Product specifications

Efficient Networks
®
Router family
Technical Reference Guide
Chapter 4: System Management
Efficient Networks
®
Page 4-47
Differentiated Services Framework (DiffServ) is a facility to prioritize the
requirements of each Class of Service (CoS) according to policies and apply policies
to network traffic. DiffServ is suited to Metropolitan Area Networks or private networks
where control over the infrastructure is guaranteed, and differentiated services can be
deployed end-to-end. Applications such as videoconferencing or IP telephony must
be able to communicate their service level requirements to an infrastructure that can
consistently meet those requirements. To do this, QoS control mechanisms must be
present in each network element. This router provides such QoS control mechanisms
and can interpret the service requirements indicated by network applications, fully
participating in any differentiated services architecture.
To employ DiffServ, each packet of data is tagged with a six-bit pattern known as the
DiffServ CodePoint (DSCP), replacing the three IP precedence bits in the ToS byte of
the IPv4 header. This tag determines the processing of each packet as a Pre-Hop
Behavior (PHB) at each DiffServ node. Each DSCP is read and network resources
are allocated to a packet according to the Class of Service defined in its associated
policy. When DiffServ is activated on your router, data packets are read and marked
according to their DiffServ priority. The packets are then queued and processed
according to the QoS policies defined for each class of service. You can create and
manage these QoS policies using either the Command Line Interface (CLI) or Web
management Interface (WMI).
Weighted Fair Queuing (WFQ) is a flow-based queuing algorithm that performs two
functions simultaneously: It schedules priority traffic to the front of the queue to
reduce response time, and it fairly distributes remaining bandwidth between
remaining queues. Consequently, WFQ ensures that queues are not starved for
bandwidth and that traffic service levels are made more predictable. Weighted Fair
Queuing adapts automatically to changing network conditions and requires minimal
configuration. WFQ is implemented on the router and applies to network traffic
passing through it. Unlike DiffServ, external nodes have no effect on QoS through
Weighted Fair Queuing.
Weighted Fair Queuing provides a means of ensuring that high priority or mission-
critical applications receive adequate levels of bandwidth. This is accomplished by
controlling two key factors in QoS policies; priority and weight.
Priority determines the order in which packets will be processed by the router. Weight
determines the amount of bandwidth to be allocated to a given application.
Manipulation of these two factors determines the quality of service to each
application. The router supports four priority levels; High, Medium, Normal and Low. A
weight value can be assigned to each of these priority levels from a minimum of 1 to a
maximum of 255.
To configure the QoS Priority/Weight Setting via the Web Management Interface, see
“QoS Configuration Page” on page 8-52 or from the command line, use the following
command:
-> qos setweight <high | meduim | normal | low> <weight>