Network+ Certification

What is the OSI Model?

The OSI Model is a conceptual framework used to understand and implement network protocols in seven layers, ranging from physical transmission to application services.

Why is a layered approach utilized in the OSI Model?

A layered approach in the OSI Model allows for modularity, simplifying troubleshooting and development. It enables different technologies to interoperate and facilitates easier updates and changes to specific layers without affecting the entire system.

What are the layers in the OSI Model?

The OSI Model consists of seven layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application. Each layer serves a specific function in the process of data communication.

What is the physical layer of the OSI Model responsible for?

The physical layer of the OSI Model is responsible for the transmission and reception of raw bitstreams over a physical medium. It deals with the hardware aspects of networking, including cables, switches, and electrical signals.

what is one of the key distinctions of the components of the physical layer?

There is no programming related to these components only encoding and signaling that is built into the physical media. They operate at the hardware level, focusing on the physical transmission of data.

What kind of data is transmitted on the physical layer?

Raw bitstreams in the form of electrical, optical, or radio signals.

What is the data link layer responsible for?

The data link layer is responsible for node-to-node data transfer, error detection and correction, and framing of data packets for transmission over the physical layer.

What is node to node data delivery?

The process of transferring data between two directly connected nodes in a network, ensuring that the data reaches its intended destination without errors.

What type of data is the data link layer responsible for creating?

Frames that determine the structure of the data for the appropriate type of network and contain a physical address used for delivery

What does framing the data define?

the correct structure for the specific type of network being used, access controls that determine which node has control over the physical medium during communication, flow contraol to manage how its transmitted and received and error control to increase reliability

what does media access management determine?

Which node currently has the ability to use the physical medium to prevent collisions

What does flow control determine?

determines the rate that data is transmitted to avoid overwhelming slower receivers

What does error control provide?

a mechanism to detect when frames are damaged or lost so they can be retransmitted.

What are the two sublayers that the data link layer is divided into?

Logical link control and medium access control

What does the logical link control sublayer do?

it acts as an intermediary for the media access layers below it and the network layer protocols above it. Determining if the communication is going to be connection less or connection oriented

What is the difference between connectionless and connection oriented?

connectionless is similar to a person giving a speech, its not directed to any specific person. you can listen if you want or dismiss it. Connection oriented is similar to a conversation between two people.

what does the media access control sublayer do?

this is where the physical address (MAC address) is processed

What is a mac address?

12 character hexadecimal value that is written in the network interface directly and is unique to each card.

What are mac addresses used for?

they make direct node to node communication possible

How do switches allow nodes to talk to each other?

they maintain a table of all of the nodes and record the MAC addresses of each node and establish the direct link between nodes with these addresses

How do nodes communicate through a hub on the physical layer?

Data is sent out to all nodes connected to the hub because there is no direct node to node communication at this layer.

What is the network layer responsible for?

packet addressing and address conversion

What type of addressing happens at the network layer?

logical addressing, these addresses can be assigned to any interface and can be changed

What is address conversion?

the conversion of the physical address to the logical address

How can devices be assigned to different networks?

by changing the local address and this is usually referred to as an Internet Protocol or IP address

How is source to destination delivery different at the network layer

the source and destination can be in completely separate networks up to and including the internet

What is routing?

the process of connecting independent networks together to form larger networks and determining the best route to take between any given source and any given destination

How do routers pass data?

From router to router it is not concerned with getting data directly to the specific host

What is internetworking?

the process of providing network to network connections by providing the logical connections that can support connecting different types of networks. ex: connecting home wifi to internet

What is logical addressing?

defining a custom addressing scheme that allows you to combine any number of networks for greater control and management over the amount of traffic that occurs within and between networks

what is packetizing?

encapsulating data into discrete units.

How are packets assigned?

using a source and destination IP address

what is fragmentation?

breaking up packets into smaller units and labeling each one

what are the benefits of fragmentation?

makes it so that the data is more easily sent out over the different types of mediums that might not support larger packet sizes

why is each fragment labeled?

so that they can arrive out of sequence but be reassembled in the correct sequence once they arrive at their destination

What is the transport layer responsible for?

