what is the thing that specify the communication distance !?

[mohammed hashim]

hi all

I read about ethernet distance support, 100m, 200m or more,

does the cables specify these distances, or the interface ??

thanks.

[Marvin Rhoads]

It's both.

The cabling (wire type, how it is twisted in the cable jacket) and connectors (termination plugs, patch panels etc.) all meet certain standards that primarily have the goal of ensuring that an electrical signal (or optical in the case of fiber) introduced at one end makes it to the other end with only a certain amount of degradation.

The ports / network interface cards / transceivers at the ends of the path have the capability to recover a signal that has been transmitted over that cabling and intervening connectors as long as it has not been degraded beyond the specification by any one of those components or the interaction between them.

So all the parts need to work together to ensure reliable end to end transmission of the signal. Often we see the cabling specification (i.e Cat 5e UTP, OM-3 fiber, etc.) cited as it is the most variable element of the equation. 

[Joseph W. Doherty]

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Posting

As Marvin has already described, distances are defined by standards, and signal quality degradation from sender to receiver much influences distance limitations.  However, there's other factors involved in setting distances.

For example, in original (shared media) Ethernet, part of the distance limitation was how long it would take for a beginning of a frame to reach another host as part of collision detection.  And, if a collision is detected, how long to transmit the "jam signal" to insure all hosts "see" it.