Re: Trying to connect to a Viewstation
- From: Brian Sullivan <briansullivan@xxxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Wed, 29 Jun 2005 10:31:08 -0400
On Wed, 29 Jun 2005 09:58:09 +0200, SnakeEater wrote:
> Hello,
>
> I have a problem:
>
> At work we have a Video Conferencing Device, a Polycom Viewstation
> V500.
> It is in the DMZ of our 3com Superstack firewall but to avoid problems
> we are allowing all traffic in and out.
>
> With a laptop running Windows XP and a Logitech Quickcam Pro 4000 I
> can connect with Netmeeting to the Polycom from the LAN and from my
> home in the Netherlands.
> At home I have cable internet (4000/512) with a Motorola modem and a
> SMC wireless router (NAT, UPnP enabled).
>
> When I take this laptop to a colleague in his office in France the
> following happens.
> - On the laptop we can see and hear the office but the sound stops and
> the image freezes after approx. 10 seconds.
> - At the Polycom we see a black screen with the name of the caller.
> After a minute the connection is terminated automatically.
>
> In France we use ADSL (1024/256) with a Netopia Cayman 3341 router.
> (NAT, uPnP enabled)
> The router manual explicitly states, netmeeting connections are
> possible without making any changes to the configuration.
> Only changes to be made were those allowing incoming calls to get
> relayed to the computer behind the NAT. After doing this placing a
> call from the Polycom has the same result.
> The Internet provider, Nerim, claims to block nothing.
>
> Also from the colleague's home the result is the same. He has a
> Wanadoo ADSL connection (1024/128) with a Sagem 3202 wireless router
> (NAT, uPnP enabled).
>
> Does anyone have a clue?
>
> Regards,
>
> Piet.
I don't know exactly what is happening but since you can connect from one
spot and not the other I would not suspect the end points ( from your
description the same laptop is used as the NetMeeting end point in all
tests?).
For NetMeeting operation from behind a NAT router the following
characteristics would be observed:
1) UPnP is not a factor NetMeeting does not use UPnP
2) Generally outgoing T.120(data only) calls will be possible with no
router configuration -- to get audio/video calls to function the router
must incorporate an H.323 proxy or gatekeeper/gateway or a separate server
must provide that function -- or -- the internal NetMeeting client must be
full exposed via a dmz like feature
3) Incoming (calls made directly to the wan IP of the router) data only
calls are possible with only tcp 1503 forwarded. Audio/video incoming calls
might be possible with tcp 1720 forwarded but generally require the target
client to have dmz designation or use a gateway/gatekeeper and have a
gatekeeper managed call made.
I don't know the specific devices you are using so I don't know if they
could be implicated in your problem -- but they are the most likely cause.
I would try to eliminate their effect from the testing situation by making
the NetMeeting client the dmz client (regardless of what the router
documentation says). Some dsl providers provide dsl modems that are also
NATs so regardless of the router configuration the modem still causes a
problem. I don't know if that could be the case in your situations ( to
test examine the router configuration to confirm that has public IP).
.
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