RFC 3143 (rfc3143) - Page 2 of 32

Known HTTP Proxy/Caching Problems

RFC 3143           Known HTTP Proxy/Caching Problems           June 2001


   3.    Security Considerations  . . . . . . . . . . . . . . . . . . 18
         References . . . . . . . . . . . . . . . . . . . . . . . . . 19
         Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 20
   A.    Archived Known Problems  . . . . . . . . . . . . . . . . . . 21
   A.1   Architectural  . . . . . . . . . . . . . . . . . . . . . . . 21
   A.1.1 Cannot specify multiple URIs for replicated resources  . . . 21
   A.1.2 Replica distance is unknown  . . . . . . . . . . . . . . . . 22
   A.1.3 Proxy resource location  . . . . . . . . . . . . . . . . . . 23
   A.2   Implementation . . . . . . . . . . . . . . . . . . . . . . . 23
   A.2.1 Use of Cache-Control headers . . . . . . . . . . . . . . . . 23
   A.2.2 Lack of HTTP/1.1 compliance for caching proxies  . . . . . . 24
   A.2.3 ETag support . . . . . . . . . . . . . . . . . . . . . . . . 25
   A.2.4 Servers and content should be optimized for caching  . . . . 26
   A.3   Administration . . . . . . . . . . . . . . . . . . . . . . . 27
   A.3.1 Lack of fine-grained, standardized hierarchy controls  . . . 27
   A.3.2 Proxy/Server exhaustive log format standard for analysis . . 27
   A.3.3 Trace log timestamps . . . . . . . . . . . . . . . . . . . . 28
   A.3.4 Exchange format for log summaries  . . . . . . . . . . . . . 29
         Full Copyright Statement . . . . . . . . . . . . . . . . . . 32

1. Introduction

   This memo discusses problems with proxies - which act as
   application-level intermediaries for Web requests - and more
   specifically with caching proxies, which retain copies of previously
   requested resources in the hope of improving overall quality of
   service by serving the content locally.  Commonly used terminology in
   this memo can be found in the "Internet Web Replication and Caching
   Taxonomy"[2].

   No individual or organization has complete knowledge of the known
   problems in Web caching, and the editors are grateful to the
   contributors to this document.

1.1 Problem Template

   A common problem template is used within the following sections.  We
   gratefully acknowledge RFC 2525 [1] which helped define an initial
   format for this known problems list.  The template format is
   summarized in the following table and described in more detail below.

      Name:           short, descriptive name of the problem (3-5 words)
      Classification: classifies the problem: performance, security, etc
      Description:    describes the problem succinctly
      Significance:   magnitude of problem, environments where it exists
      Implications:   the impact of the problem on systems and networks
      See Also:       a reference to a related known problem
      Indications:    states how to detect the presence of this problem



Cooper & Dilley              Informational