< All CompTIA Network+ Notes

Tobraham | CompTIA Network+ | Module 1.1 - OSI and TCP/IP Models

By: Tobraham | Related Course: CompTIA Network+ | Published: February 2, 2018 | Modified: February 2, 2018
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NotepadOSI - Application Layer (L7)

Application Layer – which application is necessary for the task at hand? Email? File transfer? Web page?

  • Telnet, FTP, http, DNS SMTP
  • enables apps to access the net
  • determines availability of resources by checking other layers 
  • sync communications

NotepadOSI - Network Layer (L3)

Network Layer – aka ”IP Layer” – functional means of transferring data thru one or more networks

  • Uses IP addresses (these are logical addresses, not hard coded like MAC)
  • Translate logic address into physical addresses
  • performs network routing
  • fragment (outbound)  and reassemble (inbound) packets
  • Routers and packets are Layer 3

NotepadOSI - Physical Layer (L1)

Physical Layer – cables and bits, electricity. The first point of your data in your network.  

  • pinouts
  • voltages
  • cables specs
  • NIC cards

NotepadOSI - Physical Layer (L2)

Data Link Layer 

  • packages the bits into frames
  • transfer of data from point to point (A to B)
  • MAC (Media Access Control) Address – unique to your specific hardware device
    • once a bit is sent to a MAC address, you are at L2
  • Hub – ’dumb’ packet forwarding. Not selective with its destination

NotepadOSI - Presentation Layer (L6)

Presentation Layer (L6)  – translates data into a form that app layer can understand

  • encryption / decryption
  • processing XML data
  •  EBCDIC from one PC to ASCII on another

NotepadOSI - Session Layer (L5)

Session Layer (Layer 5) – ”Traffic Control”

  • controls connections between computers
  • establishes. manages, and terminates connections
  • regulates when a computer can send and how much
  • performs handshakes and says good bye

NotepadOSI - Transport Layer (L4)

Transport Layer (L4) mgmt and control

  • manage and control the data packets
  • split communications into different packages (TCP / UDP)
    • TCP – ”Transmission Control Protocol”
      • receipt of delivery
      • allows resending of packets of they were bad
      • slower but far more accurate
    • UDP – ”User Datagram Protocol”
      • no confirmation of delivery
      • just allows for streaming with no verification
      • Skype, VOIP, streaming video
      • faster bandwidth bc no confirmation
      • dropped packets result in audio skips or fuzzy video

NotepadOSI: 7 Layer

OSI Model = Open Systems Interconnection
Means of discussing how networks work by breaking it into layers.

(Please Do Not Throw Sausage Pizza Away)
(People Don’t Need To See Paula Abdul)

  1. Physical – hardware – NIC, cables
  2. Data Link – MAC addresses, switch, frames
  3. Network – IP addresses, routers
  4. Transport – breaks up session into packets
  5. Session – management of sessions – who’s allowed to talk and when 
  6. Presentation – encrypt/decrypt, format/prepare data to be presented to us on screen
  7. Application – dictates what aspects are allowed to communicate

NotepadTCP / IP

TCP / IP – describes our networking model in a different series of layers like OSI, but the layers are slightly different

N.I.T.A. ”Never Ingest Toxic Apples
Network Interface – similar to L1 and L2 on OSI model
Internet Layer – L3
Transport Layer – L4
Application Layer – L5 – L7

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