4.a - OSI Network Model Layers Flashcards
Two dominant network model in use
The two dominant network models that are used to illustrate networks are OSI and TCP/IP.
OSI Network model
Open Systems Interconnection Model, consist of seven layers :
Physical, Data Link, Network, Transport, Session, Presentation, Application.
Memory Aid for the seven OSI layer models
Please Do Not Throw Sausage Pizza Away
OSI Layer 1: Physical
Concerned with electrical and physical specifications for devices.
At the physical layer, networks are little more than electric signals flowing in wires or radio frequency airwaves.
Example of OSI Physical layer standard
• Cabling • RS-232 • T1 • DOCSIS • 802.11aPHY• CDMA • WLAN • LTE
802.11aPHY
means the physical layer component of 802.11
OSI Layer 2: Data Link
The data link layer in the OSI model focuses on the method of transferring data from one station on a network to another station on the same network.
DOES NOT DEAL WITH ROUTERS
Example of Data link layer standards
- LAN protocol
* 80211.MAC/LLC - a portion of a well-known WI-FI protocols
OSI Layer 3: Network
Ensure the delivery of messages from one station to another via one or more networks.
DEALS WITH ROUTERS
Example of protocols at the network layer
- IP protocol
- IPSec - to authenticate, encapsulate, and encrypt IP traffic between networks
- ICMP - for communication diagnostics
- IGMP - to organize multicast group membership
OSI Layer 4: Transport
Concerned with the reliability of data transfer between systems.
Example of transport layer
- TCP, https, three-way handshake
* UPD - transfer file protocol, VoIP
OSI Layer 5 : Session
Used to control connections that are established between applications on the smae, or different , systems
Example of session layer
- NetBios
* rpc
OSI Layer 6: Presentation
The presentation layer in the OSI model is used to translate or transform data from lower layers (session, transport, and so on) into formats that the application layer can work with.
Examples of presentation layer functions include
- Character set translation - ASCII & EBCDIC
- Encryption/decryption - SSSL,
- CODECS - to encode, decode, compress, decompress audio and video data streams
OSI Layer 7: Application
contains programs that communicate directly with the end user.
Physical Network Topology
- Star - Separate cable is run from a central location to each computer.
- Ring - Consists of cabling that runs from one computer to the next.
- Bus - Consist of a central cable, with connectors along its length that would facilitate “branch “ cables that would be connected to individual computers.
Network adaptor
or Network interface card, is a device that is directly connected to a computer’s bus and contain one or more connectors to which an Ethernet network cable may be connected.
Hub
Like a repeater, they propagate packets
Gatteway
Device that acts as a protocol converter, or performs some other type of transformation of messages.
Repeater
A device that receives and re transmits the signal on an Ethernet network
A bridge
a device that is used to interconnect Ethernet networks
Switch
It’s like a hub, but it listens to traffic, and learn the MAC addresses associated to each port and will send packets only to destinations ports
