Re: bug - tcp versus DV routing

["Guo, Liang" <guol@cs.bu.edu>]

Please see the solution that I put into this list last month.


On Thu, 2 Dec 1999, Lloyd Wood wrote:

> I'm using an ns snapshot of 6 November vintage here. I wanted to
> demonstrate multipath routing in action, but couldn't. The following
> script demonstrates the problem - only routing updates are recorded in
> the tracefiles, while the tcp/ack communications are purged from
> history. Comment out the line selecting the DV rtProto, and TCP
> returns.
> 
> So, either you can have DV routing, or you can have TCP
> communications. But not, it seems, both at once. No wonder TCP reacts
> so badly to route changes; no-one's examined it in simulation...
> 
> Anyone?
> 
> thanks,
> 
> L.
> 
> so, which test script validates multiPath_?
> 
> <L.Wood@surrey.ac.uk>PGP<http://www.ee.surrey.ac.uk/Personal/L.Wood/>
> 
> 
> # this script demonstrates that you can have tcp or DV routing, but
> # not both at once.
> 
> set ns [new Simulator]
> 
> # You're probably going to have to comment out the following line to 
> # get a tcp trace.
> $ns rtproto DV 
> 
> Node set multiPath_ 1
> 
> set f [open out.tr w]
> $ns trace-all $f
> set nf [open out.nam w]
> $ns namtrace-all $nf
> 
> set g0 [$ns node]
> set g1 [$ns node]
> set g2 [$ns node]
> set g3 [$ns node]
> 
> $ns duplex-link $g0 $g1 5Mb 2ms DropTail
> $ns duplex-link $g0 $g2 5Mb 2ms DropTail
> $ns duplex-link $g1 $g3 5Mb 2ms DropTail
> $ns duplex-link $g2 $g3 5Mb 2ms DropTail
> 
> # Attach agents
> set tcp0 [new Agent/TCP/Newreno]
> $ns attach-agent $g0 $tcp0
> set ftp0 [new Application/FTP]
> $ftp0 attach-agent $tcp0
> 
> $tcp0 set fid_ 1
> $ns color 1 Red
> 
> set null0 [new Agent/TCPSink]
> $ns attach-agent $g3 $null0
> $ns connect $tcp0 $null0
> 
> $ns at 3.0 "$ftp0 start"
> 
> $ns at 6.0 "$ftp0 stop"
> 
> $ns at 7.0 "finish" ; # keep it short 
> 
> proc finish { } { 
> global ns f nf
> $ns flush-trace
> close $f
> close $nf
> exec nam out.nam &
> exit 0
> }
> 
> $ns run
> 
> 

Guo, Liang 

guol@cs.bu.edu                     Dept. of Comp. Sci., Boston Univ.,
(617)353-8924 (O)                  111 Cummington St., MCS-217,
(617)375-9206 (H)                  Boston, MA 02215