Re: Distribution CPG Protocol

[Oscar Ardaiz <oscar.ardaiz@upcnet.es>]

I think Stephen is right. 
I will try to make the L3 analogy, hope not to confuse anyone.

Dan Li content routing definition was good. From it route advertisement
can be either:a) content provider advertising its content, b) a CDN
advertising content that it is distributing c) a cache advertising
content to its siblings as in cache digests, or others. It is needed so
that clients can get content.

But we are interested in finding and selecting surrogates where to place
content. We want to create a number of "new" service points for content
X: surrogates A,B,D,F,G, so from now on content X can be fetched from
A,B,D,F,G. And this new routes have to be advertised afterwards so that
client can fetch content from there.

And the layer 3 network analogy would be: creation of a set of IP links
(either a new physical network or an overlay network) and advertisement
of routes so that traffic goes through it.
IP route advertisment is a subsequent step to network deployment.
In the same way, we first find a set of surrogates and configure them to
deploy our content service and later those locations are to be
advertised, through DNS.

Oscar

Stephen Thomas wrote:
> 
> This is an interesting perspective that is quite different from the one
> I've been stuck on. I can't completely connect all the dots, but I'm
> willing to explore it a bit.
> 
> I would characterize the main difference between Dan's perspective and my
> own as one of peer-to-peer vs. client/server. My view of the CDN peering
> problem was very definitely a client/server one. One CDN has surrogates
> (it's the "server"), and another CDN (or the content provider itself) has
> content (it's the "client"). In that view, it cannot be "the pair that gets
> advertised" since only the 'server' knows its surrogates and only the
> 'client' knows the content.
> 
> Now let me see if I can context-switch to a peer-to-peer perspective and
> ask intelligent questions.
> 
> At 05:48 PM 2001-01-12 -0800, Dan Li wrote:
> >At 04:33 PM 1/12/01 -0800, Tomlinson, Gary wrote:
> > >The fundamentals of advertising surrogates vs advertising content or both is
> > >clouding my thought processes at the moment.
> >
> >It's both. Take domain name as a simplified representation for content
> >(URL is more elaborate but you see names like "images.foo.com" that encode
> >a class of content into a name). Then, content routing is the task of
> >mapping a name to a location, similar to routing a IP to a location. Then,
> >a surrogate is mere a location for a *set* of names it supports.
> >
> >So a route advertisement would have these two parts:
> 
> So, what is a "route advertisement"? Is it a content provider advertising
> its content? Or a CDN advertising content that it is distributing? I kind
> think the latter, but it doesn't hurt to check. If that is the case, I have
> a couple of questions:
> 
> 1) This assumes that the content has already been distributed, right? I
> think that the issue I was dealing with was primarily how to get the
> content distributed in the first place? I guess, though, that a content
> provider with content on origin servers is a degenerate case.
> 
> 2) This approach seems to imply that CDNs exchange content with each other.
> But, if a new CDN wants to acquire content to distribute, wouldn't it just
> grab the content from the origin servers? It might learn about the content
> from another CDN, but it sure would be more efficient to get the content
> directly from the origin. (I can think of security/business associations
> that might, at first, create some obstacles, but I think those are actually
> fairly easy to solve.)
> 
> >1. "route to content set X is via next hop M to content server A with
> >metrics K", where A is chosen (based on metrics K) among other possible
> >destinations B, C, D, which all advertise support for the same set X).
> 
> Okay, what is the difference between M and A? Which one is the surrogate? I
> think A is the surrogate, but then I don't know what M represents.
> 
> Do you think the metrics K are an intrinsic property of the surrogate only,
> or are they a property of both the surrogate and the particular content? I
> sure would like to see something concrete for these metrics.
> 
> Stephen