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Airnet speed
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Posted by: kevinallein

Hi all, I have seen a couple of posts along that line, but never a good summary. I have a Tivo Airnet with a DLINK DWL-650 PCMCIA card. The card is modified and I have an external wireless access point antenna at the back of my Tivo. Installation was easy and after some fiddling I even managed to modify the Tivo dhclient to report the hostname to my Linksys wireless router. (Although Tivo does not support name resolution, you always need to give it an IP address)
Here is the problem: With a Laptop through 802.11b I get less than 100 KByte/s from the Tivo, with a PC with 100BaseT I get less that 200 KByte/s from the Tivo. Both is through the Linksys router. Does anybody get higher speeds ? I can not find any options how to configure the airnet module. Can people share the speeds they get and any tips they have to increase speed ?

Thanks a lot
Kevin

Posted by: jafa

Hi,

Talking through an AP to another 802.11b will automatically halve the throughput.

Max throughput is around 4Mbps tcp throughput (3.9 for a SA) = around 500kbps.

Given that you are getting half the throughput when you talk to your laptop it sounds like it might be using a lower 802.11b speed.

I can check the driver - I was thinking of adding a rate indication - not sure if I released it.

Nick

Posted by: kevinallein

Hi Jafa,
thanks for the reply. I recently downloaded the latest driver from your website and I can not see a rate indication. (Unless you have some hidden switch to activate that). If you do have a version doing that, could you please tell me, how I could get hold of it ? Is there any way to force the Airnet into a certain mode ?

Thanks a lot
Kevin

Posted by: TiVo_WillieB

Well this may not help you since it's not Airnet but I'll post anyway because it's kind of Interesting. I have been conducting a few speed tests myself. A quick review of the relevant devices in my house:

Phillips SA TiVo Series 1 with TurboNET,

TiVo connected to Network via D-Link DWL-810 Ethernet Bridge (802.11b)

Linksys WAP11 connected to Linksys 100mbps hub

Motorola 5100 Cable Modem via Ethernet to a Cisco 806 Router, Other Interface on the 806 goes to the Linksys Hub. Oh sorry, this part was irrelevant. I got carried away but hey, at least you know how I control telnet and ftp access to my TiVo..:-)

Also for the PCs for testing is my desktop, a P4 2.6GHz 512MB RAM, 120GB 8MB Cache connect directly to hub.

Laptop Athlon 1600+ 256MB RAM

Ok here are the test results

Max Speed from TiVo via Bridge through Access Point to Desktop:
Avg - 2.8mbps
Peak - 3mbps

Max Speed from TiVo directly to laptop via crossover:
Avg - 10mbps
Peak – 11mbps

Max Speed from Laptop via Bridge to Desktop:
Avg – 5mbps
Peak – 6mbps

Max Speed from Laptop via PCMCIA Demarc 100mw to Desktop:
Avg – 5.3mbps
Peak – 6mbps

I have also tested this with my Cisco 352 PCMCIA and a Aironet 1200 AP. I can average more than 6mbps and peak at slightly over 7mbps. Not bad for b but I still want g!

What is strange to me is that the laptop reaches the full available bandwidth via the Bridge. But the TiVo does not. The strange part is that the TiVo will reach 10-11mbps direct 100mbps Ethernet. This is a lot slower than I’m used to for 100BaseT but I am aware that the TiVo is only a 50-55MHz processor not designed for fast file transfers. So the 10-11mbps max is fine for me. I’d rather keep the Ethernet slow and let it perform it’s primary purpose in life… a DVR. But I still wonder why it’s slower through the Bridge than my laptop when I know it’s capable of more speed than that. Hmmm…

I plan on doing some more testing when I have time. I mainly tested using the TiVo as the source because I’m using it to extract video. Sorry for such a long post, geez! Comments or similar tests?

Posted by: jafa

Hi,

Interesting results.

The SA tivos are a bit slower than the DTivos but I would expect slightly higher throughput.

A few things to check:

- You are running the latest turbonet drivers.
- Make sure that the timing is set to optimal in nic_install.
- Make sure that the debug level is set to off in nic_install.
- Check the throughput in each direction.
- Try running a packet sniffer and check the size of the packets being sent.

