Re: [tsv-dir] Re: Transport Directorate review of draft-ietf-ipfix-imple

On 2007-9-6, at 12:01, ext Elisa Boschi wrote:
> > To be specific, how would an application using
> > IPFIX over UDP obtain the packet loss information needed to implement
> > TFRC as recommended in Section 3.1.1 of the UDP guidelines draft?
> > The IPFIX implementation guidelines draft says:
> >    The Collecting Process SHOULD use the Sequence Number in the IPFIX
> >    Message header to determine whether any messages are lost.
> > but I don't see how the Exporting Process can learn this information
> > in order to adjust its sending rate using TFRC (did I miss  
> > something?).
> > A discussion of how to implement TFRC or what to do on a dedicated
> > network when TFRC is not implemented would be useful.  The fact that
> > there was a working NetFlow implementation might be helpful in
> > configuring IPFIX to not congest the dedicated network.
> Right, so I've asked Paul Aitken from Cisco about it and this is  
> his answer:
> ---
>
> We don't take any active measures not to congest. Rather, we expect  
> the
> user to design their network well.
>
> We believe netflow export consumes 2-5% of the bandwidth of the  
> sampled
> traffic. So export over a dedicated 100M link should be able to  
> support
> netflow on 20-50 x 100M interfaces.
>
> IPFIX will be very similar.
>
> Looking at draft-ietf-tsvwg-udp-guidelines-02, I see TFRC recommended
> for "Bulk Transfer Applications" (section 3.1.1).
>
> However, I think that netflow and IPFIX export fall into the "Low
> Data-Volume Applications" category (section 3.1.2) which says:
I don't see IPFIX falling into this category. IPFIX will send many  
packets to a destination. (And even if IPFIX fell into this category,  
it'd need to implement congestion control mechanisms for low-datarate  
applications, which the draft also gives guidelines for.)
>     When applications that exchange only a small number of messages  
> with
>     a destination at any time implement TFRC or one of the other
>     congestion control schemes in Section 3.1.1, the network sees  
> little
>     benefit, because those mechanisms perform congestion control in  
> a way
>     that is only effective for longer transmissions.
>
> So I don't think discussion of how to implement TFRC for IPFIX/UDP is
> relevant.
>
> ---
>
> I agree with him on this.
>
> Would you be fine with this motivation? Maybe we could add a  
> reference to section 3.1.2 of the UDP guidelines in the text?
Lars

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