Re: [Sip-implementors] request clarification on terminology (b2bua)

[Ganesh Jayadevan]

Alex,

I realized that I need to actually broaden my question:

UAC and UAS are roles a UA can play and therefore
if a UA can act as a UAC  when sending out the initial INVITE,
it must also be able to act  as UAS for an incoming BYE, for example.

Would we be in error if we called a UA-UA as a b2bua?
This means it can do the following based on whether it is
receiving or sending requests:

1. UAC-UAC (to setup 3pcc calls)
2. UAS-UAC (for initiating calls like follow-on calling)
3. UAS-UAS (if both endpoint send BYE's -- conference-like situation)

Thanks,
Ganesh

Alex Zeffertt wrote:

The term b2bua has a rather narrow definition in Section 6 of  rfc3261.
It refers to a UAS concatenated with a UAC for incoming requests into
the UAS.  Would  it be incorrect to use the term b2bua to refer to a
UAC-UAC concatenation?

    

As I understand it, a softphone is typically both a UAC AND a UAS.  This
is because the softphone can both initiate calls and receive calls.  A
b2bua is also both a UAC and a UAS, but it will only initiate a call
(i.e. act as a UAC) if it has received a call (on the UAS).  It then
maintains two seperate calls simultaneously, and pipes the streaming
media between them.

In this context it should be clear that a UAC-UAC concatenation wouldn't
work as a b2bua, because it would have no way of receiving calls.

Alex


  

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