Crossover Twisted Pair - When to cross the brown and blue pairs

Hello.
There are 2 types of twisted pair in the network. In one version, the brown and blue pairs do not move
1 -> 3, 2 -> 6
3 -> 1, 6 -> 2



in the second they are crossed
1 -> 3, 2 -> 6
3 -> 1, 6 -> 2
4 -> 7, 5 -> 8
7 -> 4, 8 -> 5



1. What is the difference between them? Do all devices support both variants (I checked on PS3 and work with both and with a straight cable)? When should this variant be used? Can they be recognized by some other marking, or only by the colors (or tester)?

2. Is the straight cable made according to T568A or T568B? I know it doesn't make much difference, but maybe some standards describe it? After all, arranging in any order but identical on both sides would also work, but that's not the point.

3. Patchcord is only a crossover cable (crossover) - following Wikipedia - or is each twisted pair (and not only) terminated with lugs?

Many questions and maybe not the most important ones, but recently I started to earn tips and I would like to know how it should be done.

I can be wrong, let my colleagues check ...

1. Crossover of all pairs you describe applies to crossover cable for 1000Base-T 1Gb / s technology, where all pairs of wires are used.

2. As you say, it makes no difference. I often see factory A or B standard cables

3. A patch cord is usually defined as a short cable, ready-made, pre-crimped, soft, stranded ...

Yes I thought it was about speed. But can I always patch them all? Or can there be problems with older devices?

Older devices that do not have Auto MDI-MDIX functionality will have problems, and will not actually work if the wrong type of cable is used. It is best to use it as intended, because it is not always possible to predict later changes or what end devices will be connected to the network.

Older devices (running at 10 / 100Mb / s) use two pairs (green and orange) crossed according to your drawing:


So it shouldn't be a problem to patch the other two pairs (brown, blue).

In new devices equipped with the Auto MDI-MDIX function, the device's network card recognizes by itself whether the cable is straight / crossover and sets the port accordingly (depending on the needs).

Sorry for the confusion.
In the previous post, I meant, of course, the situation of using a crossover cable always, even when a simple one is required - a device without Auto MDI-MDIX will not be able to cope. When it comes to two or four pairs, as my colleague farmerro wrote - there should be no problem with older devices.

The question about patchcord came from Allegro, where there are 3 categories: * UTP, * Patchcord, * UTP (unshielded). I don't really see the difference, especially with both UTP. After all, UTP, by definition, is unshielded ...