JXTA-Overview [Compatibility Mode]

8/7/2019 JXTA-Overview [Compatibility Mode]

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JXTA Overview and Demo

M. Ranganathan

ITG/ANTD/NIST





P2P Applications• Application Characteristics:

– Centralization not possible or desired.– Massive Scalability

– Relationships are transient or ad hoc

– Resources are distributed

– Resilience is desired• Examples

– File sharing.

– Collaborative Applications

– Distributed/Grid Computing.

– Distributed Storage.

– Distributed Caches.



P2P Applications• Search the entire web and all its connected devices

(not just servers) for needed information

• Save files and information to distributed locations onthe network

• Connect game systems so that multiple people in

• Participate in auctions among selected groups of individuals

• Collaborate on projects from anywhere using anyconnected device

• Share compute services, such as processor cycles orstorage systems, regardless of where the systems orthe users are located

• Wireless tic-tac-toe / picture sharing.



JXTA Overview

JXTA is a set of open XML-based protocolsto build Peer to Peer Applications.

API bindings for the protocols are defined for

J2SE, J2ME, C++ etc.Project JXTA is sponsored by SUN.

JXTA open source community hosted athttp://www.jxta.org.



Goal/Purpose

• Enable a wide range of distributed computing

applications by developing a common set of generalpurpose P2P protocols

• Platform independence - any language, any OS, anyhardware. JXTA is a set of protocols.

• Minimal Hardware assumptions: enable newapplications to run on any device that has a digitalheartbeat (desktop computers, servers, PDAs, cellphones, and other connected devices)

• Security / monitoring features to enable commercialdeployment.



JXTA is based on Protocols

• Defines XML message formats or

protocols for communication betweenpeers.

• Protocols are used to discover eers

advertise or discover resourcescommunicate, route messages andprovide monitoring.

• Protocols can be implemented in anylanguage.



JXTA Protocol Abstractions

• Peer - A JXTA speaking process.

– Peer Service – A Fragment of code specific to a peer • Peer Groups - Peers providing a common service

– Peer Group Service – A fragment of code that is common to

the eer rou .

• Advertisements – XML Document that publishesexistence of resources

• Pipes – uni-directional, asynchronous, virtual

channels for point-point and point-multi-pointcommunication.

• Messages – XML envelopes



JXTA Abstractions

• Each JXTA resource is identified by a

UUID.

• Six types of JXTA entities with unique IDs:

– eers, eer groups, p pes, messagecontents, module classes and module

specifications.



JXTA Services

JXTA Applications

Structure

JXTA Community ServicesSun

JXTA Community Applications Sun Applications

JXTA Shell

Peer

JXTA Core

Any Peer on the Web

Security

Peer Groups Peer Pipes Peer Monitoring



The Layers• Platform Layer , also known as the JXTA core,

encapsulates the minimal and essential primitives thatare common to all P2P environments. These include thecreation of peers, peer groups and security primitives.

• Service Layer. The Service layer includes the services

a are no comp e e y necessary or ne wor ng,but are often used to make some tasks easier.

• Application Layer. Implementations of integratedapplications: i P2P instant messaging, document and

resource sharing and P2P email systems.



Peers• Peer is any networked device that implements

one or more of the JXTA protocols.• Each peer operates independently and

asynchronously from all other peers.

• Uniquely identified with a Peer ID.

• Peers publish one or more network interfaces for

use with the JXTA protocols.

• Intermediate peers may be used to route

messages.



Peer Groups

• Collection of Peers that have agreed upon

a common set of services.

• Each Peer group is identified using a

.• Peers may belong to more than one peer

group simultaneously.

• All peers belong to the NetPeerGroup.



Motivations for Peer Groups

• To Create a Secure Environment:

– Local domain of control in which a specific

security policy can be enforced. Peer group

boundaries ermit members to access/ ublish

protected contents.

• To Create a Scoping Environment:

– Allow the establishment of a local domain of

specialization.



Peer Group Services• A set of services that are replicated through the

whole peer group.• Root peer group has the following services:

– Discovery Service: search for peer group resources.

– em ers p erv ce: ccep eny new mem ers.– Access Service: Validate requests

– Pipe Service: Create / Manage pipe connections

– Resolver Service: Send generic queries to other

peers.– Monitoring Service: Allow one peer to monitor the

other members of the same peer group.



