Relationship between GlassFish and Sailfin

(from:blogs.sun.com/prsad/entry/sailfin_and_glassfish)
There have been some questions on the mailing aliases on what Sailfin is and how its related to GlassFish ! Let me make an attempt to explain that.

GlassFish is a Java EE 5 based application server with high availability and scalability aimed at the enterprise customer.Its a project on java.net , the main project therein being the application server. There are several sub-projects under the Glassfish project which use GlassFish as the runtime.

Saifin is a subproject under GlassFish. It adds the SIP Servlet Container based on JSR 289 to GlassFish. In addition to the SIP Servlet Container , Sailfin also aims to provide High Availability of the SIP Servet Container and a loadbalancer for both SIP and HTTP traffic . Given the functionality , the Sailfin codebase requires GlassFish as its underlying runtime. The WebContainer from GlassFish and the SIP Servlet Container becomes the converged container that is typical of the SIP Application Servers based on JSR289

Sailfin Application Server is built by overlaying Sailfin codebase on top of Glassfish Application Server v2.1. This becomes the open-source SIP Application Server on java.net ( the only one on open source ? )

There are two terms from the previous statement that I would like to clarify :
Why do we overlay Sailfin ?
The Sailfin codebase is loosely couple with Glassfish, in the sense that there are no code-changes made in Glassfish code base which are related to functionality provided by Sailfin. Theoretically a user should be able to add Sailfin functionality to any Glassfish Application Server .

Why Glassfish 2.1 and not Glassfish v2 ?
GlassFish v2.1 would be have some SPIs that would allow extension of the deployment and administration functionality. Sailfin makes use of these SPIs to overlay the Sailfin code on top of GlassFish. Hence in order to use Sailfin we need a version of Glassfish that exposes these SPIs and that is Glassfish v2.1 !

Here is a schematic that explains it :

How is Sailfin distributed ?
Sailfin is distributed as a single bundle with the underlying GlassFish included. The bundle comes with the same jar based installer as GlassFish. Update: The underlying GlassFish comes with all the fetaures as a normal GlassFish v2.