VNC and Zonealarm

Seb Wills saw27 "at" mrao.cam.ac.uk
Sun, 30 Sep 2001 14:33:23 +0000


Thanks for the suggestion. I don't think that's what's going on though - I
examined CPU/RAM usage. While doing a VNC screen refresh with zonealarm
enabled there is still tons of free RAM and the CPU was always at least
60% idle (the ZoneAlarm processes took about 8% CPU and VNC about 15%). So
it doesn't seem to be overstretching the CPU at all. Without zonealarm
running VNC only consumed slightly higher % CPU (less than 20%).

seb

On Sat, 29 Sep 2001, Glenn Mabbutt wrote:

> Although I personally haven't used ZoneAlarm, a general suggestion is that
> VNC (and most "remote control" apps) are fairly processor/RAM intensive.  By
> the description, I'm assuming the Win98 box has VNC and ZoneAlarm.  I would
> suggest finding a shareware prog that will let you monitor CPU/RAM usage
> (they exist, just can't remember a name off-hand), and then try it with
> ZoneAlarm enabled/disabled.  My hunch is that ZoneAlarm is simply putting
> the processor "over the edge" in terms of usage, as it's examining every
> packet that leaves/enters the box.
>
> -----Original Message-----
> From: Seb Wills [mailto:saw27 "at" mrao.cam.ac.uk]
> Sent: Friday, September 28, 2001 11:08 AM
> To: vnc-list "at" uk.research.att.com
> Subject: VNC and Zonealarm
>
>
> I use VNC between two machines on a LAN (the client being a Win98
> machine). Normally, VNC is highly responsive, and can do a full screen
> refresh in less than a second.
>
> If I enable ZoneAlarm (a free personal firewall which seems to be
> generally fairly highly regarded) on the client machine, VNC becomes
> unusably slow - it can barely keep up with moving the cursor around, and a
> full refresh takes 10s of seconds.
>
> Initially I assumed ZoneAlarm must just slow down all traffic a heck of a
> lot. But if I FTP a 5Mb file between two local machines, ZoneAlarm makes
> negligible difference to the transfer rate (433k/s instead of 466k/s).
>
> Can anyone suggest why ZoneAlarm is particularly affecting VNC performance
> and how to get round this (other than turning off ZoneAlarm when I use
> VNC)?
>
> Thanks
>
> seb
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