Computer Network Switching Technique and Protocols (ET: 1.5 Hours)
Switching Technique and Protocols
    • 1
      Protocol
      Networking Protocols
      Networking Protocol: A networking protocol is a set of rules and messages that defines how devices communicate with each other over a network. These rules specify how data is formatted, transmitted, received, and interpreted by communicating devices.
      Why Protocols Are Needed: Different devices such as computers, mobile phones, servers, routers, and printers may be manufactured by different companies. Protocols provide common rules so that these devices can communicate with each other correctly.
      Example: When a computer wants to communicate with another device on a local network, ARP can be used to find the MAC address associated with a known IPv4 address.
      Internet Standards: Networking protocol rules are commonly defined and documented through Internet standards such as RFCs (Request for Comments). For example, the original specification of ARP is documented in RFC 826.

    • 2
      Protocol
      ARP (Address Resolution Protocol)
      Definition: ARP is a protocol used in IPv4 networks to find the MAC address associated with a known IPv4 address on the local network.
      Purpose: A device may know the destination's IP address but need its MAC address to deliver an Ethernet frame on the local network. ARP performs this IP-to-MAC address resolution.
      How ARP Works:
      1. The sender knows the destination's IPv4 address but does not know its MAC address.
      2. The sender broadcasts an ARP Request asking which device owns that IPv4 address.
      3. The device having that IPv4 address sends an ARP Reply containing its MAC address.
      4. The sender stores the IP-to-MAC mapping in its ARP cache for future communication.
      Example: Suppose a computer wants to communicate with 192.168.1.20 and knows the IP address but not the MAC address. It sends an ARP Request, and the device using 192.168.1.20 replies with its MAC address.
      Key Point: ARP performs IPv4 Address → MAC Address resolution within a local network.

    • 3
      Protocol
      FTP (File Transfer Protocol)
      Definition: FTP is a protocol used to transfer files between a client and a server over a TCP/IP network.
      Purpose: FTP allows users to upload files to a server and download files from a server. It can also be used to manage files and directories on a remote FTP server.
      How FTP Works:
      1. The FTP client establishes a connection with the FTP server.
      2. The client authenticates using credentials when authentication is required.
      3. The client can request operations such as uploading, downloading, listing, or deleting files.
      4. The FTP server processes the request and transfers the required data.
      Common FTP Operations:
      • Upload: Sending a file from the client to the server.
      • Download: Receiving a file from the server.
      • List: Viewing files and directories on the server.
      • Retrieve: Requesting a particular file from the server.
      Important: Traditional FTP does not encrypt its communication. For secure file transfer, protocols such as FTPS or SFTP are commonly used.
      Key Point: FTP is mainly used for File Transfer.

    • 4
      Protocol
      SMTP (Simple Mail Transfer Protocol)
      Definition: SMTP is an application-layer protocol used to send and transfer email messages between mail systems.
      Purpose: SMTP is primarily responsible for sending outgoing email from a mail client to a mail server and transferring email between mail servers.
      How SMTP Works:
      1. A user creates an email using a mail application.
      2. The mail client submits the email to an SMTP server.
      3. The SMTP server determines where the recipient's mail should be delivered.
      4. The sending mail server communicates with the destination mail server using SMTP.
      5. The receiving mail system stores the message so that the recipient can access it.
      Example: When a user sends an email to another person, SMTP is involved in sending the message from the sender's mail system toward the recipient's mail system.
      Important: SMTP is mainly associated with sending email. Protocols such as POP3 and IMAP are commonly used for retrieving and synchronizing received email.
      Key Point: SMTP is mainly used for Email Sending and Transfer.

    • 5
      Protocol
      POP3 (Post Office Protocol Version 3)
      Definition: POP3 is an application-layer protocol used by an email client to retrieve email messages from a mail server.
      Purpose: POP3 allows a user to download received emails from a mail server to a local device such as a computer or mobile phone.
      How POP3 Works:
      1. The email client connects to the POP3 server.
      2. The client authenticates using the user's account credentials.
      3. The client checks for new messages on the server.
      4. The messages are downloaded to the client.
      5. Depending on the configuration, downloaded messages may be removed from the server or retained for later access.
      Example: A user opens an email application and downloads new messages from the mail server to their computer. POP3 can be used for this type of email retrieval.
      Important Point: POP3 is mainly designed for downloading emails from a mail server to a client. It is not designed for maintaining a synchronized mailbox across multiple devices.
      Key Point: POP3 = Email Retrieval / Download

    • 6
      Protocol
      IMAP (Internet Message Access Protocol)
      Definition: IMAP is an application-layer protocol used by email clients to access and manage email messages stored on a mail server.
      Purpose: Unlike traditional POP3 usage, IMAP allows messages to remain stored on the server and keeps mailbox information synchronized across multiple devices.
      How IMAP Works:
      1. The email client connects to the IMAP server.
      2. The client authenticates with the email account.
      3. The client retrieves information about messages and mail folders.
      4. The user can read, organize, delete, or mark messages as read/unread.
      5. Changes can be synchronized with the mail server and other devices.
      Example: A user reads an email on a mobile phone and marks it as read. When the same account is opened on a laptop, the mailbox can reflect that change because the messages and mailbox state are maintained on the server.
      Key Point: IMAP = Email Access and Synchronization

