Re: Higher level question about flow label

[Brian E Carpenter]

Michael Thomas wrote:
> 
> Brian E Carpenter writes:
>  > The point is that when a packet crosses an administrative domain boundary,
>  > the downstream ISP typically wants to reclassify the packet all over again,
>  > i.e. does not accept the incoming DSCP as definitive. This was a very
>  > clearly stated ISP requirement at the start of diffserv and is fundamental
>  > in the diffserv architecture.
> 
> Oh. I now see what I missed. Why doesn't including
> the SPI into the flow key work? You wouldn't be
> able to police based on port numbers (ie try to be
> a firewall), but some would say that's a feature
> not a bug.

That probably depends on your degree of paranoia about traffic analysis :-)

The SPI is certainly a possible way to identify a flow, but it doesn't help
you decide whether that flow needs real time or best effort service. 

   Brian
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