Project JXTA â€“ Guide to a peer-to-peer framework

1

Project JXTA –Guide to a peer-to-peer

framework

Ekaterina ChtcherbinaSiemens AG, Corporate TechnologyMunich

Thomas WielandSiemens AG, MunichUniversity of Applied Sciences, Coburg

2 © Siemens CT, Chtcherbina/Wieland, 2002

High-level agenda

! Introduction! Peer-to-Peer Computing! The Project JXTA! JXTA Concepts! JXTA Protocols! "Hello JXTA-World"

3

Introduction: Benefits of Peer-to-Peer Computing


5 Myths about P2P

! It is always fully decentralized! P2P is about People-to-People

communication! It is only about file sharing! P2P is not secure! P2P is not scalable


Distributed Search


Multi-user applications and games


Auctions


Collaboration


Resource sharing


Distributed storage and filesharing


Blackboards


Examples of P2P Applications! Building facilities (sensor equipment)! Collaboration work support (development

tools, data sharing)! Medicine (effective collaboration, file

sharing, distributed data processing)! Building site automatization! Business & entertainment communication

support! Cars (driver support, location based

services, car tracking)

13

Peer-to-Peer Computing


What is Peer-to-Peer Networking?! Traditional P2P network definition (comp. sc.

encyclopedia): “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 others.”

! Our P2P network definition: “An adaptive, self-configuringnetwork which does not rely on central servers. The peers in a P2P network are devices that can act as both servers and clients(servents).”


Disadvantages of Client/Server Systems

! Central servers (or server clusters) are potential bottlenecks and single points of failure of distributed systems

" P2P allows for efficient use of resources and robustness


Peer-to-peer and Ad Hoc Networks! Ad hoc networks require self-

configuration! Dynamic environment, unstable connectivity,

infrastructureless! Issues: addressing, service discovery &

advertisement, dynamic service composition, connection mgt., routing

" P2P enables self-configuration of dynamic distributed systems


Messages in C/S and P2P

Server

ServerCache

Traditional trafficcongestion zone

Client

Client

Client

Client

Client

ClientClient

Client

Peer

Peer

Peer

PeerPeer

Peer Peer

Peer


Centralized Distributed Computing

! Distributed networking technologies such as DCOM, CORBA and Web Services currently rely on a priori known directory servers (registry, naming server, UDDI, etc.)

DatabaseServer Service

Client

1.

3.

2.


Centralized Distributed Computing (2)! Distributed auto-configuration

technologies such as Jini also rely on directory servers

" P2P plug and play technologiessuch as UPnP are more suitable for infrastructureless environments

PeerPeer

Peer

Peer

Peer


Special Features! Decentralized ☺! Scalability/Redundancy/Fault tolerance

! P2P networks scale well with increasingnumbers of users

! Multiple distributed copies of of frequentlyaccessed resources

! Nondeterministic! Peers can appear and vanish spontaneously! Behaviour is less predictable


Requirements for P2P Systems! Metadata/Interoperability

! When are they essentially independent ?! Encapsulation? Privacy? Trust?

! Discovery! Who is out there ?! How do I reach them ?

! Messaging! QoS Security Trust/Reputation ! Peer-to-peer interaction issues

22

Security in P2P Networks


Security Issues! Authentication

! The process of determining whether or notsome entity is in fact who that entity declaresitself to be.

! Authorization! Process of giving an authenticated entity

permissions to do some action or access someresource

! Encryption and confidentiality! Integrity


Challenges in P2P Systems! Memberships and groups are dynamic! People do not trust each other

! Each peer is untrusted! Peers don't have trust relationships

! Unpredictable network latencies! Firewalls and other barriers! No central services (especially no directory)! Individuals can cause local damage that spreads ! Every peer may run run different software! Code may be mobile! Complex systems: hard to understand


Solutions! Mostly based on "web of trust"

! A trusts B, B trusts C, so A can also trust C! Users exchange their public keys and encrypt messages

with their private keys! Enrich by reputations

• Assign reputations to entities• Allow others to retrieve reputations• Use reputation to build trust relationships• Example: eBay

! Alternative: centrally issued group membership certificates (PKI)! Introduces dependencies from a server-like

infrastructure component


Further Possible SecurityTools! Encryption! Authentication! Firewalls

! May be installed on each peer! Drawbacks: Block all traffic on port, not

application; generally static rulesets

! Sandboxes! Essential for mobile code systems!! E.g. in Java/JVM, .NET/CLR

27

Search in P2P Networks


Distributed Search: Network Topology Based

Centralized(e.g. Napster)

Decentralized(e.g. Gnutella)

!Relies on the organization of the peers within the network to route requests

!Optimization focuses on the reduction of the diameter (no. of hops, round trip time) of the graph representing the distributed network


Distributed Search: Content Mapping Based! Content addressable networks:

distributed hash table. Content (or pointer to content) is stored in assigned peers" not a practical approach for content described by multiple attributes

! Publish/subscribe networks: peers agree on a certain query and advertisementtemplate. Content based routing.


