IBM SG24-4817-00 manual ATM Data Flows, ATM UNI/NNI Format Data Cells

This soft copy for use by IBM employees only.

1.The network prefix must be unique and consistent within a given ATM network. It is defined at each switch in the network and consists of an

11-byte network address and a 2-byte area identifier, which is further divided in to a 1-byte ATM Cluster Number(ACN), and a 1-byte Hub Number (HN). This results in a hierarchical network topology of:

a.An ATM network comprised of

b.ATM sub-networks (or clusters) comprised of c. ATM hubs

In any given ATM network, all switches will have an ATM address with the same first 11 bytes. In any given ATM cluster, all switches will have an address with the same first 12 bytes, and every switch will have a unique 13-byte network prefix.

This hierarchical organization allows for very efficient topology calculation and distribution, since updates can be localized to a given cluster, or, where appropriate, to devices connected to an adjacent cluster or network.

2.The network prefix must begin with either 39 (corresponding to IEEE 802

(LAN) Format), 45 (corresponding to ITU-T (E.164) Format), or 47 (corresponding to OSI Format). Generally speaking, it doesn′t matter which

format you choose, however, specific bytes have specific significance in each format, and, consequently, care should be taken in choosing a format, especially if your ATM network will be connected to other ATM networks.

1.1.4ATM Data Flows

Figure 2. ATM UNI/NNI Format Data Cells

Chapter 1. Introduction to ATM Networks 3