Quality of Service
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OmniAccess 5740 Unified Services Gateway CLI Configuration Guide
Alcatel-Lucent
QOS OVERVIEW
The term QoS commonly refers to the management of link bandwidth and the
preferential treatment of certain traffic over others. The mechanisms to support
this are many, some are complicated and for most of these mechanisms, no
standards exist.
There are, however, fairly standard algorithms that can be applied to some of the
mechanisms. Several of the QoS mechanisms have been in use for years, for
example to limit the bandwidth usage to conform to the Service Level Agreements
(SLAs). The ISP commonly makes sure this contract is honored by dropping all
traffic above the rate the customer pays for.
QoS generally involves prioritization, queuing, and shaping of network traffic. QoS
can be defined in terms of the total network "pipe" being queued and shaped to
the performance of a given server or router, or in terms of specific applications like
the source, destination, TOS, control information, and data. A network monitoring
system must typically be deployed as a part of QoS to insure that networks are
performing at the desired level.
QoS supports voice and data service simultaneously on the OmniAccess 5740
USG. This include controlled resource sharing by providing bandwidth guarantee
for different classes. It also provides features that make QoS configuration simpler
by means of Auto QoS commands.
GENERIC TERMS USED IN QOS
QOS
QoS is a term commonly used to describe a policy or a set of mechanisms used to
manage bandwidth or give certain types of traffic preferential treatment over
others.
DSCP
The DSCP (Differentiated Services Code Point) value refers to 6 bits in the TOS
byte in the IP header that can be used to mark the IP datagram with a certain
value. This value can be interpreted by devices.This packet passes through on
the way to its destination.
IP P
RECEDENCE
It has become common to use 3 bits in the TOS byte in the IP header to mark the
packet for QoS treatment. We can use IP Precedence to assign values from 0 to 7
to classify and prioritize types of traffic.
RED
RED (Random Early Detection) is a congestion avoidance technique.
WRED
WRED (Weighted Random Early Detection) is also a congestion avoidance
technique.
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