Network Services

• Peer Service: Accessible only on the peer

that is publishing the service:– Multiple instances of the service can be run

.

• Peer Group Service: A collection of

instances of the service (potentially

collaborating with each other).– Peer group services are published as part of

the peer group advertisement.



Modules

• Modules: Abstraction to represent a piece

of Code.

• Can be java class, DLL a set of XML

.• Generic Abstraction to allow a peer to

instantiate new behavior.

• JXTA platform uses moduleadvertisements to describe itself.



Modules• Module Class : identified by unique class id.

• Module Spec: Contains all the informationnecessary to access a module. Module Spec

implies network compatibility:

– For a service module spec may contain pipeadvertisement.

• Module Implementation – can be multiple

module implementations for a given modulespec.



Pipes• Virtual communication channel that may connect

peers that do not have a direct physical link.

• JXTA peers use PIPES to send messages toeach other.

•

message transfer mechanism used for servicecommunication.

• Pipes support transfer of binary/text.

• JXTA pipes may have endpoints that areconnected to different peers at different times or not connected at all.



Pipes Hide Plumbing Details



Pipes• Point-to-point Pipes:

– Connect exactly two endpoints together

• Propagate Pipes:

– Connect one out ut i e to multi le in ut i es.

– All propagation is done in the scope of a peer group.That is, the output pipe and all input pipes must

belong to the same peer group.

• Secure Unicast Pipe:– Point-to-point secure communication channel.



Advertisements• All network resources are represented by

advertisements.• JXTA protocols use advertisements to describe

and publish the existence of peer resources.

• Peers discover resources by searching for corresponding advertisements.

• Advertisement is published with a lifetime that

specifies the availability of associated resources.



JXTA Advertisement<?xml version="1.0"?>

<!DOCTYPE jxta:PipeAdvertisement>

<jxta:PipeAdvertisement xmlns:jxta="http://jxta.org">

<Id>

-

</Id>

<Type>

JxtaUnicast

</Type>

<Name>foo

</Name>

</jxta:PipeAdvertisement>



Advertisements• Peer Advertisement:

– Describes Peer Resources

• Peer Group Advertisement:

– Describes Peer rou s ecific resources.

• Pipe Advertisement:– Describes a Pipe Communication channel.

• Module Class Advertisement:

– Describes a Module Class.

– Formally documents the existence of a module class.



Advertisements• Module Spec Advertisement

– Defines a Module Specification– Provides references to the documentation needed to

create a conforming implementations of that

spec ca on.

• Module Impl Advertisement

– Defines an implementation of a module spec.

– Includes name, module spec Id , code, package and

parameter fields which enable the peer to retrieve the

data necessary to execute the advertisement.



Advertisements• Rendezvous Advertisement

– Describes a peer that acts as a rendezvous.

• Peer Info Advertisement

– escr es peer n o resources.– Holds information about the current state of a

peer.



Quick JXTA Demo• Demo will do the following:

– Make advertisements.

– Publish the Advertisements.

– .

– Use the advertised pipe to send a file from

peer to peer.



Demo• Start 3 jxta shells on the same machine.

– Make one jxta shell the rendezvous peer.– Make the other two use the rdv peer.

– Test eer discover .

– Examine the peer advertisement.

• Make a Pipe advertisement (from sh2)

– p = mkadv –p pipename

– publish –d p

– inpipe = mkpipe –i p



Demo• From shell 3 discover the pipe

– search –r #send out discovery request– search #see what arrived in cache

– cat advxx #Examine the i e advertisement

– outpipe = mkpipe –o advxx # make outpipe

• Make a message to send

– importfile –f data mydata #Create data object

– put mymsg mytag mydata #assign data tag

– cat mymsg #examine the message



Demo• Send message through pipe (sh3):

– send outpipe mymsg

• Read from other end of pipe (sh2):

– newmsg = recv np pe oc ng rea– cat newmsg #see what you got

– newdata = get newmsg mytag #extract data

– cat newdata #see what you got



Note• Asynchronous programming model

– Results are cached and cache is queried.• Mailbox like message delivery

•

• Some amount of configuration necessary.

• You can extend the shell and add new

commands to it.

• Conversely, you can imbed jxta into another

shell (tcl/tk).



