protocols standards

Web Caching-Related Protocols and Standards

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Three categories of documents are listed here:

  • HTTP/Web
  • Inter-cache Protocols
  • Miscellaneous
RFC 1738

Uniform Resource Locators
This Standards Track RFC document specifies a Uniform
Resource Locator URL), the syntax and semantics of formalized
information for
location and access of resources via the Internet
RFC 1945

This Informational RFC document describes version 1.0
of the Hypertext Transfer Protocol.
RFC 2396

Uniform Resource Identifiers
This Draft Standard RFC document
defines the generic syntax of Uniform Resource Identifiers
URI’s), and guidelines for their use. It revises and
replaces the generic definitions in RFC 1738 and RFC 1808.
RFC 2616

This Standards Track RFC document describes version 1.1
of the Hypertext Transfer Protocol. A former Standards Track
version of HTTP/1.1 is published as
RFC 2068.
RFC 2617

HTTP Authentication: Basic and
Digest Access Authentication
This document provides the specification for HTTP’s
authentication framework, the original Basic authentication scheme
and a scheme based on cryptographic hashes, referred to as “Digest
Access Authentication”. It is therefore also intended to serve as a
replacement for RFC 2069.
RFC 2965

HTTP State Management Mechanism
This Standards Track RFC document describes
a way to create stateful sessions with HTTP
requests and responses, also known as cookies.
It obsoletes RFC
RFC 2145

Use and Interpretation of HTTP Version Numbers
This Informational RFC document attempts to clarify
some confusion that surrounds proper use and interpretation
of HTTP version numbers, and interoperability
of HTTP implementations of different protocol versions.
RFC 2227

Simple Hit-Metering and
Usage-Limiting for HTTP
This Standards Track RFC document
proposes a simple [sic] extension to HTTP that permits a
limited form of demographic information colloquially called
“hit-counts”) to be reported by caches to origin servers,
in a more efficient manner than the “cache-busting” techniques
currently used. It also permits an origin server to control
the number of times a cache uses a cached response, and
outlines a technique that origin servers can use to capture
referral information without “cache-busting.”
RFC 2518

WEBDAV: HTTP Extensions for
Distributed Authoring
This Standards Track RFC document specifies a set
of methods, headers, and content-types ancillary to HTTP/1.1
for the management of resource properties, creation and
management of resource collections, namespace manipulation,
and resource locking collision avoidance).
RFC 2774

An HTTP Extension Framework
This Informational RFC
describes a generic extension mechanism for HTTP, which is
designed to address the tension between private agreement
and public specification and to accommodate extension of
applications using HTTP clients, servers, and proxies.
The proposal associates each extension with a globally
unique identifier, and uses HTTP header fields to carry
the extension identifier and related information between
the parties involved in the extended communication.
RFC 2817

Upgrading to TLS Within HTTP/1.1

This Standards Track RFC
explains how to use the Upgrade mechanism in HTTP/1.1 to
initiate Transport Layer Security (TLS) over an existing
TCP connection. This allows unsecured and secured HTTP
traffic to share the same well known port (in this case,
http: at 80 rather than https: at 443). It also enables
“virtual hosting”, so a single HTTP + TLS server can
disambiguate traffic intended for several hostnames at a
single IP address.

Since HTTP/1.1 defines Upgrade as a hop-by-hop mechanism,
this memo also documents the HTTP CONNECT method for
establishing end-to-end tunnels across HTTP proxies.
Finally, this memo establishes new IANA registries for
public HTTP status codes, as well as public or private
Upgrade product tokens.

RFC 2818

This Informational RFC
describes how to use TLS to secure HTTP connections over
the Internet. Current practice is to layer HTTP over SSL
(the predecessor to TLS), distinguishing secured traffic
from insecure traffic by the use of a different server port.
This document documents that practice using TLS.
RFC 2168

Resolution of Uniform Resource Identifiers

using the Domain Name System
This document describes the first, experimental, “resolver
discovery service.” It is implemented by a new DNS Resource
Record, NAPTR (Naming Authority PoinTeR), that provides
rules for mapping parts of URIs to domain names. By changing
the mapping rules, we can change the host that is contacted
to resolve a URI. This will allow a more graceful handling
of URLs over long time periods, and forms the foundation
for a new proposal for Uniform Resource Names.
RFC 2169

A Trivial Convention for using HTTP
in URN
This document specifies the “THTTP” resolution protocol —
a trivial convention for encoding resolution service requests
and responses as HTTP 1.0 or 1.1 requests and responses.
The primary goal of THTTP is to be simple to implement so
that existing HTTP servers may easily add support for URN
resolution. We expect that the databases used by early
resolvers will be useful when more sophisticated resolution
protocols are developed later.

