On Friday 08 October 2004 12:11 pm, Chris Green wrote:
I need a new switch to use with our new wireless broadband so, seeing as Gigabit switches are now relatively cheap, what else do I need to know about Gigabit over copper:-
Can I use existing Cat5e cables?
Yes you can, results with Cat5e should be pretty stable on Gigabit and Gigabit over cat5e is fully supported by the 1000BaseT standard. Results using standard Cat5 may be variable under high network load. In short there is no signalling standard that actually requires CAT6 at the moment. It's just better cable with more frequency headroom so in less than ideal circumstances may perform better.
The main reason for installing Cat6 is that Cat5e is at the frequency limit with 1000BaseT so the next over copper technology will probably require Cat6 as a minimum. Also in any reasonably significant installation the labour costs far outweigh the cable costs so it makes sense to use the best stuff available.
Does Gigabit degrade gracefully over less than perfect connections?
In short no, but then neither does 100BaseT. On the boarderline it will work but may fail or start sending corrupt frames during high load periods, the acceptable noise floor of the cable decreases with network load, failed frames result in retransmits with TCP, this increases traffic which results in more lost frames and so on.
Gigabit plugged into a standard gigabit switch will not automagically fall back to 100BaseT or half duplex under poor line conditions, if that's what you mean by degrading gracefully.
Are there shorter cable length limits?
No they are the same as 100BaseT (100 meters assuming perfect conditions) results will vary and honestly anything even approaching 100 meters should be done with fibre
Are Cat6 cables really necessary or won't I see much difference using Cat5 over short distances?
In short no, however any connections made over 10 meters should be constructed with solid core cable and not multicore patch cable.
Is there a good web site anywhere with all this sort of information on it?
For base standards your best bet is searching for ElA/TIA 568 for cable types and specifications and IEEE 802.3 for signalling standards (10BaseT 100BaseT) and so on.
Regards Wayne