JXTA Protocols• Allow Peers to dynamically route messages to

any other peer in the network, potentiallytraversing firewalls.

• Allow Peers advertise their resources and.

• Peers can co-operate to form self-organized andself configured peer-groups independent of their positions in the network ( edges, firewalls,

NATS, Public vs. Private Addresses), without theneed for a centralized managementinfrastructure.



Protocols• Peer Discovery Protocol - find peers, groups,

advertisements• Peer Information Protocol - learn peers’

status/properties

• Peer Membership Protocol - sign in, sign out,authentication

• Pipe Binding Protocol - pipe advertisement to pipe

endpoint• Peer Resolver Protocol - send/receive search queries

• Endpoint Routing Protocol - available routes to

destination



JXTA Protocol StackPeer Disc

Peer Info

Pipe Bind Pipe Bind

Peer Info

Peer DiscVia Peer Rslv

Via Peer Rslv

Via Peer Rslv

Network Transport Network Transport

Rendezvous

Peer Rslv

Rendezvous

Peer Rslv

Peer Endpt Routing Peer Endpt Routing

Via Peer Rslv

Via Endpt. Routing

Via Network Transport



Animation of Scenarios

Advertisement Animation

http://platform.jxta.org/graphics/adv.swf

http://platform.jxta.org/TutorialGraphics.html

Connection Scenarios



Peer Discovery Protocol (PDP)

• Peers publish advertisements and

discover about resources usingadvertisements.

published using an advertisement.

• Advertisements are XML meta data that

describe resources.



Peer Information Protocol• Once a peer is located, its capabilities and

status may be queried.• PIP ping sent to a peer to check if the peer

.

– Peer Info message used to respond to a ping



Peer Resolver Protocol (PRP)

• Enables Peer to send generic query

requests to other peers and identifymatching responses.

peer or can be propagated via rendezvous

service within the scope of a peer group.

– PIP and PDP built using PRP.



Pipe Binding Protocol (PBP)• Used by peer group members to bind a

pipe advertisement to a pipe endpoint.• Pipe is an abstract named message queue

,

(unbind), delete, send and receive.

• Pipe IDs are unique.

• PBP message sent to find a pipe endpointbound to the same pipe advertisement.



Endpoint Routing Protocol

• A protocol that allows an endpoint to

discover a route (sequence of hops) usedto send a message to another peer.

needs to find an intermediate peer or set

of peers to route the message.



Rendezvous Protocol (RVP)

• A mechanism by which peers can

subscribe to a propagation service.• Within a peer group peers can be

peers.

• RVP is used by PRP and PBP in order to

propagate messages.



Network Architecture• JXTA Peers have different capabilities:

– Micro Peer, Standard Peer, Super Peer,Rendezvous peer.

• Minimal Ed e Peer:

– Device with minimal capability. Mustimplement the Peer Resolver Protocol andEndpoint Routing Protocol.

• Full Featured Edge Peer – Will Cache advertisements.



Network Architecture• Rendezvous Peer:

– RDV peer forwards advertisements. Peersseek RDV peers in their peer groups.Discovery requests are forwarded through

peers

• Relay Peer:

– Maintains information about routes to other peers and routes messages to them.

– Forward messages on behalf of peers thatcannot directly access another peer.



Discovery Service

• Retrieve Remote / Local Advertisements– Application can dispatch queries using

getLocal/Remote Advertisements to fetchadvertisements.

• Publish Advertisements Locally• Publish Advertisements remotely

• Flush local advertisements.

• Informs the application through anasynchronous Listener Interface.– Delivers discovery event when a query is processed.



Resolver Service• Encapsulates the Resolver Protocol and hides

its complexity.– Discovery Service uses the resolver service.

• Resolver Service needs two types of messages: – eso ver query message an esponse message.

• Developer can create a Resolver Querymessage at any time and send query to aspecific Resolver handler on a remote peer.

• Developer can register a query handler for aresolver query for a given handler name.



Shared Distributed Index (SRDI)

• Optimization to reduce the number of

messages for search.• When edge peers publish new

,

to push advertisement indexes to the

Rendezvous peer.

– Queries are only propagated to RDV peers.





Security Requirements• Confidentiality – contents of a message

are not divulged.• Authentication – guarantees a sender is

who he claims to be

• Authorization – Sender is authorized tosend the message.

