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CCNA 1.1: Compare and contrast OSI and TCP/IP models (FREE LAB!)


Both the OSI model and the TCP/IP model are general-purpose conceptual models that assist in discussing how computers communicate with each other.

In the 1960's, the U.S. Department of Defense awarded contracts to develop packet switching networks. One of those contracts led to the development of the ARPANET by DARPA (Defense Advanced Research Project Association). They developed the TCP/IP protocol and sent the first successful message from a node at UCLA to a node at Stanford.  The TCP/IP model grew out of these new protocols.

In the 1970's, two international standards bodies (a French committee and the ISO in the U.S.) were working on documents that defined similar models.  In the 1980's those documents merged to become what we know of as the OSI model.


Study notes:

OSI model TCP/IP model
Application (Layer 7) Process/Application Layer
Presentation (Layer 6)
Session (Layer 5)
Transport (Layer 4) Host-to-Host (Transport Layer)
Network (Layer 3) Internet Layer
Data Link (Layer 2) Network Access Layer (Link Layer)
Physical (Layer 1)
  • Both are frameworks to help in understanding network concepts and technologies
  • OSI model is 7 layers, TCP/IP model is 4 layers
  • People talk about the OSI model in terms of a reference model.  Think in terms of the 7 individual layers.
    • Layer 7 - HTTP, FTP
    • Layer 6 - Telnet, X.25
    • Layer 5 - L2TP, PPTP
    • Layer 4 - TCP, UDP
    • Layer 3 - RIP, OSPF
    • Layer 2 - ARP
    • Layer 1 - Ethernet
  • People talk about the TCP/IP model in terms of a protocol stack. Think in terms of applications.
    • Application Layer - FTP, TFTP, Telnet
    • Host-to-Host Layer - TCP, UDP
    • Internet Layer - IPv4, IPv6, ICMP
    • Network Access Layer - ARP, MAC, PPP


PacketTracer Lab: CCNA-1.1-Compare-and-contrast-TCPIP-and-OSI-model.pkt

  • Open the lab and click the Simulation tab to make sure you're in simulation mode
  • From PC0, click the Desktop and open a command prompt.
  • In the window, enter: telnet
  • In the right window of PacketTracer, click Capture/Forward to step through each packet being sent.
  • In the Simulation panel window, click the colored boxes beside TCP when they appear.  This is the SYN, SYN-ACK, ACK handshake.
  • Make note of the device where the packet currently is and view the OSI model layers in both inbound and outbound directions.
  • Try sending and monitoring other types of traffic in the same manner (i.e. ping

Use the Simulation tab in PacketTracer to step through a telnet connection and view the different layers of the OSI model.
Pay attention to the device and direction of traffic at each step



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