Part II of Re: On-Rev Web Form Dropping Data

Richard Gaskin ambassador at
Thu Dec 2 17:50:29 EST 2010

Gregory Lypny wrote:

 > Yesterday I posted a long question (sorry about that) concerning
 > data lost from a web form submitted through my On-Rev site, where
 > two students appear to have submitted quiz answers from the same
 > IP address at virtually the same time.  Bob Sneidar replied asking
 > whether I had accounted for the possibility that more than one
 > person could sign on to my site from the same IP, and I had said
 > that I have not prohibited that.
 > Well, I have since spoken to the students who submitted blank
 > quizzes, and it turns out that they live together, share a wireless
 > network, and each has her own computer.  This probably means that
 > they have their router set to share a single IP address or some
 > such thing.  I guess what I should do is revise by sign-in script
 > to disallow multiple sign-ins from the same IP.

Most routers have a router that presents a single IP to the outside 
world even though internally transactions are mapped to individual 
computers inside the firewall.

Given that, any method of limiting access by apparent IP risks limiting 
people who are legitimately using separate computers but just happen to 
share the same firewall.

If the cookie is set during authentication, why bother with IP 
restriction at all, why not just use the cookie?

  Richard Gaskin
  Fourth World
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