Avast! slows my network with about 10-20%

[Lars-Erik]

After my ISP raised their speed I noticed that my laptop got up to 5000 kbps,
while my desktop (that is a much faster PC) only got about 4080 kbps at max.

Have tried disabling everything and when I got to avast (4.7.1043) I found...

1) Web Shield slows the speed tests with about 10-15% (even when I set it to scan only certain file-types)
2) Network Shield adds another 2% (about 100 kpbs) speed drop

I comparison ZoneAlarm doesn't add anyting that is noticable at all :-(

Why this bit performance hit???

(but there still got to be something more, even with ZA and avast! uninstalled and Window FW off I get only max 4676 kbps on my desktop compared to 5000 kbps on my slower laptop - even on WLAN. Any ideas?)

[Lisandro]

1) Web Shield slows the speed tests with about 10-15% (even when I set it to scan only certain file-types)

Hmmm... It's difficult to defend this... certain resource usage.

2) Network Shield adds another 2% (about 100 kpbs) speed drop

Bad... it shouldn't eat resources...

(but there still got to be something more, even with ZA and avast! uninstalled and Window FW off I get only max 4676 kbps on my desktop compared to 5000 kbps on my slower laptop - even on WLAN. Any ideas?)

Well... without antivirus and firewall, the guilty could be only your ISP... don't you think?

[Lars-Erik]

No, It can't be the ISP, my laptop is connected via the same router as my desktop.
So they should get exacly the same speed, still my desktop gets 4600, my laptop 5000.
And the desktop is faster, have better netwrk card (gigabit at 100 Mbit).
So what could then cause this? It's weird?

[Lisandro]

It's weird?

Indeed... but I'm empty.
Are the same programs using the connection in both computers?

[Lars-Erik]

Yep..  or actually much more is running on the laptop :-)

[alanrf]

(but there still got to be something more, even with ZA and avast! uninstalled and Window FW off I get only max 4676 kbps on my desktop compared to 5000 kbps on my slower laptop - even on WLAN. Any ideas?)

You may want to take a look at diffferences in TCP Window Size between your two systems.  Having too small a TCP Window Size relative to the speed of your ISP can restrict the maximum speed you can obtain.

[Lisandro]

Having too small a TCP Window Size relative to the speed of your ISP can restrict the maximum speed you can obtain.

Can you helping me (and the others) to 1) check and 2) tweak this situation?
Can't we improve our connection speed?

[alanrf]

A site that helps with this:

http://www.dslreports.com/tweaks

Please note that this is not recommended (see the warning on the site page) for users of Vista.

[alanrf]

One other comment.

There is a formula that can be used to determine TCP Window Size for XP systems that uses the official maximum speed of your connection to your ISP.  However if you use the maximum stated speed of your ISP (mine is 6Mbps) then you will most likely be restricted to getting close to that maximum. 

My ISP and others now provide much higher speeds (bandwidth permitting) for the first 30 seconds or so of a download and in fact at offpeak times I get a higher connection speed for longer periods than that.  As I posted the other day in another thread - speedtests show that I get in excess of 20Mbps but to get that I need to have a higher TCP window size - mine is set to (decimal) 124100. 

 

 

[Lars-Erik]

You may want to take a look at diffferences in TCP Window Size between your two systems.  Having too small a TCP Window Size relative to the speed of your ISP can restrict the maximum speed you can obtain.

Where do I set this? And what is a good value.
I though both these PCs where with standard XP setup.
But if there is a difference I'll copy the setting from the laptop :-)

[Lars-Erik]

http://www.dslreports.com/tweaks

One difference only, receive window was 65535 on desktop and 64512 on laptop.
In this test the desktop was fastest. That is not true when I test against a "local" machine in Norway.

[alanrf]

65535 is the default value for TCP window size in Windows XP when a (RWIN) size has not been chosen (ie no TCP Window size exists in the registry).

If you have a poor quality connection then a high TCP widow size will cause excessive retries and slow your connection, however in a good quality connection testing a higher TCP Window Size will not, in any way, impair your connection and may well demonstrate improved throughput. 

I recently conducted a series of tests with my good quality broadband connection using lower RWIN sizes than I have that restricted my connection speed and I have decided to stay with the setting I posted earlier.  There are many in the forums who swear by an even higher RWIN size. 

[Lars-Erik]

No packet drops or anything. I'll try switching the netwoek cables.
There's got to be a reason for one computer beeing 10% slower.
Maybe I should borrow another network card and test as well :-)

[Lars-Erik]

Found IT !!!!

I compared all settings on the two computers, and noticed some services running on mine and not on the other.

So I tested one at a time, and when I disabled the "DNS Client" (local caching of DNS entries) the speed went from 4600 and up to 4970 kpbs.

But why should the DNS client have this huge bad impact on the speed?

[Lisandro]

Lars, it seems that the service must be running in order to receive an IP address. Did you manage to keep it disable, boot, and the network working after that?