Network/internet/tcp problem

[Technoid]

I have a really weird problem on my work machine.

on our 20mbit adsl download link I get only 8mbit in tcp but full with UDP?!?

I have changed the nic, plugged directly into the dsl modem, changed the modem and I'm thinking about reinstalling

freaking weird is that I get 30mbit to and from the server on our local net ?!?

[rylan]

Service provider throttling/shaping certain traffic based on packet type?

[Technoid]

Its in my machine

the other computers get full speed.

And I suspect the OS since it didnt help to change nic

also tried with another cable..

[Jammrock]

What OS?

[Technoid]

Windows xp pro sp2

[Helevitia]

TCP has extra overhead plus it can issue retries. This can cause some slowdown. UDP is connectionless and doesn't care if the data makes it to the other side. It just blasts everything out.

Here is a quick explanation:

TCP (Transmission Control Protocol) is the most commonly used protocol on the Internet. The reason for this is because TCP offers error correction. When the TCP protocol is used there is a "guaranteed delivery." This is due largely in part to a method called "flow control." Flow control determines when data needs to be re-sent, and stops the flow of data until previous packets are successfully transferred. This works because if a packet of data is sent, a collision may occur. When this happens, the client re-requests the packet from the server until the whole packet is complete and is identical to its original.

UDP (User Datagram Protocol) is anther commonly used protocol on the Internet. However, UDP is never used to send important data such as webpages, database information, etc; UDP is commonly used for streaming audio and video. Streaming media such as Windows Media audio files (.WMA) , Real Player (.RM), and others use UDP because it offers speed! The reason UDP is faster than TCP is because there is no form of flow control or error correction. The data sent over the Internet is affected by collisions, and errors will be present. Remember that UDP is only concerned with speed. This is the main reason why streaming media is not high quality.

[Technoid]

Yes I know the difference between tcp and udp.

The test software I'm using tests both tcp and udp.

the workstation a foot to the right of mine get 98% tcp speed of the udp.

As I wrote in my earlier posts I have tried that workstations cable, an other nic, tried different Adsl modem, router, cables, etcetera because we first fought it was a network problem since the whole network was slow.

changing the nic's in the router (smoothwall box) fixed the problem for every computer in the house except mine, that is seemingly dropping every other tcp packet.

On monday I'm going to plug my workstations hdd into the other one, If that works my new mobo is going to get RMA'd (the onboard vga is wonky, i wouldn't be surprised to know that the nic is wonky to), next step is a reinstall of the OS.

[rylan]

Check the bios settings for the bus? I've seen write combining or delay transaction cause problems with certain NICs.

[VJ]

Good one!
You could also check the buffer settings for the NIC. I've seen terrible tcp performance on cheapo nic that lacked adequate buffer (long time ago - was the reason then to get decent branded nics).

Jörg

[Technoid]

It was software

Clean install, 17,70mbit tcp 18,80 udp

[VJ]

Which software? Do you mean Windows?


Jörg

[Technoid]

Probably

But to be more exact, the problem was caused by some software (OS, driver, app, etcetera).

[The PIT]

Bet you if you'd reset the TCP stack that would have fixed it.

[Technoid]

If I have time tomorrow I can always check that (ghost is your friend).

But I was on the third motherboard since the last reinstall on that machine and it had other "issues" that while not being showstoppers was beggining to annoy me