    • 7
      Protocol
      HTTP (Hypertext Transfer Protocol)
      Definition: HTTP is an application-layer protocol used for communication between clients, such as web browsers, and web servers.
      Purpose: HTTP allows a web browser to request web resources such as HTML pages, images, CSS files, JavaScript files, and other resources from a web server.
      How HTTP Works:
      1. The user enters a website address or selects a web link.
      2. The browser identifies the server that should provide the requested resource.
      3. The browser sends an HTTP request to the web server.
      4. The server processes the request.
      5. The server sends an HTTP response containing the requested resource or an appropriate status message.
      6. The browser processes the response and displays the webpage.
      Common HTTP Methods:
      • GET: Requests a resource from a server.
      • POST: Sends data to a server, commonly when submitting forms.
      • PUT: Requests creation or replacement of a resource.
      • DELETE: Requests deletion of a resource.
      Example: When a browser requests a webpage, it may send an HTTP GET request. The server can respond with a successful status such as 200 OK along with the requested content.
      Key Point: HTTP is the fundamental protocol for Web Communication.

    • 8
      Protocol
      HTTPS (Hypertext Transfer Protocol Secure)
      Definition: HTTPS is HTTP communication carried over a secure TLS connection.
      Purpose: HTTPS protects communication between a web browser and a web server so that sensitive information such as login credentials, personal information, and payment details can be transmitted more securely.
      How HTTPS Works:
      1. The browser connects to the web server.
      2. A TLS handshake is performed.
      3. The server is authenticated using its digital certificate.
      4. A secure cryptographic connection is established.
      5. HTTP requests and responses are then exchanged through the protected connection.
      Example: A website using an address beginning with https:// uses HTTPS to protect its HTTP communication with TLS.
      HTTP vs HTTPS: HTTP provides web communication, while HTTPS provides web communication protected by TLS.
      Key Point: HTTPS = HTTP + TLS Security.


    • 9
      Protocol
      SSL/TLS (Secure Sockets Layer / Transport Layer Security)
      Definition: SSL/TLS is used to provide security for communication between a client and a server. Modern secure connections use TLS; SSL is the older predecessor and is no longer considered secure.
      Purpose: TLS protects data exchanged over a network by providing important security properties such as confidentiality, integrity, and authentication.
      Main Security Functions:
      • Encryption: Helps prevent unauthorized parties from reading transmitted data.
      • Integrity: Helps detect whether transmitted data has been modified.
      • Authentication: Helps verify the identity of the server using digital certificates.
      How TLS Works:
      1. The client and server begin a secure connection process called a TLS handshake.
      2. They negotiate security parameters and cryptographic algorithms.
      3. The server provides information used for authentication, commonly through a digital certificate.
      4. The client and server establish cryptographic keys for the connection.
      5. Application data can then be transmitted through the protected connection.
      Key Point: TLS provides secure communication between network applications.

    • 10
      Protocol
      DNS (Domain Name System)
      Definition: DNS is a naming system and protocol that translates human-readable domain names into IP addresses and can provide other information about Internet resources.
      Purpose: Humans generally prefer names such as example.com instead of remembering numerical IP addresses. DNS allows a host to obtain the IP address associated with a domain name.
      How DNS Works:
      1. The user enters a domain name into a web browser.
      2. The host needs to determine the IP address associated with that domain.
      3. The host sends a DNS query to a DNS resolver.
      4. The resolver obtains the required DNS information, possibly by querying other DNS servers.
      5. The IP address is returned to the host.
      6. The host can then communicate with the destination server using its IP address.
      Example: When a user enters www.example.com, DNS can resolve the domain name to the appropriate IP address.
      Important DNS Records:
      • A Record: Maps a domain name to an IPv4 address.
      • AAAA Record: Maps a domain name to an IPv6 address.
      • MX Record: Identifies mail servers responsible for email delivery for a domain.
      • CNAME Record: Creates an alias for another domain name.
      Key Point: DNS commonly performs Domain Name → IP Address resolution.

