[Serusers] SIP & application server

Victor Gamov vit at lipetsk.ru
Wed Jul 9 16:00:02 CEST 2003

Jiri Kuthan wrote:
> At 10:19 AM 7/7/2003, Victor Gamov wrote:
>>I'm novice at SIP technology and I have some questions about it.
>>When we speak about "application server" in SIP (SER may acts as AS) what does it means?
>> Is it server which siply launch external applications (internal module or fork & exec)
>> to rewrite SIP/SDP packet and forward it to next hop or something else?
> We should have possibly avoided use of that term -- "application server" 
> is today used in too many contexts by too many marketeers and has no fixed
> technical meaning.
> Within SER, we use "Application FIFO Interface" for the interface with which
> you can access SER internals and initiate some SIP conversations, like
> IM paging or click-to-dial. It became mature in 8.11 -- 8.10 was an infant.
> It is not a B2BUA though you could use it to build one. Actually we began
> to use this interface by applications like voicemail or conferencing, and
> possibly a B2BUA will emerge too.
>> For example if I want to write application which accept external call, make some
>> decisions on it and then make external call. Is it suitable for SER or I must write
>> something like B2BUA and start it as independed application (as UA from the point of view of SER) ?
> That depends on what you exactly want to do. Most cases are perfectly fine
> with a proxy server. For example, you look at incoming INVITE, detect it
> should be routed to gateway, check it against some access control lists
> and forward it then. B2BUA is much more needed if you would wish the server
> to guide caller through multiple-stage converstation. For example, such
> a session would include first stage with an announcmenet component ("welcome to 
> lipetsk.ru"), then converstation with an IVR ("press 1 to talk to CTO")
> and eventually forwarding to a SIP telephone.

Thanks!  It is exactly just what I thought.

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