Nortel Networks 8000 - Manual (Page 394)

10 Low-speed ATM configuration
Nortel Secure Router 8000 Series
Configuration -WAN Access
OQ NOTE
The nodes 2, 3, and 4 represent the common ATM switches. SR8000 only perform the functions of
nodes 1 and 3.
10.1.4 ATM applications
IPoA
IPoEoA
PPPoA
PPPoEoA
The ATM interface of the SR8000 supports PVCs and the following four applications: IPoA,
IPoEoA, PPPoA and PPPoEoA.
IP over AAL5 (IPoA) carries IP packets.
The AAL5 serves as the data link layer for the communications between IP hosts in the same
network.
IP over Ethernet over AAL5 (IPoEoA) has three-layer architecture. The upper layer is IP
encapsulated, the middle is IPoE, and the bottom layer is IPoE over AAL5.
You can access the long-distance access server at a high speed by using the PVC to carry
Ethernet packets.
The SR8000 implements the following functions in IPoEoA:
• One Virtual Ethernet (VE) interface can be associated with multiple PVCs.
• PVCs associated with a same VE interface can be interconnected at layer 2.
PPP over AAL5 (PPPoA) carries PPP packets. You use the ATM cells to encapsulate PPP
packets. IP or other packets are encapsulated in PPP packets. AAL5 refers to the carrier layer
of PPP packets.
The PPPoA is important because PPP manages the PPPoA communication process. You can
make PPPoA use flexible and extensive PPP supported applications. Users must create a VT
interface before transmitting PPP packets over AAL5.
The PPPoE over AAL5 (PPPoEoA) carries PPPoE (PPP over Ethernet) packets. You use ATM
cells to encapsulate Ethernet packets to simulate all the functions of ethernet.
The interface management module supplies a new VE interface, enabling AAL5 to bear
Ethernet packets. This VE interface has certain characteristics of Ethernet. You can
dynamically create this by using the respective configuration commands.
Configure the protocol stack for this interface as follows:
• The bottom layer is the PVC of the ATM, through which packets may be transmitted and
received.
• The link layer is Ethernet protocol.
• The protocols for network layer and the upper layers remain the same as normal Ethernet
interface.
10-8 Nortel Networks Inc. Issue 5.3 (30 March 2009)