The ATM Backbone

An ATM backbone is the central part of the network, with a number of POP's (Point Of Prescence), each may have one or more ATM switches.  

The customer PVC's traverse several ATM backbone POP's, and often pass through multiple switches at a single POP.  

For our example ATM network, customers can connect to the provider's ASX-4000's with a number of certified pieces of equipment, including routers with ATM cards, and ATM switches such as the Marconi ASX-1000.

The edge switches connect directly to customers, and the core switches, such as the NEC20, connect to other ATM POP's via two OC3 up to OC48 IMT's (Inter-Machine Trunks).  If a customer PVC enters the Pop and then passes through more than one switch at that POP - then the number of "Hops" of a PVC will be higher than the number of ATM Pop's.