[cisco-voip] How does Transfer work?

Ryan Ratliff rratliff at cisco.com
Wed Sep 22 15:08:18 EDT 2010


A transfer works by splitting the original call into two legs.  The first leg (with the original caller) is placed on hold.  The second (new) leg becomes for all intents and purposes a new call on the phone that initiates the transfer.  This leg is used for the consultative call.  When the Trnsfr softkey is hit for the second time the two call legs are joined back together.

There are several places within this process that can result in the call dropping.  Media negotiation is one, and would generally be a codec mismatch at the joining of the two call legs.   A sneakier one is where the hold fails for the original call leg.  This isn't always immediately obvious and so the transferring party will go on with the new call until they find that the transfer completion fails (either gracefully with a message to the phone or both legs just drop).

If you are having a tough time with debugging just open a TAC SR.  We see these quite frequently.

-Ryan

On Sep 22, 2010, at 1:55 PM, Scott Voll wrote:

Sounds really stupid, I know.

But how does a transfer work?

With a Conference, it uses the Conference resource.

We are having intermittent calls drop during a transfer and I'm trying to find an all in compassing reason.

originally I thought it was a soft phone issue.  but it looks to be happening in house too.

So even on a completely G711 call I'm getting calls drop.  Unfortunately I don't have Caller ID on the incoming calls so it's making it even harder to troubleshoot.

I can NOT reproduce on demand but it's happening frequently enough to try and get to the bottom of it.

TIA

Scott 
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