Scalable Ad Hoc Routing: The Case for Dynamic Addressing

INFOCOM 2004

Jakob Eriksson, Michalis Faloutsos, Srikanth Krishnamurthy

University of California, Riverside

Introduction Why dynamic addressing?

Address equals to identity is impropriate in ad hoc (especially mobility) networks

Dynamic addressing in ad hoc network: How to allocate address? How to route? How to perform node lookup?

The methods should be: Localize overhead Avoid centralized protocols or special nodes Minimize manual configuration

Terminologies Identifier: globally unique Address: changes with node movement Address tree: the address space can be

viewed as the leaves of a binary tree Address subtree: a range of addresses with

a common prefix Level-k sibling

Example of address tree, address subtree, and level-k sibling

xxx

0xx 1xx

00x 01x 10x 11x

000 001 010 011 100 101 110 111L0

L1

L2

Address allocation The responding node splits its controlling

address into half

000A

01x00x 10x 11x

0xx 1xx

xxx

100B

1. B joins via A

110C

2. C joins via B

010D

3. D joins via A

Characteristics of the method Level-0 sibling: physically connected directly The leaves of the same subtree: form a physically

connected sub-graph

000 001 010 011 100 101 110 111D C A B S E - -

00x 01x 10x 11x

0xx 1xx

xxx

SA B

D EC

010 011 100

101001000

Node S enters the networks through node D, should these two nodes be physically connected?

Routing

xxx

1xx

10x

100

0xx 11x101

A node keeps one entry for each level-i sibling in its routing table

Routing example

000 001 010 011 100 101 110 111D C A B S E - -

00x 01x 10x 11x

0xx 1xx

xxx

Node S = 100

Level 2 : B

Level 1 : E?

Level 0 : E

Node B = 011

Level 2 : S

Level 1 : C

Level 0 : A

Node C = 001

Level 2 : E

Level 1 : B

Level 0 : D

SA B

D EC

010 011 100

101001000

Node lookup Each mapping is stored on one node in the

network XOR-distance criterion

A

Addr:000ID:0101

B

Addr:001ID:1101

C

Addr:010ID: 0010

Where should store the mapping of C?A: 000 xor 010 = 010B: 001 xor 010 = 011C: 010 xor 010 = 000 Stores in B

Can be replaced by any prior known functions

Improvements in node moving and lookup entry updates Challenge:

Lookup entries have to be updated when moving

Improving method: Use xor-distance criterion with 1 or more of

the most significant bits removed Choose a local node that fits the criterion

Simulation environment NS-2 network simulator v 2.26 with Random

Waypoint mobility model with Max speed: 10m/s, min speed: 0.5m/s Duration = 300 s (Traffic load: 12000 packets of 512 bytes, not

restricted to particular source or destination) Ignore node lookup process, replaced by a global

lookup table Simulator developed by themselves.

Based on NS-2, replace MAC and physical layers with a simple reliable message exchange to improve simulation times

Simulation result A: address space utilization # of nodes: 12~4,000 nodes 64-bit address Node degree: between 6 and 8

Simulation result B: path stretch Path stretch: routing path length is over the

shortest path length Create static random topologies with size ranging

from 125 to 1000 nodes

Simulation result C: routing scalability CEF: frequency of connection establishment Network size: 400 nodes Connection frequency: ½ to 50 per second

Topology and address allocation Star-like topology

If the central node has address [000…0], its neighbors will be [100…0], [010…0], [001…0], ... [000…1]. Only l addresses are available

Typical ad hoc networks: not realistic, unless considering natural obstacles

Base station

Topology and address allocation String topology: worst case scenario

If address of u0: [000…0], u1 to un-1 will be [100…0], [110…0],…[111…1], respectively

Extremely uncommon Address space locally exhausted use

NAT Many identifiers are mapped to a single

address The “inner” address can serve many nodes

Conclusion Present methods for dynamic addressing

Distinguish id and address Routing complexity: O(logN), not based on

flooding or broadcasting No manual configuration No need for central servers or geographical

information (GPS)

Pre-reading advice J. Eriksson, M. Faloutsos, and S.

Krishnamurthy, Peernet: Pushing peer-2-peer down the stack. in IPTPS, 2003