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Understanding MPOA and NHRP

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Although the connection between any two MPSs can be supported by an ATM

PVC, RFC 1577 SVC (ATM Classical IP), or emulated LAN (ATM LANE), the

connection between any MPC and its MPS must always be supported by an

ELAN, as shown in Figure 1-1 on page 1-2

Cut-through routing is based on the fact that, in most cases, data transfer occurs at

a steady rate of flow. For example, data or file transfer from one legacy Ethernet

LAN to a remote counterpart usually involves multiple frames. A file transfer of

approximately 45 KB requires about 30 Ethernet frames, all addressed to the same

destination.

In an MPOA environment, it is possible to:

• Identify, from the address field in the first frame of a data/file transfer, the

recipient of that data or file.

• Establish an SVC to the recipient.

The software then disassembles all 30 or so frames into approximately 900 ATM

cells and transmitts them to the recipient by way of the virtual channel provided

by the SVC.

Network performance improves as the cells follow a predetermined direct path, in

contrast to the hop-by-hop routing of the Ethernet frames. Network performance

improves markedly in the case of steady-stream deterministic data flows, such as

video.

MPOA Logical Components

MPOA operations are based on logical components, which can be implemented in

various configurations of hardware and software. MPOA logical components

include the following:

•MPOA clients

An MPOA client (MPC) resides in each ATM edge device (for example, an

ATM switch) served by an MPOA router. BayRS does not provide MPC

functionality. The primary function of the MPC is to act, in ATM terminology,

as an ingress or egress point for traffic establishing and subsequently using

network cut-throughs.

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Avaya Configuring MPOA Services Manual de usuario Pagina 23