN

Various Ad Hoc Routing Projects

• DSR (Dave Johnson, CMU)

• WINGs (JJ Garcia/UCSC)

• ROAM (JJ Garcia/UCSC)

• WAMIS (Gerla/UCLA)

• ODMRP (Gerla et.al/UCLA)

• TRAVLR (Kleinrock/UCLA)

• Tora/IMEP (Park, Corson/UMD)

• Link Quality (Rohit Dube/UMD)

• LAR (Texas A&M)

• TBRPF (SRI)

• OLSR (Inria: Clausen./Jacquet)

• DSDV (Dest. Sequence #'s)

• AODV (refinement of DSDV)

• AOMDV (Multipath – Das/Marina)

• Hierarchical (Akyildiz/Georgia Tech)

• GPSR (Karp/Harvard)

• CBRP (Singapore)

• Terminodes (EPFL)

• MMWN (Steenstrup/BBN)

• ABR (C.K. Toh)

• STAR (JJ Garcia/UCSC)

• ZRP (Zygmunt Haas/Cornell)

• Fisheye/Hierarchical (UCLA)

• CEDAR (Urbana-Champaign)

16 © NOKIA FILENAMs.PPT/ DATE / NN

Distance Vector Routing Protocols

• Route table has (metric, next hop) – i.e., (distance, vector).

• Other metrics (e.g., time) may be more useful in many cases

• “Distributed Bellman-Ford” algorithms

• Can be made loop-free

• Easy to program

• Low memory and processor utilization

• Localized update operations (important for ad hoc)

• Susceptible to counting-to-infinity problem

• Previous solutions (poison reverse/split-horizon) must be undone