[Tmrg] TCP evaluation suite round-table

[Lars Eggert]

Hi,

On 2007-8-21, at 7:36, ext Lachlan Andrew wrote:
> Can we assume that Moore's law now allows Dummynet to run at
> 622Mbit/s?  If so, I'd strike 400Mbit/s off in favour of OC12.

during my thesis, I found that dummynet doesn't simulate high- 
datarate paths very accurately anymore once the CPU becomes loaded:

    However, simulating wide-area Gigabit links with Dummynet
    is problematic [ZEC2003]. Dummynet uses the kernel firewall
    to identify packets for processing, and depends heavily on
    the kernel timers to control when packets leave the
    transmission buffer. Both mechanisms incur significant
    overheads at high data rates. Furthermore, high data rates
    cause high interrupt loads, which can decrease system
    responsiveness and eventually lead to livelock [MOGUL1997].
    Because Dummynet processing occurs at the IP layer, device
    interrupts cause delays that reduce the accuracy of the
    simulation. These delays can also interfere with user-space
    processing, and as a result affect the benchmark processes
    themselves.

    [ZEC2003] Marko Zec and Miljenko Mikuc. Real-Time IP Network
    Simulation at Gigabit Data Rates. Proc. International
    Conference on Telecommunications (ConTEL), Zagreb,
    Croatia, June 11-13, 2003.

As you said, Moore's law may have pushed up the region of bandwidth  
that can be accurately simulated, but it'd be good to have some  
verification.

Lars
-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/pkcs7-signature
Size: 2446 bytes
Desc: not available
Url : http://mailman.ICSI.Berkeley.EDU/pipermail/tmrg-interest/attachments/20070821/c6095385/attachment.bin