I have intermittent latency issues on a daily basis (multiple times). This occurs most often during 6-11pm EST but that may be correlated to it being the highest usage time for my household rather than a relation to the actual time as the problem has exhibited itself at other times.
The intermittent latency issue manifests as continuous, often for 10+ minutes, high latency (300ms-2000+ms). Previously, this also resulted in persistent disconnects during the high latency; however, recent visits by AT&T DSL techs resolved the disconnect issue when they installed a filter at the NID and separated the RJ-11 jack my modem connected with so it is the only jack receiving the green/white cat5 data wires. Since then, the disconnects are gone but the latency is still an issue. This latency has existed for well over a year.
I have purchased shielded cat-6a cabling and shielded phone cabling to eliminate possible interference from my house as well as separated the modem from other devices and while that lowered the attenuation dB by ~1.5, it has not affected the latency issue.
The AT&T DSL tech believes that the issue emanates from AT&T as this is a frequently cited issue in the area. I have attached a history of my modem stats from this month showing stats before and after various ATT technicians attempts to resolve the problem.
I should also note I am on my 4th modem. Two of the previous modems were 2wire modems that eventually died and I'm currently using my own D-Link modem as the ATT DSL Tier 1 technician could not confirm my warranty information and send me a new modem. Though I do use a router (three different ones over the period of this problem), the issue occurs even when no router is present. I'm using the latest firmware on the modem and router.