[e2e] TCP Option Negotiation
braden at ISI.EDU
Thu May 17 09:15:37 PDT 2001
*> From hari at chive.lcs.mit.edu Thu May 17 08:57:44 2001
*> To: Bob Braden <braden at ISI.EDU>
*> cc: end2end-interest at postel.org
*> Subject: Re: [e2e] TCP Option Negotiation
*> Mime-Version: 1.0
*> Date: Thu, 17 May 2001 11:57:39 -0400
*> From: Hari Balakrishnan <hari at chive.lcs.mit.edu>
*> > Alex,
*> > This seems to be another manifestation of the standard problem of old
*> > duplicate packet. Your scenario is a violation of TCP's "quiet time"
*> > requirement upon host crash and restart (it's the same host if it has
*> > the same IP address). Quiet time is a vital part of TCP's machinery to
*> > protect against old duplicates.
*> Not quite.
*> Unfortunately the statement: "it's the same host if it has the same IP address"
*> is increasingly untrue because of dynamic IP address assignment (e.g., via
*> DHCP). This may well be a theoretical problem, but I've observed (in my home,
*> from my FreeBSD DHCP server), turning off a laptop and turning another one on,
*> and having the latter receive the former's IP!
No, my statement is exactly true as far as TCP is concerned; it is the
IP address that identifies the host. You are saying that immediate
reuse of IP addresses is a fact of life. OK, we have built an Internet
that consistently violates TCP's reliability mechanism. That should be
a cause of concern to somebody...
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