Well tcp stack sends packets. It all has to do with the single write length that most likely goes out as a packet. If the write is large it will fill one or more full vpn packets that can't be fragmented and will be dropped. You can try it yourself. To tell you the truth I am not a TCP expert so I cant tell you the exact reason. I am sure that if you run ethereal you can find some clues rather quickly.

All I know that lowering MTU on my VPN interface fixed these problems.

Regards,
Alex


James Weatherall wrote:
Hi Alex,

VNC doesn't send packets at all - it runs over TCP.

Cheers,

Wez @ RealVNC Ltd.
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Alex Pelts
Sent: 25 April 2006 19:14
To: James Weatherall
Cc: 'S B'; [email protected]
Subject: Re: VNC freezing on Win XP Media Center Edition SP2

The VPN has MTU larger than MTU of physical network. Lots of packets are dropped as somehow VNC sends rather large packets. I had this problem myself until I lowered MTU to below of the physical network MTU.

The symptoms were:
1. screen would render half way and then stop.
2. screen updates were extremely slow
3. Connection would go for some short time and then would be dropped.

I am not sure why MTU is causing that effect. I think that VPN packets can not be fragmented so they are dropped and there is a large packet loss. I am not sure how VNC reacts to large packet loss.

Regards,
Alex


James Weatherall wrote:
Hi Alex,

Can you provide any more information on why that causes the
effect SB is
seeing?

Cheers,

Wez @ RealVNC Ltd.


-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Alex Pelts
Sent: 25 April 2006 07:07
To: S B
Cc: [email protected]
Subject: Re: VNC freezing on Win XP Media Center Edition SP2

MTU is too large on your vpn connection.

Regards,
Alex


S B wrote:
Hi,

I just bought a new computer from Dell (Intel dual core
2.8GHz, 1GB RAM
running Win XP Media Center w/ SP2), and downloaded VNC 4.4
viewer on it.
When I VNC to my work machine, VNC viewer freezes
intermittently. Some times
immediately after logging in and some times after 10-15
minutes of work. Did
anyone here faced a similar problem? How do I fix this problem.

Thanks,
- SB
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