Zte ZXR10 5900 Product Description page 35

 Customized service: users of an ISP (Internet Service Provider) probably will send
out voice, video-sending or other real-time services. QoS enables ISP to
differentiate the different packets and provide different services.
Coexistence of various requirements: it can provide bandwidth and low delay

guarantee for time-sensitive multimedia services, and won't be influenced by other
services using the network.
QoS doesn't create bandwidth. It just manages bandwidth based on the needs of
application and network status. QoS has a set of performance parameter including:
Service availability: the reliability of linking between the users and Internet services.

Transmission delay: the interval of packet sending and receiving between two

points of reference.
Variable delay: also called jitter, which indicates the difference in time interval

among packets of one stream of data flow sent over one route
Throughput: the rate of packet sending over the network. It can be put in the form of

average rate or peak value rate.
Packet drop ratio: the highest rate of packets dropped during the process of packets

transmission. Dropping of packets generally results from network congestion.
To ensure that users can obtain service quality they need from ISP, the users have to
sign SLA (Service Level Agreement) with ISP. And ISP also has to build TCA (Traffic
Condition Agreement) among each other. SLA standardizes the service types and traffic
volume for each type of traffic from the client-side network. TCA standardizes certain
criteria need to be fulfilled by data traffic different ISPs.
Therefore, when there is data flow entering a DS area, the ingress node will perform
traffic classification and conditioning, record status information of the flows (single data
flow or aggregated flow), and also the node will perform metering, marking, shaping and
dropping based on the stream profile agreed with the users in order to make the input
stream in compliance with SLA. Meanwhile, DSCP value is marked on the packet header,
which is added to the corresponding BA (Behavior Aggregate). Egress nodes possibly
need to regulate the output stream to ensure it's in compliance with TCA of downstream
DS area.
To realize the above objective, the network elements in QoS domain provide the
following functions:
 Packet Classification and Coloring
 Traffic Policing
 Traffic Shaping
Congestion Avoidance

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