[Serusers] RE: Back to Back INVITE?

[xwang at cascotec.com]

Hello

I have SER and RTPPROXY installed. Everything works fine till we debug a
softphone. I use SPA3000 to dial, the receiver is a softphone. The softphone
registers correctly.

When dialing from SPA, here is the handshaking sequence

SPA3000 -- INVITE --><-- TRYING SER -- INVITE -- INVITE --><--TRYING RING
softphone.

There is a back-to-back INVITE sent out immediately by SER to the softphone.
I don't see those sequence to call other UAs.
Does anyone know why SER sends two INVITE?

Thanks!
Steven