Lec-17: Packet Switching In Computer Networks | Imp for GATE and UGC NET

Summary

The video explains packet switching, highlighting its differences from circuit switching. In packet switching, data is divided into small packets and transmitted through various network layers (Application, Transport, Network, and Physical). The key concepts of store-and-forward, efficiency, delay, and pipelining are discussed in detail. Unlike circuit switching, which requires a pre-established connection, packet switching allows data to be sent without this setup, increasing efficiency. The video also covers the concepts of Data Gram Service and Virtual Circuits, explaining how packet switching improves overall network performance despite higher transmission times.

Takeaways

• 😀 Packet switching breaks data into small packets for transmission, unlike circuit switching where a dedicated path is used for continuous data flow.
• 😀 In packet switching, data passes through multiple layers like the Application, Transport, Network, and Physical layers, with the Network layer responsible for dividing the data into packets.
• 😀 Packet switching is more efficient than circuit switching because it doesn't require a dedicated path, allowing better resource utilization.
• 😀 Datagram service and Virtual Circuits are the two main types of packet switching, operating at the Network and Data Link layers, respectively.
• 😀 Packet switching uses the 'store and forward' mechanism where data is temporarily stored at switches before being forwarded to the next destination.
• 😀 Unlike circuit switching, packet switching doesn’t require a pre-established connection, allowing more flexible and scalable data transmission.
• 😀 The store-and-forward technique in packet switching may introduce delays, as each switch stores and processes packets before forwarding them.
• 😀 Circuit switching offers low delay due to its dedicated path, but packet switching can achieve better efficiency through dynamic packet routing.
• 😀 Pipelining in packet switching allows multiple packets to be transmitted in parallel, improving efficiency and reducing delays.
• 😀 In packet switching, the total transmission time depends on both the transmission time and propagation time, with delays accumulating at each switch along the path.

Q & A

What is packet switching?

Packet switching is a method of transmitting data where large messages are divided into smaller packets, which are sent through various paths in a network. Each packet may take a different route, and they are reassembled at the destination.

How does packet switching differ from circuit switching?

In packet switching, data is split into packets and sent independently, with no dedicated path established for the transmission. In circuit switching, a dedicated connection is established before the data transfer begins, and it remains open throughout the communication.

What layers are involved in packet switching?

Packet switching operates across several layers of the OSI model: the Application Layer, Transport Layer, Network Layer, Data Link Layer, and Physical Layer. Data is passed through these layers, with the Network Layer responsible for dividing data into packets.

What is the role of the Data Link Layer in packet switching?

The Data Link Layer is responsible for dividing the data into smaller packets, ensuring reliable transmission over the physical network, and handling error correction. It essentially prepares data for transmission through the network.

What is the concept of store-and-forward in packet switching?

Store-and-forward is a process where a packet is temporarily stored in a buffer at intermediate switches before being forwarded to the next node in the network. This allows efficient routing but introduces some delays.

Why is efficiency higher in packet switching than in circuit switching?

Packet switching does not require a dedicated path for the entire communication. Resources are allocated dynamically based on current traffic, resulting in more efficient use of network resources compared to circuit switching, which reserves resources even when no data is being transmitted.

How does the pipeline concept work in packet switching?

In packet switching, the pipeline concept allows multiple packets to be transmitted simultaneously. While one packet is in transit, another can be sent, reducing delays and improving overall throughput.

What is the impact of store-and-forward on packet switching delays?

Store-and-forward introduces delays because packets are temporarily stored at switches while they are processed and forwarded. The more switches a packet passes through, the greater the delay, although this can be minimized using techniques like pipelining.

How does the transmission time in packet switching compare to circuit switching?

In packet switching, transmission time depends on the number of switches the packet passes through and the time it takes for each switch to process and forward the packet. In circuit switching, transmission time is fixed once the connection is established, as there is no need for buffering or dynamic routing.

What are the two types of packet switching mentioned in the script?

The two types of packet switching discussed are Datagram Service and Virtual Circuit. Datagram Service treats each packet independently, while Virtual Circuit establishes a logical connection before transmitting data.