Hybrid approach:

locally centralized +globally decentralized +publish/subscribe

(e.g. JXTA Search)

Hybrid Search

$ No perfect solution, choice depends on the application

SuperPeer


Support for Message Exchange! Routing in multi-hop ad hoc networks! Caching mechanism (relaying) for overcoming

! Disruptive connectivity! Firewalls

RelayPeer

MobilePeer

PeerA

PeerB

Firewall

PeerC

RelayPeer

Polling


Peer-to-Peer Systems! P2P platforms

! Sun Microsystems: JXTA

! Distributed computing! SETI@home! Entropia

! File sharing! Freenet! Gnutella! KaZaA

! Messagingframeworks! Open Source: Jabber

! Collaboration! Engenia Software, Inc

! Others! Magi: Endevors

33

Project JXTA


What is JXTA?conceptual framework for Peer-to-Peer applications

! serves as a specification, an effort to create a common platform for building distributed services and applications

! neither a standalone Peer-to-Peer application nor a concrete framework implementation!

! But: Sun has provided a reference implementation (in Java) which incorporates the specified components

! Napster, Gnutella, Freenet & Co. provide users with limited ability to share resources and are unable to share data with other, similar applications


The Project JXTA! Started as a research project at Sun

Microsystems by Chief Scientist Bill Joy! First official release of a Java reference

implementation in April 2001! Since then put under an open-source license

The name JXTA is derived from the word juxtapose, meaning to place two entities side-by-side or in close proximity. By choosing this name, the development team at Sun recognized that P2P solutions would always exist alongside the current client/server solutions, rather than replacing them completely.

Brendon Wilson


Key Assumptions! Platform Independence (any language, any OS, any

hardware)! But: JXTA dependence

! Allow for absolute heterogeneity of peers! Highly unreliable & changing network

environment! Asynchronous,Unreliable,Uni-directional

transport! Idempotent protocol exchanges – No protocol

state! Applications to build their own security &

encryption models


Technology! JXTA technology is based on XML, Java

technology, and key concepts of UNIX operating system

! Transmitted information is packaged as messages ! Messages define an XML envelop to transfer

any kind of data! The use of Java language is not required

! JXTA protocols can be implemented in C, C++, Perl, or any other programming language

38

JXTA Concepts


JXTA Architecture

Application Level

JXTA Services

JXTA Platform

pipes peers peer groupsComponents

resolver pipe discovery membership

peer groups

Core Services

propagation service

router and relay services

transports


Key Aspects

! XML documents (advertisements) used to describe network resources

! Abstraction of pipes to peers, and peers to endpoints! without reliance upon a central

naming/addressing authority

! A uniform peer addressing scheme(peer IDs)


Peers and Peer Groups

Peer

Peer Group

Net Peer Group


Pipes

Peer APeer B

Point-to-point pipe

Peer A

Peer B

Peer C

Peer D

Peer E

Propagate pipe


Advertisements! Representation of JXTA resources

! Like peers, peer groups, pipes etc.! Metadata structures! Used to decribe and publish peer

resources, e.g.! Peer advertisement: Comprises name, ID,

endpoints, etc.! Peer group advertisement: name, ID,

decription, specification! Pipe advertisement: ID, pipe type


Kinds of peers

! Minimal peer! Simple peer! Rendevour peer! Relay peer


Security in JXTA! Usual issues

! Confidentiality, integrity, availability - authentication, access control, encryption, secure communication, etc.

! Developing more concrete and precise security architecture is an ongoing project

! JXTA does not mandate certain security polices, encryption algorithms or particular implementations!

! JXTA 1.0 provides Security Primitives:! crypto library (MD5, RC4, RSA, etc.)! Pluggable Authentication Module (PAM) ! password-based login! transport security mechanism modeled after SSL/TLS


Security Model! Role based trust model with four basic requirements

! Confidentiality! Authorization! Data Integrity! Refutability

! XML messages allow meta data such as credentials, digests,certificates

! Credential – a token when presented in a message uniquely identifies the sender, helps verify the sender’s right to send a message to the endpoint

! Credential – default mechanism, Applications to implement mechanisms for better security

! Need to establish trust among peers

47

Summary


Lessons from P2P! P2P is not a new concept, but it offers new possibilities! P2P applications

! Sharing of files and other resources! Distributed computation! Instant messaging! Self-configuring compound services

! P2P applications need a standard open platform! P2P networking does not suit to all application scenarios

! No QoS guarantee (variable connectivity)

! Hybrid solutions


JXTA summary (for themoment ...)! JXTA – An open-source framework and launching pad for

p2p systems! Aims to be Interoperable, platform independent and

ubiquitous! Peers are required to implement a low over-head stack of

six JXTA protocols that standardize ! Peer discovery! Self organization into peer groups! Peer-to-peer Communication! Peer monitoring

! Challenges ! Naming & Binding services! Security & Trust models! Solutions to overcome limitations on NAT gateways &

firewalls


Thanks

! Stay tuned for more details to come! Any Questions?

Documents

Project JXTA â€“ Guide to a peer-to-peer framework