    • 11
      Protocol
      DHCP (Dynamic Host Configuration Protocol)
      Definition: DHCP is a protocol that automatically provides network configuration information to hosts on a network.
      Purpose: Without DHCP, users may need to manually configure network settings on every device. DHCP allows a network to automatically assign the information required for communication.
      DHCP Can Provide:
      • IP Address
      • Subnet Mask
      • Default Gateway
      • DNS Server Address
      How DHCP Works:
      1. DHCP Discover: The client broadcasts a message to locate available DHCP servers.
      2. DHCP Offer: A DHCP server offers network configuration information to the client.
      3. DHCP Request: The client requests the offered configuration.
      4. DHCP Acknowledgment: The DHCP server confirms the assignment and provides the configuration details.
      Example: When a laptop connects to a new Wi-Fi network, it can automatically receive an IP address, subnet mask, default gateway, and DNS server information from the DHCP server.
      Key Point: DHCP automatically provides Network Configuration Information to hosts.
      Four Things Required for Internet Connectivity
      1. IP Address: Identifies the host on the network.
      2. Subnet Mask: Determines the size of the network and helps the host identify whether a destination is on the local network or a different network.
      3. Default Gateway: The IP address of the router used to communicate with devices on other networks.
      4. DNS Server Address: Used to translate domain names into IP addresses.

      Role of DHCP in Internet Connectivity DHCP can automatically provide the four important network configuration parameters required by a host:
      • IP Address
      • Subnet Mask
      • Default Gateway
      • DNS Server Address
      Therefore, when a device connects to a new Wi-Fi network, it normally does not require the user to manually enter all these values. DHCP can provide the required configuration automatically.

    • 12
      Protocol
      Telnet
      Definition: Telnet is an application-layer protocol that provides remote terminal access to another computer over a network.
      Purpose: Telnet allows a user to remotely connect to a device and execute commands as if they were using a terminal directly on that device.
      How Telnet Works:
      1. The client establishes a connection with a remote Telnet server.
      2. The user authenticates if authentication is required.
      3. The client sends commands to the remote system.
      4. The remote system executes the commands and returns the results.
      Example: An administrator can use Telnet to remotely access a network device and execute command-line operations.
      Important: Telnet does not encrypt the communication. Usernames, passwords, commands, and other data can be transmitted in plaintext. Therefore, Telnet is generally considered insecure for modern remote administration.
      Key Point: Telnet = Remote Terminal Access

    • 13
      Switching Technique
      What is Switching and Network Switching? Explain Its Need and Types
      Switching Switching is the process of forwarding data from one device or port to another device or port in a communication network. It helps data reach the correct destination through an appropriate path.
      Network Switching Network Switching is the process of forwarding data packets from one port to another port that leads toward the destination in a computer network. When data enters a switch port, it is called ingress. When data leaves a port, it is called egress. In a network, data does not always move directly from one computer to another. It passes through different devices, cables, fiber optics, or wireless media. Switching helps data choose the proper path to reach the correct destination.
      Need for Switching Switching is needed because connecting every device directly with every other device is costly and complex. If a single shared line is used, network performance may decrease and collisions may increase when the number of devices becomes large. Switching solves this problem by allowing multiple devices to share network resources in an organized and efficient way.
      Switch in Computer Network A switch is a networking device that forwards data only to the correct destination device. Unlike a hub, a switch does not send data to all connected devices. It reduces unnecessary traffic and improves network performance. Switches are widely used in LANs, data centers, and enterprise networks.
      Types of Switching
      1. Circuit Switching − A dedicated path is established before data transmission begins.
      2. Message Switching − The complete message is stored and forwarded from one node to another.
      3. Packet Switching − Data is divided into packets and each packet is forwarded independently.
      Broad Categories of Switching
      • Connection-Oriented Switching − A path is established before data transfer.
      • Connectionless Switching − Data is forwarded using forwarding tables without prior connection setup.

    • 14
      Switching Technique
      Circuit Switching
      Circuit Switching is a switching technique in which a dedicated path is established between the sender and receiver before data transmission begins.
      In Circuit Switching, the connection must be established first. Only after the connection has been established can data transfer begin.
      Once the connection is established, all communication uses the same dedicated and reserved path between the sender and receiver.
      Example: The traditional telephone network is a well-known example of Circuit Switching.
      In a telephone network, the sender first dials the receiver's number. After the connection is established, both parties can communicate with each other.

      2. Phases of Circuit SwitchingCircuit Switching has three main phases:
      1. Connection Establishment
      2. Data Transfer
      3. Connection Disconnection
      2.1 Connection EstablishmentIn the first phase, a dedicated connection or circuit is established between the sender and receiver.
      Data is not transferred before this connection is established.
      2.2 Data TransferAfter the connection has been established, the sender can transmit data to the receiver.
      All communication uses the established and reserved path between the sender and receiver.
      2.3 Connection DisconnectionAfter the communication is completed, the established connection is terminated.
      The reserved resources are released after the connection is terminated.

      3. Circuit Switching ExampleSuppose a sender wants to communicate with a receiver through a large network.
      First, a dedicated path is established between the sender and receiver. This is the Connection Establishment phase.
      After the path has been established, the sender transmits the message through that path. This is the Data Transfer phase.
      After the communication is finished, the connection is terminated. This is the Connection Disconnection phase.
      Therefore, the most important idea of Circuit Switching is that the connection is established before data transfer begins.

    • 15
      Switching Technique
      Message Switching
      Message Switching is a switching technique that uses the Store-and-Forward mechanism to transfer a complete message from the sender to the receiver.
      In Message Switching, there is no dedicated path established between the sender and receiver before data transmission.
      The complete message is treated as a single unit. An intermediate node receives and stores the complete message before forwarding it to the next node.

      2. Store-and-Forward MechanismThe main concept of Message Switching is Store-and-Forward.
      When a sender wants to send a message, the message is transferred to an intermediate node.
      The intermediate node first stores the complete message.
      After receiving the complete message, the intermediate node forwards the complete message to the next node.
      This process continues from one intermediate node to another until the complete message reaches the receiver.

      3. Message Switching ExampleSuppose there is a sender and a receiver with an intermediate node between them.
      The sender sends a complete message to the intermediate node.
      The intermediate node first receives and stores the complete message.
      After the complete message has been received, the intermediate node forwards the message to the receiver.
      Therefore, the basic process is:
      Store the complete message → Forward the complete message

      4. Limitation of Message SwitchingMessage Switching is not suitable for streaming media and real-time applications.
      For example, consider a real-time Voice over IP (VoIP) communication between two people. Real-time communication needs continuous data transfer with low delay.
      In Message Switching, an intermediate node must receive and store the complete message before forwarding it. This can introduce significant delay.
      Therefore, Message Switching is not suitable for applications such as:
      • Real-time communication
      • Voice communication
      • Streaming media
      • Live data transfer

    • 16
      Switching Technique
      Packet Switching
      Packet Switching is a switching technique in which a large message is divided into smaller units called packets, and these packets are transmitted through the network.
      The Internet is a packet-switched network.
      Packet Switching is similar to Message Switching because the original message is divided into smaller parts. However, there is an important difference.
      In Message Switching, the complete message is stored at an intermediate node before it is forwarded.
      In Packet Switching, the message is divided into packets and the packets can be forwarded individually.

      2. Packets in Packet SwitchingSuppose a large message is divided into five packets:
      Packet 1, Packet 2, Packet 3, Packet 4 and Packet 5.
      Each packet can be transmitted independently through the network.
      Because packets are transmitted individually, each packet needs information that helps identify its source and destination.
      Packets can contain addressing information such as source and destination IP addresses.

      3. Sequence NumberPackets may not always arrive at the destination in the same order in which they were sent.
      For example, if five packets are sent in the order:
      1 → 2 → 3 → 4 → 5
      they may arrive in another order because different packets may experience different delays.
      Therefore, sequence information can be used to identify the order of packets and help the receiver reconstruct the original data.

      4. Functions of Sequence Numbers
      1. Reordering Packets: The receiver can use sequence information to arrange packets in their correct order.
      2. Detecting Missing Packets: The receiver can identify whether an expected packet has not arrived.
      3. Supporting Acknowledgements: Protocols such as TCP use sequence information together with acknowledgements to track received data.
      For example, if expected data is not received within an appropriate period, retransmission may occur in a reliable transport protocol such as TCP.

      5. Approaches of Packet SwitchingPacket Switching has two main approaches:
      1. Datagram Approach
      2. Virtual Circuit Approach

      6. Datagram ApproachDatagram Approach is a connectionless packet-switching technique in which each packet is treated independently.
      Each individual packet is called a datagram.
      Each datagram contains destination information. Intermediate network devices use this information and routing information to forward the datagram toward the destination.
      In the Datagram Approach, a fixed path is not established before the packets are transmitted.
      Therefore, different datagrams belonging to the same original message may take different routes.

      7. Datagram Approach ExampleSuppose an original message is divided into four datagrams:
      Datagram 1, Datagram 2, Datagram 3 and Datagram 4.
      Datagram 1 may take one route, while Datagram 2 takes another route. Datagram 3 and Datagram 4 may also take different routes.
      Because the datagrams may travel through different routes, they may arrive at the receiver in a different order.
      For example, they may arrive as:
      1 → 2 → 4 → 3
      The receiver can use sequence information, when provided by the relevant protocol, to reorder the received data and reconstruct the original message.

      8. Characteristics of Datagram Approach
      • It is connectionless.
      • No dedicated path is established before transmission.
      • Each datagram is treated independently.
      • Different datagrams may take different routes.
      • Datagrams may arrive out of order.
      • Forwarding decisions are made by intermediate network devices.

      9. Virtual Circuit ApproachVirtual Circuit Approach is a connection-oriented packet-switching technique in which a logical path is established before data packets are transmitted.
      Unlike the Datagram Approach, where each packet can independently take different routes, the Virtual Circuit Approach establishes a logical route before data transfer.
      The path is fixed for the duration of the logical connection.
      A Virtual Circuit Identifier (VCI) or similar identifier can be used to identify the logical connection.
      Control procedures or special packets may be used to establish the connection before data transfer begins.

      10. Virtual Circuit ExampleSuppose a sender wants to communicate with a receiver through several intermediate network devices.
      First, a logical path is established between the sender and receiver.
      After the virtual circuit is established, packets belonging to that logical connection travel through the established route.
      For example:
      Packet 1 → Packet 2 → Packet 3 → Packet 4 → Packet 5 → Packet 6
      All these packets normally follow the established logical path during that connection.
      After the data transfer is completed, the virtual circuit can be terminated or released.

      11. Important Point About Virtual CircuitIf the same two computers want to communicate again later, the same route is not necessarily guaranteed for the new logical connection.
      A new route may be selected depending on network conditions, routing information and resource availability.

    • 17
      Switching Technique
      Difference Between Datagram and Virtual Circuit
      FeatureDatagram ApproachVirtual Circuit Approach
      ConnectionConnectionlessConnection-oriented
      PathNot fixedLogical path is established
      RouteEach datagram may take a different routePackets normally follow the established route
      SetupNo connection setupConnection setup is required
      Packet OrderMay arrive out of orderNormally follows the established path
      IdentifierDestination informationVirtual Circuit Identifier

    • 18
      Switching Technique
      Overall Comparison of Switching Techniques
      FeatureCircuit SwitchingMessage SwitchingPacket Switching
      Basic IdeaDedicated pathStore complete message and forwardDivide message into packets
      ConnectionConnection-orientedNo dedicated connectionConnectionless or connection-oriented
      Data UnitContinuous dataComplete messagePackets
      PathDedicatedNo dedicated pathDepends on approach
      ExampleTelephone NetworkStore-and-forward messagingInternet

    • 19
      Switching Technique
      Circuit Switching (Short)
      Circuit Switching Circuit Switching is a connection-oriented switching technique where a dedicated communication path is established between the sender and receiver before data transmission begins. Once the path is created, all data travels through the same route until the communication ends. In this method, network resources remain reserved for the entire communication session, even if no data is being transmitted for some time. Because of the dedicated path, communication becomes stable and predictable with very little delay after the connection is established. However, this method wastes bandwidth because the reserved path cannot be used by other users during the communication.
      Example of Circuit Switching Traditional telephone systems are the best example of circuit switching. When a person makes a phone call, a dedicated path is established between the caller and receiver. This path remains reserved throughout the conversation, and no other user can use that communication channel until the call ends.


    • 20
      Switching Technique
      Packet Switching(Short)
      Packet Switching is a connectionless network switching technique where data is not transmitted as one continuous message. Instead, the complete message is divided into many smaller units called packets. Each packet is transmitted independently through the network. Unlike circuit switching, packet switching does not require any dedicated communication path before data transmission begins. Every packet may travel through different paths depending on network traffic, congestion, link availability, and routing decisions. Because of this flexibility, packet switching provides better bandwidth utilization and allows multiple users to communicate simultaneously. Packet switching is widely used in modern computer networks and the Internet.
      How Packet Switching Works
      1. Message Division
        • The sender divides the complete message into smaller packets.
        • Each packet contains:
          • Actual data (payload)
          • Source address
          • Destination address
          • Packet sequence number
          • Error checking information
      2. Packet Transmission
        • Packets are transmitted independently as soon as they are ready.
        • There is no need to wait for the complete message before transmission.
        • This reduces transmission delay and improves network efficiency.
      3. Routing by Routers
        • Routers receive packets and examine their header information.
        • Based on routing tables, congestion level, and available paths, routers decide the best next hop for each packet.
        • Different packets from the same message may travel through completely different routes.
      4. Packet Reordering at Destination
        • Packets may arrive out of order because they travel independently.
        • The destination system uses the sequence numbers stored in packet headers to reorder the packets correctly.
        • Transport layer protocols such as TCP are mainly responsible for packet reordering and reconstruction of the original message.
        • If any packet is missing or corrupted, the destination requests retransmission.
      Role of Router in Packet Switching Routers play a very important role in packet switching. A router receives a packet, reads its destination address, checks routing information, and forwards the packet toward the best available path. Routing decisions depend on:
      • Network traffic
      • Congestion
      • Link speed
      • Availability of paths
      Because of this intelligent routing process, packet switching is more flexible and reliable than circuit switching.
      Advantages of Packet Switching
      • Efficient use of bandwidth.
      • Supports multiple users simultaneously.
      • No dedicated path is required.
      • Reliable and flexible communication.
      • Better network utilization through statistical multiplexing.
      Disadvantages of Packet Switching
      • Packets may arrive out of order.
      • Network congestion can increase delay.
      • Packet loss may occur during heavy traffic.
      Example of Packet Switching The Internet is the best example of packet switching. Applications such as:
      • E-mail
      • Web browsing
      • Cloud storage
      • Online file sharing
      • Instant messaging
      • Video streaming
      all use packet switching for communication.