Tunneling TCP protocols through Web proxy servers
This expired
Internet Draft
specifies a generic tunneling mechanism for TCP based
protocols through Web proxy servers.
RFC 3229

Delta encoding in HTTP
This Proposed Standard RFC
describes how delta encoding can be supported as a
compatible extension to HTTP/1.1.
Many HTTP requests cause the retrieval of slightly modified
instances of resources for which the client already has a
cache entry. Research has shown that such modifying
updates are frequent, and that the modifications are
typically much smaller than the actual entity. In such
cases, HTTP would make more efficient use of network
bandwidth if it could transfer a minimal description of the
changes, rather than the entire new instance of the
RFC 3230

Instance Digests in HTTP
This Proposed Standard RFC describes instance digests.
HTTP/1.1 defines a Content-MD5 header that allows a server
to include a digest of the response body. However, this is
specifically defined to cover the body of the actual
message, not the contents of the full file (which might be
quite different, if the response is a Content-Range, or
uses a delta encoding). Also, the Content-MD5 is limited
to one specific digest algorithm; other algorithms, such as
SHA-1, may be more appropriate in some circumstances.
Finally, HTTP/1.1 provides no explicit mechanism by which a
client may request a digest. This document proposes HTTP
extensions that solve these problems.
RFC 3507

Internet Content Adaptation Protocol
This informational RFC describes
ICAP, the Internet Content Adaption Protocol, a protocol
aimed at providing simple object-based content vectoring
for HTTP services. ICAP is, in essence, a lightweight
protocol for executing a “remote procedure call” on HTTP
messages. It allows ICAP clients to pass HTTP messages to
ICAP servers for some sort of transformation or other
processing (“adaptation”). The server executes its
transformation service on messages and sends back responses
to the client, usually with modified messages. Typically,
the adapted messages are either HTTP requests or HTTP
Inter-Cache Protocols
RFC 2186

This is an Informational RFC document that describes
the Internet
Cache Protocol ICP) version two. ICP is a UDP-based
protocol used for locating instances of cached
responses in neighbor caches. This RFC addresses only the
structure, field definitions, and allowed field values of
the protocol.
RFC 2187

Application of ICPv2
This is an Informational RFC document that describes
how ICP is used in a Web caching hierarchy, or mesh.
RFC 2756

Hypertext Caching Protocol
This Experimental RFC document describes the Hypertext Caching
Protocol — an alternative
and improvement) to ICP. In
particular, it permits full request and response
headers to be used in cache management, and expands the
domain of cache management to include monitoring a remote
cache’s additions and deletions, requesting immediate
deletions, and sending hints about web objects such as the
third party locations of cacheable objects or the measured
uncacheability or unavailability of web objects.
RFC 2324

Hyper Text Coffee Pot Control Protocol
This document describes HTCPCP, a protocol for controlling,
monitoring, and diagnosing coffee pots.

CARP, v1
This expired Internet Draft describes
the Cache Array Routing Protocol. CARP is an algorithm
for dividing “URL-space” among an array of loosely coupled
proxy caches. CARP is designed to maximize hit ratios,
and to minimize the duplication of content among a set of

Inter Cache Co-operation, Protocol Extensions
This expired Internet Draft describes three protocol
extensions to HTTP/1.1 and ICPv2. These extensions enable
purging of cached objects, tracing of HTTP requests through
a sequence of proxies, and the removal of URLs from ICP

Web Cache Coordination Protocol, v1
Internet Draft describes
Cisco’s Web Cache Coordination Protocol. WCCP is used to
associate a router with one or more Web caches so that the
router can divert HTTP traffic to the caches. It also
includes a mechanism whereby one of the caches dictates
how the router should distribute the HTTP traffic among a
set of caches.

Web Cache Coordination Protocol, v2
Internet Draft
describes version 2.0 of the Web Cache
Coordination Protocol (WCCP). The WCCP V2.0 protocol
specifies interactions between one or more routers and one
or more web-caches. The purpose of the interaction is to
establish and maintain the transparent redirection of
selected types of traffic flowing through a group of routers.
The selected traffic is redirected to a group of web-caches
with the aim of optimising resource usage and lowering
response times.
RFC 3040

Internet Web Replication and
Caching Taxonomy
This Informational RFC
is a product of the Web Replication and Caching
working group. It specifies standard terminology and the
current taxonomy of web replication and caching infrastructure
that are currently deployed. It introduces standard concepts
and protocols currently in use within this application
RFC 3143

Known HTTP Proxy/Caching Problems
This Informational RFC
catalogs a number of known problems with World Wide Web
(WWW) (caching) proxies and cache servers. The goal of the document
is to provide a discussion of the problems and proposed workarounds,
and ultimately to improve conditions by illustrating problems. The
construction of this document is a joint effort of the Web caching

Web Caching and Replication Research Issues
Internet Draft
is a product of the Web Replication and Caching
working group. It summarizes open research issues in the
support of distributed caching and replication of web
objects. The potential solutions and mechanisms described
are preliminary.

