User Manual

24-Port Gigabit (Hi-Power) PoE+ Ethernet Smart Managed Pro Switch with 2 SFP Ports
Configure Quality of Service User Manual214
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 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.
If congestion occurs, packets might be delayed, sent sporadically, or dropped. For typical
Internet applications, such as email and file transfers, a slight degradation in service is
acceptable and in many cases unnoticeable. However, any degradation of service can
negatively affect applications with strict timing requirements, such as voice and 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. T
he 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 th
en 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.