Alcatel Carrier Internetworking Solutions 8800 User Manual

Roma

OmniSwitch Troubleshooting Guide

page -23

• Separate paychecks for multicast

• Generates ingress coupons, receives egress coupons for backpressure capability

• Ingress coupon generation period: ~2 microseconds

• Paycheck generation period: 32.125 microseconds

• The BBUS provides access to individual Roma chips based on a chip index number

The Roma Driver’s primary responsibilities are to initialize, monitor, and support the central component 
of the Eagle switch/router’s switching fabric system: a set of up to ten Roma ASICs, with exactly eight 
operational during fabric operation.

The operational fabric consists of 8 slices for each connected Coronado ASIC (these 8 slices correspond 
one-to-one with the 8 operational Roma ASICs). The fundamental logic for packet switching through the 
fabric is contained in 5 basic architectural components:

• Link Control

• Calendar

• Multicast Vector Table

• IPC Mapping

• Flow Control

This establishes that Roma-Coronado communication is working on each link and is aligned across the 8 
fabric bit slices.

Each fabric port has a calendar of unicast and multicast egress destinations for the corresponding Coro-
nado. There is a limited ability to designate dequeuing frequency for some destinations, affecting the 
egress bandwidth allocated to destinations. During a given cycle of the Primary Cycle, a single calendar 
entry for each fabric port is processed (in a specified order). During other cycles, other calendar entries are 
processed. IPC packets are given absolute priority, so there are no calendar entries for IPC.

Indicates multicast domain membership for fabric ports. On fabric ingress, frames are put into a given 
fabric port’s multicast FIFO based on this vector.

On ingress, Coronado IPC QIDs are identified based on agreed upon values (for Roma the values are 
selected from offsets 12 through 15). On egress, an internal Roma table maps IPC QIDs to fabric ports 
(one-to-one).