SSh internal window size.. (again)

From: Julian Elischer (julian_at_vicor.com)
Date: 04/29/04

  • Next message: Eric Knauel: "Delegating GSS credentials fails"
    Date: Wed, 28 Apr 2004 17:54:02 -0700
    To: secureshell@securityfocus.com
    
    

    sshd:
    openssh version sshd version OpenSSH_3.5p1 FreeBSD-20030924
    ssh:
    OpenSSH_3.5p1 FreeBSD-20030924, SSH protocols 1.5/2.0, OpenSSL 0x0090701f

    So, I'm ssh-ing data from machine A to machine B using sftp.

    with ping times of 60ms, I can't get over 600KB/sec

    looking at the SYN packats going over the wire, the negotiation looks like:
    A->B S 1041192722:1041192722(0) win 65535
        <mss 1460,nop,wscale 2,nop,nop,timestamp 20289777 0> (DF)
    B->A S 1916098679:1916098679(0) ack 1041192723 win 57344
        <mss 1460,nop,wscale 0,nop,nop,timestamp 616601895 20289777> (DF)

    the recv and send default buffer sizes are set to 128K, on both sides
    window scaling is enable on both sides,
    so one would think that larger windows would result and data would flow
    faster, but..
    no. it looks as if..

    (1) there is an internal windowing going on in the ssh protocol with a 64K
      window size.. Is this changeable?).

    (2) sshd opens it's socket with a 57KB window anyhow, despite the
    higher default window size.. is this true?

    Can these things be changed? it's be nice to be able to use ssh
    to transfer data at the available bandwith..


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