computer network

CA 4 unit 5&6

1. Explain the shortest path algorithm used in routing.

Shortest path algorithm is used to find the shortest path between two nodes in a network. It is commonly used in routing protocols to determine the optimal route for data packets to travel from source to destination. The algorithm calculates the shortest path based on the distance or cost associated with each link in the network. There are various algorithms that can be used, such as Dijkstra's algorithm or Bellman-Ford algorithm.

1. Describe the distance vector routing algorithm.

Distance vector routing algorithm is a decentralized routing algorithm used in computer networks. Each router maintains a table that contains the distance to all other routers in the network. The distance is typically measured in terms of the number of hops or the cost associated with reaching a particular router. The router periodically exchanges its routing table with its neighboring routers to update the distance information. The algorithm works by iteratively updating the distance vectors until a stable routing table is achieved.

1. Explain the link state routing algorithm.

Link state routing algorithm is a centralized routing algorithm used in computer networks. In this algorithm, each router maintains a complete map of the network, which includes information about all the links and their states. The routers exchange this information with each other to build a common view of the network. Using this information, each router independently calculates the shortest path to all other routers in the network. The algorithm works by flooding the network with link state information and then using Dijkstra's algorithm to calculate the shortest path.

1. What are unicast routing protocols?

Unicast routing protocols are used to determine the optimal path for sending data packets from a single source to a single destination in a network. These protocols are typically used in point-to-point communication scenarios. Examples of unicast routing protocols include Routing Information Protocol (RIP), Open Shortest Path First (OSPF), and Border Gateway Protocol (BGP).

1. Describe congestion control algorithms used in the network layer.

Congestion control algorithms are used to manage and prevent network congestion, which occurs when the demand for network resources exceeds the available capacity. Some commonly used congestion control algorithms include:

• Random Early Detection (RED): This algorithm randomly drops packets before the network becomes congested to signal to the sender to reduce the transmission rate.

• Explicit Congestion Notification (ECN): This algorithm marks packets with a congestion flag, allowing routers to notify the sender about congestion without dropping packets.

• Traffic shaping: This algorithm regulates the rate at which packets are sent to prevent congestion by buffering and delaying packets.

• Quality of Service (QoS): This algorithm prioritizes certain types of traffic over others to ensure that critical traffic receives the necessary resources during congestion.

1. Explain the services provided by the transport layer.

The transport layer provides services to facilitate communication between applications running on different hosts. Some of the key services provided by the transport layer include:

• Connection-oriented communication: The transport layer establishes a reliable, end-to-end connection between the sender and receiver before data transfer begins. This ensures that data is delivered in the correct order and without loss or duplication.

• Multiplexing and demultiplexing: The transport layer allows multiple applications to use the network simultaneously by assigning unique identifiers, known as port numbers, to each application. This enables the transport layer to multiplex the data from different applications into a single stream for transmission and demultiplex it at the receiving end.

• Flow control: The transport layer manages the rate at which data is sent to prevent the receiver from being overwhelmed. It uses techniques like sliding window protocol to ensure that the sender does not transmit data faster than the receiver can handle.

• Error detection and recovery: The transport layer detects and corrects errors in the data transmitted over the network. It uses techniques like checksums and acknowledgments to ensure data integrity and reliability.

1. Describe the header format and handshaking operation of TCP.

TCP (Transmission Control Protocol) is a connection-oriented protocol that provides reliable and ordered delivery of data. The TCP header format consists of several fields, including source and destination port numbers, sequence numbers, acknowledgment numbers, window size, and control flags.

The handshaking operation of TCP involves a three-way handshake process to establish a connection between the sender and receiver. The steps involved are:

1. SYN: The sender sends a SYN (synchronize) packet to the receiver, indicating its desire to establish a connection. The SYN packet contains the sender's initial sequence number.

