Question

State whether each of the following is true or false. If false, explain why. a) UDP is a connection-oriented protocol. b) With stream sockets a process establishes a connection to another process. c) A server waits at a port for connections from a client. d) Datagram packet transmission over a network is reliable - packets are guaranteed to arrive in sequence. e) For security reasons, many web browsers, such as Mozilla, allow Java applets to do file processing only on the machines on which they execute. f) Web browsers often restrict an applet so that it can communicate only with the machine from which it was originally downloaded.

Short answer

a) False b) True c) True d) False e) True f) True

Step-by-step solution

Check UDP Characteristics

UDP (User Datagram Protocol) is known as a connectionless protocol, meaning it does not establish a connection before sending data. Therefore, the statement is false. UDP does not maintain any connection state between the sender and receiver.

Analyze Stream Sockets

Stream sockets are used in TCP, a protocol that establishes a connection between two processes before data can be sent. Therefore, the statement is true because it correctly describes how stream sockets facilitate communication.

Understand Server Behavior

The statement is true. A server indeed listens at a particular port, awaiting incoming connections from clients, making it possible to establish a communication session.

Evaluate Datagram Packet Transmission

Datagram packet transmission, typically associated with UDP, is not reliable. Packets are not guaranteed to arrive at all, nor in sequence. Therefore, the statement is false, as UDP does not provide these guarantees.

Investigate Applet File Processing

The statement is true. For security reasons, web browsers restrict applets by allowing them to perform file operations only on the machine where they are executed, preventing them from accessing files on other machines.

Review Applet Communication Restrictions

The statement is true. Web browsers commonly impose a security restriction so that applets can only communicate with the server from which they were downloaded, preventing potentially unauthorized network interactions.

Key concepts

User Datagram Protocol (UDP)

The User Datagram Protocol, commonly abbreviated as UDP, is a communication protocol utilized in networking for sending messages without establishing a formal connection. It is termed "connectionless" because it does not require a handshake or any preceding communication before data transmission begins. This can be advantageous for applications requiring speed and efficiency rather than absolute reliability. UDP is optimal for scenarios where the time sensitivity of data is more critical than ensuring every packet arrives perfectly intact. Examples include real-time video streaming or online gaming.

• Efficient and low-overhead
• No guarantee of delivery
• Data may arrive out of order

This means while UDP is fast, it's left to the application layer to handle any acknowledgement or retransmission, if needed.

Stream Sockets

Stream sockets leverage the Transmission Control Protocol (TCP), which is a core protocol of the Internet Protocol Suite. TCP ensures the reliable transmission of data between processes over a network. When using stream sockets, a connection is established between a client and a server before any data can be exchanged. This connection-oriented model means both parties agree on various parameters like data sequencing and error handling prior to communication. Stream sockets are used for applications where data integrity and order are essential, such as file transfers or email.

• Reliability through connection establishment
• Guaranteed in-order delivery of data packets
• Handles error correction and congestion control

TCP's robust error-checking and confirmation system ensures data is received accurately, making it ideal for crucial applications.

Applet Security Restrictions

Java applets, which are small Java programs embedded in a web page, face various security restrictions when executed by browsers. These security measures are in place to protect the end-users by limiting the applet's actions, particularly concerning file processing and network communication. Browsers like Mozilla enforce such restrictions rigorously, preventing applets running on a client machine from accessing or modifying the file system or external devices. This constraint ensures that sensitive information on the user's machine remains secure.

• Limits file operations to the executing machine
• Prevents unauthorized access to local files
• Maintains user data integrity and privacy

These measures help mitigate potential security threats from the execution of malicious code.

Server-Client Communication

In network programming, server-client communication is a foundational concept where multiple computers (clients) interact with a host computer (server). A server maintains a listening process waiting for client requests at a designated network port. When a request comes in, the server can accept the connection and facilitate data exchange. This model is widely used in applications like websites, file sharing, and email services.

• Servers listen on specific ports for client connections
• Enables request-response transactions
• Supports concurrent connections

The seamless interaction between servers and clients is critical for efficient and secure data exchange in technology-driven environments.

Reliability of Packet Transmission

The reliability of packet transmission refers to the assurance in data delivery across networks. While Transmission Control Protocol (TCP) provides mechanisms to ensure data is reliably transmitted in sequence, UDP (User Datagram Protocol) behaves differently. It does not guarantee that all packets will arrive, nor that they will arrive in order. This lack of built-in reliability attributes to UDP's connectionless nature.

• TCP ensures reliability with confirmation of data receipt
• UDP does not provide built-in guarantees of packet delivery
• Applications choose protocols based on their need for speed versus reliability

In choosing between these protocols, one must balance the trade-off between speed and reliability according to the application's specific needs.