Question About ACK

hi,

Looking at the following scenerio:
UAC's URI is 0 <at> 59.64.159.148
UAS's URI is 2 <at> 59.64.159.126
Proxy is responsible for the domain "59.64.159.126"

UAC sends ACK to Proxy. The ACK method's content is as following:

ACK sip:2 <at> 59.64.159.126:5060 SIP/2.0
Via: SIP/2.0/udp 192.168.2.14:5060;branch=1000
From: <sip:0 <at> 59.64.159.148>;tag=16
To: <sip:2 <at> 59.64.159.126>
Call-ID: [call_id]
Cseq: 1 ACK
Contact: <sip:0 <at> 59.64.159.148:5060>
Max-Forwards: 2
Route: <sip:2 <at> 59.64.159.126:5060;transport=udp>
Subject: Performance Test
Content-Length: 0

Why doesn't proxy send ACK to 59.64.159.126:5060, but send ACK back to 59.64.159.148:5060?

Thanks a million!
 				

　　　　　　　　ljzhang
　　　　　　　　xueyou38 <at> 163.com
　　　　　　　　　　2005-03-01