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Knowledge Base

Video call between 2 TE30 is not working

Publication Date:  2018-09-12  |   Views:  611  |   Downloads:  0  |   Author:  d84093304  |   Document ID:  EKB1001851629


Issue Description

2 videoconference terminals TE30 are installed in different locations, behind NAT gateways/firewalls. The schematics are like this:

TE30-A ---> NAT-GW-A ----------- Internet -----------> NAT-GW-B -> TE30-B

Problem is the following:

1. Call from TE30-A to TE30-B : call gets disconnected after cca. 30 sec. with the following error being displayed on TE30-A's web interface: "Called site has rejected your call"

2. Call from TE30-B to TE30-A : call gets immediately disconnected with the following error being displayed on TE30-B's web interface: "The called site is offline; please dial later"

Alarm Information

No alarms

Handling Process

Calls have been made from each side to the other and signaling logs were gathered. From the analysis, the following conclusions were drawn:

1. Call from TE30-A to TE30-B: this call fails due to the fact that after TE30-B responds, the TE30-A tries to initiate the H245 TCP connection and the SYN packets get no response. After 3 SYN packets sent, TE30-A disconnects the call by sending “Release Complete”

(the redacted IP's are real IPs of NAT gateways/firewalls)


2. Call from TE30-B to TE30-A: this call fails due to the fact that after TE30-A responds, the H245 TCP connection attempt is actively rejected by the NAT-GW-A firewall (you can see that after the SYN packet, the TE receives a RST packet). Therefore, the TE30-B immediately disconnects the call.




Root Cause

Incorrect implementation of the communication matrix for this type of terminals in the NAT gateways/firewalls


Implement the correct communication matrix in the NAT gateways/firewalls