This section explains the concept of bandwidth management and lists the resources the bandwidth management feature manages. Before proceeding, you need to be familiar with the concepts of ports and paths as described in the Configuring Basic Ports and Paths chapter and the Configuring Advanced Ports and Paths chapter. A glossary of terms used in this chapter is provided at the end of the chapter.

Virtual Pipe

Port bandwidth management is a process that applies static bandwidth, dynamic bandwidth, or a combination of these to provide a port with the bandwidth it needs to meet current requirements. At each port, a set of serial path resources are configured to provide a bandwidth bundle called a virtual pipe.

Bandwidth

Static bandwidth is provided by a configuration of one or more leased lines or dial paths to a port. The static resources are dedicated to a single port. Leased lines can provide continuous dedicated bandwidth to the port. Static dial paths can also provide incremental bandwidth, or bandwidth that becomes available only when a decision is made to dial them up.

Dynamic bandwidth is provided by dial-up line paths, which are allocated from a dial pool. Incremental bandwidth is provided by dial paths. The port can use either analog or digital lines that are allocated to it, and additional dial path resources can be added incrementally.

Bandwidth management operates on a port-by-port basis. It monitors line use based on rate of traffic and increases or decreases bandwidth based on limits that you specify. Network protocols that use the port are unaware of the underlying physical links, which bandwidth management bundles together into the virtual pipe to meet the port bandwidth requirements.

Bandwidth Aggregation

The main function of bandwidth management is to determine the aggregate bandwidth that will be provided to the set of protocols passing through the port. However, a WAN operates most efficiently when it can allow for variations in the type and amount of traffic passing through it. In addition to bandwidth management, the software provides the protocol reservation feature, which allocates portions of the virtual pipe to specified traffic such as the Internet Protocol (IP) or AppleTalk. As traffic passes through the pipe, the Point-to-Point (PPP) Multilink Protocol (MLP) can also be enabled to distribute packets more evenly over the virtual pipe. Figure 325 illustrates these concepts.

Figure 325 Use of Resources through the Virtual Pipe

You reserve bandwidth for the protocols traversing the WAN using the -PORT ADD ProtocolRsrv parameter; see the Configuring Mnemonic Filtering chapter for further explanation.

Load balancing equalizes traffic flow and makes sure that packets that may have been fragmented over the links arrive at their destination in the correct sequence. Load balancing is accomplished using the PPP Multilink Protocol as described in RFC 1717 and is enabled using the -PPP MlpCONTrol parameter.