Subject: Re: IP Tunneling I think ?
To: Michael Richardson <>
From: Andrew Brown <>
List: tech-net
Date: 01/27/1999 03:10:51
>    Andrew> ppp{ip{pptp{ip}}}

perry revied me.  i now thing it's ppp{ip{pptp{ppp{ip}}}}.  and it
seems (now that i've glared at the draft until it told me) that there
is also a "tcp control connection" to the pns (only microsoft could
come up with that acronym.  how would one pronouce that one? :).  i'll
"quote" section 4.3 of the draft.

  4.3.  Protocol Overview

  There are two parallel components of PPTP: 1) a Control Connection
  between each PAC-PNS pair operating over TCP and 2) an IP tunnel
  operating between the same PAC-PNS pair which is used to transport GRE
  encapsulated PPP packets for user sessions between the pair.

>    Andrew> 1) since ppp is your link layer between you and your
>    Andrew> provider...  2) ip gets the pptp packets (ip protocol
>    Andrew> number 47) from the pptp client to the pns (pptp network
>  I thought it was over UDP, but same difference. Open an IPPROTO_47 
>raw socket.

i don't think it makes much difference.  either way, the only
guarantee that the packets get there is that they probably won't get

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