PM7341 datasheet(79/413 Pages) PMC

79 / 413 page

PRELIMINARY

INVERSE MULTIPLEXING OVER ATM

PM7341 S/UNI-IMA-84

DATASHEET

PMC-2000223

ISSUE 4

INVERSE MULTIPLEXING OVER ATM

PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE

10.1.4 ANY-PHY/UTOPIA Loopback

For diagnostic purposes, the capability to loopback all Any-PHY/UTOPIA traffic

back to the Any-PHY/UTOPIA bus is provided. Cells are taken from the Transmit

group FIFOs and placed into the respective Receive Group FIFOs, or to a single

FIFO on a space available basis. If the receive interface is in Any-PHY or single

address UTOPIA L2 mode, all tx ports are looped back to the respective rx port.

If the receive Interface is in multiple port UTOPIA L2 mode and the transmit Any-

PHY is configured in 84-port Any-PHY mode, the 84 transmit ports will be aliased

onto the 31 receive ports. Transmit port numbers 31 and 63 will be blocked and

are not functional for loopback operations.

10.2 IMA Sub-layer

10.2.1 Overview

The IMA protocol provides inverse multiplexing of a single ATM stream over

multiple physical links and reassembles the original cell stream at the far-end.

The inverse multiplexing is performed on a cell basis; hence, the IMA protocol is

described as a cell-based protocol. See Figure 9 below.

The protocol is based upon the concept of an IMA frame. An IMA frame is

programmable in size and is delineated by an IMA Control Protocol (ICP) Cell. It

is recommended that the ICP cells of each link in the IMA group be offset from

each other to reduce the notification time of link/group status changes.

The transmitter is responsible for aligning the IMA frames on all links within a

group, and for ensuring that cells are transmitted continuously by adding filler

cells as necessary. To maintain frame alignment in the presence of independently

timed line clocks, a cell based stuffing algorithm is utilized.

Since the IMA frames are aligned on transmission, this allows the receive end to

recover the IMA frames and align them to remove any differential delay between

the physical links.

PM7341 Datasheet(PDF) 79 Page - PMC-Sierra, Inc