Networking Models 5

Question 0

Name the seven layers of the OSI model

Answer 0

All People Seem To Need Data Processing

Application layer
Presentation layer
Session layer
Transport layer
Network layer 
Data link layer
Physical layer

Question 1

The OSI Reference Model is

Answer 1

A network model developed by ISO for communication in open system networks. Divides the data communication process into seven tasks called layers. Each layer is designed to link the layers above it. A layer provides services to the layer above and requests service from the layer below

Question 2

describe what an open system network is

Answer 2

A network that supports multiple communication protocol suites that different vendors develop

Question 3

The layers in the OSI reference model can be classified into two functional blocks

Answer 3

Application support : consists of the upper three layers. Application, presentation, session. Primary function is to connect software programs to the network

Network support : consists of the lower four layers. Transport, network, data link, physical. Primary function is moving data on the network

Question 4

Describe the physical layer 1

Answer 4

Transmits data packets over a physical medium. Determines the mode and medium Od data transmission. Receives fully formatted data packets from the data link layer and places them in the media. Network adapters and WAP are some devices that operate at this layer.
Technologies that operate at this layer are Ethernet, fast Ethernet, token ring, FDDI, ATM Asynchronous Transfer Mode

Question 5

Describe what a packet is

Answer 5

A unit of data transmitted on a network. All packets contain three parts : header, data, and footer/trailer.

Question 6

What is a multilayer device

Answer 6

Network devices that can perform tasks on more than one layer and functions actress layers. Ex WAPs, gateways, hubs and repeaters

Question 7

Describe the data link layer 2

Answer 7

Responsible for grouping data bits into frames and attaching the address of the receiving node to each frame to form the data packet
Error free transfer of data packets between nodes on the network. After transfer waits for acknowledgement from receiving node
Adds error correction and detection codes to frames to perform error checks and corrections.

Devices operating at this layer. Switches.
Protocols operating at this layer. PPP point to point protocols and SLIP serial line Internet protocol

Can be divided into two sub-layers LLC & MAC

Question 8

LLC sub-layer of data link layer

Answer 8

Responsible for identifying network layer protocols and encapsulating so multiple upper layer protocols can share the same media. Controls how frames are places on the media by controlling the physical layer device. Checks the CRC the frame and either ACKs or NACKs the data

Question 9

The MAC sub-layer of the data link layer

Answer 9

Defines now packets are placed on the media. In contention based network responsible for detecting collisions for the carrier sense
In token passing network responsible for the token

Question 10

Describe network acknowledgement

Answer 10

A signal used by communication protocol between nodes on a network to acknowledge the receipt of data 
ACK positive successful receipt 
NACK negative bad transmission 
REJ rejection of data 
ARQ automatic request for retransmission

Question 11

Describe the network layer 3

Answer 11

Responsible for addressing data packets, routing packets from a source to the destination through the network and ensuring data delivery. Controls congestion on the network by taking proper routing decisions. Defines protocols for interconnecting two or more similar networks such as IP, ARP, DHCP, ICMP, RIP, BGP, OSPF, IGMP

Routers and switches operate at this layer.

Question 12

Describe the transport layer 4

Answer 12

Accepts data from upper layers and breaks it into smaller units called segments. Then passes these segments to the lower layers and ensures that all Segments arrive correctly at the receiving end. This layer adds a sequence number to reach segment to help reconstruct the original sequence of segments. Also responsible for error correction and sending ACK at the network level.
Defines protocols for interconnecting networks using difference protocols.
Gateways operate at this layer.
Protocols functioning at this layer TCP, UDP, IPSec, PPTP, RDP, L2TP

Question 13

Network and transport layer protocol families

Answer 13

Reliability protocols. Provide method of ensuring reliable data transfer. Checksum value in header or trailer

Connection protocols. Establish and maintain s connection less or connection oriented server for the upper layers. In connection oriented the sending and receiving nodes maintain constant communication to mediate the transfer of data
In connection less the message is Packaged, delivered, and sent when communication exists between two nodes

Routing protocols. Ensures data transfer to the correct destination.

Question 14

Explain checksum value

Answer 14

Lets the recover test the I integrity of received data. If corrupted the receiver fires back an error message to the sender to retransmit the data

Question 15

Describe the session layer 5

Answer 15

Established connections between devices and applications, maintains the connection, and then Terminates or re establishes it when required.
Controls how, when, and for how long a device can transmit or receive data.
Sockets and session establishment in TCP function at this layer.

