CS455 Syllabus 9
Switched type computer networks

• Switch

• Switch:

• A switch has N inputs and N outputs:

The data coming into an input can be forwarded onto one (or more) outputs:

• Switched Networks

• Fact:

 Switched network is always wired (because wireless transmissions cannot support switching)

• Simplest switched network: use one switch

Notice that:

 Messages from a sender is forwarded only to the intended receiver in switched networks

• Simultaneous transmission in a switch

• Important fact:

• A switch supports simultaneous transmissions as long as the transmissions are not to the same output:

The red transmission and the blue transmission can occur simultaneously !!!

• Switched network

• Switched network: uses multiple switched

Noticed that:

 Only the destination (receiver) node will receive the message Message must follow a correct path in order to reach the intended destination !!!

• Switched Network demo

• Circuit demo:

• Demo (Switch): (Demo above code)

• How to run the demo:      /home/cs455001/demo/Logic-Sim/mux-demux

• Observe the property of a switch:

 Signal (= message) is sent to a specificoutput The other outputs do not receive the signal !!

• Non-intrusive transmissions:

 Only the destination computers on the network will receive the transmission (Other computers will not be intruded upon by the message transmission)

Result:

 Switched networks can support a very larger number of computers in the network

• Expensive Hardware:

 Switching circuits is very complex and expensive to manufacture

• Requires complex software to find routes in the network:

Route discovery is not a trivial problem to solve...

(The Route discovery problem is discussed a liitle more in the next section)

• The "Routing Problem" in switched networks

• Problem in a switched network:

 In switched networks, we need to find/discover a correct route from source to destination

Example:

• Finding a route through a network is a 2 step process:

1. Discover the network topology:

 How are the nodes connected to each other ????

To solve this problem, the nodes must exchange connectivity information with each other

2. Using Dijkstra's Algorithm to compute the shortest paths to the destination

 This step can only be used after the nodes has discovered the connectivity of the network !!!!

We will discuss the routing problem in more details later