- From: Ted Hardie <hardie@thornhill.arc.nasa.gov>
- Date: Fri, 31 Jan 1997 11:01:43 -0800
- To: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com, mogul@wrl.dec.com, paulle@microsoft.com
First let me say that I appreciate all the work Jeff and Paul have done on this, and that I think the work item needs to move forward. As a counterpoint, though, I need to say that we really haven't had enough discussion about this in the working group. The design choices in this draft imply a lot about how proxies will work, how connection information might perdure, and what information dissemination model the web will use in commercial space. These are crucial issues and I think we need to focus on them. I've made a few comments below, but there are lots of talking points in the draft that require data that I don't have. I urge anyone with access to the proxy hierarchies that this would impact to report on their experience. I've made a few specific comments below, but I think they are only a portion of the broader discussion needed. Specific comments: For readability, I would move the section in 1.2 which describes what cache-busting includes into the Introduction; I believe it would help clarify what problem is being addressed. It's not clear to me what "no additional network round-trips in any critical path" means--where is definition of "critical path" in this context? In your design question in section 3.1, you note that having the origin server add the "Cache-control: proxy-mustcheck" to the response would get the proxies out of the business of adding headers to responses, and I think that this a very good thing. I am concerned, though, about exactly how to define the Connection: proxy-mustcheck (or max-age=0) header in that case, since the proxies' behavior varies (depending solely on a Meter offer and Meter response? or those and others?) In particular, how does this affect the behavior of the proxies when the server sends a Meter: header without having had the proxy volunteer (see Note in Section 3.3 near the bottom of page 11)? As I noted on previous drafts, I'm unsettled with the idea of the proxies' first use of this header being defined as applying to all subsequent requests made on the given transport connections; I appreciate the implementation advice, but I still believe that the problem should be solved generally. If we do come to a general solution of "sticky" headers and it doesn't match this model, we have a serious piece of cruft. How important is it not to repeat these particular bits on the wire? I would much rather limit the bits by including only the abbreviated forms of the directive and responses than by making a de facto sticky header. As an editorial thing, I think that the "Note on the limit on 'uses'" text in 3.3 needs to be incorporated fully into the text and flagged in big, bold letters. You may also want to think about what this means for the interpretation of a Meter: count=0/0 report in the presence of pre-fetching. I think section 8 needs to reference Koen's draft on multiple variants and it may need to define what to do in border cases. If, for example, a meter-willing cache offers a list of variants to a an end-user and it declines all of them, should that be reported? I think section 8,the note on capturing referrals, doesn't seem to belong in this draft, unless the scope is larger than the goals statement implies. As I said, thanks for all the work on this, regards, Ted Hardie NASA NIC -- Ted Hardie
Received on Friday, 31 January 1997 14:42:05 UTC