Robert Elz wrote:
>
> Date: Wed, 15 Aug 2001 08:43:04 -0500
> From: Brian E Carpenter <[EMAIL PROTECTED]>
> Message-ID: <[EMAIL PROTECTED]>
>
> This is way outside my area, but ...
>
> | Well yes, but when the packet has an ESP header you are in trouble. The idea
> | of adding some semantics in the flow label is to deal with the ESP case.
> | If you aren't prepared to believe that field then of course all is lost
> | and you can only do address based classification.
>
> I think the point was that if you believe the data, then you can be guaranteed
> that people will cheat.
>
> Therefore you cannot believe the field.
>
> Therefore all you are left with is the address.
>
> (which is pretty much as you just said, but you left off the final step)
>
> Therefore it is pointless adding any semantics to the field, because
> even if there, they can't (won't) be used.
But there's a recursion here. If you choose to believe port and protocol
numbers, then all cheaters have to do is encapsulate their low priority
packets in what look like VoIP packets and they will get real time
performance. So whatever you choose to believe (except the destination
address) could be bogus.
It turns out this doesn't matter. If somebody cheats in this way, they will
pay the tariff for better QoS anyway - so why would the ISP care? I think
that is the rebuttal to Steve Blake's argument - customers pay for the service they
actually get, even if they are disguising their traffic. So sure they can cheat,
but they are the losers.
Brian
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