< draft-wessels-icp-v2-01.txt		draft-wessels-icp-v2-02.txt >
	Network Working Group D. Wessels		Network Working Group D. Wessels
	Internet-Draft National Laboratory for Applied		Internet-Draft National Laboratory for Applied
	Obsoletes <draft-wessels-icp-v2-00.txt> Network Research/UCSD		Obsoletes <draft-wessels-icp-v2-01.txt> Network Research/UCSD
	Expires: September 25, 1997 25 March 1997		Expires: November 22, 1997 22 April 1997
	Internet Cache Protocol (ICP), version 2		Internet Cache Protocol (ICP), version 2
	<draft-wessels-icp-v2-01.txt>		<draft-wessels-icp-v2-02.txt>
	Status of this Memo		Status of this Memo
	This document is an Internet-Draft. Internet-Drafts are working		This document is an Internet-Draft. Internet-Drafts are working
	documents of the Internet Engineering Task Force (IETF), its areas,		documents of the Internet Engineering Task Force (IETF), its areas,
	and its working groups. Note that other groups may also distribute		and its working groups. Note that other groups may also distribute
	working documents as Internet-Drafts.		working documents as Internet-Drafts.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	skipping to change at page 1, line 33 ¶		skipping to change at page 1, line 33 ¶
	To learn the current status of any Internet-Draft, please check the		To learn the current status of any Internet-Draft, please check the
	``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow		``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow
	Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe),		Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe),
	munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or		munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or
	ftp.isi.edu (US West Coast).		ftp.isi.edu (US West Coast).
	Abstract		Abstract
	This draft document describes the Internet Cache Protocol (ICP) as		This draft document describes the Internet Cache Protocol (ICP) as
	currently implemented in a couple of World-Wide Web proxy cache		currently implemented in a couple of World-Wide Web proxy cache
	packages. ICP was initially developed by Peter Danzig, et. al. at		packages. A companion document (RFCXXXX, <draft-wessels-icp-
	the University of Southern California. It evolved as an important		v2-appl-00.txt>) describes the application of ICP to Web caches. ICP
	part of hierarchical caching on the Harvest research project.		was initially developed by Peter Danzig, et. al. at the University of
			Southern California. It evolved as an important part of hierarchical
			caching on the Harvest research project.
	1. Introduction		1. Introduction
	ICP is a message format used for communicating between Web caches.		ICP is a message format used for communicating between Web caches.
	Although Web caches use HTTP[1] for the transfer of object data,		Although Web caches use HTTP[1] for the transfer of object data,
	caches benefit from a simpler, lighter communication protocol. ICP		caches benefit from a simpler, lighter communication protocol. ICP
	is primarily used in a cache mesh to locate specific Web objects in		is primarily used in a cache mesh to locate specific Web objects in
	neighbor caches. One cache will send an ICP query to its neighbors.		neighbor caches. One cache will send an ICP query to its neighbors.
	The neighbors will send back ICP replies indicating a ``HIT'' or a		The neighbors will send back ICP replies indicating a ``HIT'' or a
	``MISS.''		``MISS.''
	In current practice, ICP is implemented on top of UDP, but there is		In current practice, ICP is implemented on top of UDP, but there is
	no requirement that it be limited to UDP. We feel that ICP over UDP		no requirement that it be limited to UDP. We feel that ICP over UDP
	skipping to change at page 8, line 28 ¶		skipping to change at page 8, line 28 ¶
	This flag is set in an ICP reply message (ICP_OP_HIT, ICP_OP_MISS,		This flag is set in an ICP reply message (ICP_OP_HIT, ICP_OP_MISS,
	ICP_OP_MISS_NOFETCH, or ICP_OP_HIT_OBJ) to indicate that the low		ICP_OP_MISS_NOFETCH, or ICP_OP_HIT_OBJ) to indicate that the low
	16-bits of the Option Data field contain the measured RTT to the		16-bits of the Option Data field contain the measured RTT to the
	host given in the requested URL. If ICP_FLAG_SRC_RTT is clear in		host given in the requested URL. If ICP_FLAG_SRC_RTT is clear in
	the query then it MUST also be clear in the reply. If		the query then it MUST also be clear in the reply. If
	ICP_FLAG_SRC_RTT is set in the query, then it may or may not be		ICP_FLAG_SRC_RTT is set in the query, then it may or may not be
	set in the reply.		set in the reply.
	4. Security Considerations		4. Security Considerations
	Security is an issue with ICP over UDP because of its connectionless		The security issues relating to ICP are discussed in the companion
	nature. A proxy/cache must only process ICP messages received from		document, RFCXXXX (<draft-wessels-icp-v2-appl-00.txt>).
	its known neighbors. A cache must discard messages from unknown
	addresses.
	The ICP_OP_HIT_OBJ message is especially sensitive to security issues
	since it contains actual object data in the response. In combination
	with IP spoofing it is most likely possible to pollute the cache with
	invalid objects.
	Multicasting ICP queries provides a very simple method for others to
	"snoop" on ICP messages. Cache administrators should configure the
	application to use the minimum required multicast TTL.
	5. References		5. References
	[1] Fielding, R., et. al, "Hypertext Transfer Protocol -- HTTP/1.1",		[1] Fielding, R., et. al, "Hypertext Transfer Protocol -- HTTP/1.1",
	RFC 2068, UC Irvine, January 1997.		RFC 2068, UC Irvine, January 1997.
	[2] Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform Resource		[2] Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform Resource
	Locators (URL)", RFC 1738, CERN, Xerox PARC, University of Minnesota,		Locators (URL)", RFC 1738, CERN, Xerox PARC, University of Minnesota,
	December 1994.		December 1994.
End of changes. 5 change blocks.
	20 lines changed or deleted		10 lines changed or added
This html diff was produced by rfcdiff 1.48. The latest version is available from http://tools.ietf.org/tools/rfcdiff/