High latency with two or more internet-based applications running.

To the Cox forum,

I am currently having significant latency problems when attempting to run more than one internet-based application from my residential internet service. I am subscribed to the Premier Tier and, with no other internet services running, receive anywhere from 15-20mb download and 5-7 upload (well below the advertised speeds for this tier, but that's a different problem). If I open Pandora, run an online internet game (like League of Legends or Battlefield 3) or a VoIP service like Skype or Mumble, my internet speeds plummet to 2-3mb up, 8mb down and everything starts to lag and/or buffer. I understand that these services pull significant bandwidth (Skype especially), however even Netflix (when run by itself) spends a great deal of time buffering before and during an stream.

My current setup includes a Motorola SB5120 modem (roughly 5 years old– the possible culprit here, I believe), an Apple Airport Extreme with wireless-N capability. a wired connection to my PC (for games, pandora, Skype, etc.) and wireless for my laptop and my PS3 (for Netflix). I have bypassed the router and plugged the modem directly into my PC and experienced the same problem of buffering, latency, game disconnects, etc. I live in Fayetteville, Arkansas, just a few miles west of the University campus.

Does this sound like an aging/damaged modem, or something else? If so, would upgrading to a DOCSIS3.0-capable modem be a worthwhile upgrade? I appreciate any and all advice you can give!

Thanks!