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USG2130BSR-the voice phone one-way audio problem when make IP phone

Publication Date:  2012-10-25 Views:  44 Downloads:  0
Issue Description
Abstract
A department purchased a USG2100 device, and put about 200 IP phones through USG2100 access to public network. In the actual application appeared SIP phone one-way audio problems.
1. overview
1.1 summary
Project name: A department deploys USG2100 as IP telephone access device.
Positioning content: after open detect sip function, telephone appear one-way audio. Through call a phone from the private network to public network, find that the public network can't hear the voice of private network, appearing one-way audio. But make phone from the public to the private network, bi-pass.
The main work content:
(1) positioning the root reason when open detect sip phone one-way audio
(2) analysis and positioning the reason tp - link device can bi-pass;
Test the telephone communication situation when USG2100 device transform NAT port transition segment
1.2 environment


Huawei softco 5816 connects three 32s iad device and four subscriber boxes, ims network go through the USG2130BSR (firewall) first, and then connect to softco 5816. The number of users is about 200.
Simplified diagram:
Phone - - - - - - - - SUBBOX - - - - - - - softco5816 - - - - - - - - USG - - - - - - - Internet (IMS network)
SUBBOX: SPC SW
USG: USG2130BSR router
Softco5816: Huawei access network voice terminal
IAD328: ordinary telephone integrated access device model
Alarm Information
none
Handling Process
Modify inter-domain configuration, remove detect sip, and add HRP NAT ports - segment secondary command line. To begin test, telephone bi-pass, observe a day, do not find any abnormalities.
Root Cause
Respectively use USG and TP - LINK two cases to capture packet. Then analyze. The message analysis are as following:
TPLINK and USG message contrast (NAT transition address: 113.18.132.3 public network address: 218.207.150.112) :
According to the below message to analyze:

First analyze SIP/SDP message 

TPLINK part:

USG2130BSR part:

the Layer 2 ether header of TPLINK and USG is basically consistent, only TPLINK can't identify the source MAC address another name.
IP header of TPLINK and USG is the same, all made NAT transition
TPLINK NAT transition port since 44000, but USG since 2048
after USG make NAT transition, the port is less than before, from the beginning of 2048.
 

TPLINK don't do special treatment to SIP packet, output as the same, and USG make some NAT transition to SIP packet.
Through the above analysis and contrast can find that TP - LINK don't make NAT transition to SIP packet, only make NAT transition to IP header, and port value far outweigh our device. In theory: our devices don't do ASPF processing, adjust NAT transition port to be basically consistent with TP - link, should be feasible
Suggestions
none

END