haifa labs swg (@rehovot) © 2006 ibm corporation sipping with websphere application server v6.1 uri...

Haifa Labs SWG (@Rehovot)

© 2006 IBM Corporation

Sipping with WebSphere Application Server v6.1

Uri SegevManager, SIP Infrastructure Development Team

Haifa Labs SWG (Rehovot team)

© 2006 IBM Corporation2

Agenda

JSR 116 Overview – Basic concepts and API

SIP Container Overview and Architecture

Introduction to the IBM IMS Presence Server



Agenda






Goals

Create a platform that enables creation of SIP services the same way that it is possible for HTTP

It is not possible to use the HTTP servlets paradigm since SIP control is very different from HTTP

JSR 116 (SIP Servlet API) goal is to provide a similar mechanism for SIP



What Is A Servlet?

Sun’s Definition: “A Java program that runs as part of a network service, typically an HTTP server and responds to requests from clients“



Why extending the Servlets model for SIP?

Servlets API is an open standard supported by multiple vendors

Containers manage Servlet’s life cycle, session’s state, fault-tolerance, scalability, security

Application’s developers can focus solely on their application

HTTP Servlets are widely used in Web development. Large community of developers already familiar with the concepts of the Servlets API

New Services developed as Servlets can interact with existing components (HTTP Servlets, EJBs) creating converged applications



Other Goals

Application composition – enabling a SIP servlets to be written in a way that one servlet can be called after the other servlet completes

Converged applications – enabling converging both SIP and HTTP applications

Both application composition and converged applications are not very well defined in JSR 116

The SIP container implements both but other implementations of the container may differ…



Similarities between HTTP and SIP Servlets

The container hides the low level protocol, exposes high level API

Servlets invocation is triggered by events (request/response)

The container selects the appropriate Servlet to invoke

Developers override methods in the Servlet’s base class and provide specific implementation

Servlets are grouped into applications (war/sar) and deployed with a deployment descriptor (web.xml/sip.xml)

The container manages Servlet’s life-cycle, session state



HTTP Servlets

Used for developing Web Application

A set of Servlets that process HTTP Requests. Responses are sent back to the client as HTTP responses containing web pages

Developers overrides the doGet and doPost methods of the HTTP Servlet class and provide specific functionality

HTTP Servlets and their deployment descriptor (web.xml) are packaged into a WAR file by the developer/builder and deployed to the server by administrators

Container manages Servlet’s life cycle, replication of Session state, fail-over, authentication, security



HTTP Servlet API

destroy()

service()

init()

servlet

HTTP Response

Client Servlet Methods

HTTP Response

doPut()

doPost()

doGet()

Error Response

Rules

HTTP Response

Error Response

HTTP Request

Web Container



SIP Servlets

Used for developing systems that process SIP Signaling, e.g., telecom applications (SIP), presence servers (SIMPLE)

SIP Servlets process both SIP Requests and SIP Responses

Developers extend the SIP Servlet class and override methods that they wish to process:

• doRegister(…)

• doInvite(…)

• doMessage(…)



SIP Servlets

Creating and sending a message is fast and easy (two lines of code)

SIP Servlets hide the complexity of the SIP protocol. No need to set complex headers: tag, call Id, cseq, record route, via

Containers handle retransmission of messages

Containers ensures that transactions are completed according to the spec

SIP Servlets do not store any state. Containers manage SIP Session and SIP Application Sessions



SIP Servlet API

destroy()

service()

init()

doInvite() doAck()

doOptions() doCancel()

doRegister() doPrack() doInfo()

doNotify() doMessage() doSubscribe()

doProvisionalResponse() doSuccessResponse()

doErrorResponse() doRedirectResponse()

doResponse()

doRequest()

servlet

Create Request()

Create Response()

SIP Message

Client SIP Container SIP Servlet Methods

RulesSIP Message



Differences Between HTTP And SIP Servlets

HTTP signaling less complex

– Only handles requests and generates responses

SIP signaling is much more complex

– Handle and generate requests and responses, Session management, Proxying

SIP servlets - response can be generated asynchronously

Servlet mapping for SIP servlets is done by a set of rules evaluated at runtime. Client applications are not aware of applications installed on the server.

HTTP SIP

HTTP servlets - the doService() method is expected to send a response within the same method call

HTTP request contains the name of the Servlet to invoke in the request URI



Mapping SIP Requests To SIP Servlets

Servlet engines maintain a set of mappings which specify the conditions under which particular servlets should be invoked

A rule consists of a set of conditions, each of which test some property of the incoming request.

