ATM applications

An ATM interface can implement IPoA, IPoEoA, PPPoA, and PPPoEoA to carry data encapsulated in IP, PPP, or Ethernet across an ATM network.

IP over ATM (IPoA) enables ATM to carry IP packets. In an IPoA implementation, ATM acts as the data link layer protocol for the IP hosts on the same network. To enable these hosts to communicate across an ATM network, IP packets must be encapsulated in ATM cells.

By making full use of the advantages of ATM, IPoA delivers excellent network performance and mature QoS assurance.

IP over Ethernet over ATM (IPoEoA) uses a three-layer architecture, with IP encapsulation at the top layer, IP over Ethernet (IPoE) in the middle, and IPoEoA at the bottom.

IPoEoA is suitable where Ethernet packets are to be forwarded through ATM interfaces. In IPoEoA applications, you can associate multiple PVCs with one Layer 3 virtual Ethernet (VE) interface. PVCs associated with the same VE interface are interconnected at Layer 2.

PPP over ATM (PPPoA) enables ATM to carry PPP protocol packets. With PPPoA, PPP packets, in which IP packets or other protocols' packets are encapsulated, are encapsulated in ATM cells. In this implementation, ATM is the carrier of PPP packets and the communication process of PPPoA is managed by PPP, which allows for flexibility and rich applications. To transmit PPP packets across ATM, a virtual-template (VT) interface is required.

PPPoE over ATM (PPPoEoA) enables ATM to carry PPPoE protocol packets. With PPPoEoA, Ethernet packets are encapsulated in ATM cells, through which you can use a PVC to implement the functionality of Ethernet. To carry Ethernet frames over ATM, the virtual Ethernet (VE) interface was introduced. The VE interface has Ethernet characteristics and can be dynamically created. The following is the protocol stack used by the VE interface:

• ATM PVC (the bottom layer).

• Ethernet (the link layer).

• Network layer and other upper layers (the same as those for common Ethernet interfaces).