[ntp:questions] Re: Strange IP flags set in NTP conversation

Michael Sierchio kudzu at tenebras.com
Wed Oct 15 02:40:48 UTC 2003

David -

> I wasn't aware the semantics of the TOS field had changed since I used
> those bits on the original NSFnet backbone network as of 1988. The D bit
> was set in NTP and TELNET packets and forced a route within the network
> rather than a roundabout path via ARPAnet. In any case, tcpdump shows
> Solaris sets the D bit in TCP packets now, presumably for the original
> purpose.

Relevant RFCs: 3168, 2481, 2474, 2401, 793, 791.

RFC 3168:

    The definitions for the IPv4 TOS octet [RFC791] and the IPv6 Traffic
    Class octet have been superseded by the six-bit DS (Differentiated
    Services) Field [RFC2474, RFC2780]

We'll be up to RFC 4000 in no time! Ack. Ppppt.

An intellectual historian of the Internet will probably make something
of the fact that RFCs are growing exponentially.

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