Path: utzoo!mnetor!uunet!husc6!mailrus!nrl-cmf!ames!pasteur!ucbvax!wb6rqn.UUCP!brian
From: brian@wb6rqn.UUCP (Brian Lloyd)
Newsgroups: comp.protocols.tcp-ip
Subject: Re:  Exchanging serial numbers
Message-ID: <8802281501.AA06953@wb6rqn.UUCP>
Date: 28 Feb 88 20:01:01 GMT
Sender: usenet@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 45

Thanks for the responses.  Most of the responses have been of a
philosophical rather than a technical nature but I appreciate them
anyway.  I guess that a further comment on the proposed serial number
exchange system is warrented.

The intention behind exchanging serial numbers is very simple: to keep
the software from being useful if it is copied.  It protects by
preventing an operator from gaining an advantage from the copy while the
original is still running.  In this way it is definitely a form of copy
protection.  The intention is to provide a scheme that will help protect
our software in a manner that is totally transparent to the user.  Any
protection system that in any way impedes the operations of a legitimate
user is not acceptable to us (I don't like copy protection schemes
either but I do want to protect our software).

We accept this scheme as being imperfect but useful and, as such, worth
our time to implement.  In the environment where we operate (Convergent
Technologies workstations) this will be an effective protection scheme.

As for two clients running in the same host, we have dealt with that
problem.  In our implementation of the protection scheme we bother to
exchange serial numbers only of the source and destination addresses are
different.  Should the remote system fail to return the serial number
option the connection is permitted.  The remote system has identified
that it is not one of our software implementations simply by the
omission of the serial number option in the TCP options field. 

We have never bothered to deal with multi-homed hosts since our software
assumes a 1-to-1 correspondence between a host and an IP address.
Although that is not the case with all systems in the Internet, it is
with our software.

Now I will ask my original question again.  Will the appearance of a
strange option in the TCP header cause a problem for other
implementations of TCP?  I want to know if my serial number exchange
will confuse other TCP implementations or will they just ignore and
discard the information as I suspect they should.  As I stated in my
second paragraph, we want the protection to be transparent and if it
prevents connectivity we won't use it.

Brian Lloyd, President
Sirius Systems, Inc.
(301) 540-2066
{bellcore, syscad, cp1, irs3, n3dmc}!wb6rqn!brian
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