IP address allocation

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2 total messages Started by Wong Chee Heng Thu, 27 Aug 1992 07:21

#82

Author: Wong Chee Heng
Date: Thu, 27 Aug 1992 07:21

11 lines
718 bytes

I am new to this group and do not know much about PPP. I just want to know 
how IP address is allocated in PPP, does the end user has to set it of the 
host being dialed can actually allocate before hand? 

Also what are the advantage of PPP over slip? Is there a FAQ somewhere that 
I can find answers to my questions? Thank you.


--
Wong Chee Heng
Systems Programmer

Re: IP address allocation

#86

Author: Bob Sutterfield
Date: Thu, 27 Aug 1992 18:10

45 lines
2860 bytes

In article <1992Aug27.072154.20745@nuscc.nus.sg> ccewch@nuscc.nus.sg (Wong Chee Heng) writes:
I just want to know how IP address is allocated in PPP, does the
end user has to set it of the host being dialed can actually
allocate before hand?

PPP provides the mechanism, but the implementation and the user must
specify the policy.

Here's the mechanism: Before exchanging IP packets across a PPP link,
the peers must agree on link parameters like packet size, control
character encoding, etc. during the LCP (Link Control Protocol)
negotiation phase. Then they must agree on IP addresses and TCP
header compression parameters during the IPCP (IP Control Protocol)
negotiation phase. Then they're finally ready to exchange user data
packets. (By the way, all this negotiation happens very quickly,
typically requiring only two packet round-trip times, which amounts to
a few tenths of a second over dial-up modems.)

Here's the policy: whatever semantics you want to attach to the values
agreed upon during IPCP negotiation. For example, a calling peer and
an answering peermight tell each other their addresses, but at least
the calling peer already knew the answering peer's address before
calling (how else would it know that it wanted to call?). Or maybe
the calling peer waits for the answering peer to say what the
answering peer wants the calling peer's address to be, and then the
calling peer configures itself accordingly.

If the PPP package is flexible enough, the user can implement just
about any policy {s}he can imagine. Consider what you could do with
creative DNS hacquery and a shell (or Perl) script, wrapped around a
PPP invocation...

Also what are the advantage of PPP over slip?

Read the Deficiencies section of RFC 1055, and the Introductions of
RFCs 1331, 1332, and 1333. You may also find some useful comparisons
in the paper I presented at last December's Sun User Group conference.
Get ftp.uu.net:vendor/MorningStar/papers/sug91-cheapIP.ps.Z.

Is there a FAQ somewhere that I can find answers to my questions?

Ed Vielmetti was maintaining merit.edu:pub/ppp/emv-ppp-faq-0.1.txt for
a while, but it hasn't been updated recently. Still, it's fresh
enough that you should be able to find something useful by using its
pointers.

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