[Tmrg] Traffic Generators (Harpoon and Tmix)

[Constantine Dovrolis]

folks, my apologies for jumping into the discussion, but
1. I want to loudly agree with Sally that we should be
considering non-greedy TCP flows with heavy-tailed size
distribution, and
2. we should be asking whether these non-greedy TCP flows
are generated by an open-loop flow arrival process or by a
closed-loop process that takes user thinking times (and
perhaps limited patience) into account.

A couple of related papers:
http://www.cc.gatech.edu/fac/Constantinos.Dovrolis/Papers/ravi-openclosed.pdf
http://www.cc.gatech.edu/fac/Constantinos.Dovrolis/Papers/pam07-ravi.pdf

Constantine

--------------------------------------------------------------
Constantine Dovrolis | 3346 KACB | 404-385-4205
Associate Professor  | Networking and Telecommunications Group
College of Computing | Georgia Institute of Technology
dovrolis at cc.gatech.edu
http://www.cc.gatech.edu/~dovrolis/



Sally Floyd wrote:
>  From Michele:
>> Regarding the pauses that are part of the Tmix model, these pauses are
>> used to represent the time between complete application data units
>> (ADUs), which are essentially files.  If you were modeling HTTP
>> connections, for example, the 'a's would be requests and 'b's would be
>> responses.  You are right that Tmix can model persistent HTTP
>> connections, where there are pauses in a single connection.  If you
>> wanted to have a set of long-lived greedy TCP flows, you could
>> construct connection vectors to give you such behavior.
> 
> But if one wanted to use a realistic traffic model in one's scenarios,
> that would have to include non-greedy TCP traffic (e.g., HTTP 1.1
> traffic, telnet traffic or other user-generated data, etc.)   Non-greedy
> TCP traffic is not unusual in the real world, and can be a significant
> stressor on congestion control mechanisms that it would be a pity
> to ignore - e.g., TCP flows that *might* ramp up to a high sending rate,
> have a data-limited or idle period, and then continue with a lot of
> data to send again.
> 
> When we are measuring file completion times, we can use
> greedy TCP connections to measure them, in a mix with other traffic.
> 
> The heavy-tailed distribution of user wait times within TCP connections
> has been under discussion since 1994.  E.g., "Wide-Area Traffic: The
> Failure of Poisson Modeling", Paxson, V. and Floyd, S., SIGCOMM 1994
> (or the 1995 IEEE/ACM Transactions on Networking version).  And has
> been included in traffic models in ns-2 for many years (e.g., in Polly
> Huang's traffic generator listed in
> "http://www.icir.org/models/trafficgenerators.html".
> 
> - Sally
> http://www.icir.org/floyd/
> 
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