A simple rule: <servlet-mapping> <servlet-name>Registrar</servlet-name> <pattern> <equal> <var>request.method</var> <value>REGISTER</value> </equal> </pattern> </servlet-mapping>



Mapping SIP Requests To SIP Servlets

A more complex rule: <pattern> <and> <equal> <var>request.method</var> <value>INVITE</value> </equal> <not> <contains ignore-case="true"> <var>request.from.display-name</var>

<value>Alice</value> </contains>

</not> <subdomain-of> <var>request.from.uri.host</var>

<value>ibm.com</value> </subdomain-of> </and></pattern>



SIP Servlet Life Cycle

The container initiates the server by invoking init() with the appropriate parameters

After the servlet is initialized the container can call the service method by invoking the service() method with requests and responses

When the container decides to deactivate the servlet it calls the destroy() method



SIP Servlet Example

public class RegisterSiplet extends SipServlet

{

protected void doRegister(SipServletRequest req)

{

//Let everyone Register, create an OK Response

SipServletResponse res = req.createResponse(SipServletResponse.SC_OK);

// Send response to the client.

res.send();

}

{



SIP Servlet Capabilities

A SIP Servlet has read & write access to fields in the request/response

A SIP Servlet can perform the following SIP operations:– initiate new requests - services are not limited to responding only, they

can initiate calls to clients or other servers.

– respond to incoming requests

– proxy requests forward: the container supports any combination of the following modes of operation:• parallel/sequential• record route - stay on signaling path• supervised by the application

Running within a J2EE container provides the Servlet access to : EJB, JDBC, JNDI, JMS, javaMail and more



Acting as a UAC

Creating initial requests using SipFactory

– SipServletRequest createRequest(); Creating subsequent requests using SipSession

– SipServletRequest createRequest(String method); Push Route header using SipServletRequest

– Void pushRoute(SipURI uri); Send the request

– void send(); The application is invoked for all incoming responses

Sending CANCEL using the SipServletRequest

– SipServletRequest createCancel();



Acting as a UAS

Creating responses using SipServletRequest

– SipServletResponse createResponse();

Receiving ACK

– Applications are notified of incoming ACKs for 2xx responses to INVITE.

Receiving CANCEL

– Applications are notified of incoming CANCEL for a request (which has not yet been responded)



Proxying

Proxying is relatively easy

Public void doInvite(SipServletRequst req) {

Proxy proxy = req.getProxy();

proxy.setXXX(true);

proxy.proxyTo(URI);

}

The container supports any combination of the following modes of operation:

– parallel/sequential

– record route - stay on signaling path

– Supervised by the application



Converged Application – SIP & HTTP

Servlet container are expected to support both the SIP and HTTP Servlet APIs

Advanced services will combine multiple modes of communication, for example, telephony, Web, email, presence and instant messaging



Application Composition Example

LS – Location Server

OCS – On Call Screening



SipSession

SipSession represents a point to point SIP relationship– i.e. a dialog or a pseudo dialog

Get session informationString getId();String getCallId();Address getLocalParty();

Create subsequent requestsSipServletRequest createRequest(String method);

Store and retrieve session datavoid setAttribute(String name, Object attribute);Object getAttribute(String name);Enumeration getAttributeNames();



SipApplicationSession

Unlike the HTTP model, SIP applications may consist of more than one session (conference application, converged application)

SipApplicationSession contains one or more sessions (Not necessarily SIP sessions)

Get sessions

Iterator getSessions();

Iterator getSessions(String protocol); Life cycle

setExpires, invalidate Attributes

Get, set, remove



Timer Service

A container provided service that allows application to schedule timers and receive notifications when timers expires

ServletContext sc = getServletContext();

String path = ‘javax.servlet.sip.TimerService’;

TimerService ts = sc.getProperty(path);

ts.createTimer(...(



Agenda






WAS Unified Application Server

TCP

WebSphere Application Server

SIP Container Pre-processorSIP

HTTP Container Pre-processor

SSL

HTTP

Web Container

UDP

Presence

Registrar

Session Mgr.

