H3C Technologies H3C SecPath F1000-E - Manual (Page 303)

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Configuring QoS
Feature and hardware compatibility
Feature F1000-A-EI/E-SI/S-AI F1000-E F5000-A5 Firewall module
Configuring the port
bandwidth limit
Yes No No No
Configuring line rate in
the Web interface
Yes No No No
Overview
In data communications, Quality of Service (QoS) is the ability of a network to provide differentiated
service guarantees for diversified traffic regarding bandwidth, delay, jitter, and drop rate.
The network resources are always scarce. The contention for resources demands that QoS prioritize
important traffic flows over trivial traffic flows. When making a QoS scheme, a network administrator
must plan network resources carefully considering the characteristics of various applications to balance
the interests of diversified users and fully utilize network resources.
The following part introduces the QoS service models, and some mature QoS techniques in wide use.
Appropriately using these techniques in specific environments, you can improve QoS effectively.
QoS service models
Best-effort service model
Best effort is a single-service model and also the simplest service model. In the best-effort service model,
the network does its best to deliver packets, but does not guarantee delay or reliability.
The best-effort service model is the default model in the Internet and applies to most network applications.
It uses the first in first out (FIFO) queuing mechanism.
IntServ model
The integrated service (IntServ) model is a multiple-service model that can accommodate diverse QoS
requirements. It provides the most granularly differentiated QoS by identifying and guaranteeing definite
QoS for each data flow.
In the IntServ model, an application must request service from the network before it sends data. IntServ
signals the service request with the Resource Reservation Protocol (RSVP). All nodes receiving the request
reserve resources as requested and maintain state information for the application flow.
The IntServ model demands high storage and processing capabilities because it requires all nodes along
the transmission path to maintain resource state information for each flow. The model is suitable for
small-sized or edge networks, but not large-sized networks, for example, the core layer of the Internet,
where billions of flows are present.