Networking and EMI

[KurskKnyaz]

I know that professional IT guys have special angles at which they can bend network cables when they are ran in bundles - the reason has something to do with cross talk I think.

My question is. If I run a cat 6 cable near a power line will the electrical interference from the power line slow down my data rate because there will be more errors in packets that are sent?

 

[spidey07]

As long as it's a few inches away you're fine. The great thing about twisted pair cabling is EMI doesn't really affect it much.

oh, and you never bend category cabling at a specific angle. I think the maximum bend radius is 2.5 inches.

 

[KurskKnyaz]

Thanks for the info. I just have a few questions:

1. What do you mean by bend radius?

2. Will using a staple gun to attach and compress the cable limit the speed because it will cause more errors in packets.

basically what i asking is if the signal is not clean (erroneous in this case since it is a digital signal), will the data rate slow down because of an increase in erroneous packets that would have to be corrected by ECC/PARITY/whatever checking. Are bad packet even corrected this way or just resent?

In short: does the quality of the signal effect speed?

3. Is CAT6 with the extra cost because it can carry a cleaner signal (I know that it is worth it because it is future proof.

4. How does wiring certified for in-wall use physically differ from standard CAT6? What quality about it makes it better for in-wall use?

 

[spidey07]

1 - bend radius - the radius of circle if you were to bend a cable around it
2 - do not use a stable gun, you will very likely harm the cable and have very difficult to troubleshoot problems

The quality of the signal affects speed, absolutely

3 - all new installations should be cat6. There is no compelling reason not to
4 - the jacket of the cable is stronger so when it's ran vertically the cable doesn't stretch

Basically if you follow all the category 6 standards and installation practices you'll be fine. If you don't, no guarantee on performance or if you'll have problems. You don't have to baby the cable, just don't bend it, kink it, put heavy objects on it, staple it or bend it at sharp 90 degree angles. The cabling is the single most important part of any network, as such it is also the most common (80% or higher) cause for problems.

 

[KurskKnyaz]

Thanks, good info. I once read in a computer book about a network that kept having errors. They ran the cables through the ceiling. It turns out that incandescent lights generate a lot of interference. When an experienced IT guy shut the lights off the network was fine.

What about my other question: how is erroneous data corrected over a network. Are the packets dropped and resent or is some sort of ECC-Parity-like checking used.

one last question: are NIC 100mbit/sec both directions at the same time or one direction. If I was to set up a server in a medical office would it be more efficient to use 2 NICs one for incoming and one for outgoing traffic.

 

[spidey07]

All modern NICs are full duplex transmit and receive at the same time. If you need performane use 1000 Base-T NICs.

Any corrupt or malformed data on the wire is discarded at layer2, every frame has a CRC or frame checksum included. It is then up to upper layer protocols (TCP or L7) to resend the packet which is then framed and put on the wire.

If this is for a medical or other business then you should not be doing the cabling. It should be professionally installed and certified.

 

[KurskKnyaz]

Originally posted by: spidey07
All modern NICs are full duplex transmit and receive at the same time. If you need performane use 1000 Base-T NICs.

Any corrupt or malformed data on the wire is discarded at layer2, every frame has a CRC or frame checksum included. It is then up to upper layer protocols (TCP or L7) to resend the packet which is then framed and put on the wire.

If this is for a medical or other business then you should not be doing the cabling. It should be professionally installed and certified.

so a 100mbit NIC would be able to send 50mbit in each direction simultaneusly assuming the incoming and outgoing data rate is the same.

You should see this office, there is nothing professional about their network at all, infact it is the most ridiculous network you will ever see. When I opened the closet with the modem, switch, and router was a web of unlabeled cables. They only have 5 computers. I can run cables through walls to a switch and install jacks thats is not a problem. I'm just making sure about certain variables that affect performance.

 

[kevnich2]

What spidey is saying is if this network is to be used in a business setting, you shouldn't be doing this yourself. Setting up a small network for your home and setting one up for a business are two different things. In a business network, it cannot go down. Every minute a business network is down, money is lost as pretty much no work can be done. There are rules and in many cases, laws that have to be followed. If a business network isn't up to par with the law and something happens, insurance doesn't pay to have it fixed as it wasn't installed correctly in the first place. My recommendation to you, hire a network installation company to install this network for this business and then take training classes yourself and get certified (CCNA, MCSE, etc)

 

[Jamsan]

Originally posted by: kevnich2
What spidey is saying is if this network is to be used in a business setting, you shouldn't be doing this yourself. Setting up a small network for your home and setting one up for a business are two different things. In a business network, it cannot go down. Every minute a business network is down, money is lost as pretty much no work can be done. There are rules and in many cases, laws that have to be followed. If a business network isn't up to par with the law and something happens, insurance doesn't pay to have it fixed as it wasn't installed correctly in the first place. My recommendation to you, hire a network installation company to install this network for this business and then take training classes yourself and get certified (CCNA, MCSE, etc)

Agreed.

Also, a 100MB NIC, theoretically, can transfer up to 200MB/s, as it's a 100MB connection, and full duplex, so it can do 100MB each way at the same time (theoretically, of course)

 

[Crusty]

Originally posted by: Jamsan

Originally posted by: kevnich2
What spidey is saying is if this network is to be used in a business setting, you shouldn't be doing this yourself. Setting up a small network for your home and setting one up for a business are two different things. In a business network, it cannot go down. Every minute a business network is down, money is lost as pretty much no work can be done. There are rules and in many cases, laws that have to be followed. If a business network isn't up to par with the law and something happens, insurance doesn't pay to have it fixed as it wasn't installed correctly in the first place. My recommendation to you, hire a network installation company to install this network for this business and then take training classes yourself and get certified (CCNA, MCSE, etc)

Agreed.

