Draytek Vigor3200 Series User Manual page 185

headquarter, a teleworker may enforce an index of QoS Control to reserve bandwidth for
HTTPS connection while using lots of application at the same time.
One more larger-scale implementation of QoS network is to apply DSCP (Differentiated
Service Code Point) and IP Precedence disciplines at Layer 3. Compared with legacy IP
Precedence that uses Type of Service (ToS) field in the IP header to define 8 service classes,
DSCP is a successor creating 64 classes possible with backward IP Precedence compatibility.
In a QoS-enabled network, or Differentiated Service (DiffServ or DS) framework, a DS
domain owner should sign a Service License Agreement (SLA) with other DS domain owners
to define the service level provided toward traffic from different domains. Then each DS node
in these domains will perform the priority treatment. This is called per-hop-behavior (PHB).
The definition of PHB includes Expedited Forwarding (EF), Assured Forwarding (AF), and
Best Effort (BE). AF defines the four classes of delivery (or forwarding) classes and three
levels of drop precedence in each class.
Vigor routers as edge routers of DS domain shall check the marked DSCP value in the IP
header of bypassing traffic, thus to allocate certain amount of resource execute appropriate
policing, classification or scheduling. The core routers in the backbone will do the same
checking before executing treatments in order to ensure service-level consistency throughout
the whole QoS-enabled network.
However, each node may take different attitude toward packets with high priority marking
since it may bind with the business deal of SLA among different DS domain owners. It's not
easy to achieve deterministic and consistent high-priority QoS traffic throughout the whole
network with merely Vigor router's effort.
In the Bandwidth Management menu, click Quality of Service to open the web page.
This page displays the QoS settings result of the WAN interface. Click the Setup link to
access into next page for the general setup of WAN interface. As to class rule, simply click the
Edit link to access into next for configuration.
175 Vigor3200 Series User's Guide