Reading IEEE 802® Standard for Local and Metropolitan Area Networks: Overview and Architecture document i came upon thins:

An IEEE 802 LAN is a peer-to-peer communication network that enables stations to communicate directly on a point-to-point, or point-to-multipoint, basis without requiring them to communicate with any intermediate stations that perform forwarding or filtering above the PHY. LAN communication takes place at moderate to high data rates and with short transit delays, on the order of a few milliseconds or less.

I couldn't understand the PHY part. Given that switches forward packets at the DLL, am I right to conclude that a network switch could separate my home network in two LANs?


It is saying that you can write your own networking stack to the IEEE 802 LAN specification. Your stack need not include anything to do with the OSI model, or any other existing model. If you are successful in your programming efforts, the IEEE 802 LAN compliant hardware will transport your data from one device running your stack to another directly connected device running your stack. The PHY doesn't deal with switch or router specifications or functions. A dumb repeater (hub) would work with your stack.

Basically, the PHY is completely independent of any layers above it.

  • So instead of meaning that standard LAN can not require above PHY processing, it means LAN need not to require above PHY processing to be standard compliant? Makes sense to me, thank you :-) – villasv May 20 '15 at 18:44
  • @Victor, the PHY, itself cannot require any specific sort of process (DLL or otherwise) in the stack above it. Your stack could, or not, include DLL, or any other method, for the next layer. You could have a single or multiple layers above the PHY, and the PHY has no say in what your stack does, or does not, include. – Ron Maupin May 20 '15 at 18:59
  • I know, I was talking about the LAN requiring "above PHY" processing. The way I was reading that sentence was "LAN can't process anything above PHY", instead of "sandard comliant LAN rely only on PHY". – villasv May 20 '15 at 19:09
  • In short, nodes talk through a switch not to the switch. The DA (MAC) is that of the node, not the switch. In the case of a point-to-point (direct) link, there isn't a switch in there. – Ricky Beam May 20 '15 at 20:26
  • "... LAN ... enables stations to communicate directly ... without requiring them to communicate with any intermediate stations that perform forwarding or filtering above the PHY" IMHO stated that LAN can't require communications through a switch. @RickyBeam So this is not the case because switches don't count as intermediate station, only nodes transparent to point-to-point communication? I guess this is a different answer and actually would accept it instead. – villasv May 21 '15 at 12:25

The 802 Committe in the IEEE is not referring to switches, or bridges, or routers. They are talking bits, not frames or packets. Think hub or repeater. Frames are not relevant at this physical layer.

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