    • 21
      Switching Technique
      Message Switching
      Message Switching is a connectionless switching technique where the complete message is transmitted from one node to another without establishing any dedicated path before communication begins. In this method, the entire message is treated as a single unit. Each intermediate node receives the complete message, stores it temporarily, checks it, and then forwards it to the next node. Because of this mechanism, message switching is also known as Store and Forward Switching. Unlike circuit switching, message switching does not require a continuous connection between sender and receiver.
      Characteristics of Message Switching
      • No dedicated path is required between sender and receiver.
      • The complete message is sent as one unit.
      • Intermediate nodes use the store and forward method.
      • Messages are stored in queue if the transmission line is busy.
      • Messages may travel through different routes depending on network conditions.
      • Reliable communication is possible even during congestion.
      How Message Switching Works
      1. The sender prepares the complete message and attaches the destination address.
      2. The message is sent to the nearest switching node.
      3. The switching node receives and stores the complete message temporarily.
      4. The node checks the message for errors and examines the destination address.
      5. If the next route is free, the message is forwarded immediately.
      6. If the route is busy, the message waits in a queue until the path becomes available.
      7. This process continues hop-by-hop until the message reaches the destination.
      Example of Message Switching The postal system is a common example of message switching. A letter first reaches one post office, where it is stored temporarily. Then it is forwarded to the next post office until it finally reaches the receiver. Similarly, in message switching, the complete message moves from one node to another using the store and forward method.

    • 22
      Switching Technique
      Comparision between Different switching technique

Topic Wise Question Bank
All Topics
    • ☆
      1
      Computer NetworkSwithcing Technique & Protocol
      Explain packet switching. A packet passes through 4 routers with each router introducing 2 ms processing delay. Transmission delay per link is 5 ms. Calculate total end-to-end delay (ignore propagation).
      Combined Bank, AE(IT)/AME, 26 | AME/ANE/AE

      Packet Switching

      • Packet Switching is a method of data transmission where data is broken into small packets.
      • Each packet travels independently through the network and may take different paths.
      • At the destination, packets are reassembled to form the original message.

      End-to-End Delay Calculation:

      • Number of routers = 4
      • Processing delay per router = 2 ms → Total = 4 × 2 = 8 ms
      • Number of links = routers + 1 = 5
      • Transmission delay per link = 5 ms → Total = 5 × 5 = 25 ms
      • Total Delay = Processing + Transmission
      • = 8 ms + 25 ms = 33 ms

    • ☆
      2
      Computer NetworkSwithcing Technique & Protocol
      What is DHCP? How does it work? What is DHCP function?
      Pubali, JHE, 23 |

      DHCP (Dynamic Host Configuration Protocol) is a network protocol that automatically assigns IP addresses and other network configuration details to devices connected to a network.

      Step-by-Step Working of DHCP

      Step 1: DHCP Discover

      When a device connects to a network, it broadcasts a DHCP Discover message to find available DHCP servers.

      Step 2: DHCP Offer

      The DHCP server responds with a DHCP Offer message that contains an available IP address and configuration details.

      Step 3: DHCP Request

      The client selects one offer and sends a DHCP Request message to request the offered IP address.

      Step 4: DHCP Acknowledgement (ACK)

      The DHCP server sends a DHCP ACK message confirming the IP address assignment along with subnet mask, gateway, and DNS details.

      Result

      The client can now communicate on the network using the assigned IP address.

      Example

      When you connect your laptop to a Wi-Fi network, the router (DHCP server) automatically assigns an IP address to your laptop.



    • ☆
      3
      Computer NetworkSwithcing Technique & Protocol
      Explain how do DHCP work?
      Pubali, HE, 23 | Bank

      How DHCP Works

      DHCP (Dynamic Host Configuration Protocol) is a network protocol that automatically assigns IP addresses and other network configuration details to devices connected to a network.

      Step-by-Step Working of DHCP

      Step 1: DHCP Discover

      When a device connects to a network, it broadcasts a DHCP Discover message to find available DHCP servers.

      Step 2: DHCP Offer

      The DHCP server responds with a DHCP Offer message that contains an available IP address and configuration details.

      Step 3: DHCP Request

      The client selects one offer and sends a DHCP Request message to request the offered IP address.

      Step 4: DHCP Acknowledgement (ACK)

      The DHCP server sends a DHCP ACK message confirming the IP address assignment along with subnet mask, gateway, and DNS details.

      Result

      The client can now communicate on the network using the assigned IP address.

      Example

      When you connect your laptop to a Wi-Fi network, the router (DHCP server) automatically assigns an IP address to your laptop.



    • ☆
      4
      Computer NetworkSwithcing Technique & Protocol
      What is DNS? How DNS work?
      Sonali Bank, ADA, 26 | ADA

      DNS (Domain Name System)

      DNS is a system that translates domain names (like google.com) into IP addresses (like 142.250.190.78). It works like the phonebook of the internet.

      How DNS Works:

      • 1. User Request: User enters a domain name (e.g., www.google.com) in the browser.
      • 2. DNS Resolver: The request goes to a DNS resolver (usually ISP or local cache).
      • 3. Root Server: If not cached, resolver queries the Root DNS server.
      • 4. TLD Server: Root server directs to TLD server (.com, .org).
      • 5. Authoritative Server: TLD server provides the authoritative DNS server for the domain.
      • 6. IP Address Returned: Authoritative server returns the IP address.
      • 7. Connection: Browser uses the IP to connect to the website.

