Wrestling With QoS
The next menu in the list was "Maintenance", which allowed me to check the status of the router as well as to back up my configuration and change the administrator password. Under the "Advanced" menu, there were a number of features available. Highlights included port forwarding, port triggering (Figure 5), DMZ, Dynamic DNS setup, and LAN DHCP setup.
Figure 5: Port Triggering
Under WAN setup, I found the first configuration items related to VoIP usage: QoS and Bandwidth. The help text for QoS (which stands for "quality of service") described it as a way to assign priority to voice traffic over data traffic, and specified that it should only be set "If you experience delays or drop-outs on VoIP calls" . Its default state was off, so I turned it on just to see what it would do. When I hit the "Apply" button, I got the pop-up shown in Figure 6. Evidently, turning on QoS also required me to set bandwidth, which in-turn had a relationship to the MTU setting which was also available in this menu.
Figure 6: QoS warning
According to the help on the page, the MTU should be specified in Bytes, and the bandwidth should be specified in kiloBytes per second (KBytes/sec), but the label next to the Bandwidth field (Figure 7) indicated that the value entered should be specified in kbps, i.e. kilobits per second.
Figure 7: Bits or Bytes?
To enable to me to accurately fill out the form, I ran a speed test, which showed my highly asymmetric cable modem was giving me around 3900 kbps download and 354 kbps upload. Since my upload speed was going to be the limiting factor, I used that value for my bandwidth. I first attempted to enter 354 (kbps) for bandwidth, but a pop-up complained that the value didn't match my MTU. Next I attempted to enter 44 (KBps) but a pop-up complained that the value had to be greater than 127.
Digging a little deeper to see just what NETGEAR wanted in this menu, I viewed the HTML source for the page. It revealed that NETGEAR had commented out pop-up suggestions on what values to enter for MTU based on your bandwidth. Instead they just put in directions indicating that you should see the Help page. When I looked at the help, it suggested that the MTU should not be changed at all "unless you are sure it is necessary for your ISP connection".
So it boils down to that fact that turning on QoS requires you to make sure your Bandwidth setting (measured in either KBps or Kbps), matches up with your MTU setting (measured in Bytes). Your Bandwidth is a fixed value reflecting your ISP account, and you are advised not to change the default MTU. I, uh, think there's room for improvement here. I left QoS turned off, and moved on.