symmetric vs. asymmetric [was: Verizon Policy Statement on Net Neutrality]

Fri Feb 27 22:32:29 UTC 2015

>I'll disagree on the home part. I doubt that most homes are symmetric.

I agree, most homes are not symmetric, the two biggest services are cable modem and DSL which are usually asymmetric.

>Of course, what needs to happen is for standards bodies to start thinking more dynamic when they build their protocols where possible. 
>Passive splitters obviously have the limitation of limiting frequencies, but our xDSL technologies and cable technologies do not have the restriction to my >knowledge. Future protocols ideally would have a signaling band, recognition of frequency support bidirectionally and perhaps support dynamic allocation of >those channels as-needed.

>If an end node is saturating the upload but not using the download, why shouldn't the system shift the frequency usage? If only 10mb/s is being used out of >a 50mb/s circuit for download, why not allow that extra capacity to be used for upload, temporarily shifting it's direction?

You could do that.  The only issue is that you are putting in more intelligent CPE that has to be frequency agile and signal to the head end what is happening.  Carriers are very sensitive to CPE costs so I don't think that is likely to happen especially since I think that DSL is not considered leading edge service any more.  I would expect the carriers to devote more effort to FTTP efforts than to keep trying to advance DSL.

>My 2 cents. I don't design these things, but you'd think people would start realizing that static allocation is kind of limiting. Giving someone 50mb/s with >20mb/s waste is annoying when they are saturating 3mb/s the opposite direction. Wouldn't it be cool if your backup at night could use 50mb/s upstream >and drop your downstream to 5mb/s because you aren't downloading anything?

Again, not a technical problem.  It is a CPE intelligence and cost issue.  Unless a whole lot of customers want that, the money is not going to be spent to support that.

>For that matter, is there a reason we don't dynamically adjust frequencies on Ethernet? My servers would definitely love 1.8gb/s transmit since they receive >very little.

Sorry, no frequencies to play with on Ethernet.  Ethernet is a baseband technology (i.e. DC voltage, not AC frequencies) One pair is transmitting, one pair is receiving in gigE.    If you want to use both pairs in the same direction to double up the bandwidth, that could be done but it would not be Ethernet anymore.   If you want to talk both ways on the same pair, that is half duplex, we've left that idea in the dust years ago.

Steven Naslund
Chicago IL