Other



Scalability & Failover

The containers replicate session information between them

When a container crashes the other containers in the cluster take over and deal with the sessions of the failing container

The proxies route messages according to load between the containers

When a container crashes the proxy knows how to route messages to the appropriate containers that holds the failed sessions



Load Balancing / Fail Over

TCP

SIP (TCP)

UDP

WEB Container

Logic

Servlet

Servlet

Servlet

Servlet

HTTP Transport

SIP Transport

WEB Container

Logic

Servlet

Servlet

Servlet

Servlet

HTTP Transport

SIP Transport

WEB Container

Logic

Servlet

Servlet

Servlet

Servlet

HTTP Transport

SIP Transport

WEB Container

Logic

Servlet

Servlet

Servlet

Servlet

HTTP Transport

SIP Transport

IHS

HTTP (TCP)

SIP (UDP)

Proxy

Plug-in



Agenda






Connectivity Layer Comprised of routers and switches to access a network

Control Layer Comprised of control servers for managing calls and sessions

Applications Layer Comprised of applications to execute services for the userPresence

Server

HSS

IP, GSM or others

I-CSCF

GLS IM

S-CSCF

P-CSCF

Presence for IMS



publish

Presentity

notify

subscribe

fetc

h

publish notify

Fetcher

Subscriber

accepts, stores, and distributes the

presence information

PresenceServer

Presence Model

no

tify



Presence Server Capabilities

Allows people to know the status of others Used in a buddy list application

User sends a PUBLISH to indicate their own status User status is defined in XML

• Base schema is part of the SIMPLE extensions• But as with all XML, it is infinitely extensible

User sends a SUBSCRIBE to express interest in another user The server will respond with a NOTIFY indicating the current status

of the specified user If requested in the SUBSCRIBE, the server will continue to issue

NOTIFYs every time the specified user changes status



Presence Information Flow

External Provider

Data

PresenceServer

Raw Presence Document

Composed Presence Document

Storage

Location Service

Calendar

Publishing presence

information



Presence Information Flow

Privacy

SubscriptionRequest

Subscribing on presence information

PresenceServer

Storage

AllowedForbidden

Sending the stored

presence information to

watchers



Architecture

IBM Websphere Presence Server is based on SIP technology SIP Container - Web container extension for SIP applications Implements RFCs and drafts relevant to presence

IBM Websphere Presence Server is developed on top of WAS Fully integrated with J2EE architecture Includes EJBs, JDBC, JMS, Java servlets (SIP servlets) Can be deployed in a distributed environment

IBM Websphere Presence Server supports Standard presence objects (user, conference) Custom presence objects (taxi, printer, game)



Architecture

IBM Websphere Presence Server is made up of a collection of inter-working services and utilities

Presence Service – handles PUBLISH and SUBSCRIBE requests and sends NOTIFY messages

Miscellaneous services (external providers, resource list, privacy)

IBM Websphere Presence Server is extensible New services and utilities New types of presence information New sources of presence information



Extensions

External providers

RLS providers

XML manipulation utilities



External Provider – Location-based Service

GPSMobile Location Protocol

Wireless Base

Station

RawPresenceDocument

ComposedPresenceDocument

includesgeographic

al location

WebspherePresence

Server

External Provider

Provides a set of APIs for external

providers

John is about to join a meeting. He changes his status to ‘busy’ ‘in a meeting’ and publishes the presence document



Extensions to WPS

External providers

RLS providers




RLS Providers

Alice

Joe

Bill

Andrew

Tony

Creates a list of buddies [email protected]

Creates a list of buddies [email protected]

LDAP

WMM

XCAP

RLS Provider

Provides a set of APIs for RLS providers

SIP NOTIFY

Websphere Presence

Server

SIP SUBSCRIBE [email protected]

Storage

PUT

GET



Extensions to WPS

External providers

RLS providers




XML Manipulation Utilities

Presence information is presented in XML format

Presence schema is defined by IETF in RFC 3863 but …it can be extended

IBM Websphere Presence Server provides support for the pidf schema

IBM Websphere Presence Server provides two extension points to handle custom XML

– Aggregator

– Document processor



Default Aggregator

IETF RFC 3903 – Publish define the natural decomposition of a presence

<?xml version="1.0" encoding="UTF-8"?> <root entity="pres:[email protected]" xmlns="test:ns"> <test id="old attr1"> <child>old child 1 </child> <child>old child 2 </child> </test></root> <?xml version="1.0" encoding="UTF-8"?>

<root entity="pres:[email protected]" xmlns="test:ns"> <test id="old attr1"> <child>old child 3 </child> <child>old child 4 </child> </test> </root>

Aggregator

<?xml version="1.0" encoding="UTF-8"?> <root entity="pres:[email protected]" xmlns="test:ns"> <test id="old attr1"> <child>old child 1 </child> <child>old child 2 </child> </test> <test id="old attr1"> <child>old child 3 </child> <child>old child 4 </child> </test> </root>

haifa labs swg (@rehovot) © 2006 ibm corporation sipping with websphere application server v6.1 uri...

Documents

sip servlets http

sip slide

sip servlets response

sip servlets i

spec sip servlets

sip requests

responses sip

sip session