User Manual

8-Port or 16-Port Gigabit Smart Managed Pro Switch Model GS418TPP, GS510TLP, and GS510TPP
Configure Quality of Service User Manual265
Manage Differentiated Services
The QoS feature contains Differentiated Services (DiffServ) support that allows traffic to be
classified into streams and given certain QoS treatment in accordance with defined per-hop
behaviors.
Standard IP-based networks are designed to provide best effort data delivery service. Best
effort service implies that the network delivers the data in a timely fashion, although there is
no guarantee. During times of congestion, packets might be delayed, sent sporadically
, or
dropped. For typical Internet applications, such as email and file transfer, a slight degradation
in service is acceptable and in many cases unnoticeable. Conversely, any degradation of
service can negatively affect applications with strict timing requirements, such as voice or
multimedia.
Defining DiffServ
To use DiffServ for QoS, you must first define the following categories and their criteria:
1. Class. Create classes and define class criteria.
2. Policy. Create policies, associate classes with policies, and define policy statements.
3. Service. Add
a
policy to an inbound interface.
Packets are classified and processed based on defined criteria. The classification criteria are
defined by a class. The processing is defined by a policy’
s attributes. Policy attributes can be
defined on a per-class instance basis, and it is these attributes that are applied when a match
occurs. A policy can contain multiples classes. When the policy is active, the actions taken
depend on which class matches the packet.
Note the following about the DiffServ process:
• Packets are filtered and processed based on defined criteria. The filtering criteria is
defined by a class.
The processing is defined by a policy's attributes. Policy attributes can
be defined on a per-class instance basis, and it is these attributes that are applied when a
match occurs.
• The configuration process begins with defining one or more match criteria for a class.
Then one or more classes are added to a policy
. Policies are then added to interfaces.
Packet processing begins by testing the match criteria for a packet.
The All class type option
specifies that each match criteria within a class must evaluate to true for a packet to match
that class. The Any class type option specifies that at least one match criteria must evaluate
to true for a packet to match that class. Classes are tested in the order in which they were
added to the policy. A policy is applied to a packet when a class match within that policy is
found.