The tivo does have a problem with its tcp stack where it may only send 1k packets rather than 1.5k packets... it seams to depend on how the socket is created. When it is sending 1k packets the throughput will be noticably slower in the direction where the tivo is sending.

Nick

Posted by: TiVo_WillieB

I've never used nic_install. I have 3.0 so I didn't have to install the drivers, etc. Should I just run it or is there a way to change those settings with the current driver?

Posted by: jafa

Ah, ok, I get it now... turbonet through a bridge, not airnet.

I would recommend using the nic_install cd from www.silicondust.com

You can set the timing to optimal which will speed things up quite a bit, and there are some tweaks in the updated driver.

Nick

Posted by: TiVo_WillieB

Well that would require me to take the drives back out. I'm surely not doing that just to try to get the speed faster. I noticed at the bottom of the software instructions it had this:

"If you can telnet into your tivo or have access to bash over serial then you can also reconfigure by using nic_config_tivo (20020810 install only)."

I wonder if I can run this on my TiVo to configure it again since I never had to install the driver in the first place? Also I'm not sure what the 20020810 is.

I'm kind of leary of messing with it since it is working right now.

Posted by: jafa

nic_config_tivo only works after you have completed an initial install with the nic_install cd.

Another option is is manually edit /etc/rc.d/rc.net and add timing=3 to the ax88796 insmod line.

This should give you most of the performance boost.

Nick

Posted by: TiVo_WillieB

ax88796 insmod line?

bash-2.02# pwd
/etc/rc.d
bash-2.02# cat rc.net
#!/bin/bash
# Copyright (c) 2001-2002 TiVo Inc.
#

if [ "$DEBUG_BOARD" != true -o "$dhcp" == true ]; then
if detectDynamicNet; then
mkdir -p /var/state/dhcp
/sbin/dhclient -q "$DYNAMIC_NET_DEV" 2>/dev/null &
fi
fi

bash-2.02#

Posted by: jafa

Oops - must be in rc.sysinit

Posted by: TiVo_WillieB

Nope, not in there either but that's ok. I'll live with 1.3mbps. Thanks anyway. :)

Posted by: kevinallein

Hi Jafa,
on a Philips SA Tivo (HDR312) and Airnet - what should the timing parameter be when loading the airnet module ? Currently my rc.net sets it to timing=6. This is with 64 bit WEP enabled.
Is that good or do other parameters give better performance ?

Thanks
Kevin

Posted by: jafa

With a SA running Airnet you could try timing=5.

Also WEP will slow it down about 10%.

Nick

Posted by: kevinallein

Thanks Jafa,
did you have a chance to look at the code for rate indication ?

Thanks
Kevin

Posted by: jafa

Not yet, will do.

Posted by: kevinallein

Hi jafa,
I changed timing from 6 to 5, but data rates actually went a tick down. With timing=6 I got values from 260 KBytes/s up to 277 KBytes/s, with timing=5 I got 250 KBytes/s up to 262 KBytes/s.
In some thread I read of people with considerable higher data rates. What do I do wrong ?

Thanks
Kevin

Posted by: kevinallein

One more thing:
In some older thread jafa mentioned, that the Tivo had some bug in its TCP stack, so that it would never create a TCP packet with more than 576 Bytes, regardless of the actual MTU of the link. I asume, this is a bug in the Linux 2.1 kernel. Did anyone ever fix that and create a new version for the Tivo ?

Thanks
Kevin

Posted by: jafa

Hi,

Do you get the same speeds in both directions?

Nick

Posted by: kevinallein

jafa,
with the current timing=6 I tried several times over 3 days. From Tivo to PC is roughly 260 KByte/s, from PC to Tivo is 370 KByte/s. Is that the difference in MTU size of the Tivo only doing 576 Bytes and the PC (Windows 2000 Server) creating TCP packes with the max segment size allowed for Ethernet (1516 Bytes minus headers) ? I am asuming here, that 802.11 creates the same size Ethernet frames as 802.3.

Thanks
Kevin

Posted by: kevinallein

Jafa,
Sorry to bother, but did you have a chance to look at the speed indication code in the Airnet code ?

Thanks,
Kevin