Network Deployment (Distributed operating systems), v8.0 > Applications > SIP applications
SIP in WAS
WAS delivers rich SIP functionality throughout its infrastructure.
Session Initiation Protocol (SIP) has grown considerably since it first became an IETF standard in 1999. SIP was originally intended purely for video and audio but has now grown to become the control protocol for many interactive services, particularly in the peer-to-peer realm. SIP, and the standards surrounding SIP, provide the mechanisms to look up, negotiate, and manage connections to peers on any network over any other protocol.
The SIP Servlet 1.0 specification allows enterprise applications to use SIP and to support SIP-predominant applications in the Java EE environment.
WAS also provides tooling for the development environment and high performing Edge Components to handle distributed application environments.
In the application server, the web container and SIP container are converged and are able to share session management, security and other attributes. In this model, an application that includes SIP servlets, HTTP servlets, and portlets can seamlessly interact, regardless of the protocol.
High availability of these converged applications is made possible because of the tight integration of HTTP and SIP in the base application server.
In front of a clustered application sits the proxy server, managing the traffic and workload of the SIP and HTTP traffic to the container. This proxy server is a stateless SIP proxy and a HTTP reverse proxy together, which uses the unified clustering framework and high availability manager services to seamlessly monitor the health of the servers. The proxy server also can act as a stand-alone stateless SIP proxy in front of the SIP container in the application server when no HTTP traffic is present.
The proxy server uses the unified clustering framework, and high availability manager services to perform failover work, when necessary. With the converged proxy and converged container, session failover is done with affinity to the application, allowing the HTTP and SIP sessions to be tied together automatically. Having the SIP and HTTP sessions automatically tied together from the container to the proxy is another way the application server solution excels in converged environments.
It's important to note that the SIP function in the proxy server is stateless. The SIP RFC defines two types of proxy servers, one stateful and one stateless. Normally, a SIP proxy is a stateful instance and stateless proxies are specified as such. A stateful proxy participates in the call flows and is implemented using SIP servlets.
The stateless SIP proxy functionality in the proxy server allows the proxy to handle the workload, routing, and session affinity needs of the SIP container with less complexity. Being stateless, the proxy server can be fronted by a simple IP sprayer, such as the load balancer component. If a proxy server fails, the affinity is to the container and not to the proxy itself so there is one less potential failure along the message flow.
- SIP Infrastructure
The SIP infrastructure is a multi-tiered architecture made up of SIP containers, SIP proxies and an IP sprayer. The SIP container is a general purpose SIP application server. The SIP infrastructure consists of:
- SIP container – web container extension that implements JSR 116 plus a SIP protocol stack that implements all pertinent RFCs.
- SIP proxy – Stateless edge device that handles I/O concentration, load balancing, and other functions, in a similar manner to the reverse HTTP proxy. This is not the same as the SIP proxy defined by RFC 3261.
- Load balancer – SIP enabled to interoperate with SIP proxies and SIP containers. The extendable SIP proxy handles session affinity, load balancing, and failover. The load balancer functions as a highly available IP sprayer to dispatch messages to the proxies.
SIP is a key element for many new applications, especially when converged with HTTP, including:
- Click-To-Call
- Voice over IP
- Third Party Call Control and Call Monitoring
- Presence and Instance Messaging
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