OSI Model for Cisco Networking

Part of the Cisco Networking All-in-One For Dummies Cheat Sheet

While you may not use the OSI model every day, you should be familiar with it, specifically when working with Cisco switches and routers (which operate at Layer 2 and Layer 3, respectively). Here are some of the items that operate at each level of the OSI model:

Layer Description Examples
7. Application Responsible for initiating or services the request. SMTP, DNS, HTTP, and Telnet
6. Presentation Formats the information so that it is understood by the receiving system. Compression and encryption depending on the implementation
5. Session Responsible for establishing, managing, and terminating the session. NetBIOS
4. Transport Breaks information into segments and is responsible for connection and connectionless communication. TCP and UDP
3. Network Responsible for logical addressing and routing IP, ICMP, ARP, RIP, IGRP, and routers
2. Data Link Responsible for physical addressing, error correction, and preparing the information for the media MAC address, CSMA/CD, switches, and bridges
1. Physical Deals with the electrical signal. Cables, connectors, hubs, and repeaters
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