PCA Forums

My friend has two computers setup with comcast. One which we'll call the "downstairs computer" hte other which will call the "upstairs computer." The downstairs computer has two network cards (one goes to the cable modem, one goes to the hub) My friend then has his computer hooked up to the hub. Has ICS on the downstairs computer.

With that said, he recently is having problems playing games with his ping spiking. We pinged the gateway downstairs and it never timed out. Then we tried pinging the downstairs computer from his and it never timed out. I'm kinda confused since all the computers seem to be communicating with eachother well--yet he still complains of his ping spiking in games. We disabled a ton of the startup apps on the downstairs computer, thinking maybe too much was tryin' to get online and was laggin' him down, but that didn't do anything. They dont have a firewall of any kinda so thats not it either.

Got any clues?

He having this problem on both computers or just the one upstairs?

Was Comcast ever connected directly to one computer and did that work fine?

If he's having this problem on only the upstairs computer then it's a local issue (ICS problem, bad hub, bad cable between the upstairs computer and the downstairs, or a bad setting on the upstairs system).

If the downstairs computer (the one that's directly connected to the cable modem) has this problem then it's a problem with that computer or a problem with Comcast.

Try disabling ICS and see if you still have the problem. If that cures it then it may be an IRQ issue with the two NICs on the downstairs system.

It's not easy finding 2 NICs that can co-exist in the same system. It may SEEM to work okay, but you may have IRQ issues which is causing the system to pause every once in a while and that would cause a ping spike. You have to beware of IRQ Channel Sharing issues as discussed here: http://soldcentralfl.com/quakecoop/glfaq5.htm#5_9

I often wind up using a USB Nic (Linksys makes a nice one you can get for $25 mail order) for the Cable/DSL NIC to avoid IRQ issues with the PCI Nic.

Are you running anything in the background of the downstairs system? You shouldn't - not even a screen saver ESPECIALLY if it's running an non-NT OS like Win98. Even a stupid screen saver could cause your problem.

Does he have GOOD cables (store bought or did he make them himself). It's EASY to make an intermittent cable. Also many people don't seem to understand the importance of using the correct color code when making cables. You CAN'T just use any wire as long as they connect to the same pin on both ends.

With Cable routers so cheap (you can often find them for under $100 mail order) he should really consider using one of those instead of futzing with ICS.

If you've got a Cable Router handy for testing, it'd be worth a try to see if it eliminates the problem.

Hope this helps...

Also many people don't seem to understand the importance of using the correct color code when making cables. You CAN'T just use any wire as long as they connect to the same pin on both ends

You CAN use any color wire you want as long as they match at each end. I've only been making cables for 12 years, so can't offer the breadth of experience you have FP, but on 10 or 100BT networks I have yet to see or hear of the color of the wire within a CAT5 cable causing a problem.
Stretching the wires to make them match and causing a break? yes.
Not getting a good solid crimp on one or both ends? Absoluetly.

but not wire color.
I know the cabling professionals like to say the colors should be as dictated, but they have never been able to explain why. Does one or more of the 8 wires in there have different physical characteristics than the other wires? No really. I would like to put this one to bed in my own mind.

Are you aware of any reason other than 'it's a standard and we expect it to look like X' to follow the guideline you mentioned?

At first I thought hah it's the same freakin kind of wire who cares what color as long as they match at each end. Then I started thinking... I think they are twisted together in certain pairs to eliminate crosstalk... Yeah, I'm pretty sure that's the reason. Have to do some research on it. I've always made them accoring to the standards anyway.

I found the following:

http://www.linuxdoc.org/HOWTO/Ethernet-HOWTO-5.html

If you hold the RJ-45 connector facing you (as if you were going to plug it into your mouth) with the lock tab on the top, then the pins are numbered 1 to 8 from left to right. The pin usage is as follows:


Pin Number Assignment
---------- ----------
1 Output Data (+)
2 Output Data (-)
3 Input Data (+)
4 Reserved for Telephone use
5 Reserved for Telephone use
6 Input Data (-)
7 Reserved for Telephone use
8 Reserved for Telephone use

If you want to make a cable, the following should spell it out for you. Differential signal pairs must be on the same twisted pair to get the required minimal impedance/loss of a UTP cable. If you look at the above table, you will see that 1+2 and 3+6 are the two sets of differential signal pairs. Not 1+3 and 2+6 !!!!!! At 10MHz, with short lengths, you *may* get away with such errors, if it is only over a short length. Don't even think about it at 100MHz.

