Re: [ns] goodput for TCP connection

[Eric Weigle <ehw@lanl.gov>]

Hello-

> However, nrexmitpack_ does not seems to work for TCP Vegas. Can anyone tell me
> whether it's a program omission or I have done something wrong ?
I don't think the problem is with nrexmitpack_ unless you have some data with
improper numbers. There is, however, a known bug concerning ndatapack_ in the
TCP vegas implementation of 2.1b6 which has been mentioned a couple times on
this list. This would obviously cause goodput calculations (ndatapack_ -
nrexmitpack_) to go astray.

Here's the bug: there is a line is missing from tcp-vegas.cc around line 440, in
the output function:
----------
    /* support ndatabytes_ in output - Lloyd Wood 14 March 2000 */
    int bytes = hdr_cmn::access(p)->size(); 
    ndatabytes_ += bytes; 
MISSING:  ndatapack_++;
    send(p, 0);
    if (seqno == curseq_ && seqno > maxseq_)
        idle();  // Tell application I have sent everything so far
------------

I don't know if it's been fixed in the snapshot yet, but if you just add that
'ndatapack_++' and recompile ns things should work.

-Eric

--------------------------------------------
 Eric H. Weigle   CCS-1, RADIANT team
 ehw@lanl.gov     Los Alamos National Lab
 (505) 665-4937   http://home.lanl.gov/ehw/
--------------------------------------------