purohit_810 Fri, 08/31/2007 - 10:45

As in small word we can say.. PPP use error correction and detection work vary on wich WAN machinisam you use on it also.

But ideally IT doesn't do error correction at LAYER-2.

PPP is designed for simple links which transport packets between two peers. These links provide full-duplex simultaneous bi-directional operation, and are assumed to deliver packets in order. Although PPP is not tied to a particular type of packets it transports, its most common use is the encapsulation of IP packages over Modem lines. Basically, PPP is similar to SLIP, but it has the advantages of not being limited to one type of Protocol it can transport, a configuration negotiation phase at the start of a connection (for determining connection configuration parameters automatically), and the possibility to use standardized Authentication procedures for automated login. The two authentication schemes supported by PPP are PAP and CHAP.



Dharmesh Purohit

FbradleyS_2 Sat, 09/01/2007 - 18:10

I agree with your statement about PPP not performing layer-2 correction. Mohamed has an excellent description of how PPP performs some limited correction.

I appreciate your information. It has helped me clear up a very good question that was presented to me.

Mohamed Sobair Fri, 08/31/2007 - 10:54


PPP does support error detection & error correction at Layer-2 , here is the idea:

when you type the command (PPP reliable-link) interface command, it will watch packet specially UDP packet which is not reliable by default, so it if any error occurs it can detect and correct it.

Another great interface command is (PPP quality 80) , what this does, PPP will watch the sending bytes and check the receiving bytes at other end, so if there is lot of bytes missing it will gurantee 80% of Successful traffic deleviery. but it has withdraw, if the Successful traffic of sending & receiving went bellow 80%, then it will drop the connection.

The good thing is that (PPP quality percent) is configurable , so you can adjust it based on ur environment, people use it normally for Modem connections to ensure the quality of the lines.


Mohamed Sobair

FbradleyS_2 Sat, 09/01/2007 - 18:07

Thanks Mohamed! I appreciate the information and the additional commands.

Mohamed Sobair Sun, 09/02/2007 - 08:22

Hi Fabradley,

You are welcome, we all here to share information & Technical points with each other, This is the most credential point.

PS: Sorry for the delay reply as I was away,


Mohamed Sobair


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