<br><div class="gmail_quote"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Somewhere in my mail archive I have a permission from Broadsoft or
<br>Cylantro to implement this - before they<br>published it as a draft. They wanted Asterisk to include this<br>functionality. After that, they published it openly<br>as a draft, so there should be no problems.</blockquote>
<div><br>It's probably also supported by the fact that this specification is publicly available on BroadSoft's company website: <br><a href="http://www.broadsoft.com/pdf/BW-SIPAccessSideExtensionsInterfaceSpec-R1301.pdf">
http://www.broadsoft.com/pdf/BW-SIPAccessSideExtensionsInterfaceSpec-R1301.pdf</a><br><br>If we speak about SLA specifically, they've basically extended SIP on three fronts:<br><br>1. Additional parameters in the existing Call-Info header
<br>2. Call-Info SIP event-package<br>3. Line-Seize SIP event-package<br><br>The Call-Info event-package pretty much accomplishes the same thing as the standard dialog event-package (i.e. it notifies the state changes of the shared line to SLA stations).
<br><br>The Line-Seize event-package solves an arbitration issue that happens in en-bloc signaling protocols such as SIP. It allows the entire SLA group to be immediately informed as soon as one SLA station seizes the shared line. This allows an SLA station to "win" the line. The other phones render the line busy while one phone is dialing. I've seen different commercial PBX vendors solve this problem in their own proprietary way.
<br><br>There is one more interesting aspect to these SIP extensions -- they're built on the concept of Call Appearance. Call Appearance means that a unique line can have multiple calls active on it at the same time. So, you're not only telling the phones which line underwent a state change, but also which appearance of it.
<br><br>Does the current Asterisk SLA implementation support the Call Appearance concept?<br><br>--<br>Raj<br><br></div></div>