4 ms·
Why does fiber have lower latency to the exchange than copper? That surprises me. I thought that ISPs generally run fiber for most of the distance, and coax is
by spenczar5 5y ago
Why does fiber have lower latency to the exchange than copper? That surprises me.
I thought that ISPs generally run fiber for most of the distance, and coax is only used for the last few hundred meters. The speed of signal propagation is actually faster in copper than fiber, but nobody (afaik?) does long runs over copper so it’s a moot point.
- digitallyfree 5y agoYes the ISP runs fiber to the DSLAM or the CMTS, and copper is used for the final hop to your home. The latency comes from the buffering and processing required to get a clear signal over copper - for DSL I think you can get in a perfect scenario 7ms or so with fastpath, more if you use interleaving. For fiber you can pretty much treat it as like an Ethernet connection, with latency determined almost solely by distance.
- tomxor 5y agoYup I remember fastpath, it's a choice of low latency vs higher bandwidth. I'm not sure if ISPs still actually bother offering this option to end users anymore though? I mean it's all turned into scripted tier 1 support nonsense if you call an ISP these days.
- digitallyfree 5y agoI had to specifically ask for fastpath for my DSL connection, without it I get around 35ms to the exchange. You however do need a decent connection to the DSLAM for it to work properly without packet loss. You can get the same bandwidth over fastpath as interleaving if the line is clean.
- weepy 5y agowoah what is this fastpast magic ?!
- spenczar5 5y agoAhhhh interesting - so the latency comes from the noise in copper, which forces you to do extra work, which adds latency per bit? That makes sense - thanks!