Which of the following statements are true? (a) Three broad categories of Networks are: (i) Circuit Switched Networks (ii) Packet Switched Networks (iii) Message Switched Networks (b) Circuit Switched Network resources need not be reserved during the set up phase.
(a) and (c) only
Understanding Network Switching Methods
Network switching methods determine how data is moved from a source to a destination across a network. Different methods use different approaches for setting up connections, allocating resources, and transferring data. Let's analyze the given statements about network categories and switching methods.
Analyzing Statement (a): Network Categories
Statement (a) says: Three broad categories of Networks are: (i) Circuit Switched Networks, (ii) Packet Switched Networks, (iii) Message Switched Networks.
This statement lists three fundamental types of switching techniques used in communication networks. These are widely recognized categories based on how data is handled and routed through the network.
- Circuit Switching: A dedicated communication path (circuit) is established between the sender and receiver before data transmission begins. Resources are reserved for the duration of the connection.
- Packet Switching: Data is divided into smaller units called packets. Each packet travels independently across the network, potentially taking different paths. Resources are shared among users.
- Message Switching: Data is transmitted as complete messages. The message is stored at intermediate nodes (store-and-forward) before being forwarded to the next node. This method is less common today for real-time communication compared to packet or circuit switching.
Given these definitions, statement (a) accurately lists three prominent network switching categories. Therefore, statement (a) is true.
Analyzing Statement (b): Circuit Switched Network Resources
Statement (b) says: Circuit Switched Network resources need not be reserved during the set up phase.
In Circuit Switched Networks, the setup phase is crucial. During this phase, a dedicated physical or logical path is established between the source and destination. Network resources, such as bandwidth and switch capacity along this path, are exclusively reserved for the duration of the call or connection. This reservation ensures that once the connection is set up, the data flow experiences minimal delay and consistent bandwidth. The statement claims resources *need not* be reserved, which directly contradicts the fundamental principle of circuit switching.
Therefore, statement (b) is false.
Analyzing Statement (c): Packet Switching Resource Allocation
Statement (c) says: In packet switching there is no resource allocation for packets.
This statement can be interpreted in different ways. In a strict sense, network resources like buffer space at routers, link bandwidth, and processing power are indeed used (allocated dynamically) by packets as they traverse the network. However, compared to circuit switching where resources are *reserved* and *dedicated* end-to-end for the entire duration of communication, packet switching does not typically involve such fixed, upfront resource reservation for a whole connection or session in basic datagram packet switching. Resources are shared among multiple users and packets, and allocated on demand.
Given the context and contrast with statement (b) about circuit switching reservation, statement (c) likely refers to the absence of dedicated, reserved resources for an entire communication session as found in circuit switching. In this interpretation, where "resource allocation" implies dedicated, pre-reserved resources for the connection lifetime, the statement holds true. Packets contend for shared resources dynamically rather than having resources reserved specifically for them end-to-end beforehand.
Therefore, interpreting "resource allocation" as dedicated end-to-end reservation for a session, statement (c) is true.
Conclusion on True Statements
Based on our analysis:
- Statement (a) is true.
- Statement (b) is false.
- Statement (c) is true (under the interpretation of lack of dedicated end-to-end reservation).
Thus, statements (a) and (c) are true.
Revision Table: Comparing Network Switching Methods
| Feature | Circuit Switching | Packet Switching | Message Switching |
|---|---|---|---|
| Connection Setup | Required (Setup Phase) | Not Required (for Datagrams); Setup for Virtual Circuits | Not Required |
| Resource Allocation | Dedicated Resources Reserved during Setup | Resources Shared, Allocated Dynamically per Packet/Flow | Resources Shared, Allocated per Message (Store-and-Forward) |
| Data Handling | Continuous Data Stream | Data broken into Packets | Data as Complete Messages |
| Delay | Setup Delay; Low Transmission Delay | Variable Packet Delay (queuing, transmission) | Variable Message Delay (store-and-forward) |
| Efficiency | Inefficient for bursty data (resources idle when not transmitting) | Efficient for bursty data (resources shared) | Can be inefficient due to storage requirements |
Additional Information on Network Switching
Understanding network switching is fundamental to studying computer networks. Each method has its advantages and disadvantages, making them suitable for different applications.
- Circuit Switching Applications: Traditionally used for voice communication (like the public switched telephone network - PSTN) where a consistent and dedicated connection is preferred.
- Packet Switching Applications: Widely used for data communication (like the Internet). It is efficient for bursty data traffic, where users transmit data in short bursts rather than continuously.
- Message Switching Characteristics: An older method. It has large delays due to the store-and-forward nature, where an entire message must be received before it can be forwarded. It doesn't require a dedicated path or strict resource allocation like circuit switching but is generally less efficient for real-time data than packet switching.
Modern networks, like the internet, primarily use packet switching. Techniques like Virtual Circuits exist within packet-switched networks to provide some level of connection orientation and resource management, but they differ significantly from the dedicated physical circuits of traditional circuit switching.
Important Questions from Data Link Layer
Which of the following protocols is responsible for converting higher level protocol addresses to physical network addresses?
Which of the following devices takes data sent from one network device and forwards it to the destination node based on MAC address?
Which of the following statements is/are true with regard to various layers in the Internet stack?
P: At the data link layer, a packet of transmitted information is called a frame
Q: At the network layer, a packet of transmitted information is called a segment
Given below are two statements:
Statement I: The laws of nature put two fundamental limits on data rate of a channel. The H.Nyquist limit restricts the number of independent samples per second to twice the band-width in a Noiseless channel.
Statement II: Shannon's major result about noised channel is that maximum data rate of a channel whose band width is H Hz, and whose signal-to-noise ratio is S/N is given by:
Maximum number of bits/sec \(= H \;log_2 \left(1+\frac{S}{N}\right)\) is given by:
In the light of the above statements. choose the correct answer from the options given below
The sender window size to get the maximum efficiency is
