Siemens 2000 - Manual (Page 37)

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37
Quality of Service(QoS): Protocol Settings
Navigation: Admin > Quality of Service
To improve the quality of your telephone connections you can request
preferential treatment for the telephone data (voice packets and signals) in
the Internet.
Quality of Service for IP
The DiffServ procedure distinguishes between several quality of service
classes and various priority levels. The sender enters the required quality of
service class (DSCP class) in the protocol header of each separate data
packet. The DSCP field (Differentiated Service Code Point) is used for this.
This is evaluated in the routers and gateways on the route to the recipient
and the data packet is handled accordingly.
Whether or not a higher quality of service class will actually improve the
quality of your telephone connection depends on the IP network behind
your access point.
You can specify a DSCP Class for Voice and a DSCP Class for Signalling.
To do this, select the required class in both lists.
A distinction is made between the following quality of service classes:
Best Effort
The data packets are not preferred. This means: lowest priority level and
therefore longer execution times with high network utilisation and random
packet losses. It is possible to change the packet sequence.
Best Effort generally offers acceptable quality of service with minimal use
of resources.
Assured Forwarding 1 ... Assured Forwarding 4
Four priority classes are defined for assured forwarding. The class with the
lowest priority is Assured Forwarding 1.
Resources (data throughput/bandwidth, buffer store) are made available to
the classes independently of one another. In the event of an overload,
surplus data packets are rejected (packet loss). Within each class there are
three levels of packet loss probability (drop preference levels): Low,
Medium, High. If the data packets in a class are in a queue, data packets
with a High drop preference level are rejected first. A low drop preference
level therefore means better quality of service within the class. You specify
the drop preference level in the Drop Preference Levels for Voice or Drop
Preference Levels for Signalling field. The field will appear when you
select one of the assured forwarding classes.
Expedited Forwarding
Data packets are forwarded with the highest priority. A minimum
bandwidth is guaranteed (irrespective of network utilisation).