Cisco Systems 8600 Series manual ATM Cell Headers, ATM Cell Format

Functional Description

Figure 2-7

header

ATM Cell Format

H81

ATM Cell Headers

There are two basic header types defined by the standards committees, a UNI header and a NNI header; both are quite similar. Cisco has expanded on these header types to provide additional features beyond those proposed for basic ATM service. Usage of each of the various cell header types is described as follows:

•The UNI header (see Figure 2-8) must be specified for each User-to-Network Interface. A UNI is any interface between a user device, such as an ATM router, and an ATM network.

•The NNI header (see Figure 2-9) must be specified for each Network-to-Network Interface. This is used, for example, at the interface between a user’s private ATM network and a service provider’s public ATM network.

•The STI header (see Figure 2-10)is an extension of these two header types and is used between Cisco switching nodes to provide advanced network features, including ForeSight, that improve performance, efficiency, and congestion control.

2-8Cisco BPX 8600 Series Reference