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The goal of classification is to categorize each traffic stream that passes through the network. By identifying all traffic, the server is able to perform different types of processing depending on the stream type such as prioritization, quality of service and class based speed limiting.
The class system inspects each network packet and identifes which stream it belongs to. It does this by checking the properties for the packet including the network adapter it arrived on, source and destination addresses, protocol, size and other information. After the packet is identified the server places the packet into a corresponding queue for further processing.
Packets are stored in the queue for a short period of time until they are ready to be sent by the processing system. Rules determine the delay, queue depth, priority and other processing information that applies to each queue.
The server operates at Layer 2 in the network stack which allows it to view all of the properties for each stream including Ethernet, IP and TCP/UDP information. At this layer the traffic is broken down from streams into packets which range between 54 and 1518 bytes in size.
Each packet contains identifing information in the form of a virtual envelope called a header. Headers comprise of protocol specific data such as source and destination address, packet size, layer number and other properties.
Each layer in the network stack attaches its own header to the packet containing information that is specific to that layer. This allows the server to classify all layered protocol information such as MAC address and packet size information at layer 2, IP addresses at layer 3 and TCP ports at layer 4.
There are also types of stream information that are not specific to any layer such as direction and network adapter. These properties are recorded and used to classify packets into their appropriate queues.
There are a number of methods available to sort traffic into queues. The different criteria that may be used to classify streams are as follows:
Group policies are used in situations where an entire group of users must be classified into a single queue. Rather than specifying an address as the local or remote endpoint, a group policy is used to specify a collection of addresses.
Group policies are implemented in the form of Address Groups which are configured in the View, Address Groups menu within the client application. The Address Group window allows the administrator to define the groups that can be used for rule classification. Once a group is created it is stored on the server and may be used in any rule endpoints as long the the classification critera contains a protocol that supports addressing such as IP, TCP, UDP or ICMP.
Following are some of the benefits of using address groups: