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Alcatel-Lucent
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OmniAccess 5740 Unified Services Gateway Web GUI Users Guide
Q
O
S (Q
UALITY
OF
S
ERVICE
)
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 part of QoS to insure that networks are
performing at the desired level.
A
LCATEL
-L
UCENT
S
PECIFIC
O
VERVIEW
ON
Q
O
S
QoS functionality and features supported are implemented at two stages - ingress
QoS processing and egress QoS processing. Ingress QoS processing deal with
features that are applicable while the packet gets into the OmniAccess 5740 USG.
For e.g., policing is a feature that admits packets into the system only if they arrive
at a committed rate. Policing functionality is normally applied at the ingress QoS
processing stage. Egress QoS processing deals with features that are applicable
to packets that leaves OmniAccess 5740 USG. For e.g., shaping that fits the
outgoing traffic in to a committed rate envelope is implemented at the egress QoS
processing stage.
Packets at the ingress are classified using common classifier, and exploits the
one-pass classification feature on the OmniAccess 5740 USG. These packets,
based on classification are grouped into a class. QoS is applied on each flow.