[e2e] TCP Option Negotiation

Vernon Schryver vjs at calcite.rhyolite.com
Thu May 17 10:32:29 PDT 2001

> From: Hari Balakrishnan <hari at chive.lcs.mit.edu>

> > 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!

But have you seen this happen within an MSL?  I thought the ISC dhcpd
had more than hysteresis than that, if only by virtue of the lease time.

If you have, then you've seen vastly more likely problems, such as
floods of ICMP Port Unreachables and TCP RST's.

Vernon Schryver    vjs at rhyolite.com

More information about the end2end-interest mailing list