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Home > Archive > CCNA > September 2003 > Ppp?
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| justindu 2003-09-17, 3:20 pm |
| I have seen different study materials show PPP defined at Layer 1 and 2, and Layer 1, 2 and 3..
Does anyone know the right answer?
Thanks,
Justin | |
| asteheske 2003-09-17, 4:04 pm |
| While PPP is considered a data link(Layer 2) layer protocol,it does offer both physical and network layer services(Layer 1 & layer 3)
THe basic purpose of PPP is to transport Layer-3 packets across a Layer 2 point-to-point link.
PPP have 4 main components :
1)EIA/TIA-232-C:
-A Physical Layer International standard for serial communication.(RS 232)
2)HDLC :
-A method for encapsulating datagrams over serial links
3)LCP:
- method of establshing,configuring,mainta
ining and terminating point-to-point connection
4)NCP :
-a method of establishing and configuring differetn Layer 3 protocols.
Having said that,it is Important to note that the PPP protocol stack is specified at Physical Layer & Datal Link Layer (Layer 1 & Layer 2)only
NCP is used to allow communications of multiple
Network Layer (Layer 3) protocolby encapsulating the protocols across a PPP data link
::Hope this helps::
Cheers~~ | |
| edmonds_robert 2003-09-17, 9:27 pm |
| NCP may encapsulate network layer protocols, but that doesn't make it a network layer protocol. Remember, as data moves down the protocol stack on the sending station, it goes through all of the lower layers. If we used that definition for everything, Ethernet would be an application layer protocol because my e-mail moves across an Ethernet network.
The basic rule I use is, if it can't be routed, it ain't network. |
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