Protocol model question

stubbyhs · 14 Dec 2011

Hi all,

I realise this isn't a question just Win7 related but I am trying to wrap my head around this and this forum is always very good at answering my questions.

I am studying about the OSI protocol model at the minute and am trying to understand what is probably a very basic thing that I have twisted in my head.

For transferring data across networks, data is first input using the app layer of the TCP/IP Model, then is encapsulated into segments for the Transport Layer, packets for the Internetwork Layer and Frames for the Network Access Layer.

I was just looking at routers and how they take a packet and forward it on. If the data travels down the entire protocol stack then surely a frame is the PDU that arrives at the router?

Sorry if this is garbled but any help would be welcome.

Thanks,
StubbyHS

stubbyhs · 14 Dec 2011

Ah doesn't matter, I think I have it.

Frames are decapsulated and re-encapsulated at every device before it is sent on to the next hop with a different trailer and header on it.

lehnerus2000 · 14 Dec 2011

That's correct.
The source and destination MAC addresses (in the frame) change at each router.

if you are a Cisco Networking Academy student, try downloading Cisco Packet Tracer.
You can get it from Cisco.

It is a network simulator.
It comes with networking tutorials and scenarios.
You can view network data information as it travels through a simulated network.

stubbyhs · 14 Dec 2011

Yeah messin around with it now thanks!