Circuit Switching ,Packet Switching Structure or further types

1. Presented By : ANAM SANA
BS(CS) 7th semester
GCUF

2. Types of switching structure
 CIRCUIT SWITCH STRUCTURE
1. Space Switch structure
Crossbar switch structure
Multistage switch structure
2. Time division Switch structure
Time slot interchange
 PACKET SWITCH STRUCTURE:
 Input port
 Output port
 Routing processor
 Switching Fabrics
Crossbar switch
Banyan Switch
Batch Banyan switch
•

3. Switching network
consists of series of
interlinked nodes
called switches

4. We use switches in two types of networks.
 CIRCUIT SWITCHED NETWORK
 PACKET SWITCHED NETWORK

5. Circuit switches use either of two technologies
 SPACE DIVISION SWITCHES
 TIME DIVISION SWITCHES

6. • Originally developed for analog environment & has been
carried over to digital domain.
• Transfer Signal from a given input to a specific
output(same for any switch).
• Provide separate physical connection between inputs
and outputs.
• Essentially a crossbar matrix.
• Having electromechanical crossbar at each point which
may be enabled or disabled using control unit

8. Space Division Switches fall into two categories:
Space Division Switch
Crossbar Switch Multistage Switch

9. • Connects n inputs to m outputs in a switch using micro
switch
• at each cross-point.
• For example:
• To connect 1000 inputs to 1000 outputs requires a switch
with 1000,000 cross-points.

10. CROSSBAR SPACE DIVISION SWITICH:

11. • The number of cross-points grows within the square of the
number of attached stations.
Costly for large switch.
• Cross points are inefficiently utilized.
Only a small fraction can engaged if many of stations
wants send data.
• Solution is to build Multistage switch

12. • By splitting the cross bar switch into smaller units &
interconnecting them , it is possible to built multistage
switches with fewer components.
• If one path fails then their ‘ll be possibility of another path.
• Reduce number of cross-points.
• More than one path network.
• Increased Reliability.
• More complex Control.
• May b blocking.

13. We Follow these steps:
STAGE 1: We divide the N input lines into groups ,each of
n lines. For each group we use one crossbar of size n*k,
where k is number of Crossbars . The first stage have N/n
crossbars of n*k cross-points.
STAGE 2: We use k crossbars ,each of size (N/n *N/n) in
middle stage.
STAGE 3: We use N/n crossbars, each of size k*n at the
third stage .

14. • We can calculate the total number of cross-points as
follows:
N/n(n*k)+K(N/n*N/n)+N/n(k*n)^2
FIRST STAGE SECOND STAGE THIRD STAGE

15. • First stage second stage Third stage
In three stage switch , the total number of crosspoints
is
2kN+k(N/n)^2

16.  DESIGN OF THREE STAGE SWITCH, 200* 200 switch where (N=200) with k=4
and n=20
Solution:
Formula:
N/n(n*k) + K(N/n*N/n) + N/n(k*n)
200/20(20*4) + 4(10*10) + 10(4*20)
In first stage , we have N/n or 10 crossbars , each of size 20 *4.
In second stage ,we have 4 crossbars, each of size 10*10.
In third stage ,we have 10 crossbars, each of size 4*20.
Also calculated by General Formula:
2kN+k(N/n)^2
= 2*4*200+4(200/20)^2=2000 cross-points

17. N=200 , n=20, k=4
200/20 200/20
n
N
n
20*4
20*4
4*20
4*20
10*10
10*10

18. • Blocking during periods of heavy traffic.
• The whole idea of switching is to share the cross-points
in middle stage crossbars.
• Sharing can cause a lack of availability ,if resources are
limited and all users wants a connection at same time.
• Blocking refers to times when one input cannot be
connected to an output because there is no path
available between them.
• In large system having 1000 inputs and outputs ,the
number of stages increased, As stages increases the
blocking possibilities increases as well.

21. • Both voice and data can be sent through digital signals.
• All modern circuits uses time division switches.
• Time division switching uses time-division
multiplexing(TDM) Inside a switch said to be Time slot
interchange(TSI).

22. • Changed the order of slots based on desired connection.
Time slot interchange combines:
• TSI consists of Random Access Memory
The size of each location is same as the size of single
time slot.
The RAM fills up with incoming data from the time slots in
order
received or we can b said sequentially controlled.
• Control retrieve data from memory and passed to output
in desired manner. Selectively ,not sequentially.

23. Advantage of space division is that it is instantaneous.
Disadvantage is number of cross-points required to make
space division switching .
Advantage of time division switching it needs no cross-
points
Disadvantage in case of TSI each connection creates
delays.

24. Switch structure has four components:
Input ports
Output ports
Routing processor
Switching fabric

25. • An input port performs the physical and data –link
functions .
• Bits are constructed from received signal
• Packets are de-capsulated from frame
• Errors are detected and corrected
• Packet is now ready to be routed by network
• In addition to physical-layer processor and data link
processor , the input buffers to hold the packet.

26. • Output performs the same as input functions but in
reverse order.
• First the outgoing packets are queued , then packet is
encapsulated in frame.
• Finally the physical layer functions are applied to frame to
create the signal to be sent on line.

27. • The routing processor performs the functions of Network
layer
• Destination address is used to find the address of next
hop.
• Routing processor searches from Routing table.

28. • Packet switch is to move packet from input to output
queue.
• Speed affects the size of input/output queue.
• Overall delay in packet delivery
• Input port stored packet in memory
• Output port retrieve packet from memory
Types of switch fabrics:
• Cross-bar switch(same as discus previous)
• Banyan switch .
• Batcher banyan Switch.

29. • Multistage switch with micro-switches at each stage that
route the packets based on output port represents as a
binary string
• For n inputs and n outputs ,we have log2n stages with
n/2 micro-switches at each stage
• Having three stages left bit ,middle bit and right
bit.

31. • Problem in Banyan switch: possibility of internal collision.
• Solve it by sorting arriving packets based on destination
port.
• Trap module prevents duplicate packets from passing to
banyan switch .

32. • https://www.youtube.com/watch?v=ApPruOqzd3M
• https://www.youtube.com/watch?v=9yYqNqTNnqI
• http://www.slideshare.net/sheekha_11/switching-
41817972
• William Stallings 2nd ed, Wireless Communication
&Networking
• Data-Communications-and-Networking-By-Behrouz-A.
Forouzan