Amit Singh Dahal

g5638545

Content Addressable

Network(CAN)Structured P2P Network

Outline

Introduction

Overview

Construction

Routing

Maintenance

Evaluation

Future Improvements

Introduction

one of the original four distributed hash table

proposals, introduced concurrently with

Chords, Pastry, and Tapestry.

developed at UC Berkeley

CANs overlay routing easy to understand

scalable indexing system for large-scale

decentralized storage applications

has a good performance

Overview

distributed, decentralized P2P infrastructure

system that maps keys onto values

keys hashed into d dimensional Cartesian space

Interface:

insert(key, value)

retrieve(key)

associate to each node and item a unique

coordinate in an d-dimensional Cartesian space

Overview

entire space is partitioned amongst all the nodes

every node “owns” a zone in the overall space

can store data at “points” in the space

can route from one “point” to another

point node that owns the enclosing zone

Overview

y

x

State of the system at time t

Node

Resource

Zone

Fig:2 dimensional space with a key mapped to a point (x,y)

Construction

Bootstrapnode

new node

Construction

I

Bootstrapnode

new node 1) Discover some node “I” already in CAN

Construction

2) Pick random point in space

I

(x,y)

new node

Construction

(x,y)

3) I routes to (x,y), discovers node J

I

J

new node

Construction

newJ

4) split J’s zone in half… new owns one half

Routing

data stored in the CAN is addressed by name

(i.e. key), not location (i.e. IP address)

have some routing mechanism

A node only maintains state for its immediate

neighboring nodes

Routing

y

Node

M(x,y)

N(x,y) d-dimensional

space with n zones

where d=2 and n=8

2 zones are

neighbor if d-1 dim

overlap

Algorithm:

Choose the neighbor

nearest to the

destination

M(x,y) Query/

Resource

key

Maintenance

Use zone takeover in case of failure or leaving of

a node

Send your neighbor table update to neighbors to

inform that you are alive at discrete time interval t

If your neighbor does not send alive in time

t, takeover its zone

Zone reassignment is needed

Evaluation

Scalability

-For a uniformly partitioned space with n

nodes and d dimensions:

* per node, number of neighbors is 2d

*average routing path is (d*n1/d)/3

hops (due to Manhattan distance

routing, expected hops in each

dimension is dimension length * 1/3)

*Can scale the network without

increasing per node state

Robustness

-no single point of failure

Future Improvements

Multi-dimension

-increase in dimension reduces path length

Caching and replication techniques for better

performance

Overloading the zone

-increases availability, reduces path

length, reduces per hop latency

Uniform partitioning

-compare the volume of the zone with its

neighbors

-partition the zone having largest volume

THANK

YOU!!!