See their FAQ on WCIP:
>How does the ESI invalidation specification compare to Web Cache
>Invalidation Protocol (WCIP)?
>
>WCIP and similar solutions try to solve a different problem than ESI
>invalidation. Although both are a means
>of communicating invalidations (and possibly other information) from a Web
>site to caches and CDNs, they
>have different scopes and applications.
>
>WCIP allows a large number of clients to subscribe to a channel, on which
>they'll get invalidations and other
>kinds of updates. The primary problems that WCIP addresses are a) scaling
>to a very large number of
>clients and b) making the service to all of those clients reliable.
>
>ESI invalidation, on the other hand, has a one-to-one relationship; there
>is no channel mechanism. Instead,
>an invalidation message passes from the origin server directly to the
>local cache or CDN. This is more
>appropriate for sending invalidations to a small number of servers, or
>when the origin server doesn't have
>responsibility for propagating the message (such as when a CDN is used).
>
>Both WCIP and ESI invalidation might share a common payload (that is, the
>invalidation message), but
>WCIP attempts to address much more difficult problems, and is still
>experimental. ESI invalidation is
>simpler, more robust, and more appropriate for sending invalidation
>messages to a known party.
Would the Squid PURGE message (or HTTP DELETE) be good enough for the ESI
type of invalidations already? or there's some value-add by XMLize this
type of invalidation?
On the other hand, is WCIP too heavy? do people see a middle ground between
Squid PURGE-tyle invalidation and WCIP-or-heavier-style invalidation? Or,
how can we keep it simple & effective, with possible future extensions to
*much* more value-add?
At 02:15 PM 5/1/01 -0700, Ian Cooper wrote:
>If you haven't seen it already, you might want to take a peek at:
> http://www.akamai.com/esi_spec/index.html
>
>more particularly:
> http://www.akamai.com/esi_spec/invalidation.html
>
>
>I'm not too sure what the word "open" means at this point (read the
>copyright notice).
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