Communication Systems Revision Set 1

1.

During transmission data is represented using a:

A.

Transmitter
B.

Medium
C.

Message
D.

Wave

Correct Answer
D. Wave

Explanation
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.

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2.

The MAC address is primarily used at which of the following layers of the OSI model?

A.

Network
B.

Transport
C.

Data link
D.

Presentation and application

Correct Answer
C. Data link

Explanation
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.

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3.

Establishing and negotiating the rules for communication is the process known as:

A.

Handshaking
B.

Protocol assignment
C.

Sliding windows
D.

Routing

Correct Answer
A. Handshaking

Explanation
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.

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4.

Which of the following is TRUE for all IP addresses?

A.

They are transmitted as dotted decimals
B.

They always correspond to a unique domain name
C.

They are assigned by hardware manufacturers and cannot readily be changed
D.

They included a network ID and a host ID

Correct Answer
C. They are assigned by hardware manufacturers and cannot readily be changed

5.

Why would an HTTP HEAD method be used?

A.

To upload a new version of a file to a web server
B.

To determine if the user is permitted to download an HTML file
C.

To test the speed of a TCP/IP connection prior to download
D.

To determine if a file has been altered compared to the local cached version

Correct Answer
D. To determine if a file has been altered compared to the local cached version

Explanation
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.

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6.

The system known as "sliding windows" is used to:

A.

Ensure TCP segments are acknowledged prior to further segments being sent
B.

Monitor and record the destination of files sent form a web server
C.

Adjust the speed of transmission during TCP sessions
D.

Equitably share the bandwidth of communication channels

Correct Answer
C. Adjust the speed of transmission during TCP sessions

Explanation
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.

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7.

In term of the protocol stack, what occurs at the interface between source and transmitter?

A.

Messages ascend the stack
B.

Messages descend the stack
C.

Messages are stripped of their headers and trailers
D.

Each protocol is influenced by the protocols operating at adjoining layers

Correct Answer
B. Messages descend the stack

Explanation
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.

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8.

Data collisions, if possible, are detected by protocols operating at which layers of the OSI model?

A.

Layers 1 and 2
B.

Layers 2 and 3
C.

Layers 3 and 4
D.

Layers 4 and 5

Correct Answer
A. Layers 1 and 2

Explanation
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.

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9.

As messages move across the Internet the protocols that change for each network hop would most likely operate at which level?

A.

Transmission Level
B.

Communication Control and Addressing Level
C.

Application Level
D.

Addressing and Routing Level

Correct Answer
A. Transmission Level

Explanation
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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10.

Which list includes only protocols that perform error checking?

A.

TCP, IP
B.

Ethernet, TCP
C.

HTTP, UDP
D.

Ethernet, IP

Correct Answer
B. Ethernet, TCP

Explanation
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.

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