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CDN Mechanisms

The Client-Server-Resource model for Content Distribution Networks of varying node dynamics and density

Similar network models: Grid, Peer-to-Peer, CDN

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Grid

Computational GRIDs basic layer for harnessing processing power by

distributing massive computational tasks to numerous resources (compute cycles and data storage) over matching communication links.

data archives

instruments

MPPsclusters

workstations widearea

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More grids

Information and knowledge GRIDs allowing access to dispersed information, and knowledge

discovery and extraction from spread knowledge resources. They make use of cognitive techniques and tools such as data mining, machine learning, content semantics, ontology engineering, information visualisation and intelligent agents.

Grid technologies are also to be interpreted in a broad sense including technologies for Peer-to-Peer Computing (P2P) using commodity hardware to enable the co-ordinated use

of geographically distributed resources without central control.

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Peer-to-peer Network

Classic definition "A type of network in which each workstation has

equivalent capabilities and responsibilities. This differs from client/server architectures, in which some computers are dedicated to serving the others." [Webopedia]

Modern (ad hoc) definition P2P is a class of applications that takes advantage of

resources --storage, cycles, content, human presence-- available at the edges of the Internet. P2P nodes must operate outside the DNS system and have

significant or total autonomy from central servers…

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CDN

Content distribution networks are coordinated caching systems.

CDNs are a multi-million-dollar business already.

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A DNS-redirecting CDN

DNSredirector

Client

HTTPserver

HTTPserver

HTTPserver

A

B

C

example.com ?

B

GET http://example.com/foo

http://example.com/foo

Network Model

Network Model

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Mechanisms

Deployment: where service is located ( Cooperation:

Query routing Consistency

Internal resource management: Replacement Prefetching

Selection (based on dns, multicast, anycast, metrics) request distribution Server selection

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Scenarios

Node dynamics: Hosts close to backbone, dedicated, permanent, versus

PC close to network edge, part-time, eventual, transient

Node density About 10K nodes (Akamai) About 100K-1000K nodes &+ (gnutella, freenet,

morpheus, etc.)

BLCA

Nodedynamics

Node density

AKAMAI

Morpheus / P2P

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Organisation

Tree, grid or any other “organised” topology (CDN) Mesh, small network topology (P2P)

E.g. map of the gnutella network

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Xweb

Web OS, Active ServicesWeb

Content Distribution Networks

Per overlay (garantee service, mgmt)

Dynamic Programming

Manual Modifications

Service Control

Programmability

None (Best-effort Service, No

mgmt,...)

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Solution: XWeb

DM

Spawn

Spawn

Spawn

Squid

Squid

Squid

parent

parent

avant

pc1

pc2

mosaicRA

RA

RA

RA

DM

Deployment Manager @ Service Providers

Resource Agent @ Resource Providers

Deployment Mechanisms

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WWG/laColla P2P environment for group collaboration

Reduced scale groups on a large scale network

Event distribution based group communication Three mechanisms:

Event distribution (to group members)

Group membership Repository agents

(where history and documents are stored)

Simulation (JavaSim)

The number and locationdepends on many factors

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A Demand based Algorithm for Rapid Updating of Replicas

Simulation (Network Simulator NS)

A Distributed Magazine ... demand is an important+changing factor ...

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Influence of the Document Validation/Replication Methods onCoop. Web Proxy Caching Performance of cooperative web

caching schemes (hieracy, mesh, hybrid) with

different doc. validation/replication methods (TTL, invalidation, pushing, etc.)

Cost: combination of factors Response time Bandwidth consumption Number of stale docs

Simulation (Network Simulator NS)