Ipoa; Ipoeoa; Pppoa; Pppoeoa - 3Com MSR 50 Series Configuration Manual

Overview of IPoA, IPoEoA, PPPoA and PPPoEoA Applications 129

IPoA

IP over AAL5 (IPoA) carries IP packets over AAL5. AAL5 provides the IP hosts on
the same network with the data link layer for communications. In addition, to
allow these hosts to communicate on the same ATM network, IP packets must be
tuned somewhat.
As the bearer network of IP services, ATM provides high speed point-to-point
connections which considerably improve the bandwidth performance of IP
network. On the other hand, ATM also provides excellent network performance
and perfect QoS.

IPoEoA

IPoE over AAL5 (IPoEoA) adopts a three-layer architecture, with IP encapsulation at
the uppermost layer, IP over Ethernet (IPoE) in the middle, and IPoEoA at the
bottom.
When a device is connected to a remote access server at high speed to access an
external network, PVC over ATM is used because of the long distance. In this case,
it is required for the ATM port of the server to carry Ethernet packets, which is
known as IPoEoA.
For IPoEoA, the device can implement the following basic functions:
In the application of IPoEoA, one virtual Ethernet (VE) interface can be associated
with multiple PVCs.
PVCs associated with the same VE interface are interconnected at layer 2.

PPPoA

PPP over AAL5 (PPPoA) means that AAL5 bears the PPP protocol packets: Its
essence is that ATM cells are used to encapsulate PPP packets, while IP or other
packets are encapsulated in PPP packets. In this way, AAL5 may be simply viewed
as the bearer layer of PPP packets. PPPoA is important because the communication
process of PPPoA is managed by PPP, and thus it can make use of PPP's flexibility
and extensive applications. Before transmitting PPP packets over AAL5, users must
create a virtual template (VT) interface. For more information about virtual
template interfaces, refer to "VT and VA Interface" on page 534.

PPPoEoA

PPPoE over AAL5 (PPPoEoA) carries PPPoE packets over AAL5. This is to
encapsulate Ethernet frames in ATM cells. In this case, a PVC to simulate all
functions of Ethernet. To allow AAL5 carry Ethernet frames, the interface
management module provides the virtual Ethernet (VE) interface. This VE interface
has Ethernet characteristics and can be dynamically created through configuration
commands. The following is the protocol stack for the VE interface:
ATM PVC at the bottom layer
Ethernet at the link layer
Protocols the same as those for the Ethernet interface at the network layer and
upper layers
For more information about the VE interface, please refer to "Introduction to VE"
on page 536.