followup on TCP stuff.
Bill Manning
bmanning at ISI.EDU
Wed Jun 9 22:06:47 UTC 1999
> Bill,
>
> Can you forward my reply here, and
> tell Nanog'ers to check TCPIMPL for
> more info?
>
> Thanks,
>
> Joe
>
>
> > >To: alan at globalcenter.net, nanog at merit.edu, tcp-impl at lerc.nasa.gov
> > >Subject: Re: TOS issues with non RFC compliant TCP stacks
> > >Cc: touch at ISI.EDU
> > >
> > >> From owner-tcp-impl at lerc.nasa.gov Tue Jun 8 23:27:07 1999
> > >> Date: Tue, 8 Jun 1999 22:45:11 -0700
> > >> From: Alan Hannan <alan at globalcenter.net>
> > >> To: nanog at merit.edu, tcp-impl at lerc.nasa.gov
> > >> Subject: TOS issues with non RFC compliant TCP stacks
> > >...
> > >> It has come to our attention that a notable fraction of the
> > >> internet client community uses a TCP stack which is not RFC
> > >> compliant, as far as we can determine.
> > >>
> > >> Certain versions of MacTCP send a RST when they receive SYN ACK
> > >> packets of TOS!=0.
> > >
> > >Far as I have found, the spec (STD7) says that TOS is a TCP
> > >per-connection property (page 12).
> > >
> > >On page 36 it appears to clearly state that (case 2):
> > >
> > > terminated then). If our SYN has been acknowledged (perhaps in this
> > > incoming segment) the precedence level of the incoming segment must
> > > match the local precedence level exactly, if it does not a reset
> > > must be sent.
> > >
> > >> So, the empirical part: We implemented TOS bit-setting for the
> > >> purpose of tracking traffic flows and traffic levels. For an
> > >> entirely arbitrary reason, we chose TOS=5 for the default of
> > >> traffic. We found that MacTCP ceased functioning. The MacTCP
> > >> stack would initiate an RST when receiving SYN ACK packets with
> > >> a TOS=5, as the SYN packets had a TOS=0. Therefore, all TCP
> > >> sessions would fail.
> > >
> > >Granted, this is a first cut read, but wouldn't this appear
> > >to indicate that NOT sending the RST is the violation of the
> > >spec?
> > >
> > >Can you clarify?
> > >
> > >Joe
> > >
--bill
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