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

Overview:

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

 

THIS LAB FREE!
PacketTracer Lab: CCNA-1.1-Compare-and-contrast-TCPIP-and-OSI-model.pkt

  • Open the lab and wait about 20-30 seconds to let the devices fully power on before starting the lab.
  • Press Shift+S to enter simulation mode.  This mode will walk you through step by step the packets traversing the network.
  • Select PC0 > Desktop > Command Prompt
  • In the command prompt window telnet to Router0 at 192.168.1.1
C:\>telnet 192.168.1.1
  • In the PacketTracer Simulation Panel under Play Controls, click Capture/Forward 6 times to step through each SYN, SYN-ACK, ACK handshake packets as they traverse from PC0 to the switch to the Router0 and back.
  • In the Simulation panel window, click the colored boxes beside TCP when they appear to view more details about the SYN, SYN-ACK, ACK process.
  • Select the colored information box when the Last Device is SW, the At Device is R0 and the Type is TCP.  Inbound to the Router is destination port 23, source IP 192.168.1.2 and Destination IP 192.168.1.1.  This information is reversed on the outbound layers after being processed by the router.  The protocol shows TCP instead of Telnet because the devices are still  participating in the three-way handshake.
  • Click Capture/Forward 7 more times.  In the command prompt window you will be logged into the router and the router prompt will be displayed
R0>
  • As you step through in simulation mode, make note of the device where the packet currently is and view the OSI model layers in both inbound and outbound directions to get a better sense of the layers.  For example, the switch will only display layers 1 and 2 since it it a layer 2 device.  The router will only display layers 1, 2 and 3 since it is a layer 3 device.  The PC will display all 7 layers since that is where the application is running.
  • Try sending and monitoring other types of traffic in the same manner (i.e. ping 192.168.1.1)

 

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