4 ms·
2.5Gb is downshifted 10Gb with the same line coding, just with 1/4 the symbol rate. This means that it inherits all the complexities of 10GbE, while tolerati
by RF_Savage 4y ago
2.5Gb is downshifted 10Gb with the same line coding, just with 1/4 the symbol rate.
This means that it inherits all the complexities of 10GbE, while tolerating cheaper connectors and cables.
10GbE uses DSQ128 PAM-16 at 800Msym/s. 2.5G just does quarter-rate at 200Msym/s.
1000BaseT uses trellis coded PAM-5, a significantly less complex modulation.
When one factors in the complexity of the line code and all equalisation and other processing in the analog frontend things get expensive.
Copper 10Gb interfaces run very hot for a reason. It takes quite a bit of signal processing and tricks to push 10Gb over copper, at least for any significant distances.
- throw0101b 4y ago> tolerating cheaper connectors and cables I always find the graphic below handy for telling which Cat cable can handle which Gig speed: * https://en.wikipedia.org/wiki/Ethernet_over_twisted_pair#Variants https://en.wikipedia.org/wiki/Ethernet_over_twisted_pair#Var...
- toast0 4y agoIt's not really about can handle, but more is specified to handle at maximum length in a dense conduit. At shorter lengths, and in single runs, it's always worth trying something beyond what the wiring jacket says. I've run gigE over a run with a small section of cat3 coupled to a longer cat5e run (repurposed 4-pair phone wire), and just recently setup a 10G segment on a medium length of cat5e. The only thing is while I think 2.5G/5G devices do test for wiring quality, the decimal speeds don't, auto-negotiation happens on the 1Mbps link pulses, unmanaged devices can easily negotiate to speeds that won't work, if your wiring is less than spec, you need to be able to influence negotiation on at least one side, in case it doesn't work out.