End to end message delivery and error checking

What information does the transport layer add to the packet?

a port number to determine if its supposed to be used by a particular application at the address

How does end to end message delivery work in the transport layer?

The primary protocols at this level define values (ports) to distinguish one type of application protocols from another

Do layers on one system communicate with other layers on another system?

No they only communicate with their counterpart layer

What are some other transport layer functions?

message acknowledgement, traffic control, session multiplexing and service point addressing

What is session multiplexing?

taking several message streams or sessions and combining them into a single logical link while still keeping track of which message streams belong to which sessions

What is service point addressing?

the process of specifying and applying the port value just mentioned

What are the two most common protocols at the transport layer?

User Datagram Protocol (UDP) and Transmission Control Protocol (TCP) which are both responsible for data delivery

which transport protocol is used for connectionless transmissions?

UDP

which transport protocol is used for connection oriented transmission?

TCP

What is the trade-off of connection oriented communications?

slower connections bc its required to establish a connection between two endpoints before any data is transmitted

What is the benefit of connection oriented communications?

reliability bc the sender must wait for acknowledgement from the receiver before any more data will be sent

What is the session layer responsible for?

overall management of communication between two devices including the establishment of a session, maintenance during communications and termination of the session

What are the protocols used in the session layer responsible for?

defining the parameters of the connection and managing the transfer of data by specifying who can transfer and for how long

What is a common support requirements of establishing a session?

name recognition and/or login to ensure all security considerations have been met

What is dialog control?

the process that determines which device will communicate first and how data will be sent by each device in terms of who can transmit and when

What are the three types of dialog control?

simplex, half dupelx and full duplex

What is simplex dialog control?

communication only occurs in one direction, one device transmits and the other receives

What is an example of simplex?

listening to the radio

What is half duplex dialog control?

traffic can occur in both directions but only in one direction at a time

what is full duplex dialog control?

when traffic can be two-way at the same time. Both devices can transmit and receive simultaneously

What are some of the protocols that work in the session layer?

Network Basic Input Output System (NetBIOS), Domain Name System (DNS), Remote Procedure Call (RPC) and Network File System (NFS)

What are NetBIOS and DNS protocols used for?

name recognition and resolution

What is RPC used for?

client server redirection where requests are generated on clients but executed on servers

What is NFS used for?

allowing client systems access to server based resources such as folders and files

What is the presentation layer responsible for?

presenting data in a uniform format to the application

What are some of the functions of the presentation layer?

character code translation

what is character code translation?

a mechanism to convert the standard characters humans use into binary (ones and zeros)

What are the two most common methods of character code translation?

American standard code for information interchange (ASCII) and Extended binary coded decimal interchange code (EBCDIC)

What is bit order?

the order that the bits are received

What are some components of the character code conversion process?

bit order, how to interpret instances of carriage return and/or line feed, and interpreting integers vs floating point numbers

What are the three processes the presentation layer is responsible for?

encoding/decoding, encrypting/decrypting, and compression/decompression

What does data compression do?

reduce the number of bits that are being transmitted on the network

What is a common method of compression?

token conversion

How does token conversion work?

Takes certain redundant strings of bits and replace them with something else that requires fewer bits

How does data encryption work?

replaces characters to scramble the data

What is the application layer responsible for?

supporting the functionality of an application using app layer protocols

What are two common application layer protocols?

HTTP and SMTP

What is Simple Mail Transfer Protocol (SMTP) used for?

sending emails

What is Hypertext transfer protocol used for?

transporting data over the internet

What is file transfer protocol used for?

transferring files from one system to another usually over the internet

What is dynamic host configuration protocol responsible for?

assigning IP address configuration to client systems

What is Domain Name system responsible for?

resolving domain names

What does using the correct application protocol do?

allows the user to interact with the application and makes the app compatible with others