CCNA certification exam training is all about learning the details, and an important part of your CCNA test prep is knowing the differences between Cisco router and switch technologies that are somewhat similar. Packet switching and circuit switching are both methods of getting packets from "point A" to "point B", but the methods used are very different - and you must know these differences to earn your Cisco CCNA certification.



In my last CCNA training tutorial, I discussed packet switching. In case you missed that article, packet switching is a method of transporting packets from source to destination via different paths; that is, the packets will not necessarily share the same physical path. The packets are put into their proper order at the destination. Packet switching is highly effective, but should not be used for delay-sensitive traffic such as voice or video packets. Not only is Frame Relay a big topic for your CCNA certification exam, it's also an excellent example of a packet-switching technology.

In circuit switching, a dedicated path is built between the source and destination, and the packets will all be sent over this dedicated path. If this sounds like a telephone call, you're right! A phone call is a great example of circuit switching. On a Cisco router, ISDN is a circuit-switching technology.

The deciding factor between circuit switching and packet switching comes down to the tolerance for delay. Not to say that packet switching is slow, but any reassembly takes time. While most packet-switching technologies are cheaper to run than most circuit-switching technologies, that cost is offset by the slight delay inherent to packet switching. For voice and video, circuit switching is the most effective.

Packet switching and circuit switching both have their place in today's Cisco networks, and don't be surprised if both topics show up on your CCNA certification exam as well!