LAN Segment Length


Thread Starter


i am using some Ethernet based devices connected in star network on cat5 cable. for distant devices i need to use switch to extend the segment length from 100mtrs.

as we know that all Ethernet cat 5, 6, 6a cables has specified max length around 100m. but if i using 10base-t (full duplex) network card can i go more then 100mtrs by using cat 6 or cat 6e cable instead of using cat5 cable?

please explain max LAN speed vs distance for cat cables.
Hi kk -
You need to read a wiki about 10bT/10b2 Vs 100bT.

I'm a little rusty on this - but this is my short version;
The original spec for distance was based on 10b2 over 300m, unswitched with collision detection/backup - and this was maintained for 10bT.

The timing for 10b2 at 300m was designed to ensure that the sender could detect a collision in the cable (10b2 was coaxial) with the minimum possible packet size while the transmission was in progress.
This meant long transmissions for 300m were necessary as back in the 90's no one could afford switches - and hubs were a luxury.

Reducing the maximum distance from 300m to 100m (still with hubs at this stage) meant the packets could be smaller and faster, and still handle the collision detection.

I think the difference between 100b and 1gb is only in the
information density - timing is all the same.

Hope this helps!
this is ok. as we know that cat cables designed for 100mtrs range and upgraded to higher level cat5 to6 and so on to maintain the max length with increasing frequency demand. as frequency increases, more crosstalk and attenuation so, cable characteristic upgraded to match with max 100 mtrs segment length. its pretty ok. but if i am using 10base t connection (full duplex mode) with cat6 cable, which is designed for higher freq (250mhz) signal transmission over a length of 100mtrs. whether it is not possible in my case that i can extend this segment length further to get minimum signal acceptable level at receiver end.

please explain

Curt Wuollet

It's not an attenuation distance problem, it's a propagation delay problem. The segment length is limited by the time needed for the collision sensing. If the signal takes too long to get to the end node, there is not enough time for it to listen before it transmits. In other words, both ends could be transmitting before they see the signals from the other end. The more exact explanation is beyond our scope. Cat 6 and cat 5 both have about the same velocity factor so the segment lengths are about the same, as the propagation time is about the same.