Comments on: Degraded Network Performance Mystery

By: network_ninja

network_ninja — Wed, 09 Dec 2009 02:16:41 +0000

Unfortunately, auto negotiation between ethernet interfaces fails more often than not. It's been de riguer for as long as I can remember to hard code data rates on Cisco ethernet switches and interconnected devices

By: edrabbit

edrabbit — Wed, 25 Nov 2009 02:52:36 +0000

Looks like the "bad checksum" errors may just be a result of TCP checksum offloading

By: edrabbit

edrabbit — Tue, 24 Nov 2009 23:23:09 +0000

The Media Server is configured to be 100Mbps Full Duplex. When I configured my MBP to be 100Mbps I set it to full duplex as well. Both machines have flow control enabled.

By: edrabbit

edrabbit — Tue, 24 Nov 2009 23:20:22 +0000

When I have the Media Server on the Linksys 10/100 router I have no speed problems, even when my MBP is on the DLink gigabit switch.

The Xbox 360 has been off for my testing and does not show an active light on the gigabit switch. When I tried unplugged the Linksys 10/100 router I still got the same crap speeds.

Several reboots both server and MBP side means new DHCP leases. Leases for both machines are static DHCP on the Linksys router.

By: Starchy

Starchy — Tue, 24 Nov 2009 22:59:41 +0000

Unfortunately, this could be the problem. If only one side is autonegotiating (or autonegotiating properly), you could end up at half-duplex (worse yet, with only one side at half-duplex) which is one way to get collisions up the cat6-hole.

By: kale

kale — Tue, 24 Nov 2009 22:56:32 +0000

Do you experience the same terrible speeds with the switch completely off the network?

What kind of speeds do you get if you disconnect the xbox and wrt (leaving the macbook and media server and the switch, configured with static IP addresses)?

Silly question, have you released and renewed your DHCP leases on all devices?

By: edrabbit

edrabbit — Tue, 24 Nov 2009 22:19:18 +0000

Even more confusing…
I just took my MBP and plugged it into the 10/100 router in the other room and had the same terrible speeds yet no “bad checksum” reports in Packet Peeper.

By: edrabbit

edrabbit — Tue, 24 Nov 2009 22:11:22 +0000

Yeah, I recognize that the speed will be clocked down to 100mbps, but from my understanding this should happen automatically and 1gb and 100mb NICs should be able to talk happily to each other, negotiating the correct speed.

It's weird that my MBP says it's not connected only when it's manually set to 100mbps.

As I replied to kale below I did some packet sniffing and it looks like the issue is bad checksums. As to what is causing the corruption, I don't know.

Unfortunately I don't have another switch to swap out and test.

By: edrabbit

edrabbit — Tue, 24 Nov 2009 22:02:38 +0000

Can't hard-set the switch. It's totally unconfigurable in any way. hehe I loaded up Packet Peeper and it's littered with packets saying “bad checksum”. :(

By: MrOtsKrad

MrOtsKrad — Tue, 24 Nov 2009 22:00:13 +0000

Hmm, well when your streaming from the media server to the Xbox, your going to see the degradation of speed, the xbox being the bottleneck being only 10/100. Thats why you saw the performance hit when you added the gigabit switch to the fray.

When you set the XP machines NIC from 1000 to 100 you got some performance back because the two 100s had an easier time talking to each other, but still not as well if you had a

GGB Switch > 1000 XP machine > 1000 Xbox

but better than

GGB Switch > 1000 XP machine > 100 Xbox

But if your MBP is having the connectivity issues as you say, you may have a faulty switch if its saying its not even connected when you clearly see physically it is. Which is odd in itself. There a layer thats not communicating somewhere correctly, and thats whats prolly causing the speed degradation across the board. But thats is beyond my troubleshooting abilities :(

Do you have a regular 100mbps switch to swap the 1000 out to do a speed test?