      Example:

      • User types www.facebook.com
      • DNS converts it to an IP (e.g., 157.240.x.x)
      • Browser connects to that IP and loads the website

    • ☆
      5
      Computer NetworkSwithcing Technique & Protocol
      Differentiate between Collision Domain and Broadcast Domain in computer network. What is the function of DNS and DHCP?
      Rupali, ANE, 23 | AME/ANE/AE

      1. Difference between Collision Domain and Broadcast Domain

      AspectCollision DomainBroadcast Domain
      DefinitionA network area where data packets can collideA network area where broadcast packets are forwarded
      Device ControlBroken by switches and bridgesBroken by routers
      Data IssueData collision may occurNo collision, only broadcast traffic
      ExampleDevices connected to a hubDevices in the same LAN

      Explanation: Collision domain is related to data collision, while broadcast domain is related to broadcast message distribution.

      2. Function of DNS

      DNS (Domain Name System) converts human-readable domain names into IP addresses so that computers can locate and communicate with each other on a network.

      Example: DNS converts www.google.com into an IP address like 142.250.190.14.

      3. Function of DHCP

      DHCP (Dynamic Host Configuration Protocol) automatically assigns IP address and network configuration parameters to devices in a network.

      Example: When a computer connects to Wi-Fi, DHCP assigns it an IP address automatically.



    • ☆
      6
      Computer NetworkSwithcing Technique & Protocol
      Do you prefer packet switching compared to circuit switching in communication network? If Yes, why? How does packet switching work step by step? What applications use packet switching?
      Rupali, ANE, 23 | AME/ANE/AE

      1. Do we prefer Packet Switching over Circuit Switching?

      Yes, in most modern communication networks packet switching is preferred over circuit switching because it uses network resources more efficiently and supports many users at the same time.

      Why Packet Switching is Preferred (Reasons)

      • Efficient Bandwidth Use: No dedicated path is reserved, so bandwidth is shared and not wasted when a user is idle.
      • Better for Burst Traffic: Internet data is usually bursty (not continuous), and packet switching handles this well.
      • Scalability: Works efficiently for large networks like the Internet.
      • Reliability: If one route fails, packets can take alternative routes.
      • Cost Effective: Shared infrastructure reduces overall cost.

      2. How Packet Switching Works (Step by Step)

      • Step 1: The sender’s message is divided into small units called packets.
      • Step 2: Each packet gets a header containing source address, destination address, sequence number, and error-check info.
      • Step 3: Packets are sent into the network and travel through routers and switches.
      • Step 4: Each router reads the destination address and forwards the packet to the next best route (routing decision).
      • Step 5: Packets may take different paths and may arrive out of order due to congestion or routing changes.
      • Step 6: At the receiver side, packets are checked for errors, arranged by sequence number, and reassembled into the original message.
      • Step 7: If any packet is missing or corrupted, it is retransmitted (common in reliable protocols like TCP).

      3. Applications that Use Packet Switching

      • Internet browsing: HTTP/HTTPS (websites)
      • Email services: SMTP, IMAP, POP3
      • File transfer: FTP, SFTP, cloud file sharing
      • Video streaming: YouTube, Netflix, IPTV
      • VoIP and video calls: WhatsApp call, Zoom, Google Meet (packet-based voice/video)
      • Online gaming: Multiplayer games over the Internet
      • Messaging apps: WhatsApp, Messenger, Telegram


    • ☆
      7
      Computer NetworkSwithcing Technique & Protocol
      ARP used in TCP/IP for perform some operation, write the functions of ARP.
      CB, SO(IT), 20 | Senior Officer (IT)

      Functions of ARP (Address Resolution Protocol)

      ARP (Address Resolution Protocol) is a protocol used in TCP/IP networks to find the MAC address corresponding to a known IP address on a local network.

      Main Functions of ARP:

      1. IP-to-MAC Address Mapping:
      ARP determines the MAC address of a destination device when its IP address is known.

      2. Sending ARP Request:
      If the MAC address is unknown, the source device broadcasts an ARP Request asking which device owns the specified IP address.

      3. Receiving ARP Reply:
      The device having that IP address sends an ARP Reply containing its MAC address.

      4. Maintaining ARP Cache:
      ARP stores recently learned IP-to-MAC address mappings in an ARP Cache so that repeated requests are not necessary.

      5. Supporting Local Packet Delivery:
      ARP provides the MAC address required to deliver an IP packet over an Ethernet or other local-area network.