Known HTTP Proxy/Caching Problems
This Internet Draft
is a product of the Web Replication and Caching
working group.
It catalogs a number of known problems with World Wide Web
proxy and cache servers. The goal of the document is to
provide a discussion of the problems and proposed workarounds,
and ultimately to improve conditions by illustrating problems.
Navigator Proxy Auto-Config File Format The “official” documentation for the proxy auto-configuration
technique invented by Netscape. This page describes how
to write the

Web Proxy Auto Discovery
This expired Standards Track Internet Draft
describes the Web Proxy Auto-Discovery Protocol. WPAD is a
mechanism that enables Web browsers and other clients to
automatically locate an appropriate proxy cache within their
domain. This is a nice alternative to so-called transparent
connection hijacking. WPAD is already implemented in recent
versions of Internet Explorer. Ian Cooper submitted an edited
version of the original draft, named draft-cooper-webi-wpad-00.txt,
which is also now expired.

Network Element Control Protocol
This expired Internet Draft
describes “NECP,” a lightweight protocol for signaling
between servers and the network elements that forward
traffic to them. It is intended for use in origin servers,
proxies, transparent proxies, so-called L4 or content-aware
switches, and load-balancing routers. NECP provides methods
for network elements to learn about servers’ capabilities,
availability, and hints as to which flows can and can not
be serviced. This allows network elements to perform load
balancing across a farm of servers, redirection to transparent
proxies, and cut-through of flows that can not be served
by the farm.

Caching Support in RTSP/RTP Servers
This expired Internet Draft
presents the issues facing streaming media caching. It
proposes a set of mechanisms to enable streaming media
caching between standards-based RTSP/RTP servers and proxies.
A list of RTSP enhancements and open issues are presented.
This document is intended to be a starting point for
discussion between various parties interested in standardizing
the mechanism used by RTSP/RTP servers to enable streaming
media caching.

Requirements for Intermediary
Discovery and Description
This Internet Draft
establishes a set of requirements for a system that would
make discovery of application level intermediaries by web
clients efficient and practical.

Requirements for a Resource Update Protocol
This Internet Draft
provides guidelines for the development of a Web
Resource Update Protocol to facilitate cache coherence in Web
intermediary systems such as caching proxies and surrogates. Such a
protocol is useful to maintain consistency in an environment where
periodic revalidation is unacceptable in terms of performance and/or
cache consistency. This memo suggests invalidation methods as the
only required functionality of a candidate protocol, but outlines
other functionality that should be supported (possibly at a later

Support for out-of-order responses in HTTP
This Internet Draft
a simple, compatible, and optional extension to HTTP to
allow a server to issue responses out of order which could
significantly reduce HOL blocking. In this extension,
clients add short ID fields to their requests, and servers
echo these IDs back in their responses. This extension is
defined as a hop-by-hop rather than end-to-end mechanism,
so it avoids much of the complexity of the end-to-end

WCIP: Web Cache Invalidation Protocol
Cache consistency is a major impediment to scalable content
delivery, because periodical revalidating objects one by
one is unacceptable in terms of performance and/or cache
consistency. This Internet Draft describes the
Web Cache Invalidation Protocol (WCIP). WCIP uses invalidations
and updates to keep changing objects up to date in web
caches. It thus enables proxy caching and content distribution
of large amounts of frequently changing web objects.

Middle boxes: taxonomy and issues
This Internet Draft is intended as input to IETF
discussion about “middle boxes” – defined as any intermediary
box performing functions apart from normal, standard
functions of an IP router on the data path between a source
host and destination host. This document establishes a
taxonomy of middle boxes, cites previous or current IETF
work concerning middle boxes, and attempts to identify
issues and areas where further work is necessary.

Registration procedures for message header fields
This Internet Draft
defines registration procedures for the message
header fields used by Internet mail, HTTP, news and other


HTTP Header Field-Name Registries
This Internet Draft defines the initial IANA
registration for some HTTP message header fields.


HTTP Authentication Credential Caching Extension
This Internet Draft proposes an HTTP cache-control extension mechanism that
allows caching of authentication credentials, thereby allowing
authenticated resources to be served from cache without incurring the
cost of a round-trip to the origin server more than once during the
freshness lifetime of the credentials.


Web Active Resource Monitoring
This Internet Draft describes
WARM, a straw-man proposal for a solution to the RUP requirements
of the WEBI WG which reuses the Web Architecture (and HTTP). In
particular, it provides a mechanism for distributing cache
invalidations from HTTP servers to clients.


Web Content Distribution Protocol v2.0
This Internet Draft describes
the Web Content Distribution protocol (WCDP), which is an
invalidation and update protocol to maintain cache consistency
for a large number of frequently changing web objects.
WCDP supports different levels of consistency: strong,
delta, weak, and explicit consistency.


DHCP Option for Proxy Server Configuration
This Internet Draft defines a new Dynamic Host
Configuration Protocol (DHCP) option, which can be used to
configure the TCP/IP host’s Proxy Server configuration for
standard protocols like HTTP, FTP, NNTP, SOCKS, Gopher, SLL
and etc. Proxy Server provides controlled and efficient
access to the Internet by access control mechanism for
different types of user requests and caching frequently
accessed information (Web pages and possibly files that
might have been downloaded using FTP and other protocols).

$Date: 2004/09/22 16:19:45 $