PM7323 datasheet(72/219 Pages) PMC

72 / 219 page

STANDARD PRODUCT

PM7323 RCMP-200

DATASHEET

PMC-960543

ISSUE 2

ROUTING CONTROL, MONITORING, & POLICING

200 MBPS

Proprietary and Confidential to PMC-Sierra, Inc.

and for its Customer’s Internal Use.

Note:

Multicasting has limited utility in the ingress direction. Because the cells for all

VCs are queued at the Output Cell Interface, multicasting may result in head-of-

the-line blocking. Provided the multicasting cannot result in an instantaneous

rate greater than the bandwidth supported by the Output Cell Interface (e.g.

200Mbit/s with a 25MHz 8-bit bus), no problems shall occur. It is the Connection

Admission Control entity's responsibilty to ensure the traffic is within the rate

supported.

Cell counting, cell rate policing and OAM processing is performed on the

received cell, if so enabled. Therefore, the connection statistics for the multicast

group are available in the VC Table Record at the head of the linked list. If the

received cell is discarded due to policing, no multicasted cells are created. If the

received cell is tagged, all multicasted cells are also tagged.

For multicast connections not at the head of the linked list, policing and cell

counting are suppressed, in order to conserve bandwidth. The CLP=1, CLP=0

and non-compliant counts are not valid.

Each branch connection has its own VC Table Record. Therefore, header

translation and OAM is supported independently for each branch.

9.5

Output Buffering

The output buffer consists of a four cell FIFO which transfers the oldest cell to the

switch port whenever it signals that it will accept a cell. The FIFO output is a

slave to the switch port. If the output buffer becomes full, it provides back-

pressure to the Cell Processor which in turn back-pressures the Input Cell

Interface.

9.6

Congestion Control

Congestion control is handled by a single signal, CONG, entering the device.

When this signal indicates that congestion is being experienced by the switch

core, all low priority cells (high CLP bit) are discarded. This includes cells which

are made low priority during the policing process.

PM7323 Datasheet(PDF) 72 Page - PMC-Sierra, Inc