Architecture
The Multiservice switches are made up of a shelf of 16 cards. There are two key types of cards to consider:
- the Control Processor or CP is the switch fabric processor: it controls shelf functionality, as well as controls routing as well as manages the provisioning interface;
- the Function Processor or FP is in essence a line card, but there is processing logic and queue logic on the card. This allows for packets to be directly manipulated on the FP, decreasing the load on the CP. FPs normally process data frames on the ingress path and can autonomously forward frames to egress ports without further processing by protocol or control software on the egress FP. This is done by implementing backplane transfer, egress queuing and subsequent transmission all using ASICs.
A shelf can have up to 2 CPs (1 master, 1 hot spare) and 14 FPs (including hot spares).
The MSS has historically gone through two generations of Fabric Control Processors, starting with the i960 initially, and later moving to PowerPC.
MSS software development started in 1990 before MSS hardware was available by applying paravirtualization techniques to VxWorks and running each CP or FP application payload on Sun SPARC workstations, each as a Unix user process.
Read more about this topic: Multiservice Switch
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