*BSD News Article 34170


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Newsgroups: comp.os.386bsd.questions
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From: gordon@sneaky.lonestar.org (Gordon Burditt)
Subject: Re: PPP
References: <30n5qj$3s1@portal.gmu.edu> <michaelv.774892571@ponderous.cc.iastate.edu>
Organization: "Gordon Burditt"
Date: Fri, 5 Aug 1994 18:56:59 GMT
Message-ID: <Cu2sMz.12M@sneaky.lonestar.org>
Lines: 72

Is there a way to get fully automatic PPP?  I may be asking for the moon
here, but I'd like to be able to set up PPP so that the connection
is established and disconnected as needed.

- Routing is set up when the system is booted without necessarily needing
  to set the link up at this point.  Daemons get started as needed.
- The PPP connection is established when needed for useful traffic by 
  dialing an internet services provider and logging in.  Provision is
  made to try alternate numbers, alternate modems, and alternate
  internet services providers.
- PPP can be connected over any dialout line allowed and not in use.
  (You probably don't want it running over a 1200 modem).  Potentially
  these are different modem types (different dialing methods) at 
  different speeds.  It uses locks so it can co-exist with UUCP 
  outdial and logins.
- If the connection drops and there is traffic, it will redial on
  the same or a different line.
- Since a lot of the modem dialing and line info is also used by UUCP,
  it would be nice if they could share some of the control files.
- The PPP connection is disconnected after a user-configurable period
  of time (e.g. a few minutes) with no useful traffic.
- Traffic can be classified by user configuration into three types, 
  "useful", which calls for establishing or keeping established a PPP 
  link, "non-useful", which is allowed when the link is up already but
  is not cause for establishing the link and gets dropped if the link is
  down, and "forbidden", which is not allowed on the PPP link at all.
- Examples of "non-useful" traffic include broadcast messages, NTP, rwho,
  and other stuff I haven't thought of that would generate periodic traffic
  and keep the link up all the time without accomplishing much.
- Examples of "useful" traffic include SMTP, ftp, NNTP, NFS,
  nameserver queries, telnet, and most other services which should start
  up a PPP link if it's needed.
- Examples of "forbidden" traffic would mostly depend on the security
  environment, would probably duplicate the function of a "firewall",
  and might include incoming telnet, incoming ftp, incoming rlogin, etc.

- It should be possible to disconnect the link while keeping logical
  connections alive.  For example, I nfs-mount a server's file system
  read-only, copy a few files to a local disk, start compiling them 
  (which no longer requires the remote file system), the link times out 
  and disconnects.  An hour later I discover I forgot a few files, start 
  copying them and the link comes up again (no remount required).  I
  ftp to another site and start a big transfer, then go to lunch.  The
  link drops when the transfer is done, but leaves the ftp session up.
  (Yes, I know hogging ftp sessions on public-access servers is anti-social 
  if done for a long time.) Yes, I'm leaving open the possibility of 
  having NFS mounts, FTP sessions, telnet sessions, etc., staying up 
  for weeks and months using only minutes of internet-service-provider time.

- When the link isn't being used for PPP, it can be used for outgoing
  UUCP or tip, incoming UUCP, or incoming PPP from the service provider
  if the provider is willing to do that.  If the link's not available
  when needed (on the same line or a different one), the packets get 
  dropped and whatever sent them times out eventually.  This means that
  a network session can potentially stay up through (external) modem 
  replacements, phone line replacements, phone company central offices 
  burning down and being rebuilt, and Internet Service Providers 
  going bankrupt and being replaced (assuming I can keep my IP address).
  

How much of a pipe dream is this?  Is establishing a ftp session going to
be possible if the first packet sent through (bringing the link up)
takes a minute to transmit?  Are TCP "keepalives" going to keep the link
up all the time anyway?

In what areas does the existing PPP implementation (pick your favorite
platform:  FreeBSD, NetBSD, Linux) fall short of what I want, and
is it possible (with lots of work, probably) to add it?  Without
kernel mods other than the usual reconfiguration?

						Gordon L. Burditt
						sneaky.lonestar.org!gordon