Question

Q8.1 Describe the need for switching and define a switch.

Q8.2 List the three traditional switching methods. Which are the most common today?

Q8.4 Compare and contrast a circuit switched network and a packet-switched network. (How are they alike and how are they different)

Q8-8 What is TSI and what is its role in time-division switches.

Q8-10 List four major components of a packet switch and their functions.

Answer 1

Q8.1 Describe the need for switching and define a switch.
Answer:--------
A switched network consists of a series of interlinked nodes, called switches. Switches are devices capable of creating temporary connections between two or more devices linked to the switch. In a switched network, some of these nodes are connected to the end systems (computers or telephones, for example). Others are used only for routing.

Q8.2 List the three traditional switching methods. Which are the most common today?
Answer:----
The three traditional switching methods are circuit switching, packet switching, and message switching. The most common today are circuit switching and packet switching.

Q8.4 Compare and contrast a circuit switched network and a packet-switched network. (How are they alike and how are they different)?
Answer:-----
Circuit switching : It is used for voice communication which requires dedicated connection between calling and called party to take care of latency requirements of real time voice calls.
Packet switching : It is used for data communication which does not require dedicated connection. It is useful for less time sensitive internet data or emails.

Packet switched networks quality of service (QoS) is not guaranteed while in circuit switched networks quality is guaranteed. Packet switching is used for time insensitive applications such as internet/email/SMS/MMS/VOIP etc.
In circuit switching, even if user is not talking the channel cannot be used by any other users, this will waste the resource capacity at those intervals. The example of circuit switched network is PSTN and example of packet switched network is GPRS/EDGE.

Q8-8 What is TSI and what is its role in time-division switches.
Answer:-----
Time-slot interchange (TSI) is technology in time division switching. It contains Random Access Memory (RAM) with numerous memory locations. The RAM receives incoming datafrom time slots in the order it is received. Based on the decisions of the control unit, the slots are sent out in order.

Q8-10 List four major components of a packet switch and their functions.
Answer:-----
Input Ports – functions consists of the physical and data link layers of the packet switch. Bits are constructed from a received signal, packet is decapsulated, and errors are detected and corrected.

Output Ports – same as the input functions but in reverse. Outgoing packets are queued, then encapsulated in a frame.

Routing Processor – performs the table lookup function in the network layer. The destination address is used to find addresses for the next hop and determines the output number to send out.

Switching Fabric – moves packets from the input queue to the output queue.