View Full Version : Interesting Tystream Network Observations

01-03-2003, 01:00 PM
Well I was just doing some performance comparisons to see how the Linksys Powerline bridges compared to 10Mbs and 100Mbs Ethernet. While doing so, I noticed a boatload of what I thought were collisions. Turns out what I was seeing was a % utilization that never went below 60% and frequently went over 70%. These numbers are WAY high for Ethernet, which doesn't do well with anything over 30-40%.

Next I did some packet captures, and found that the data packets coming from the Tivo are all exactly 590 bytes (536 data bytes). The ACKs are all 60 bytes long. What this adds up to is a very busy network. It also would go a long way towards explaining why the switched networks are performing so much better. I haven't tested a forced 10Mbs switched connection, but I'm over 95% sure even switched 10 would blow away shared 10.

jdiner, when you get a chance, can you look into stuffing the packets from tserver_mfs to the full 1500 byte payloads? That should help a great deal to mitigate some of this overhead.

01-13-2003, 12:44 AM
I believe this comes actually from the MTU (maximum Transfer unit) setting in the Linux TCP/IP stack. You can see a number of settings in the /proc/sys/net/core and ipv4 directories, but strange enough many values resident in a standard linux kernel are not listed and you can not enable them. Have not looked into the source, but I asume there is something that should be changed here.

01-13-2003, 01:21 AM
Well I won't be able to test this until Thurs., but I'll run some FTP xfers and see if they have the same MTU.

03-21-2003, 12:27 PM

Did you ever find anything out? I notice that I get much better xfers when my TiVos/PCs are running off of my hub, and way slower when running off of my Linksys Router. Doesn't make sense, but that's what happening. I'd like to figure this out.

03-21-2003, 01:33 PM
Originally posted by SR712

Did you ever find anything out? I notice that I get much better xfers when my TiVos/PCs are running off of my hub, and way slower when running off of my Linksys Router. Doesn't make sense, but that's what happening. I'd like to figure this out.

There are several things going on here, some which are/were related to the packet size in TyTools, some not. Josh's latest versions of TyTools has the double-socket option, which for some, but not all, folks got them to full packet sizes.

There also appears to be a group that swear they get better performance on 10Mbps vs. 100Mbps. Since I'm not there, I can only speculate from what I've seen, which is if you mistakenly set one side to full duplex and not the other, or you try to use full-duplex on a hub instead of a switch. (I don't know what your router has built in.) Full-duplex only works with a true switch, or a direct cross-over cable connection. 10/100 hubs are NOT switches.

Some people say the TCP/IP driver/stack is an issue on the Tivo side, but so far I haven't been able to prove/disprove that.

The last possibility is the Linksys router is a total POS. Based on my experience with their wireless stuff, I don't rule that out either. Interesting that cisco bought them yesterday, maybe they'll turn out better equipment soon!

Mr. Smith
03-21-2003, 02:05 PM
My setup...

Windows XP pro 2600 build

1700+ AMD XP / 40 GB / KT400 chipset / DDR sticks


Tivo 2.5.2 update with xplusz 3.0

TyTool 6r3 and tserver_mfs6 (Double Socket)

NIC settings - 100MB/FullDuplex

Tivo DSR 6000 w/turbonet - Channel 0

My extraction speed...

2.25 MB per second... it works for me.

03-21-2003, 02:07 PM
Do you know what the TurboNet/Tivo drivers are... half or full duplex?

03-21-2003, 02:16 PM
Mr Smith-

What kind of throughput are you getting with mfs-ftp... extraction and inserting... that's where I am noticing significantly slower rates.

Mr. Smith
03-21-2003, 02:22 PM
Not sure, will have to check when I get home.

03-21-2003, 02:31 PM
OK. I see 17Mbps on both the router and on the hub with TyTool. But, with mfs_ftp using the hub, I get 1.2 MBps (insert from PC) and 2.0 MBps (extract to PC)... which is OK, but it drops to like 40KB/s if I put them both on the router.

03-21-2003, 03:38 PM
re: ethernet utilization

if you are useing half duplex with several things happening at once ethernet starts to collapse after ~30%, if you are useing it as a point-to-point link for a single application (i.e. 10Mb link to a tivo and all you are doing is transfering a file) you can get to 60-70% before it starts to collapse

if you go to full duplex (sometimes works with crossover depending on the cards, should work with a switch) then you can get to 80-90% untilization wihtout a problem. note that very little equipment supports 10Mb full duplex.

there was a bug discovered in the turbonet drivers a few weeks ago that caused the driver to loose a packet it was sending if it received a packet at the same time. updating the driver is getting people 300-500KB/sec on full duplex setups (I've seen over 2MB/sec since the update with 2.5.2 and 3.1 seems slightly faster). if dropping to 10Mb improves things definantly try this update.

03-21-2003, 07:29 PM
Allright. I xfered over the new version of ax88796.o (had to do the net0 thingy), and then powered down ALL of my gear, including the TiVos. Then, plugged ethernet cables from TiVos to router, then powered up from the router out. Transfer times and rates are now fine. It must have been that the TiVos were running in half-duplex mode, or something. I'm seeing 1.2Mbs from PC->TiVo, and 2.12Mbs from TiVo->PC. (as reported in SmartFTP). Thanks for everyone's help. :)