Network Layer

From amongst the TCP-IP Layers, the Third Layer is the Network Layer.

  • HTTP asks for the Web pages from a Web Server, TCP provides guaranteed delivery through Error recovery feature & TCP/IP Network Layer's IP provides Addressing for Host identification in the Network & like Zip codes used in the postal Service IP address groups are used in the Network.

  • The most commonly used Network Layer protocol is IP & it provides the features like Addressing & Routing like a Postal Service.

  • For E.g. You (or PC's Application & Transport Layer) created & put a letter in the mailbox with the stamps, Addressing & envelop& they are now ready to be delivered by the postal service to the other side of the town.

  • The postal Service (Lower Layers) treat each letter differently. For the letter to be sent across the town it will just put it on the local delivery truck but for it to be sent across the country then the postal service sends it to another post office & so on until it gets delivered.

  • You (Upper Layers) created the letter but do not need to know about the path the letter is going to take but the postal Service (Lower Layers) needs to know everything except the Data in that letter.

  • Some other Network Layer features which are related to IP Routing are DNS, ARP & PING.

Reference:

  • CCNA 200-301 OCG, Volume 1, Pg. 23 - Wendell Odom.

  • CCNA 200-301 OCG, Volume 1, Pg. 76 - Wendell Odom.

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