Challenged Networking

An Experimental Study of New Protocols and Architectures

Erik Nordström

Unchallenged Networking

• Wired• Stationary• Conversational• Structured• End-to-end

The Challenges

• Mobile computers• No structures• Intermittent connectivity• No end-to-end paths• No pre-established

names and addresses

How to enable communication when requirements and assumptions change?

The Solutions

• Make existing protocols work better

• Develop new protocols• Make existing and new

protocols interoperable• Develop evaluation

methodologies and testbeds

Main Contributions

• Experimental testbeds and methodologies– Ad hoc Protocol Evaluation (APE)

• Protocol implementation and evaluation– AODV-UU, DSR-UU routing protocols

• New communication paradigms– Interest-based dissemination

• New network architectures– Haggle

Challenges of Experimental Evaluation

• Repeatability– Mobility– Radio

• Management– Scaling– Configuration

• Cross-environment– Simulation, emulation, real-world

Related Work in TestbedsOrbit [Raychaudhuri et. al 2005]

DieselNet [Burgess et. al 2006]

[Above photo (c) 2006 Daily Hampshire Gazette]

•Netbed/Emulab [White et. al 2002]•Whynet [Zhou et. al 2005]•Etc.

Roofnet [Aguayo, et. al 2003]

Experiment Choreography1. Go to position B in the middle of the corridor (5 secs)2. Continue to position C at the end of the corridor (5 secs)3. Go back to starting point (10 secs)

Log SNR

Log traffic

Log parameters

0 1 2 3

Experimental Setup

Relay node swap

Ping!

Routing protocol implementations:•AODV-UU•DSR-UU•OOLSR

Thesis page 204

Link cache poisoning

Mean over 10 experiments

0

3

0

3

Simulation

Real world

Source route at receiver

Source route at sender

Flip-flop routing

DSR-UU

DSR-UU

Source routes

Haggle – An Architecture for Challenged Networking

• Scenario:– People carry information– Ad hoc/opportunistic interactions– Heterogeneous connectivity

• Problems:– How to agree on names and addresses?– How to exchange information?– How to agree on which information to exchange?

The Haggle Approach: Searching

Interests

Interests

Search for matching content

Search for matching content

4 3 21

12 3 4

Interest-based Dissemination

message

interest

Match at least two interests!

Three Interest-based Dissemination Strategies

Wait – only disseminate from source

Content – intermediate nodes may re-disseminate

(forward)

Flood – any node may re-disseminate

What is the Correlation between Contacts and Interests?

List of interests

AffiliationNationality

Technical interests…

3 cm

Trace-based Simulation

1000 messages uniformly spread

over the trace.Match affiliation or

nationality.

Conclusions• Protocols and architectures for challenged networks

cannot be designed solely based on simulations and emulations

• Protocols need to be designed for intermittent connectivity, but they should also exploit full connectivity

• Protocols need to rely more on decision making based on (long term) measurements of the environment, or on a-priori knowledge rather than lookup services

• New naming and addressing schemes required. Schemes that support searching can be attractive for flexible content exchanges