Communication Systems Revision Set 1

Handshaking is the process of establishing and negotiating the rules for communication between two devices. It involves a series of back-and-forth messages that allow the devices to agree on parameters such as data transmission speed, protocol, and other settings. Handshaking ensures that both devices are synchronized and ready to communicate effectively. It is an essential step in establishing a reliable and efficient communication link.

The MAC address is primarily used at the data link layer of the OSI model. This layer is responsible for the reliable transmission of data between two directly connected nodes on a network. The MAC address, also known as the physical address, is a unique identifier assigned to each network interface card (NIC) in a device. It is used to identify and differentiate devices on a local area network (LAN) and is essential for the proper functioning of protocols like Ethernet.

The HTTP HEAD method is used to request the headers of a resource without actually retrieving the entire resource. It is commonly used to check if a file has been altered compared to the local cached version. By comparing the headers of the cached version with the headers of the server version, it can be determined if the file has been modified. This can be useful in scenarios where the file may have been updated on the server and the client wants to check if it needs to download the new version.

During transmission, data is represented using a wave. In data communication, information is converted into electrical signals that travel through a medium, such as cables or air. These signals are in the form of waves, which can be analog or digital. Waves are used to carry the data from the transmitter to the receiver, where they are decoded back into meaningful information. This process allows for the efficient and reliable transfer of data over long distances.

At the interface between source and transmitter in the protocol stack, messages descend the stack. This means that the messages are passed down from higher layers to lower layers of the stack. Each layer adds its own headers and trailers to the message as it descends, until it reaches the lowest layer where it is transmitted over the network. This process allows for the proper encapsulation and formatting of the message according to the protocols operating at each layer.

Data collisions occur when two or more devices on a network try to transmit data at the same time, resulting in a collision and the loss of data. The protocols that operate at Layers 1 and 2 of the OSI model, which are the Physical and Data Link layers respectively, are responsible for detecting these collisions. Layer 1 protocols, such as Ethernet, can detect collisions by monitoring the network for electrical signals that indicate simultaneous transmissions. Layer 2 protocols, such as CSMA/CD (Carrier Sense Multiple Access with Collision Detection), also detect collisions by listening for collisions on the network and taking appropriate actions to resolve them.

Ethernet and TCP are the only protocols in the given list that perform error checking. Ethernet is responsible for error detection at the data link layer, while TCP performs error detection and correction at the transport layer. IP and UDP do not perform error checking, as IP is a network layer protocol and UDP is a transport layer protocol that does not include error detection or correction mechanisms. Therefore, the correct answer is Ethernet, TCP.

The protocols that change for each network hop would most likely operate at the Transmission Level. This level is responsible for the physical transmission of data over the network, including the encoding and decoding of data into electrical or optical signals. As messages travel across the Internet, they pass through multiple network devices, such as routers, switches, and gateways, each of which may require different protocols to transmit the data efficiently. Therefore, the protocols that change for each network hop would operate at the Transmission Level.

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The system known as "sliding windows" is used to adjust the speed of transmission during TCP sessions. Sliding windows is a flow control mechanism that allows the sender to dynamically adjust the amount of data it can send before waiting for acknowledgment from the receiver. This helps in optimizing the transmission speed by allowing the sender to send multiple segments without waiting for each individual segment to be acknowledged. By adjusting the window size, the sender can increase or decrease the amount of data sent, depending on the network conditions and receiver's ability to handle the data.