The ESI Initiative

Mark Nottingham

for OPES Meeting, IETF 51

What is ESI?

Currently, three specifications;
- Architecture (framework for origin-to-surrogate relationship)
- Edge Side Includes Language (assembly 'on the edge', tailored for caching)
- ESI Invalidation (point-to-point invalidation API)
Badly named - ESI started with the language, has grown since then
Current situation: 'thin pipe' between the origin and surrogate; HTTP cacheability semantics and not much else
Provides beginnings of an architecture that enables applications to be moved to surrogates, by:
- standardizing rich and well-understood metadata to affect resource handling
- enable arbitrary processing on surrogates
- enable find-grained caching, through edge assembly

Published as a W3C NOTE - see submission package
More than 10 vendors involved
- content providers and application server vendors involved and implementing
Upcoming W3C Workshop to investigate Web infrastructure/scaling issues

W3C 'owns' the Web; issues that ESI addresses are more Web-related than appropriate for the IETF
large number of application server vendors are Members, and interested in ESI

OPES Architecture is intermediary-centric; it models flows around actions that the intermediaries take, and how to enable them. Concentration on an architecture to deploy.
ESI aims to be content-centric; to provide a platform on which Web resources and applications can be described and moved to the edge of the network. Concentrates on semantics between the origin and the 'edge'.
ESI Language can be implemented over ICAP, etc., but is intended to be a larger framework, not used in isolation.

SOAP-based invalidation
Processing model APIs and tools for surrogates
Metadata schema, for distribution, caching, processing and service
Metadata association by multiple mechanisms, whether in-document, out-of-band, in HTTP headers, etc.
Overall, ESI encompasses the definition of a platform for content providers to code to, in order to distribute their resources to intermediaries that they have a trust relationship with.