• Integrity- Message was not modified in

transit.• Refutability – guard against replay attack.



JXTA Security

• Peer group is a “web of trust”– Group can have an authentication method for allowing peers to

join the group.

• Authentication method using X.509v3 certificates:– Peer must have X509 root cert of any peer with which it wishes

to communicate securely– When peer joins the PG, it receives PG creator’s Root cert under

TLS

– Certificate Service Request is used to acquire group

membership cert.– Peers can authenticate each other using the group membership

certificate.



Virtual TLS• JXTA pipe might span multiple relays.

• When a JXTA secure pipe is created and theassociated endpoints are resolved, an end toend TLS channel is created. Independent of therelays and underlying physical transport.

• Peer certificates are exchanged and verifiedduring initialization of the secure pipe.

• Peer certificates are digitally signed by the JXTAplatform.

– JXTA creates a self signed root certificate and issuesa peer certificate based on that root certificate.



Security• XML meta data in advertisements provide

Credentials, Certificates, Digests and PublicKeys.

– Credential – token that can be used to identify the

sender.

– Credentials are used for authorization and

authentication.

• Message can be encrypted/decrypted using

private/public key pairs.

• Certificates are distributed using TLS.



JXTA Security API• API are based on the JAVA Smart Card

API.• JXTA API does not provide support for key

.

• Provides support for cypher / decypher,

hash computation and digital signature.



JXTA based Grid Broker Service

broker

Broker – matches jobs to available resources

Res. Avail Adv

Resource Adv

Resource or User Registration –

Peer Advertisements

User wants to submit the job to broker –

Job Advertisement

Broker matches jobs and resource –

Pipe Message sent back to User Job Submission –

Using Pipe to send the job to resource

http://www.unix.globus.org/cog/projects/jxa/?Projects=&

JOB Resource

o v

User Adv

Discover Pipe

Publish



JXTA XML RPC and JXTA SOAP

• SOAP – Simple Object Access Protocol.

• Tunnel XML RPC (lightweight SOAP) or SOAPon JXTA Pipes.

•

a firewall-controlled environment.– Free the web from the tyranny of system

administrators.

– Everybody can run a web server like in the good olddays!



Voice Over P2P• Try to stream voice over JXTA pipes.

• Why? Firewalls.• Advantages

– Instant deployment

– No need for complex protocol (RADIUS/DIAMETERwhatnot).

• Disadvantages:– Voice quality will likely be bad.

– People will tolerate bad quality for convenience.

http://vop2p.jxta.org/



Project Ideas (discussion)• Measurements of peer to peer protocol

performance.• A simulation of JXTA vs other P2P protocols:

– Decentralization and timeouts means inconsistencies

in application state are possible.

– How to tune cache advertisement timeouts.

– The variation of responsiveness and peer discovery

with group size (what is the latency of finding a pipe

or advertisement as a function of networkparameters).



Project Ideas (discussion)• Firewalls are here to stay:

– Firewalls are a huge barrier for IP Telephony.– Effective FW solution is a huge win (see

. .

the beta client in a single day).



Project Ideas (discussion)• JXTA allows P2P interaction through firewalls:

– What bandwidth/delay characteristics can we expect.– How can we bridge between SIP/SDP (which

specifies RTP parameters) and JXTA?

– Can we build a gateway which will allow you to do

voice calls through a SIP phone using JXTA as a

transport for everything (signaling and voice)?

– If so you can use your MSN messenger or SIP phone

through a FW and deployment would be easy (couldbe an applet). What performance can you expect?



JXTA vs. JINI• Language dependence

– JXTA is XML based.– JINI relies on java object serialization.

– JXTA rotocols are lan ua e inde endent.

• Centralization– JXTA assumes no centralization (well, except

for the RDV peers??).

– JINI uses a centralized service locationbroker.



Material for this talk• JXTA Protocol Specification

– http://spec.jxta.org

• JXTA Programmers Reference– http://www.jxta.org

• JXTA in a Nutshell by Scott Oaks, BernardTravesat and Li Gong– O’Reilly publishing

• JXTA by Brendon Wilson

– New Riders Publishing ( Free PDF available fromhttp://www.brendonwilson.com )

Documents

JXTA-Overview [Compatibility Mode]