Intermediaries are commonly deployed to help scale the WWW. Lack of mechanisms to control and communicate with them brings about scalability issues with intermediaries themselves, and lack of strong, scalable coherence mechanisms limits their adoption by both end users and content publishers.
Furthermore, access providers who wish to provision caching proxies in their networks have no standardized mechanism to announce such devices to user agents. As a result, many access providers resort to the use of interception proxies, which break the end-to-end relationship between client and server at the transport layer, leading to undesired behaviors.
Accordingly, the group's work items are to:
1) Develop a resource update protocol.
2) Gather requirements for an intermediary discovery and description mechanism.
It is expected that after requirements for intermediary discovery and description are gathered and evaluated, the working group will re-charter to continue that work.
Issues pertaining to coordination between multiple administrative domains are explicitly out of scope in this group's work items. Work associated with the modification of messages by intermediaries is also out of scope. Additionally, this group will only address application-level (e.g., HTTP) intermediaries.
| Feb 01 | Submit Requirements for Resource Update Protocol as an Interne Draft | |
| Mar 01 | Meet at Minneapolis IETF | |
| Jul 01 | Submit Requirements for Intermediary Discovery and Description as an Internet-Draft | |
| Aug 01 | Meet at London IETF | |
| Nov 01 | Submit Resource Update Protocol as an Internet Draft | |
| Dec 01 | Meet at Salt Lake City IETF | |
| Feb 02 | Submit Resource Update Protocol to the IESG for consideration as standards-track publication |
Current Meeting Report
Here are my notes from the WEBI Working Group Meeting. Please give me corrections/additions by Friday, 29 Mar 2002.
David E. Martin
Program Director, Internet Standards and Technology
IBM
One IBM Plaza
330 N. Wabash Ave.
Chicago, IL 60611
312 245-7691
FAX: 248 920-0639
martinde@us.ibm.com
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The WEBI WG meeting was held on Tuesday, March 19, during the 13:00-14:00 time slot. 56 people signed the blue sheet.
Introduction, David Martin
Mark Nottingham and Ian Cooper couldn't make it, so David Martin is acting as chair. Ian and Mark are available via AOL Instant Messenger during the meeting if questions arise. David said that participation is still low and activity on the mailing list is required to keep the group viable. CDI and OPES are now chartered and we may be able to get momentum from them. WEBI, CDI and OPES chairs held a coordination call last week and will try to hold them regularly. WEBI could try to quickly wrap up requirements work and start concentrating on IDD. Discussion:
- WEBI still has a long way to go to finish the requirements and protocol work.
- It may be possible to get a very simple set of requirements and protocol out quickly.
Issues List, David Martin
David led a run through of the issues on draft-ietf-webi-rup-reqs-03.txt. David used the latest issues list posted to the WEBI mailing list. Points that came up during the presentation/discussion:
- An example using the WSI and WCIP protocols would be very useful.
- "Guarantee" is not a good term. Maybe we should use degrees of consistency, with a good definition of the degrees.
- It is a requirement to determine the consistency level, but maybe not a requirement to require any particular strength of consistency.
- Fragments do not need to be explicitly addresses, since they can be addressed via a URI.
- The guidelines are not really necessary. Maybe move them to an appendix.
- The granularity of content location updates should be groups if possible, but not a requirement.
- We should explicitly allow notification to non-subscribing clients.
- Security needs to be better addressed. Perhaps a detailed threat analysis would help.
- A list of threat and how WEBI mitigates them would probably be enough.
- Interested people should post useful references to the mailing list.
Web Content Distribution Protocol (WCDP) 2.0, Renu Tewari
Renu gave a presentation of work done by Thirumale Niranjan, Srikanth Ramamurthy and herself. The Web Content Distribution Protocol was designed in IBM, but does not represent the protocol used by any current (or necessarily future) products.
Some points that came up during the presentation/discussion:
- WCDP is more than just a cache invalidation protocol. It also allows data to be updated via a refresh directive.
- The origin server determines the refresh wait time and thus can mitigate the load.
- The grouping can be totally arbitrary. It is up to the intermediary to keep URL to channel mappings.
- Invalidation messages operate on a group as a whole. If atomic, then all either succeed or fail.
- Intermediaries actively subscribe to a content group.
- Four types of consistency: explicit, strong, delta, mutual.
- When a client doesn't hear a heartbeat, he assumes the server is dead and reverts to explicit consistency.
- When the serve doesn't get an invalidation response from the client (after a timeout), he assumes the client is dead.
- The protocol is designed to be used in the CDN and enterprise space with a hierarchy of intermediaries.
- It should scale to a few hindered intermediaries fanning out at each level. The organization of the hierarchy is outside the scope of the protocol.
- Future work: SOAP based implementation, security
WARM, David Martin
David led a short presentation and discussion on Mark Nottingham's WARM straw man proposal. There was little comment, but a general agreement that using existing HTTP infrastructure was a useful idea.
Last announcements
- Abbie Barbir has agreed to do an informal BOF during the afternoon break on Wednesday to describe his ideas for a Virtual Private Content Network (VPCN). All are invited. See the message board for details.
- Ian Cooper has set up a mailing list for discussion of content networking terms:
Post message: content-networking-terminology@yahoogroups.com
Subscribe: content-networking-terminology-subscribe@yahoogroups.com
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List owner: content-networking-terminology-owner@yahoogroups.com
- Please participate on the list!!!
Slides
Agenda
Web Content Distribution Protocol