Changes between Version 24 and Version 25 of TmixDetails


Ignore:
Timestamp:
10/19/12 13:18:15 (7 years ago)
Author:
Ben Newton
Comment:

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  • TmixDetails

    v24 v25  
    33
    44== The a-b-t Model ==
    5 A TCP/IP header trace is obtained from a real-world link, and is then "reverse compiled" into a higher-level representation.  For every TCP/IP connection in the trace a connection vector is generated.  The connection vector represents an entire single connection between "''a''", the connection initiator, and "''b''", the connection acceptor.  The connection vector also stores the start time "''T''" of the connection. 
     5[[Image(TmixImages:tmixConnection.png, 450, right)]] A TCP/IP header trace is obtained from a real-world link, and is then "reverse compiled" into a higher-level representation.  For every TCP/IP connection in the trace a connection vector is generated.  The connection vector represents an entire single connection between "''a''", the connection initiator, and "''b''", the connection acceptor.  The connection vector also stores the start time "''T''" of the connection. 
    66
    77Rather than modeling the individual packets or TCP segments, Tmix instead uses inferences to characterize connections as a sequence of request-response exchanges between "''a''" and "''b''".  Each request or response transfers one application-data unit (ADU), which is a generic term for the object or protocol element being transferred.   Further, each exchange (request then response) is called an epoch, and includes the sizes of the ADUs transferred, and the requester side "think" or processing time, "''t''". 
    88
    9 [[Image(TmixImages:tmixConnection.png, 450, right)]] More formally, a simulation would consist of a set of ''n'' connection vectors ''C'',,1...''n'',,, starting at times ''T'',,1...''n'',,.  Each connection vector includes a set of ''k'' epochs, ''C'',,''i'',,=<''E'',,1,,,''E'',,2,,,..., ''E'',,k,,>, where each epoch is defined by ''E,,i,,'' = (''a,,i,,'',''b,,i,,'',''t,,i,,''). Each epoch includes ''a'',,''i'',,, the size of the ''i ''^th^ ADU sent from the connection initiator to the connection acceptor, ''b,,i,,'', the size of the ''i ''^th^ ADU sent from the connection acceptor to the connection initiator, and ''t,,i,,'', the "think" or processing time between the receipt of the ''i ''^th^ "response" ADU and the transmission of the (''i''+1)^st^ "request".  The figure to the right shows a connection that includes three epochs, with the important features of the a-b-t model labeled.  Note that Tmix does not require the any information from application layer headers. 
     9More formally, a simulation would consist of a set of ''n'' connection vectors ''C'',,1...''n'',,, starting at times ''T'',,1...''n'',,.  Each connection vector includes a set of ''k'' epochs, ''C'',,''i'',,=<''E'',,1,,,''E'',,2,,,..., ''E'',,k,,>, where each epoch is defined by ''E,,i,,'' = (''a,,i,,'',''b,,i,,'',''t,,i,,''). Each epoch includes ''a'',,''i'',,, the size of the ''i ''^th^ ADU sent from the connection initiator to the connection acceptor, ''b,,i,,'', the size of the ''i ''^th^ ADU sent from the connection acceptor to the connection initiator, and ''t,,i,,'', the "think" or processing time between the receipt of the ''i ''^th^ "response" ADU and the transmission of the (''i''+1)^st^ "request".  The figure to the right shows a connection that includes three epochs, with the important features of the a-b-t model labeled.  Note that Tmix does not require the any information from application layer headers. 
    1010
    1111== Workload Generation ==