Slow sftp/scp access despite fast network

From: Kris Harris (kjharris_at_sdf.lonestar.org)
Date: 11/27/05

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    Date: Sun, 27 Nov 2005 01:22:49 +0000 (UTC)
    To: secureshell@securityfocus.com
    
    

    Hello, trying to track down this problem. Between two computers
    (gutowksy,ramsey), I get quite reasonable access via web (wget measures
    578.09 KB/s, with ramsey serving), but when transferring via sftp or scp,
    the access crawls to a halt (starts at 30 kb/s then stalls, jumps to 30
    kb/s then stalls ...). It takes 1 min to transfer a file via wget, but 3/4
    of an hour via sftp!? Iperf also measures a reasonable connection rate
    between the two)

    the problem persists from various boxes running a range of openssh
    versions connecting to gutowksy (can't transfer in reverse using ramsey's
    sftp-server which works, because it's behind a firewall I don't control
    ...). So, it seems that the OpenSSH_3.5p1 pat OpenSSH_3.* running on
    gutowsky is failing somehow (installed as corresponding redhat package).
    Anyway, I then compiled a new version (openssh-4.2p1.tar.gz) and ran it on
    a different port (just so I don't lock myself out - gutowsky's several
    hundred miles away!) - but found no change at all. Any ideas?

    p.s. I saw the message-list-archive post about slowness on solaris,
    and tried altering misc.c to become:
    /* disable nagle on socket */
    void
    set_nodelay(int fd)
    {
             int opt;
             socklen_t optlen;

             return;

    ...

    }

    -> i.e., I just through in the return as suggested (to jump out of
    subroutine?)

    kjharris@sdf.lonestar.org
    SDF Public Access UNIX System - http://sdf.lonestar.org


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