7. Priority Based QoS

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There's another itch that small networkers have, and that a managed switch can scratch: bandwidth control. Want to keep your teens from bogging down the family Internet connection with their BitTorrent activity? A little dab of QoS should do the trick.

Unfortunately, once again, Netgear's documentation tells you the knobs and switches that are available to tweak, but leaves you on your own to figure out how to use them. This is too bad, because the 728TS provides both priority-based and rate limiting QoS features, and options within those features.

Figure 10: CoS settings

Priority-based QoS - also called CoS or Class of Service - works just as you'd imagine it would from the name. It lets you assign each physical port on the switch a priority value from 0 to 7, where 7 represents the highest priority (see Figure 10). Data from ports with higher priority values gets put ahead of data from lower-valued ports, into one of four egress (outgoing) queues. This means that higher-priority data gets a larger chunk of your upstream bandwidth, which is typically more limited than the downstream.

Note that the priority-based QoS works on egress data only; that is, data flowing out of the switch. It also does not discriminate based on the type of traffic, i.e. you can't assign priorities to applications, only physical switch ports.

Also note that the Software Admin guide erroneously says that there are eight queues, when there are in fact four.

The 728TS supports use of both VLAN Priority Tag (VPT) and DiffServ Code Point (DSCP) tags. You can separately map CoS values - which I'm assuming uses VPT tagging - and DSCP values (which run from 0 to 63) to the four egress queues (see Figure 11). But again, since no explanation is given of why you would do this, I'd leave the defaults alone.

Figure 11: QoS to Queue