>>> michael rabinovich <misha@research.att.com> 09/07/99 07:47AM >>>
>> From fberzau@novell.com Mon Sep 6 06:52 EDT 1999
>>
>> A reverse cache is not by definition "controlled by a content provider".
>>
>> In most cases this will be the case. But it does not need to be. Everyone can set up an accelerator everywhere. Just as an example, we usually set up an accelerator (reverse cache) for www.novell.com in technical trainings. Or, yet another example, internally I've setup accelerators for various popular sites on a test server. By using a reverse cache internally Ican improve performance dramatically. All I need to do is "hack" the dns entry, so with my browser I access the reverse cache instead of the origin server on the internet (or I simply access the reverse cache by ip address). I'm doing it for example with my own website, which is hosted at an outside internet service provider, who doesn't even know that the site is reverse cached.
>>
>> The point is, a reverse cache MAY (and will most likely be), but definitely MUST NOT be under the same administrative control than the origin server that it accelerates. I would define a "reverse cache" as a device that acts on behalf of the origin server. The dns record for the server is modified so that it points to the reverse cache instead of the origin server. The reverse cache will fill the cache from the origin server for any requests coming in. It is using the same algorithms than the forward cache to control object freshness.
>>
>> Frank
>>
>I think we are talking about the same thing, and the misunderstanding
>confirms that my wording was sloppy. I did not mean necessarily
>administrative control in a narrow sense that the origin server and
>the reverse proxy share the same ISP or corporate network. The main
>thing is that
>clients or client ISPs are oblivious to the reverses proxy: it is the
>responsilibity of the content provider to deliver requests to it.
>Also, since content provider MUST
>be aware of the reverse proxy, it can implement all sorts of things
>like strong cache consistency, usage reporting, etc. In other words,
>it can have as much *control* over the reverse proxy as it chooses.
>The fact that
>the reverse proxy may reside in a different ISP does not change the
>fact that the content provider has control over it.
>Your examples fall right into this. If you agree with the meat of it,
>we can work together on the exact wording.
>Your wording suggestion that a reverse proxy acts "on behalf of the
>content server" looks too vague to me. I'd say that the forward
>proxy (esp. the transparent one) acts on behalf of the end-server as
>well when sergving the object for the cache (and impersonating the
>end-server).
I'll argue the agency role of a reverse proxy isn't germane to the definition of what a reverse proxy is. The agency role is determined by the network authority hosting it and the policy assigned by that authority.
A classic case is one of surrogacy, in which the reverse proxy (accelerator) is acting in behalf of the content provider, either in the content providers network, or as a delegate in a content distributors network. This begs for the completion of the term SURROGATE.
>Also, putting into the definition a particular mechanism (DNS-based)
>for delivering requests to the reverse proxy is too narrow.
>For example, we here at AT&T were seriously considering using WCCP at
>the access routers to transparently divert requests from our users to
>reverse proxies. (We currently decided in favor of DNS solution,
>but it does not change my point.)
And here is another case, in which the reverse proxy is under the authority of a consumer network acting in behalf of the consumers.
It looks like we are converging on a definition for reverse proxy. Lets try and wrap this up. Will one of you, either Misha or Frank submit a edited definition for the group to review?
We'll need to tackle the definition for SURROGATE next. With it in place, we can then document the roles reverse proxies are commonly delpoyed in.
The following was listed as a surrogate advantage in the BOF chaired by Ted Hardie at the 4th Web Caching Workshop. Does anyone like this as a starting point for the definition of a surrogate?
"Surrogates work on behalf of a content provider, so a business relationship exists for traffic analysis, copyright, and authentication"
>>
>> >>> michael rabinovich <misha@research.att.com> 05.09.99 4.11 >>>
>> Here are my definition drafts. Apologies if wording is sloppy in some
>> places - this can be corrected at a later time. Your examples
>>
>> Misha Rabinovich.
>> A reverse cache is the cache that is controlled by a content provider.
>> ^^^^^^^^^^^^^^^
>> It is the responsibility of the content provider to deliver requests
>> to the reverse cache. Clients are oblivious to the existence of
>> reverse caches.
>>
Gary
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