Question 16

Describe the presentation layer 6

Answer 16

Responsible for encoding data into a standard network compatible format. Used to enable devices with different representation techniques to communicate with each other. Adds data compression and encryption.
Technologies and protocols operating at this layer are : MME, SSL, TLS, GIF, JPEG, TIFF

Question 17

Technologies operating at the presentation layer 6

Answer 17

MME. Mesh Made Easy. Used for routing in wireless networks
GIF. Graphics Interchange Format. Graphic interchange format used on the Internet
JPEG. Joint photographic Experts Group. Graphical file format that reduced file size
TIFF. Tagged Image File Format. Digital format used to handle images used in publishing and photography

Question 18

Protocols that function at the transport layer 4

Answer 18

TCP. Transmission Control Protocol 
UDP. User Datagram Protocol
IPSec. Internet Protocol security 
PPTP. Point to Point Tunneling Protocol 
RDP. Remote Desktop Protocol
L2TP Layer 2 Tunneling Protocol

Question 19

Describe the application layer 7

Answer 19

Provides utilities and services that allow applications to access the network and it resources. Defines protocols for tasks, advertises itself to server resources available in each system for usage on the network. User directly interacts with this layer
Technologies, protocols and services that function at this layer: HHTP, DNS, FTP, Gopher, NFS, NTP, SNMP, SMTP, Telnet

Question 20

Technologies, protocols, and services operating at the application layer 7

Answer 20

HTTP. hyper text transfer protocol 
DNS. Domain Name Service 
FTP. File Transfer Protocol 
NFS. Network File System
NTP. Network Time Protocol
SNMP. Simple Network Management Protocol 
SMTP. Simple Mail Transfer Protocol 
Telnet 
Gopher

Question 21

Application, presentation, session layer protocol families

Answer 21

Terminal emulation protocols. Enable computers to act as standard terminals to access hosts
File access and file transfer protocols. Enables nodes to access files on the network
Email protocols. Email delivery and message handling
Remote action and multiple session protocols. Determines if processes performed remotely on s client node or directly by a server
Network management protocols. Provide tools for setting up and maintaining the network.
Task to task protocols. Enable software processes to communicate Over the network
Codeset and data structure protocols. Define the representation of data. Translate data for nodes using different coding schemes.

Question 22

Describe the overall process of data transmission through the OSI model

Answer 22

During Data transmission data is added to the application layer 7. It is then forwarded to the lower layers until the physical layer 1 transfers the data to the network media.
During data reception, data is added to the physical layer 1. Then it is forwarded to the layers above it until it reaches the application layer 7. Each layer removes the information it needs before transmitting the remaining data to the next layer

Question 23

Define the TCP/IP protocols

Answer 23

A network protocol suite that is routable and allows computers to communicate across all types of networks. Protocol of the Internet. Is non-proprietary.

Question 24

The TCP/IP Network Model

Answer 24

A four layer model developed by the United States Department of Defense. Allows the addition of new technologies and create a more flexible architecture to modify existing protocols. 
Application layer 4
Transport layer 3
Internet layer 2
Network interface layer 1

Question 25

Describe the TCP/IP application layer

Answer 25

Provides definition of protocols for file, email, and http. Handles the encoding of data, controls the sessions, and defines the socket services over TCP/IP

Makes up the application 7, presentation 6 and session 5 layers of the OSI model

Question 26

Describe the TCP/IP transport layer

Answer 26

Provides connection establishment and communication services. Defines protocols for end to end transfer of data, and error flow controls. The two transport layer protocols are TCP and UDP

Question 27

Describe the TCP/IP Internet layer

Answer 27

Provides addressing and routing services. Controls congestion in the network. Involves transferring data from a source to a destination network when multiple networks are connected together.

Similar to the network 3 layer of the OSI model

Question 28

Describe the TCP/IP network interface layer

Answer 28

Provides services to send and receive data packets On the network. Defines protocols for moving dats frames between adjacent nodes and for accessing the medium by the devices. Defines the protocols for encoding and transmitting data over the network media.

Makes up the data link 2 and physical 1 layers of the OSI model

Question 29

Each layer uses different terminology for a unit of informstion

Answer 29

Layer                Term 
Application       Data
Transport.         Segment
Internet.            Datagram or packets 
Network            Frames 
interface

Question 30

Data encapsulation is

Answer 30

The process of adding delivery information to the actual data transmitted on each layer. Takes place in the transmission end as data is passed down the layers.

Question 31

De-encapsulation is

Answer 31

The process of removing the added information, the header or trailer, which ensure proper delivery, as data passes to the next higher level.

Question 32

What is protocol binding

Answer 32

Assigning a protocol to a NIC as it creates a oath for the flow of data. Multiple protocols can be bound to a NIC. Any of the protocols can be used to communicate with other nodes on the network. The first compatible protocol in the list that the two nodes have in common is the one they is used.