Data Communication and Networking MCQs Set-4

To calculate the number of frames in a TDMA system given the total duration of traffic and the duration of each frame, you can use the following formula:

Number of frames = Total duration of traffic / Frame duration

In your case, the total duration of traffic is 100 seconds, and each frame in the TDMA system has a duration of 5 seconds. Plugging these values into the formula, we get:

Number of frames = 100 seconds / 5 seconds = 20 frames

Therefore, in this specific TDMA system configuration, there would be 20 frames included for the traffic.

The default port number for HTTP (Hypertext Transfer Protocol) is port 80. It is the standard port used for unencrypted communication between web browsers and web servers. When a user enters a URL (Uniform Resource Locator) without specifying a port number, the browser assumes port 80 by default for HTTP connections.

However, it's important to note that there are other port numbers associated with HTTP as well. For example, port 8080 is often used as an alternative HTTP port, particularly for development servers or when the standard port 80 is already in use by another application. Additionally, various protocols, such as HTTPS (HTTP Secure) which uses SSL/TLS encryption, use different port numbers such as 443.

So, while port 80 is the default for HTTP, it's not the only port that can be used for HTTP-based communication.

The port number commonly used for the Simple Mail Transfer Protocol (SMTP) is port 25. This port is used for outgoing mail transfer from an email client or mail server to the recipient's mail server. However, it's worth noting that port 25 is often blocked or restricted by internet service providers (ISPs) to prevent spam and abuse. As an alternative, the use of port 587 (submission) or port 465 (SMTPS) with SSL/TLS encryption is recommended for secure and authenticated email communication.

TCP (Transmission Control Protocol) is a reliable, connection-oriented transport protocol in the Internet Protocol Suite.

TCP is considered a reliable, connection-oriented transport protocol due to several key characteristics:

1. Reliability: TCP provides reliable data delivery by implementing mechanisms for error detection, error correction, and retransmission of lost or corrupted packets. It ensures that data sent from one endpoint is received correctly and in the same order by the other endpoint.

2. Acknowledgment and Retransmission: TCP uses acknowledgments (ACKs) to confirm the receipt of data packets. If the sender does not receive an ACK within a specified time, it assumes that the packet was lost and retransmits it. This mechanism ensures that data is successfully transmitted and received even in the presence of network congestion or packet loss.

3. Flow Control: TCP incorporates flow control mechanisms to manage the rate of data transmission between sender and receiver. It prevents the sender from overwhelming the receiver by regulating the amount of data sent based on the receiver's ability to process and buffer the incoming data.

4. Connection-oriented: TCP establishes a connection between two endpoints (usually referred to as a TCP socket) before data transfer begins. This connection establishment involves a handshake process, where both endpoints exchange control information to establish parameters for the communication session. The connection-oriented nature of TCP ensures reliable data exchange with sequencing and acknowledgment.

These features make TCP well-suited for applications that require data integrity, sequencing, and guaranteed delivery, such as web browsing, file transfer, email, and other applications that rely on error-free and ordered data transmission.

One network protocol that is based on UDP (User Datagram Protocol) and is a component of the Internet Protocol Suite defined by the IETF (Internet Engineering Task Force) is the DNS (Domain Name System) protocol.

The DNS protocol is responsible for resolving human-readable domain names (such as www.example.com) into IP addresses that computers and network devices can understand. It uses UDP as the transport protocol for most DNS queries and responses.

DNS operates at the Application Layer of the Internet Protocol Suite and uses UDP port 53 for communication. It is a critical protocol for translating domain names to IP addresses and plays a crucial role in the functioning of the internet.

SNMP (Simple Network Management Protocol) is not based on UDP. SNMP is a network management protocol that is used to monitor and manage devices on an IP network. It operates at the Application Layer of the Internet Protocol Suite.

SNMP primarily uses UDP as its transport protocol for sending SNMP messages. However, SNMP can also use TCP (Transmission Control Protocol) for some specific operations. UDP is the default and most commonly used transport protocol for SNMP.

So, while SNMP utilizes UDP as its primary transport protocol, it is not solely based on UDP.

In the X.25 protocol suite, the protocols are defined from the Data Link Layer to the Network Layer.

Specifically, the X.25 protocol suite defines protocols that operate at the following layers of the OSI (Open Systems Interconnection) model:

1. Data Link Layer (Layer 2): X.25 includes the LAPB (Link Access Procedure, Balanced) protocol, which is responsible for establishing reliable data link connections over the physical layer.

