Section 13.9. Summary

13.9. Summary

Switch fabrics are the core segments of switching devices as routers. A crossbar is a nonblocking switch and can be used as the building block of other switch fabrics. A crossbar requires n ² crosspoints. Blocking switches constructed with crossbar switches are Omega , Banyan , and Delta networks, each requiring log _d n stages; the fourth, the Bene network, requires 2 log _d n - 1 stages. The Bene network consists of a combined Delta network and its mirrored Delta network. Clos networks are nonblocking switches constructed with crossbars. A Clos network is strictly nonblocking if k 2 d - 1. Concentration-based and expansion-based switching networks are two special-purpose switch fabrics.

In a different approach for switching, time domain , a memory controlled by another memory, without using any crossbar, performs the task of switching. Finally, various techniques such as deploying buffers in the structure of switches, offer better performance. The case study presented a switch fabric constructed with a crossbar and buffers in its structure. We estimated the delay and throughput for this switch.

Having finished networking issues in switch fabrics, we are ready to study the basics of optical switching networks and other optical networking topics. An optical network is the backbone of high-speed networking and is presented in the next chapter.