[lwip-users] Re: [lwip] Compression of fields....

[Muhammad Ashraf]

Hi

When you have negotiated the LCP with Address and Control field Compression
and Protocol field Compression options,
in the next phase like PAP.You will not include 0xFF03(Address and Control
field) in your packet but you have to include 0xC023 for PAP as protocol
field and similarly for IPCP phase you have to include 0x8021 for protocol
field.
Now when PPP Connection is Up, next time for  IP packet your Protocol field
will contain 0x0021 if you did not negotiated Protocol field compression but
as you have negotiated Protocol field Compression, your packet will only
have one byte for it having 0x21.So one byte has compressed.

hope this will help

ashraf

----- Original Message -----
From: Omer Mohsin <address@hidden>
To: <address@hidden>
Sent: Tuesday, March 26, 2002 10:34 AM
Subject: Re: [lwip] Compression of fields....


> hi
> thanks for your reply. I am basically trying to dial ISP through C
> program. I am including these options in my connection extablishment
> phase. Now, I want to know how I can map 2 byte data into 1 byte? I mean
> the mapping to be used. RFC 1661 does not explain the mapping. Like our
> next protocol is PAP whose code is c023 and requires 2 bytes, so how I can
> write c023 in 1 byte.
>
> Thanks,
> Omer Mohsin.
>
>
>
> On Tue, 26 Mar 2002, Muhammad Ashraf wrote:
>
> > Hi
> >
> > In order to Compress Protocol field and Address and Control field to one
byte, You must have to negotiate these options during PPP Connection
establishment phase.
> > These Options are negotiated during LCP phase of Connection
establishment.You have to
> > include these two options in your LCP configure request packet.
> >
> >                                     i) Address and Control field
Compression
> >                                     ii) Protocol field Compression
> >
> > You can found the packet format and other details related to PPP in the
Rfc 1661.
> >
> > hope this will help you.
> >
> >
> > ashraf
> >   ----- Original Message -----
> >   From: Omer Mohsin
> >   To: address@hidden
> >   Sent: Monday, March 25, 2002 6:16 PM
> >   Subject: [lwip] Compression of fields....
> >
> >
> >   Hi,
> >
> >   I appreciate your support. I am not building PPP for lwip, instead I
am doing my Final Year Project of sending mail through embedded system.
Currently I am trying to send e-mial using C++ program. I have evetually
solved CRC problem, but now I am facing problem regarding Address and
Control field compression and Protocol field compression. I'll appreciate if
any of you may inform me about that. I want to know how we can convert 2
byte data into 1 byte (the mapping involved). Which RFC or site can help me?
> >
> >   Thanks,
> >   Omer Mohsin Mubarak.
> >   Faculty of Electronic Engineering,
> >   GIK Institute, Topi. Pakistan
> >
>
> [This message was sent through the lwip discussion list.]

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