2. SYN-ACK: Upon receiving the SYN packet, the receiver sends a SYN-ACK packet back to the sender. The SYN-ACK packet acknowledges the receipt of the SYN packet and contains the receiver's initial sequence number.

3. ACK: Finally, the sender sends an ACK (acknowledgment) packet to the receiver, confirming the establishment of the connection. The ACK packet also acknowledges the receipt of the SYN-ACK packet.

Once the three-way handshake is completed, the connection is established, and data transfer can begin.

1. Explain the header format of UDP.

UDP (User Datagram Protocol) is a connectionless protocol that provides unreliable and unordered delivery of data. The UDP header format consists of four fields: source port number, destination port number, length, and checksum.

The source port number identifies the application or process on the sender's host that is sending the data. The destination port number identifies the application or process on the receiver's host that should receive the data. The length field specifies the length of the UDP header and data in bytes. The checksum field is used for error detection, allowing the receiver to verify the integrity of the UDP datagram.

1. Describe the Domain Name System (DNS) in the application layer.

The Domain Name System (DNS) is a hierarchical naming system used to translate human-readable domain names (e.g., www.example.com) into IP addresses (e.g., 192.0.2.1) that computers can understand. It acts as a distributed database that stores information about domain names and their corresponding IP addresses.

When a user enters a domain name in a web browser, the DNS system is queried to resolve the domain name to its corresponding IP address. The DNS system consists of multiple servers, including recursive resolvers, authoritative name servers, and root servers, that work together to provide this service. The DNS protocol operates over UDP or TCP and uses a client-server model for communication.

1. Explain the process of sending emails in the application layer.

The process of sending emails in the application layer involves several steps:

1. Composing the email: The user composes the email message using an email client or webmail interface. The email includes the recipient's email address, subject, and message content.

2. Address resolution: The email client resolves the recipient's email address to the corresponding IP address using the DNS system.

3. Establishing a connection: The email client establishes a connection with the mail server of the sender's email provider using the Simple Mail Transfer Protocol (SMTP).

4. Sending the email: The email client sends the email message to the sender's mail server using SMTP. The email server then relays the email to the recipient's mail server.

5. Delivery to the recipient: The recipient's mail server receives the email and stores it in the recipient's mailbox.

6. Retrieving the email: The recipient can access the email using an email client or webmail interface to retrieve and read the message.

7. Describe the File Transfer Protocol (FTP) in the application layer.

The File Transfer Protocol (FTP) is a standard protocol used for transferring files between a client and a server over a network. It operates in the application layer of the TCP/IP protocol suite.

FTP uses a client-server architecture, where the client initiates the connection to the server and requests file transfers. The client and server communicate using a control connection for commands and responses and a separate data connection for actual file transfers.

FTP supports various operations, including uploading (put), downloading (get), renaming, deleting, creating directories, and listing directory contents. It also provides authentication and authorization mechanisms to ensure secure access to files.

FTP can operate in two modes: active mode and passive mode. In active mode, the server initiates the data connection to the client, while in passive mode, the client initiates the data connection to the server. Passive mode is commonly used to bypass firewall restrictions.

1. Generate a question and answer related to the topics covered in this unit.

Q: What is the purpose of the distance vector routing algorithm? A: The distance vector routing algorithm is used to determine the optimal path for data packets to travel from a source to a destination in a network. It calculates the shortest path based on the distance or cost associated with each link in the network.

Q: How does TCP ensure reliable data delivery? A: TCP ensures reliable data delivery by using a combination of techniques such as acknowledgments, sequence numbers, and retransmissions. It requires the receiver to acknowledge the receipt of each data segment, and the sender retransmits any segments that are not acknowledged within a certain time period.

Q: What is the role of DNS in the application layer? A: The Domain Name System (DNS) in the application layer is responsible for translating human-readable domain names into IP addresses. It acts as a distributed database that stores information about domain names and their corresponding IP addresses, allowing users to access websites using domain names instead of IP addresses.

Q: How does UDP differ from TCP in terms of reliability