Re: Distribution CPG Protocol

[Oliver Spatscheck <spatsch@research.att.com>]

Phil,
Alex,

	as you might guess I disagree with this conclusion. Let me explain
why. However, first let me clarify that we (I and others at AT&T) are mainly
interested in: Peering between CDNs. Phil is writing about the content
provider who unless he is also a CDN is not part of the peering process
according to our architecture.

To continue Phil's online offline argument let me bring it to an
extreme. Since we already negotiate capacity off line on a daily basis (we
have to account for events like the superbowl, new customers of the CDNs
etc..)  why do we have to negotiate which content goes where dynamically. Just
after finishing our daily personal capacity conference call give your peers a
printed list of URL's (maybe you can put it on a floppy ...). Oh yeah, and for
accounting just give them the paper bill that day.  AT&T always encourages the
use of long distance FAX.

Now somewhat more serious. The way our peering currently works is by making
off line capacity arrangement with near real time (within minutes) load
feedback. However, as the off line billing we use the off line capacity
reservation will not scale. I think we are perfectly fine negotiating the
more static nature of a peering SLA (like proximity, cost, ...) off
line, but at least the capacity should be an online process since in a
CDN to CDN peering arrangement we have to change the capacity we
use very frequently (at least once a day).

I would also be perfectly happy if we use the proposed 3 stage approach (or
something similar) in which a legal capacity value is "best effort". (This
could be the only capacity value a CDN has to support to be compliant.)
However, I strongly believe that the protocol should support a simple capacity
reservation and I don't see why this would make the protocol overly complex if
it is not the mandatory behavior. (I assume of course that all CDNs which
want to peer with us will eventually support it ...)

Another note is that in many CDNs capacity reservations on the caches are
already possible. Another observation is that for typical Web traffic
the storage requirement on the cache is rarely the bottleneck on a CDN.
This of course changes as soon as we talk about multimedia traffic.


Oliver