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From John Heidemann <jo...@ISI.EDU>
Subject updated version of paper about P-HTTP/TCP interactions
Date Tue, 13 Aug 1996 17:42:54 GMT

I've updated the web page about P-HTTP/TCP interactions to describe
the third problem I alluded to before, the potential to have 4.4BSD-
and Linux- derived TCP connections slow-start mid-stream.  This
problem cannot be worked around at the application level, so it's not
an immediate issue to Apache developers.

   -John Heidemann


    title: Performance Interactions Between P-HTTP and TCP Implementations
    url: <>


    This document summarizes several performance problems resulting from
    interactions between the Apache-1.1b4 implementation of
    persistent-HTTP (P-HTTP) and BSD-based implementations of TCP. Two of
    these problems tie P-HTTP performance to TCP delayed-acknowledgments,
    thus adding up to 200ms to each P-HTTP transaction. A third results in
    multiple slow-starts per TCP connection. We discuss each problem and
    summarize solutions.  Unresolved, these problems result in P-HTTP
    transactions which are 10 times slower than standard HTTP and 20 times
    slower than potential P-HTTP for machines connected by a 10 Mbps
    Ethernet. After fixing these problems we observe that P-HTTP
    successfully performs better than HTTP on a local Ethernet.

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