Also, a 100MB NIC, theoretically, can transfer up to 200MB/s, as it's a 100MB connection, and full duplex, so it can do 100MB each way at the same time (theoretically, of course)

Wrong. It can not do 200mbps. It will do 100mbps receiving and 100mbps sending at the same time. Not 200mbps. Also, MB = megabyte not megabit. So your numbers are off by a factor of 8.

 

[Jamsan]

Originally posted by: Crusty

Originally posted by: Jamsan

Originally posted by: kevnich2
What spidey is saying is if this network is to be used in a business setting, you shouldn't be doing this yourself. Setting up a small network for your home and setting one up for a business are two different things. In a business network, it cannot go down. Every minute a business network is down, money is lost as pretty much no work can be done. There are rules and in many cases, laws that have to be followed. If a business network isn't up to par with the law and something happens, insurance doesn't pay to have it fixed as it wasn't installed correctly in the first place. My recommendation to you, hire a network installation company to install this network for this business and then take training classes yourself and get certified (CCNA, MCSE, etc)

Agreed.

Also, a 100MB NIC, theoretically, can transfer up to 200MB/s, as it's a 100MB connection, and full duplex, so it can do 100MB each way at the same time (theoretically, of course)

Wrong. It can not do 200mbps. It will do 100mbps receiving and 100mbps sending at the same time. Not 200mbps. Also, MB = megabyte not megabit. So your numbers are off by a factor of 8.

You're right on the MB vs. Mb, rush typing on my part. *Theoretically*, if you can do 100Mb send and 100Mb receive, that's 200Mb that can be pumped at any given moment. I never said it was 200Mb in each direction.

 

[spidey07]

Originally posted by: Jamsan
wrong. It can not do 200mbps. It will do 100mbps receiving and 100mbps sending at the same time. Not 200mbps. Also, MB = megabyte not megabit. So your numbers are off by a factor of 8.

You're right on the MB vs. Mb, rush typing on my part. *Theoretically*, if you can do 100Mb send and 100Mb receive, that's 200Mb that can be pumped at any given moment. I never said it was 200Mb in each direction.

Negative. All network speeds are measured only in one direction because most all network technologies are full duplex.

Also, theoretically you can never get 100 Mbs due to interframe gap. More like 99.3 Mbs depending on frame size.

Not to get technical or anything.

 

[Crusty]

In opposite directions though, when my NIC can receive information at 200mbps feel free to call it a 200mbps NIC! Sure, if you look at it bit by bit with no care for where the direction the information is going you could say the card can do 200mbps... but that's not how things work

 

[KurskKnyaz]

Originally posted by: kevnich2
Every minute a business network is down, money is lost as pretty much no work can be done.

If only this guy would understand that. This is not a place a work at. I do freelance computer repair and they are a returning customer. They run Lytec medical billing software (total POS, the company that makes it should be sued for extortion). Lytec recommends 4GB on the server and at least 1GB per workstation. Their server has has 512mb and the workstation run between 192mb and 256mb. On top of that the workstations are Celerons on VIA chipsets (see my "Should I call an exorcist" thread).

My prices aren't high but I once charged the office $90 to run a network cable from the lab, through the ceiling, to the router. I had to do the drilling since this is a basement. Why did it cost so much if I charge $40 1st hour and $20 each additional hour? When I opened the closet with the network hardware I found about 20 unlabeled CAT 5 cables. There are only 6 computers so by the time i was through figuring out which ones I can and can't unplug I ended up removing an unnecessary white box with NIC ports that was made in china and had no name. I have no Idea what it was, hub, router, or switch. The lady that is incharge of the billing department (the one who calls me to do the work) is in a lot of shit right now because they aren't getting much done with all the problems and the boss has a hard time understanding that it is not her fault. He is the one that chose a "budget" network. Believe me this network is as budget as it could possibly get. Who the hell runs XP on 128BM ram?

I would not do the wiring for a business but I can do a much better job than the previous people and I can bet he payed them a lot more. When his network completely bombs or he realizes that he is paying for the 5-10 seconds that each worker has to wait when opening and saving a claim (it adds up), I will propose the idea of a proper network.

BTW: what is your opinion on charging $40 for the first hour and $20 for every following hour?

 

[spidey07]

Standard professional cabling is 175-250 per drop. That's in an office environment where a lift or other fixture work isn't needed.

 

[ScottMac]

Originally posted by: Jamsan

Originally posted by: kevnich2
What spidey is saying is if this network is to be used in a business setting, you shouldn't be doing this yourself. Setting up a small network for your home and setting one up for a business are two different things. In a business network, it cannot go down. Every minute a business network is down, money is lost as pretty much no work can be done. There are rules and in many cases, laws that have to be followed. If a business network isn't up to par with the law and something happens, insurance doesn't pay to have it fixed as it wasn't installed correctly in the first place. My recommendation to you, hire a network installation company to install this network for this business and then take training classes yourself and get certified (CCNA, MCSE, etc)

Agreed.

Also, a 100MB NIC, theoretically, can transfer up to 200MB/s, as it's a 100MB connection, and full duplex, so it can do 100MB each way at the same time (theoretically, of course)

This falls into what's called "Marketing Math"

It's totally bogus (which is the norm for marketing and politicians).

It's a 100Mbps NIC. While is can "theoretically" be transmitting and receiving at the same time, it rarely, if ever will. The driver software and / or the operating system and / or the host hardware generally are not set up to do it, especially on bargain brand hardware.

That's part of what makes a "server platform" a "server-class" machine. It's built to do things like that, and drivers for "server" hardware are written to enable that kind of operation; that's one of the reasons it costs more. That's also why it's a dumb idea to put cheap user-class stuff into a server-class box ... you're crippling it and, more often than not, creating a bottleneck to save a few bucks.