[Cerowrt-devel] [Cerowrt-users] QOS settings vs speedboost and random bandwidth

Michael Richardson mcr at sandelman.ca
Mon Nov 26 16:27:47 EST 2012

>>>>> "dpreed" == dpreed  <dpreed at reed.com> writes:
    dpreed> It observed the IPv4 headers of *large* TCP/IP datagrams
    dpreed> going upstream, so that it could construct "no-op"
    dpreed> "content-free" datagrams that would certainly pass muster
    dpreed> through all the filters and be routed exactly the same as
    dpreed> the TCP/IP datagrams  that were carrying large flows.  It
    dpreed> would remember only the most recent one. 

I don't know that you need to be so precise in creating the packet, but
I guess the point is not just the ACLs, but also any traffic shapers?

    dpreed> The TTL expiration causes an ICMP packet to be sent back.
    dpreed> My code intercepts that packet based on its contents, and
    dpreed> removes it as "handled" before it gets processed by the
    dpreed> TCP/IP state machines. 

This is perhaps the biggest problem with this method... having to remove
the magic ICMP so that it does no harm.  Without this requirement, it
could be done entirely in userspace I think.

]       He who is tired of Weird Al is tired of life!           |  firewalls  [
]   Michael Richardson, Sandelman Software Works, Ottawa, ON    |net architect[
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