Does 802.11b use a lot of resources?
bsd at kelleycows.com
Tue Mar 1 23:04:55 PST 2005
Bob Johnson wrote:
>On Friday 25 February 2005 12:06 am, Christopher Kelley wrote:
>>Have I tried too hard to squeeze usability out of an old computer?
>>I have a Pentium-166 that has been a faithful router & firewall (FreeBSD
>>5.3 and pf) for a couple years now. It has no trouble with the 3 to 4
>>Mbps I get from my broadband connection, at least not with ethernet.
>>I wanted wireless, so I could use my laptop around the house. I
>>dutifully read the section in the manual about setting up FreeBSD as an
>>access point. I'm using a Netgear MA311 802.11b card (Prism 2.5
>>chipset). And it does work, except it's very slow. Now I know that I
>>can only expect about 50% of the rated speed with wireless, but I
>>figured even if I got only 4Mbps, I'd be fine. But I get less than
>>1Mbps. I've updated the firmware, added a signal booster and hi-gain
>>antenna, and I have "excellent" signal strength throughout my house.
>>So my question is, is there more overhead with wireless than with
>>ethernet? TOP doesn't seem to show that I'm taxing it too hard, idle
>>never goes below about 70% with polling enabled (Hz=1000), and never
>>below about 80% with polling disabled. Am I expecting too much out of
>>an old Pentium-166?
>My experience is that:
>1) 50% throughput is probably the best you should expect. I generally plan on
>3-4 Mbps for an 11 Mbps 802.11b card.
>2) Using 128-bit encryption (WEP) will significantly slow down some (many?)
>cards. The WEP processing is done on the card (I think), and they simply
>don't have hefty processors. If you use 128-bit WEP, try 64-bit WEP and see
>if that speeds things up. 64 bit WEP is adequate to keep out casual
>snoopers, and 128 bit is not adequate to keep out a serious attacker, so the
>difference in security may not be as important as some believe. 64-bit WEP
>is also known as 40-bit, and similarly for 128-bit WEP.
>3) Turning on power management seriously slows things down for me, to well
>below 1 Mbps. Do a "wicontrol" and make sure Power Mgmt is "0".
Well, 3-4 Mbps would be fine, as that's about what my broadband runs at
anyways. At the risk of being pedantic, when you say 3-4 Mbps, do you
mean including overhead or not? In other words, if you use say the
bandwidth tester extension for firefox, would you expect to see 3-4
Mbps, or rather somewhat less than that due to overhead? I realize it
may seem a stupid question, I just want to make sure I'm comparing
apples to apples.
Just for testing, I turned off WEP completely, and verified that power
management was off. No change. Drat.
Now I am wondering if it's very firmware sensitive. I'm using Primary
1.1.1 and Station 1.8.0 - I guess I could "downgrade" the firmware to
either 1.3.4 or 1.4.9 - I had figured that more recent would be better,
but now I'm wondering. The man page is 2 years old, though, so I don't
know what versions were actually available when it was written.
Thanks for your help, I really do appreciate it, even if it doesn't
actually "solve" my problem.
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