CPT 121 OSI Model |
| Application | provides user interface | provides services such as FTP, e-mail, and database access | packet creation begins here | initiates or accepts a request | ||
| Presentation | data compression | data encryption | protocol conversion | translation of data | redirector |
|
| Session | starts connection | manages and terminates connections | adds traffic-flow control information (full duplex, half-duplex, simplex) | determines who can send and who can receive during communications | ||
| Transport | messages are broken into packets at sender | packets are reassembled into messages at receiver | ensure packets are delivered error free, in sequence, with no losses or duplication | provides reliable end-to-end error recovery and flow control | ||
| Network | routing | IP addressing | supports communications between logically separate networks | circuit & message & packet switching | network
congestion control |
routers switches |
| Data Link | LLC | transmission timing & synchronization | error control | flow control | software
drivers |
bridges switches |
| MAC |
network
adapter card driver |
physical
(MAC) address |
controls
the way multiple devices share the same media channel |
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| Physical | defines physical channel | passes information directly to its counterpart on another computer | sends data as a bit stream | multipoint or point-to-point | baseband or
broadband multiplexing analog or digital |
repeaters hubs cabling |