      Example:



  • What is a networking protocol? Explain why protocols are necessary for communication between devices in a computer network. Give suitable examples of networking protocols.
  • What is ARP? Explain the functions of ARP and describe step-by-step how ARP resolves an IPv4 address into a MAC address.
  • What is FTP? Explain the purpose of FTP and describe how a client transfers a file to or downloads a file from an FTP server.
  • What is SMTP? Explain its role in sending email messages. Describe the basic process of sending an email from a sender to a recipient.
  • What is POP3? Explain how POP3 works and discuss its main characteristics and limitations.
  • What is IMAP? Explain how IMAP works and describe why IMAP is suitable for accessing email from multiple devices.
  • Differentiate between POP3 and IMAP based on email storage, synchronization, multiple-device access, server-side management, and typical usage.
  • What is HTTP? Explain the request-response model of HTTP. Describe the basic steps involved when a web browser requests a web page from a web server.
  • What is HTTPS? Explain how HTTPS provides secure communication between a client and a web server. Discuss the role of encryption and digital certificates.
  • What is SSL/TLS? Explain how TLS helps provide confidentiality, integrity, and authentication during network communication.
  • What is DNS? Explain why DNS is required and describe step-by-step how a domain name is converted into an IP address.
  • What is DHCP? Explain the main functions of DHCP
  • What is Telnet? Explain how Telnet works and discuss its major advantages and security limitations.
  • Differentiate between DNS and DHCP. Explain the main function of each protocol and describe how they are used together in a network.
  • What is switching in a computer network? Explain network switching, its need, and the major types of switching techniques.
  • Compare Circuit Switching and Packet Switching based on connection establishment, resource allocation, delay, bandwidth utilization, reliability, and practical applications.
  • Differentiate between Datagram Packet Switching and Virtual Circuit Packet Switching. Discuss connection establishment, routing, packet ordering, and failure handling.
📘 Switching Tecnique and Protocol
1. What is a network protocol?
2. Which protocol is used to map an IPv4 address to a MAC address on a local network?
3. What is the primary function of ARP?
4. Which protocol is primarily used for transferring files between a client and a server?
5. Which ports are traditionally associated with FTP control and data connections?
6. Which protocol is primarily used to send email from a mail client to a mail server or between mail servers?
7. Which protocol is commonly used to download email messages from a mail server to a client?
8. Which protocol keeps email messages synchronized with the server and allows access from multiple devices?
9. Which protocol is mainly used for sending email?
10. Which protocol is mainly used for retrieving email while maintaining server-side mailbox synchronization?
11. What is the default port number of HTTP?
12. What is the default port number of HTTPS?
13. What is the main difference between HTTP and HTTPS?
14. What is the main purpose of TLS in HTTPS?
15. What does DNS stand for?
16. What is the primary function of DNS?
17. Which port is commonly used by DNS?
18. Which transport protocol is commonly used for ordinary DNS queries?
19. What is DHCP primarily used for?
20. Which sequence correctly represents the DHCP DORA process?
21. Which DHCP message is initially broadcast by a client seeking an IP configuration?
22. Which DHCP message contains an IP configuration offer from a DHCP server?
23. Which DHCP message does the client send to indicate which offered configuration it wants to use?
24. Which DHCP message confirms that the server has successfully assigned the configuration?
25. What is the main purpose of Telnet?
26. What is a major security weakness of Telnet?
27. Which protocol is commonly preferred instead of Telnet for secure remote administration?
28. What is circuit switching?
29. Which traditional communication system is a classic example of circuit switching?
30. What is the main disadvantage of circuit switching for bursty data traffic?
31. What is message switching?
32. What is a major disadvantage of message switching?
33. What is packet switching?
34. What is the main advantage of packet switching over circuit switching for bursty traffic?
35. Which switching technique is primarily used by the modern Internet?
36. In packet switching, what is a packet?
37. In a datagram packet-switched network, packets from the same message may
38. Which statement best describes a virtual-circuit packet-switched network?
39. What is the main difference between a datagram network and a virtual-circuit network?
40. Which switching technique generally provides predictable dedicated bandwidth during a session?
41. A packet passes through 4 routers, each adding 2 ms processing delay. If there are 5 links and each link has 5 ms transmission delay, what is the total delay ignoring propagation?
42. A packet travels through 3 routers. Each router introduces 4 ms processing delay and each of the 4 links introduces 6 ms transmission delay. Ignoring propagation delay, what is the total delay?
43. Which switching technique stores the complete message at an intermediate node before forwarding it?
44. Which switching technique divides a message into packets before transmission?
45. Which switching technique requires a connection setup phase before data transmission?
46. Which switching method can route packets independently without establishing a dedicated end-to-end circuit?
47. Which switching technique is most suitable for traditional telephone calls?
48. Which protocol is used to transfer web pages and other web resources between a client and server?
49. Which protocol is used to securely access a website using encrypted HTTP communication?
50. Which protocol is responsible for automatically providing a default gateway to a DHCP client?
51. Which protocol would a host use to discover the MAC address of its local default gateway when the gateway's IPv4 address is known?
52. Which protocol is most appropriate for retrieving email while keeping messages synchronized across multiple devices?
53. Which protocol is primarily responsible for sending an email from a mail client to a mail server?
54. Which protocol would be used to translate www.example.com into an IP address?
55. Which protocol and port combination is correct?

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