Справочник Пользователя для Dynalink RTA1025W

Chapter 4: Web Configuration 

                                                                                                                                                                                       

QoS (Quality of Service) is an industry-wide initiative to provide preferential 
treatment to certain subsets of data, enabling that data to traverse the Internet or 
intranet with higher quality transmission service.   

There have been two generations of quality of service architectures in the Internet. 
The interpretation of the Type of Service Octet in the Internet Protocol header varies 
between these two generations.   

The refined definition of the initial Type of Service Octet looks like this: 

2^7 2^6 2^5 2^4 2^3 2^2 2^1 2^0 

Precedence 

  Type of Service Field 

   

The Differentiated Service Code Point is a selector for router's per-hop behaviors 
(PHB). As a selector, there is no implication that a numerically greater DSCP implies 
a better network service. RFC2474 redefined the Type of Service Octet to be: 

2^7 2^6 2^5 2^4 2^3 2^2 2^1 2^0 

Differentiated Services Code Point 

ECT 

CE 

The fields ECT and CE are nothing to do with quality of service. They are spare bits 
in the IP header used by Explicit Congestion Notification. As can be seen, the DSCP 
totally overlaps the old Precedence field. So if values of DSCP are carefully chosen 
then backward compatibility can be achieved. This leads to the notions of "class", 
each class being the group of DSCP with the same Precedence value. Values within 
a class would offer similar network services but with slight differences. Classes were 
initially defined as: 

0 0

Best 

effort 

8 1

Class 

1 

16 2

Class 

2 

24 3

Class 

3 

32 4

Class 

4 

40 5

Express forwarding 

48 6

Control 

56 7

Control 

Now, DSCP is what we are using for the QoS configuration on this device.   

Among the classes you will see on the webpage, the BE (Best Effort) class 
possesses no guaranteed rates; the CS (Class Selector) values enable backward 
compatibility with the older IP-Precedence scheme ranges 0~7; the EF (Expedited 
Forwarding) class is a low-loss, low-latency, low-jitter, assured-bandwidth, 
end-to-end service; AF (Assured Forwarding) provides for the delivery of IP packets 
in four independently forwarded AF classes, AF1x through AF4x. Within each AF 
class, an IP packet can be assigned one of three different levels of drop precedence. 
This class is used when a service (application) requires a high probability of packets 
being forwarded, so long as the aggregate traffic from each site does not exceed the 
subscribed information rate (profile). Each of the four AF classes allocates a certain 
amount of forwarding resources, such as buffer space and bandwidth in each 
network node. When congestion occurs, the drop precedence of a packet 
determines the relative importance of the packet within the AF class. 

You can start to configure the Bridge QoS/IP QoS rules on the Quality of Service 
webpage for your router.