Another good one too:

http://www.duxcw.com/digest/Howto/netwo ... cable4.htm

It reduces crosstalk and noise.

You can use ANY PAIR but you cannot use ANY WIRE. There is no shield in Cat 5 cable and the shielding is accomplished by virtue of the twisted pairs.

The pairs are actually twisted around each other within the jacket and THIS creates an electrical shield.

If you wire a cable disregarding this it will work if it's short, but anything over a few feet - ESPECIALLY if it runs near an electical noise source such as a flourescent light ballast transformer - will degrade the signal, resulting in packet loss.

You MAY get away with it in a small office environment with only a few computers that don't use a lot of bandwidth (so maybe your 100 Mbit cable will only push 10 Mbit - no big deal especially if all you're using it for is printing and Internet access), but if your network requires bandwidth then it'll be a serious issue.

It'll also show up on a gamer's system as a performance hit since packet loss results in poor game performance.

So bottom line is this: it doesn't matter WHAT pairs you use (if you use the green pair for pins 1 and 2 or the brown pair for 1 and 2 it really doesn't matter) but it's VERY important that you maintain your pairs properly (as Schwartz explains above). There are four pairs and if you use any wire abitrarily and break a pair you change the shielding and impedance characteristics of the wire.

There's no need to stick to the official color code, but since the pairs are not sequencially positioned in the connector (the green or input data pair for instance is on pins 3 and 6) it's easy to get confused if you just make up your own color code as you go along. It's actually more work that way. Easier to stick with the standard to avoid confusion.


Oh, and to clear something up, that chart Schwartz posted is for 10base-t which uses 2 twisted pairs. 100base-tx uses 4 twisted pairs.

Thanks both of you. That's logical. Truth told I almost Always use soldered ( manufactured ) cables these days to avoid Crimping errors and carry my cable tester anyway: The clients I had Were usually small ( less than a dozen systems ) and well within the run lengths quoted by .... the IEEE? for whatever type of physical network was present. Getting lucky repeatedly is good. Knowing why is much better

Oh, and to clear something up, that chart Schwartz posted is for 10base-t which uses 2 twisted pairs. 100base-tx uses 4 twisted pairs.

I thought it was the same for both? 2 TP used total. 2 wires transmit and 2 receive.

http://techsolutions.hp.com/fe/cable_types.html

Well I know that if you don't wire pins 4,5,7 & 8 your cable will NOT work for 100Mbit - it'll be detected as a 10Mbit connection.

Older 10Mbit cables (I still see them packed with Cable modems) only have 4 wires. All modern 100Mbit cables use 8 wires.

Interesting, this page seems to imply that you don't need to maintain pairing for 4,5,6 & 8 - just for the RX & TX pairs: http://www.pin-outs.com/datasheet_92.htm

Sorry it took me so long to reply. Comcast has always been and still is connected to the downstairs computer. I thought the same as you, FP. Knowing the downstairs computer seemed to act fine, I thought it was some sort of hardware/software conflict with his computer--only it's odd that this has happened out of nowhere (not so much if it's a hardware issue because he does take his computer/hub lanning with him on occasion)

I'm pretty sure the NIC's and everything downstairs is setup right cause it has always worked in the past, but I'll pass on this thread to my friend to read. I appreciate comments peeps, I'll try to let ya'll know if it gets fixed

If the one downstairs has no problems, I'd suspect his two cables between the downstairs, the hub, and the upstairs.

You said hub - is it really a hub or a switch? If he's using a hub are there any other computers connected to it or just the upstairs?

If there's more than one computer using the hub he might be getting collision problems - even with light traffic. When you're gaming you don't EVER want to see a collision light on the hub.

If he has a crossover cable handy I'd connect the upstairs directly to the downstairs and bypass the hub to see if that helps. If it does, lose the hub entirely or replace it with a switch if there's other computers. Even better, spend a bit more on a Cable/DSL Router and use that instead of ICS.

As I mentioned above, I've often seen problems with poor performance on a second NIC due to IRQ issues. You won't get an IRQ error in device manager, but network performance will be poor.

Hope this helps...