1.2 Explain devices, applications, protocols and services at their appropriate OSI layers.

Question 1

OSI

Answer 1

Model for how applications communicate over a network.
Open Systems Interconnection

Question 2

The advantages of the OSI model

Answer 2

It distinctly separates services, interfaces, and protocols.
It supports both connection-oriented services and connectionless services.
Troubleshooting model

Question 3

The dis-advantages of the OSI model

Answer 3

It is purely a theoretical model
When OSI appeared, the TCP/IP protocols were already implemented.
There is a duplication of services in various layers. Services like addressing, flow control and error control are offered by multiple layers.

Question 4

Charateristics of OSI Layer 1

Answer 4

Physical Layer.
sets standards for sending and receiving electrical signals between devices.
How digital data bits are converted to electric pulses, radio waves or pulses of light and moved across network cables
specifications for cables an connector
physical topology.

Question 5

What PDU does layer 2 use and name 4 features.

Answer 5

Layer 2, also known as the Data Link Layer.

• Framing: It encapsulates network layer packets into frames, adding a header and a trailer to each frame for synchronization and error checking.
• Physical Addressing: It uses MAC addresses to ensure that frames are delivered to the correct endpoint within a network.
• Error Detection and Correction: It employs mechanisms like CRC (Cyclic Redundancy Check) to detect errors in frames and sometimes correct them.
• Flow Control: It manages data transmission rates to prevent fast senders from overwhelming slow receivers.
• Access Control: When two or more devices are connected to the same link, Layer 2 protocols determine which device has control over the link at any given time.

This layer ensures that data is transferred reliably and efficiently from one node to another, making it a foundational element for network communication. If you need more detailed information or have other questions, feel free to ask!

Question 6

data link layer LLC

Answer 6

The Logical Link Control (LLC) is the upper sublayer of the Data Link Layer (Layer 2) in the OSI model. It serves as an interface between the Network Layer and the Medium Access Control (MAC) sublayer. Here’s a brief overview of its functions:

• Multiplexing: LLC allows multiple network protocols (like IP, IPX, and DECnet) to coexist within a multipoint network and be transported over the same network medium.
• Flow Control: It can manage the data flow between devices to prevent data congestion.
• Error Management: LLC can provide automatic repeat request (ARQ) error management mechanisms to ensure data integrity.
• Interface Role: It acts as a bridge between the MAC sublayer and the network layer, facilitating communication and protocol management.

The LLC is particularly important in IEEE 802 networks, such as Ethernet, Wi-Fi (IEEE 802.11), and others, where it plays a crucial role in managing frame synchronization, error checking, and network protocol multiplexing¹²³⁴.

Question 7

layer 3

Answer 7

Describes how data is routed access networks and on to the destination.

Question 8

Layer 4

Answer 8

Transport.the sending application choose between connection-oriented TCP and connectionless UDP

Question 9

layer 5 session.

Answer 9

This layer allresponible for establishing, maintaining and terminating connection between programs on communicatin devices.
ows users on different machines to establish active communications sessions between them.

Question 10

ISO

Answer 10

International Organization for standardization = created OSI

ISO is derived from the Greek “isos”, meaning equal.