sundance-communications.com/forum Forums TDM Business Telephone Systems Samsung Telephones & Systems ITP Phone Dropping

We have a OS7400 running behind a firewall/nat. We have 7 remote ITP phones working behind a firewall/nat. Every thing works fine, then one or two of the phones starts to drop calls after one minute or less. If you look at the SMDR data the ITP phone is Registering then Clearing its registaration over and over again in minute intervals. The only way to fix it is to go to MMC 840 and clear that phones registration info and reboot the phone. All the other ITP phones stay working. Currently I'm thinking off three possible casuses for this

1)The DHCP IP lease time is expiring
Should I make the network static IP based no DHCP?

2)Problem do to the desktop PC getting its LAN connection from the back of the ITP Phone
3)To much network traffic

I'm going to call samsung support tomorrow any help or ideas would be great.

Usually the reason for a dropped call is a buffer issue. If the jitter buffer becomes too full the system will flush the buffer out thus dropping the call. Reasons for the buffer to become full is poor throughput on the network side. Run a continuous ping from the system end to one of the routers on the remote end with the problem. If the reply is all over the place Ie: 20msec then 180msec, 700msec, then back down to 20 it could be the problem. The are of course lots of other reasons that could cause the problem. Odd that the phones are clearing thier registration though. I haven't seen that before. After the phone dropps a call is it rebooting on it's own? If not can another call be made right away? What kind of bandwidth do you have at the system end and also at the remote ends that have the problem?

I ran a ping test for a minute it stayed between 136 to 152 ping from system side to remote only once. The phone stays working calls cant last more then 1 minute before it drops tho its just that the SMDR data prints ITP REGISTRATION CLEAR for that extention. The system bandwidth is 10meg/1.5meg, the remote location with the IP phoes is 1.5meg/867k. Should I try and adjust the jitter setting if so should I increase it or lower it.

I would suggest using a network sniffer that would tell you alot of why an IP phone loses it connection. You speak about the lease for DHCP being to short, you should be able to see in the sniffer program on a reset of the IP phones. It would also show if you are having a problem with the firewall or NAT settings. You may have an IP conflict that is showing up when you are in the middle of the conversation dropping the call and resetting the phone.

I adujsted the Max Jitter value to 200 and the Jitter OPT to 06 in MMC 835. It seems to be holding up today "Knock on Wood". I'll run EtterCap on their network if I have any more problems.

Hi Mininet
Did you find any answers for this problem, I have got four sites with the same problem Samsung are looking into it.
I have got an old ITP5014 setup next to a ITP5114 at four different remote sites, the 5114 cuts out every minute but the old 5014 works fine. So it can't be a networking issue. I have got wireshark (ethereal) captures that show the voice stops transmitting from the system then the phone resets. I happens on every call till like you said, I clear the registry.