2. Network Layer (Layer 3): X.25 defines the Packet Layer Protocol (PLP), which is responsible for packetizing data and providing error control, flow control, and sequencing at the network layer. It also includes the X.25 addressing scheme.

It's important to note that the X.25 protocol suite predates the OSI model, and while it aligns closely with the Data Link Layer and Network Layer of the OSI model, it doesn't strictly adhere to the exact layering.

Two additional advantages of cell relay, such as ATM, are high-speed transmission and multiplexing capabilities:

1. High-Speed Transmission: Cell relay networks, like ATM, are designed to support high-speed transmission. By utilizing fixed-size cells and dedicated hardware for cell switching, ATM networks can achieve high data rates, making them suitable for applications that require fast and efficient data transfer, such as multimedia streaming and high-speed data communication.
2. Multiplexing Transmission: Cell relay networks excel at multiplexing different types of traffic onto a shared network infrastructure. By utilizing virtual channels or virtual paths, multiple data streams can be multiplexed and transmitted simultaneously over the same physical link. This multiplexing capability enables efficient utilization of network resources and allows for the integration of various types of traffic, such as voice, video, and data, within a single network infrastructure.

These advantages make cell relay technologies like ATM attractive for specific use cases that demand high-speed transmission and the ability to efficiently multiplex different types of traffic. However, it's important to note that ATM has seen limited deployment in recent years, with packet-switched technologies like IP (Internet Protocol) becoming more prevalent due to their flexibility, compatibility, and scalability.

When compared with the OSI (Open Systems Interconnection) reference model, the IEEE (Institute of Electrical and Electronics Engineers) standard does not strictly define layers that directly align with the OSI model. However, there are IEEE standards that address functionalities similar to some layers of the OSI model. The following is a general mapping of IEEE standards to the corresponding layers of the OSI model:

1. Physical Layer: IEEE 802.3 (Ethernet) standard defines the physical layer specifications for wired Ethernet networks, including the physical media, signaling, and basic transmission characteristics.

2. Data Link Layer: IEEE 802.2 (Logical Link Control) standard specifies the data link layer protocol for local area networks (LANs), including the frame format, error detection, and flow control mechanisms.

3. Network Layer: IEEE does not have a specific standard that corresponds directly to the network layer of the OSI model. Network layer functionalities, such as addressing, routing, and packet forwarding, are typically addressed by various IP (Internet Protocol) standards.

4. Transport Layer: IEEE does not have a specific standard dedicated to the transport layer. Transport layer functionalities, such as reliable data delivery and flow control, are typically handled by protocols like TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) defined by the Internet Engineering Task Force (IETF).

5. Session, Presentation, and Application Layers: The IEEE standards do not specifically address the session, presentation, and application layers of the OSI model. These layers are usually implemented by various application protocols and are not directly covered by IEEE standards.

It's important to note that the IEEE standards and the OSI model have different scopes and objectives. While the OSI model provides a conceptual framework for understanding network protocols, the IEEE standards focus on specific aspects of networking technologies, particularly at the physical and data link layers.

In a token ring network, the stations are connected to a physical ring or loop. The stations are arranged in a ring topology, where each station is connected to its adjacent stations forming a closed loop.

In this network configuration, a token circulates around the ring, allowing stations to transmit data when they possess the token. The token passing mechanism ensures that only the station in possession of the token can transmit data, providing a controlled and orderly communication process in the network.

Each station on the token ring network has a physical connection to the ring, typically through a dedicated network interface card (NIC) or similar hardware. The stations' connections to the ring are usually made using twisted pair cables or fiber optic cables, depending on the specific implementation and requirements of the network.

The synchronization preamble is typically more than one byte in size.

In network communications, synchronization preambles are usually several bytes long. The exact length can vary depending on the protocol or system being used. For example, Ethernet frames typically use a preamble of 8 bytes, while some wireless protocols may use longer preambles.

The synchronization preamble's purpose is to allow the receiver to synchronize its clock and bit timing with the incoming data stream. By transmitting a known pattern of bits at the beginning of a transmission, the receiver can adjust its clock and align its timing with the sender.

Therefore, a synchronization preamble is typically longer than a single byte to provide a sufficient sequence of bits for accurate clock synchronization.