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  • IP Phone Keeps Losing Connection

    We have just moved from TZ 170 SP to a TZ 210 with the enhanced OS. I was able to use the configuration tool and upgrade properly to the enhanced OS.

    Ours is a very simple setup as we have about 12 remote desktops users (VPN) going from windows 7 machines to server 2008. No Problem there.

    Our ISP is Logix and we have a network connection into the black box(from out network switch) to run the phone system- no problem there.

    The only problem we have is with one person in Houston (we are in Dallas) with his remote ip phone. *This is not, nor do we want VOIP) They had no problem prior to my exchange of firewalls last week. After the hookup, the phone had no problem connecting from either end just by pressing the same keys on the ESI phone system that we always have. However for no reason and at different times the remote phone will disconnect in the middle of a conversation and then reconnect some 30-40 seconds later. IT is not losing power. Internet connectivity is fine at both ends- no loss there.

    The current settings as "translated " from the original using UDP port 59001

    are: (under Network/nat policy/ Original source -Any, translated source- any, original destination-any, translated destination- 192.168.0.50, original source -Remote phone, translated source-Original, inbound and outbound interface- any, NAT policy is checked. Nat method on advanced page is "sticky IP" and is grayed out- so no change is possible.

    The firewall policy is wan to lan, service-remote phone, source-any, destination-wan interface ip, all users allowed and always on.


    We use none of the security services of the firewall.


    Does anyone see any problem with this configuration that would allow in the middle of the conversation for the remote phone to try and reconnect. The phone service man- thinks there is something wrong internally with the phone and that may be, however I am concerned about the coincidence of the problem occurring at the time of the exchange of firewalls. Is it possible that the IP phone which is a first generation is not keeping a connection due to some incompatibility with the new enhanced sonic OS?


    Any suggestions, ideas or considerations. They are all quite welcomed.

    Thanks
    Tom in Dallas

  • #2
    Re: IP Phone Keeps Losing Connection

    You say this is not VOIP but its an ip phone? That doesnt make sense. Is the phone using ip for transport? If so then it is voip. I assume this remote user is connecting via vpn for phone and data? What type of vpn? Remember there is some overhead with vpn traffic. During the time it goes down do you notice any congestion on either end of the circuit? Do you have any QoS mechanisms in place to prioritize call/control traffic over say web traffic? Have you looked to see if any traffic is being dropped over the vpn? Have you looked at the call logs to see why there call is terminating? What codec is being used? Alot of variables. Have you tried replacing the remote users phone to see if the phone itself is the issue? Any excessive delay/jitter issues?
    CCNA, CCNA-Security, CCNP
    CCIE Security (In Progress)

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    • #3
      Re: IP Phone Keeps Losing Connection

      Originally posted by auglan View Post
      You say this is not VOIP but its an ip phone? That doesnt make sense. Is the phone using ip for transport? If so then it is voip. I assume this remote user is connecting via vpn for phone and data? What type of vpn? Remember there is some overhead with vpn traffic. During the time it goes down do you notice any congestion on either end of the circuit? Do you have any QoS mechanisms in place to prioritize call/control traffic over say web traffic? Have you looked to see if any traffic is being dropped over the vpn? Have you looked at the call logs to see why there call is terminating? What codec is being used? Alot of variables. Have you tried replacing the remote users phone to see if the phone itself is the issue? Any excessive delay/jitter issues?

      The phone is part of an ESI system and no other phone will work- even a newer ip phone unless they replaced the entire interface of the system.. The firewall is merely port forward the ip phone to the black box that contains the phone. He is not and never did under the old system authenticate or use vpn transport.system in the main office. No traffic is being dropped on the log of any sort. We have a limited number of users who log in directly (2) and they are only on for about 20 minutes each 3 or 4 times a day and the rest do some uploads/downloads in the evening and it takes about 4 minutes for each one of these. I have tested with him on the phone at the time and logged in remotely from 5 of the remotes and nothing happens at all. Then later in the middle of the conversation, I loose connection and 30 seconds later he reconnects.

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      • #4
        Re: IP Phone Keeps Losing Connection

        Well the call is being dropped for a reason. Not familair with the call management system but there has to be a log of the calls and a way to see when/why a call was dropped. If not then there isnt much more you can do to troubleshoot it. Does the remote users internet connection experience issue's when this happens? Your using udp so there is no reliable transport like using tcp. Its possible its being dropped in transit.
        CCNA, CCNA-Security, CCNP
        CCIE Security (In Progress)

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        • #5
          Re: IP Phone Keeps Losing Connection

          Originally posted by auglan View Post
          Well the call is being dropped for a reason. Not familair with the call management system but there has to be a log of the calls and a way to see when/why a call was dropped. If not then there isnt much more you can do to troubleshoot it. Does the remote users internet connection experience issue's when this happens? Your using udp so there is no reliable transport like using tcp. Its possible its being dropped in transit.
          That may make sense. That was my first thought that the remote user was having an internet connection problem, but he can be working and moving on the internet and phone goes to static and then reconnects. Should I change from udp to tcp or some other custom protocol using the required port?

