PM8621 datasheet(157/184 Pages) PMC

157 / 184 page

NSE-8G™ Standard Product Data Sheet

Preliminary

Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use

156

Document ID: PMC-2010850, Issue 1

12.13 Switch Setting Algorithm

NSE/SBS fabrics require an algorithm to map from customers’ connection requirements to

settings in the switch function control registers in these devices. Four constraints apply to this

algorithm:

• The algorithm must succeed for arbitrary permutation requests (i.e., neither the fabric nor

thealgorithm can fail to connect any one-to-one connection request).

• The algorithm must permit connection of 2-cast requests (port replication for either snooping

or for advanced redundancy fabrics). In fabrics with spare capacity and multicast/broadcast

servers, the algorithm must permit mapping of multicast/broadcast requests, up to the

capacity of the fabric and the servers.

• This algorithm must be fast enough to satisfy requirements for response to operator requests

for connection changes.

• This algorithm must be fast enough to satisfy requirements for protection responses to

equipment failures.

There are several aspects of this problem:

• Reconnection requests may be made individually in which case an incremental connection-

setting algorithm is desired, or as complete batches in which case a batch algorithm may be

desirable.

• Reconnection requests may be pre-computed for fast protection fail-over mechanisms.

12.13.1 Problem Description

The basic scheduling problem is to find the switch settings to properly route a set of connections.

This is more formally described using the definitions in the following paragraphs.

Port: An STS-12 input/output data stream. The serial ports on the SBS devices and the NSE-

devices operate at STS-12 rates and utilize STS-12 frames. Since the intention of the NSE-8G is

to serve as a DS0-granularity switch, these STS-12 frames must be treated as repeating on a cycle

of 12*9*90 = 9720 octets. All connections considered by this algorithm are octet connections.

Higher aggregations of traffic are handled as collections of octets, and are ignored for the

purposes of describing this algorithm.

Timeslot: A specific octet location in the 9720 octet cyclic structure.

Spacetimeslot: A timeslot on a specific port, identified by a space component and a time

component: for example, octet 9 on port 3 of SBS device 2

Connection: A mapping of an input spacetimeslot to an output spacetimeslot. Connections come

in two varieties, multicast and unicast. Unicast connections are a mapping of a single input

spacetimeslot to a single output spacetimeslot. Multicast connections are a mapping of a single

spacetimeslot to multiple output spacetimeslots. This algorithm is only concerned with the unicast

problem.

PM8621 Datasheet(PDF) 157 Page - PMC-Sierra, Inc