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What is the purpose of a network model?
Purpose of a Network Model:
A network model, such as the OSI (Open Systems Interconnection) model or the TCP/IP model, provides a structured framework for understanding and designing network protocols and communication processes. Its primary purpose is to:
Standardize Communication: Define clear layers and protocols to ensure compatibility between different systems and devices.
Simplify Troubleshooting: Allow easier isolation of network issues by separating functions into distinct layers.
Facilitate Development: Enable developers to focus on specific layers without needing to understand the entire system.
Promote Interoperability: Ensure that products from different manufacturers can work together.
How does the TCP protocol differ from the UDP protocol?
TCP (Transmission Control Protocol):
Connection-Oriented: Establishes a connection before data is sent.
Reliable: Ensures that data is delivered accurately and in order, using acknowledgments and retransmissions.
Flow Control: Manages the rate of data transmission to avoid overwhelming the receiver.
Error Checking: Provides error detection and correction.
UDP (User Datagram Protocol):
Connectionless: Sends data without establishing a connection first.
Unreliable: Does not guarantee delivery, order, or error checking, making it faster but less reliable.
Lower Overhead: Lacks mechanisms for flow control and error correction, making it suitable for real-time applications where speed is crucial.
What functions are performed by Application layer protocols?
Functions Performed by Application Layer Protocols:
Application layer protocols are responsible for providing end-user services and facilitating communication between applications over a network. They:
Define Data Formats: Specify how data is formatted and interpreted (e.g., HTTP for web data, SMTP for email).
Establish Communication Rules: Set rules for how applications interact and exchange data.
Support Application Services: Provide protocols for various services like file transfer (FTP), email (IMAP/POP), and remote access (SSH).
Handle Error Reporting: Provide mechanisms for applications to report errors and manage communication issues.
How does TCP negotiate a connection with a remote host?
TCP Connection Negotiation:
TCP uses a three-way handshake to establish a connection between a client and server:
SYN: The client sends a SYN (synchronize) packet to the server to initiate a connection.
SYN-ACK: The server responds with a SYN-ACK (synchronize-acknowledge) packet, acknowledging the client’s SYN and sending its own SYN.
ACK: The client sends an ACK (acknowledge) packet back to the server, completing the handshake. Once this is done, data can be exchanged.
What functions are provided by the Internet layer?
Role of Port Assignments in Application-to-Application Communications:
Ports are logical endpoints in network communication, used to differentiate between multiple services or applications running on a single device. They:
Direct Traffic: Ensure that incoming data is directed to the correct application or service (e.g., web traffic goes to port 80 or 443 for HTTP/HTTPS).
Support Multiple Services: Allow multiple applications to run simultaneously on the same device without interfering with each other.
Enable Communication: Facilitate proper routing of data to and from the correct application through unique port numbers.
What are MAC addresses? How are they used by the Link layer?
Functions Provided by the Internet Layer:
The Internet layer, primarily associated with the IP protocol, is responsible for:
Routing: Determines the best path for data to travel across networks and forward packets accordingly.
Addressing: Uses IP addresses to identify and locate devices on the network.
Packetization: Breaks down data into packets for transmission and reassembles them at the destination.
Error Handling: Provides mechanisms for packet errors and may include ICMP (Internet Control Message Protocol) for reporting errors and network diagnostics.
What role does port assignments play in application-to-application communications?
MAC Addresses and Their Use by the Link Layer:
MAC Addresses:
Definition: Media Access Control (MAC) addresses are unique identifiers assigned to network interface cards (NICs) for use in network communication at the data link layer.
Format: Typically 48 bits long, represented as six pairs of hexadecimal digits (e.g., 00:1A:2B:3C:4D:5E).
Usage by the Link Layer:
Local Communication: MAC addresses are used to identify devices within the same local network segment (broadcast domain).
Frame Delivery: The link layer uses MAC addresses to encapsulate data into frames and ensure it is delivered to the correct device on a local network.
Network Topology: Helps in determining network topology and managing data transmission within a local area network (LAN).
Application layer
layer, also called the Process-to-Process layer, corresponds to the Session, Presentation, and Application layers of the OSI model.
Transport layer
layer, also called the Host-to-Host layer, is comparable to the Transport layer of the OSI model. It is responsible for error checking and reliable packet delivery. The Transport layer breaks the data stream into segments and assigns sequence numbers so that the segments can be reassembled correctly at the destination.
Internet layer
layer is comparable to the Network layer of the OSI model. It is responsible for moving packets through a network. This involves addressing and making routing decisions to identify how the packet traverses the network.
Link layer
layer corresponds to the functions of the Physical and Data Link layers of the OSI model. It is responsible for describing the physical layout of the network and how messages are formatted on the transmission medium. Sometimes this layer is divided into the Data Link and the Physical layers.