          Comment


          • #6
            Re: IP Phone Keeps Losing Connection

            Most voice (RTP - Realtime Transport Protocol) runs over udp to alleviate the acknowledgments used in tcp connections.Where in tcp is connection orientated.(3 way handshake). If I dont get an acknowledgement with tcp then the packet is retransmitted. Using udp with voice alleviates this as waiting on ack's could cause delay and jitter along the path as voice is very delay sensitive. Even if you where using tcp and a voice packet was dropped there is no way for the voice traffic to be retransmitted as the voice packet is happening in real time. The downside is that its sent blindly on the wire and hopefully the other side gets it. Thats why when troubleshooting voice your rely heavily on debugs and logs. Since udp is the standard then I am not sure if you can use another encapsulation type.
            Last edited by auglan; 5th November 2012, 18:59.
            CCNA, CCNA-Security, CCNP
            CCIE Security (In Progress)

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            • #7
              Re: IP Phone Keeps Losing Connection

              Originally posted by auglan View Post
              Most voice (RTP - Realtime Transport Protocol) runs over udp to alleviate the acknowledgments used in tcp connections.Where in tcp is connection orientated.(3 way handshake). If I dont get an acknowledgement with tcp then the packet is retransmitted. Using udp with voice alleviates this as waiting on ack's could cause delay and jitter along the path as voice is very delay sensitive. Even if you where using tcp and a voice packet was dropped there is no way for the voice traffic to be retransmitted as the voice packet is happening in real time. The downside is that its sent blindly on the wire and hopefully the other side gets it. Thats why when troubleshooting voice your rely heavily on debugs and logs. Since udp is the standard then I am not sure if you can use another encapsulation type.

              Thanks

              That is what i had thought, but was looking at a quick solution, but thought TCP might cause a slight latency or delay issue.

              The problem I keep wondering is why it drops it at all. The users are very limited in the office and by remote and we have a T3. I can clearly see the packets as they are transmitted, but no logging.

              What would you think the chances are that the first generation ip phone is not completely compatible with the new enhanced OS and new firewalls. There is no trouble in the handshake or connection. Do you think changing the dscp marking action in QoS from preserve to explicit or to map or none would have any affect?

              Thanks

              Tom

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              • #8
                Re: IP Phone Keeps Losing Connection

                I cant say how the Qos mechanisms work on your firewall but from a "Cisco" qos perspective the rtp stream always gets priority from a queueing perspective with a bandwidth restriction. Just realize that any kind of queuing only occurs if there is congestion on the link so if you see packets being queued you have congestion.
                CCNA, CCNA-Security, CCNP
                CCIE Security (In Progress)

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                • #9
                  Re: IP Phone Keeps Losing Connection

                  Originally posted by auglan View Post
                  I cant say how the Qos mechanisms work on your firewall but from a "Cisco" qos perspective the rtp stream always gets priority from a queueing perspective with a bandwidth restriction. Just realize that any kind of queuing only occurs if there is congestion on the link so if you see packets being queued you have congestion.
                  Bandwidth is not a problem or even close to it here. During the day, at most there are 3 people hooked to the sever- 2 from vpn and one internally that bypasses the vpn. On a T3, our bandwidth is not close to being a problem. I would feel great if it did not hook at all, but it does and just in the middle of a conversation, at different time intervals it disconnects and then reconnects on it's own. Do down internet, no problem with any other connection. I am very baffled.

                  Would using the DMZ, just for the phone system be of any value??

                  Thanks again

                  Comment


                  • #10
                    Re: IP Phone Keeps Losing Connection

                    Dont think putting it in the dmz would be of any value but its something you could try. At least the phone traffic would be separate from the local lan traffic if thats where the issue is. Like is said it could be dropped in transit by the ISP or any upstream router as delivery isnt guaranteed like on a point to point circuit.
                    Last edited by auglan; 5th November 2012, 21:05.
                    CCNA, CCNA-Security, CCNP
                    CCIE Security (In Progress)

                    Comment


                    • #11
                      Re: IP Phone Keeps Losing Connection

                      How do your users connect to the office??

                      Are you using the VPN Client software, NetExtender or something else??

                      Also this might be of use

                      http://www.binarytelecom.com/SonicWallSIP.htm
                      Last edited by wullieb1; 6th November 2012, 14:11.

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