Comments on architecture doc, Sect. 5

["Mark Day" <markday@cisco.com>]

draft-green-cdnp-gen-arch-01.txt

Section 5:

> CDN peering must provide the ability for the content provider to
> collect data from surrogates that are delivering their content
> directly to clients.

This doesn't seem right. What a content provider needs is information about
content delivery, yes.  It's collected at surrogates, yes. But this makes it
sound as though the content provider is collecting data directly from
surrogates, which is certainly not what I thought we would support.

Also, it seems redundant to talk about a surrogate delivering content
"directly to clients". A surrogate is a content-delivery node, end of story;
I don't think we need to muddy the issue by talking about "directly" (does
that mean no proxies? Somehow I doubt it...) etc.

> ACCOUNTING CPGs retrieve the data from
> SURROGATEs that collect and store the data locally. This interior
> data may be collected from the SURROGATEs by ACCOUNTING CPGs using
> SNMP or FTP, for example.

Is it always a "pull" by the CPG?  It seems reasonable that the data could
also be deposited directly to a CPG by the interior ACCOUNTING SYSTEM.

Since the SURROGATE role in accounting and storage is inside the CDN black
box, it would seem that we should say as little as possible about
how/whether the SURROGATEs collect or store data, and how/whether that data
is transferred from SURROGATEs to CPG.  I would think that what we can
actually define is a fairly abstract interface between a CPG and an
ACCOUNTING SYSTEM, and a very concrete protocol between two CPGs.

> ACCOUNTING CPGs transfer the data to
> exterior neighboring ACCOUNTING CPGs on request or in an
> asynchronous manner.

This needs to be tied into an overall model of how accounting data moves
between peered CDNs. Is it primarily driven by the source of the data
"pushing" data, by the sink "pulling" data, or do we have to support both
modes (and negotiate the mode at peering time)?

> Figure 4 ACCOUNTING PEERING system Architecture

Somewhere the document should indicate that the rightmost CDN could also
have SURROGATES, they're just omitted to simplify the diagram.  Right now it
looks as though the BILLING ORGANIZATION has to be connected through an
ACCOUNTING CPG with no SURROGATES.

I don't think the other CPGs should be directly connected to SURROGATEs. I
thought that the ACCOUNTING CPG would be connected to an ACCOUNTING SYSTEM,
which in turn is connected to SURROGATEs.

> In addition information needs to be exchanged between ACCOUNTING
> CPGs
  [....]
> applicability to CDN
> peering accounting.

This whole paragraph seems out of place in an Overview.  Maybe it fits
better into Problems or Requirements, maybe it needs a short section of its
own on the relationship to other IETF/IRTF work.

Much of the rest of Section 5 strikes me as having an unclear relationship
to the planned revision of the accounting document. Since that document will
talk about requirements and issues, shouldn't Section 5 basically identify
the place where ACCOUNTING CPGs fit in and then point off to the accounting
document for details?