Company Confidential 1 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials Towards a mobile content delivery network with a P2P architecture Carlos Quiroz

1 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials

Company Confidential

Towards a mobile content delivery network with a P2P architectureCarlos Quiroz



Overview

• Analysis of P2P architecture for a mobile oriented content delivery system

• Open Questions• Is there value on using P2P instead of traditional techniques for large scale

delivery systems

• What characteristics of a delivery system for mobile devices make using P2P techniques appealing

• How to measure those benefits

• Hypothesis: A P2P architecture would enable certain scenarios involving mobile terminals not support by current architectures



Content Sharing and Delivery Service

• Content Delivery network for both mobile and web based clients

• Content is created mostly in the mobile nodes, e.g. pictures, movies, etc.

• Differences to traditional CDN• Clients are mobile and have unreliable

connections• Most of the content is produced at the

edges

• In normal operation content is uploaded automatically

• Service also acts a backup service

• Sharing (Content Delivery) is enable among users or to everybody

Storage systemMetadata DB

Web server

Web serverMobile server

Mobile server

Mobile server



Life cycle of a media item

• Objects are created in the device (e.g. picture)

• They are automatically uploaded to the service and a unique ID is generated

• On the service side they are stored and entries into a metadata DB are created

• Files made public or set as shared can be requested based on the ID (Security restrictions apply)

• What is the best way to store and distribute those files in a scalable way?

Storage systemMetadata DB

Web server

Web serverMobile server

Mobile server

Mobile server



Deferred uploading

• In some cases automatic uploading is not optimal• While roaming

• Low battery situations

• Very slow connections

• In those cases media is not uploaded completely:• Metadata is sent to the service (Searches are enabled)

• Possible a low-resolution object is uploaded

• But we still want to allow for publication



Content Delivery Networks

• Classical client-server architecture (Normally in the form of large clusters)

• Storage in the form of Storage Area Networks (SAN) or distributed file systems

• Content Delivery Networks:• Complement client-servers for the delivery of static content• They are composed of several large clusters distributed globally• Each cluster has its own replica stored locally

• Peer-to-peer CDNs• Unstructured networks (Gnutella, BitTorrent) are not adequate for

interactive operation• But, research structured delivery networks are available

• Most of them are DHT based• Not yet proven as better alternative than existing system



Supporting storage systems

• SANs• Well known and robust

• Expensive to buy and operate

• Distributed file systems (Google FS)• Cheaper

• Robustness given by software

• Both are easy to use from the point of view of applications

• P2P file systems (PAST, Ivy)• Require a structured network for reliably locating files

• Keeping the structure is expensive, especially for mobile devices



Architectures

SAN

Metadata DB

Metadata DB

Architecture with centralized storage Architecture with P2P storage



Issues on current architectures

• Centralized file systems cannot easily deliver content still in the mobile devices

• Solutions through e.g. mobile web servers are possible

• Structured P2P networks create overhead on keeping the structure

• Direct P2P delivery is not feasible for web based interactive applications



Proposal for a hybrid architecture

• Delivery and queries to/from web based clients are done in the traditional way

• Use a P2P storage system based on DHT (Like Chord or PAST)• Each node has a set of items stored locally and it knows its IDs

• Make the devices part of the P2P storage system• Allows to access item still in the phone

• This is only used if needed

• The set of IDs in a node are augment with those of the devices connected to

• Metadata is still kept centrally to enable queries and use when the device is out of range



High-level view

Metadata DB

Query

Item found inthe cluster

Item found inthe device

ObjectID

Retrieve Object

Chord style network



Open issues

• Validate the concept through simulation and/or implementation

• Are existing DHT-based routing protocols enough to make this workable

• Creations of metrics to compare different systems

• Security is an issue since mobile clients become part of the storage system

• Is it worth the effort? Are there other subsidiary benefits



Q&A

Documents

Company Confidential 1 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials Towards a mobile content delivery network with a P2P architecture Carlos Quiroz