User Manual

24-Port and 48-Port Gigabit Ethernet PoE+ Smart Switches with 4 SFP Ports
Configure Quality of Service User Manual307
7. For each DSCP value, select from the corresponding Queue menu which internal traffic
class must be mapped to the DSCP value.
The traffic class is the hardware queue for a port. Higher traffic class values indicate a
higher queue position. Before traffic in a lower queue is sent, it must wait for traf
fic in
higher queues to be sent.
The allowed Per Hop Behavior (PHBs) values, apart from other DSCP experimental
values, are as follows:
• Class Selector (CS) PHB. These values are based on IP precedence.
•
Assured Forwarding (AF) PHB. These values define four main levels to sort and
manipulate some flows within the network.
•
Expedited Forwarding (EF) PHB. These values are used to prioritize traf
fic for
real-time applications. In many situations, if the network exceeded traffic and you
need some bandwidth guaranteed for an application, the EF traffic must receive this
rate independently of the intensity of any other traffic attempting to transit the node.
8. Click the Apply button.
Your settings are saved.
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.