Core services for wireless networks

1
Core services for wireless networks

• Vivek Raghunathan, Vikas Kawadia, Nitin Gupta,
  P. R. Kumar

2
Usage models

• Providing Internet access
• Other possibilities
• Communication with people in the community (mesh
  networks)
• Applications that exploit proximity

3
Core services

• Automate and simplify the setup procedure in ad
  hoc/mesh networks.
• Automatic address configuration
• Duplicate detection and recovery
• A distributed name service
• Pro-active discovery of user identities
• Robustness to IP address volatility
• A routing protocol for adhoc/mesh networks
• Pro-active (DSDV/Adaptive DSDV)

4
Architecture
5
Proximity-enabled applications

• Meet strangers in
• coffee shops,
• airports, trains etc.
• Lecture/talks in a University/School
• Collaboration in a meeting/conference

6
In the pipeline the Chatmate application

• A canonical example of the kind of applications
  we envision
• An IM client that automatically discovers users
  in the vicinity
• Cryptographic mechanisms to verify identity
• Works in both ad-hoc and infrastructure modes

7
If you wanted details
8
Usage Scenarios

• A walks into Green Street Coffee House and
  connects using the AP. Her instant messenger
  software automatically discovers other users in
  the coffee shop and allows her to chat/share
  files with them.
• B is attending the CU Wireless Summit which does
  not have wireless Internet access (yes!). Its
  past the lunch hour and hes feeling just a
  little sleepy. He discovers other users around
  him and fires up Unreal Tournament.

9
Address configuration daemon (ACDC)

• Use MAC addresses to generate almost unique IP
  addresses.
• Freshly selected address not used until after a
  safe period.
• During safe period, routing (DSDV) only listens
  to updates to build its routing table and does
  not send updates.
• Duplicate detection by monitoring the kernel
  forwarding table for a route to myself.
• On duplicate detection, flush the kenrel
  forwarding table and re-start DSDV.

10
Distributed Dynamic Name Service (DDNS)

• Harvest addresses of other nodes in the network
• With an ad-hoc network and proactive routing
  (like DSDV), this information is in the kernel
  forwarding table.
• With an infrastructure network, this information
  can be obtained by a 1-hop broadcast.
• With an ad-hoc network and reactive routing (like
  DSR), this information needs to be obtained by a
  network-wide flood.

11
Distributed Dynamic Name Service (DDNS)

• Inform all harvested nodes of own address mapping.
• On receiving a mapping from another node, update
  /etc/hosts.
• Higher-layer applications can transparently use
  gethostbyname() to resolve the name as usual.

12
Dynamic Sequence Distance Vector Routing (DSDV)

• DSDV is a pro-active routing protocol which is
  guaranteed loop-free.
• User space daemon implementation in C on Linux.

13
If you wanted even more details

• Contact
• Vikas Kawadia
• kawadia_at_uiuc.edu
• Vivek Raghunathan vivek_at_control.csl.uiuc.edu