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    SubjectRe: Packet Scheduling
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    >>>>> "Mark" == Mark Shapiro <mark@award.bios.net>
    >>>>> wrote the following on Tue, 27 Jan 1998 14:59:03 -0500 (EST)

    >> Kevin Lentin writes:
    >> > What I want is for interactive telnet sessions to be responsive while an
    >> > ftp or http request is being processed. Under term, packets were
    >> > prioritised based on client. I'm expecting you can't do that in tcp but
    >> > size should be a good approximation.
    >>
    >> I haven't tried linux packet scheduling yet, but my guess is that, since
    >> the scheduler can only control transmit queues, interactive sessions'
    >> performance while doing FTP transfers over serial links will not be much
    >> improved. Am I right?
    >>
    >> Unless, of course, the other side is Linux too, which happens more and
    >> more often to me. ;)

    Mark> Given that FTP is usually ports 20/21, HTTP is usually 80, and
    Mark> Telnet is almost
    Mark> always 23, a packet scheduling based on port number, where port
    Mark> 23 is given
    Mark> the highest priority, and all other ports are given a lower
    Mark> priority,
    Mark> should be possible...

    It is. Using the firewall rules you can set the TOS bits. As Alexeej
    Kuznestov once expalined to me:

    Dumb applications does not set any TOS, so that normal data have
    priority 1. Telnet, rlogin (seems, almost all implementations) sets it to
    LOWDELAY and, hence, goes via band 0 (the highest priority).
    ftp sets LOWDELAY for control channel and HIGHTHROUPUT for data channel,
    that puts it to the lowest priority band (it is not quite corect,
    because ftp_data is not background channel, but the approximation
    is pretty good). The same thing is made by sendmail and
    innd(LOWMONETARYCOST is also mapped to band 2).


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