Forwarding this to the list just so its in the archives. ---------- Forwarded message ---------- From: Larry Brigman <larry.brigman@xxxxxxxxx> Date: May 11, 2006 10:16 AM Subject: Re: HTB at 100+ Mbits/sec To: Muthukumar S <muthukumar@xxxxxxxxx> On 5/10/06, Muthukumar S <muthukumar@xxxxxxxxx> wrote:
Hello all, I've been trying to test HTB performance for different link bandwidths to find potential limits and this is what I have so far: http://home.comcast.net/~msethuraman/htbtest/ Can members please go over the setup, test procedure and the results and answer a few questions? 1. Is the testing methodology okay and can the results be considered accurate? If so, is this a decent representation of behavior outside the lab?
Iperf has a demonstrated behavior that when running more than one copy at the same time on the same box (client side); that the timing of each will start to effect the other copies. This is a function of how Iperf does it's timing (spin loops). If you are just wanting to test HTB, the router/bw limiter will be in the way of making accurate measurements of what HTB is doing to the traffic. Also with the router in the middle and using TCP; TCP will try to level itself to the path bw between the end points. UDP might be a better method here as you have no round trip.
2. Does anyone know of any limits (theoretical or observed) beyond which HTB will not work or will be inaccurate?
None that I know of. Most likely the limits will be that of the driver/hardware not allowing you to reach wire saturation (ie YMMV).
3. I've never quite understood the recommendation for setting the root HTB to 85-90% of the link. All these tests used 100%. Can someone please explain or point me to some explanations for the 90% recommendation and why it is considered necessary?
The basic reasoning for limiting to < 100% of link rate is to make sure none of the choke points on the path have any reason to discard your packets. The burst and cburst parameters allow HTB to overstep the limited rate for some period of time when coming from an under-utilized link. This burst rate may be enough for your cable/DSL modem which does not have a large buffer to discard packets. Most of what I have seen here seem to indicated that a 95-98% of link rate when using rate-shaping disciplines typically works well provided you don't have too large of burst parameters. _______________________________________________ LARTC mailing list LARTC@xxxxxxxxxxxxxxx http://mailman.ds9a.nl/cgi-bin/mailman/listinfo/lartc
