- Switch:
- A switch has
N
inputs and
N
outputs:
The data coming into an input can be forwarded onto one (or more) outputs:
- A switch has
N
inputs and
N
outputs:
- Fact:
- Switched network is
always
wired
(because wireless transmissions cannot support switching)
- Switched network is
always
wired
- Simplest switched network: use
one
switch
Notice that:
- Messages from a sender is forwarded only to the intended receiver in switched networks
-
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 !!!
- A switch supports
simultaneous transmissions
as long as the transmissions are
not to the
same output:
- 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 !!!
- Only the
destination (receiver) node
will receive the message
- Circuit demo:
- Demo (Switch):
(Demo above code)
- Prog file:
click here
- How to run the demo: /home/cs455001/demo/Logic-Sim/mux-demux
- Prog file:
click here
- Observe the
property of a
switch:
- Signal (= message)
is sent to a specificoutput
- The other outputs do not receive the signal !!
- Signal (= message)
is sent to a specificoutput
- Advantage:
- 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
- Only the
destination computers
on the network will
receive the
transmission
- Non-intrusive transmissions:
- Disadvantage:
- 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)
- Expensive Hardware:
- 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:
-
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
- 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
-
Discover the
network topology: