AC208-DS03-R datasheet(19/58 Pages) BOARDCOM

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Preliminary Data Sheet

AC208

07/08/02

B roa dcom

Document

AC208-DS04-405-R

Addressing Algorithm, Routing, Learning, and Aging

Page 11

FORWARDING SCHEME

The store-and-forward algorithm is used. The incoming packet has to be completely stored in the buffer and verified error-

free before forwarding operations take place.

BRIDGE BUFFER MANAGEMENT AND QUEUES

The bridge buffering management continues to store received packets into memory. The buffer size for 100M port is 16K

bytes, and 8K bytes for 10M port.

Figure 4: Basic Memory Management Concept

The bridge uses the six pointers to control per port buffer status. Start Address point is the beginning of memory address for

each port and the End Address point is the last address of memory for each port. The Read/Write and shadow Read/Write

pointers are dynamically changed depending on the current outgoing and incoming packets in the storage. If the Write

pointer reaches the Read pointer and the size between write and read pointers is smaller than 2K bytes, buffer is full. On the

other hand, when read/write pointers are equal, the buffer is empty.

Table 3:

Embedded Memory Structure

0x0000

2K x 32 for address lookup table

0x07FF

0x0800

4K x 32 for 100M Bridge Port

0x17FF

0x1800

2K x 32 for 10M Bridge Port

0x1FFF

Write Point

End Address

Start Address

Read Point

Free buffer

Per Port Buffer Management

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