Renumbering Still Needs Work
draft-carpenter-renum-needs-work-05

Network Working Group                                           J. Allen
Request for Comments: 2651                                WebTV Networks
Category: Standards Track                                    M. Mealling
                                                 Network Solutions, Inc.
                                                             August 1999

         The Architecture of the Common Indexing Protocol (CIP)

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1999).  All Rights Reserved.

Abstract

   The Common Indexing Protocol (CIP) is used to pass indexing
   information from server to server in order to facilitate query
   routing. Query routing is the process of redirecting and replicating
   queries through a distributed database system towards servers holding
   the desired results. This document describes the CIP framework,
   including its architecture and the protocol specifics of exchanging
   indices.

1. Introduction

1.1. History and Motivation

   The Common Indexing Protocol (CIP) is an evolution and refinement of
   distributed indexing concepts first introduced in the Whois++
   Directory Service [RFC1913, RFC1914]. While indexing proved useful in
   that system to promote query routing, the centroid index object which
   is passed among Whois++ servers is specifically designed for
   template-based databases searchable by token-based matching.  With
   alternative index objects, the index-passing technology will prove
   useful to many more application domains, not simply Directory
   Services and those applications which can be cast into the form of
   template collections.

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RFC 2651                  The CIP Architecture               August 1999

   The indexing part of Whois++ is integrated with the data access
   protocol. The goal in designing CIP is to extract the indexing
   portion of Whois++, while abstracting the index objects to apply more
   broadly to information retrieval. In addition, another kind of
   technology reuse has been undertaken by converting the ad-hoc data
   representations used by Whois++ into structures based on the MIME
   specification for structured Internet mail.

   Whois++ used a version number field in centroid objects to facilitate
   future growth. The initial version was "1". Version 1 of CIP (then
   embedded in Whois++, and not referred to separately as CIP) had
   support for only ISO-8895-1 characters, and for only the centroid
   index object type.

   Version 2 of the Whois++ centroid was used in the Digger software by
   Bunyip Information Systems to notify recipients that the centroid
   carried extra character set information. Digger's centroids can carry
   UTF-8 encoded 16-bit Unicode characters, or ISO-8859-1 characters,
   determined by a field in the headers.

   This specification is for CIP version 3.  Version 3 is a major
   overhaul to the protocol.  However, by using of a short negotiation
   sequence, CIP version 3 servers can interoperate with earlier servers
   in an index-passing mesh.

   For unclear terms the reader is referred to the glossary in Appendix
   A.

1.2 CIP's place in the Information Retrieval world

   CIP facilitates query routing. CIP is a protocol used between servers
   in a network to pass hints which make data access by clients at a
   later date more efficient. Query routing is the act of redirecting
   and replicating queries through a distributed database system towards
   the servers holding the actual results via reference to indexing
   information.

   CIP is a "backend" protocol -- it is implemented in and "spoken" only
   among network servers. These same servers must also speak some kind
   of data access protocol to communicate with clients. During query
   resolution in the native protocol implementation, the server will
   refer to the indexing information collected by the CIP implementation
   for guidance on how to route the query.

   Data access protocols used with CIP must have some provision for
   control information in the form of a referral. The syntax and
   semantics of these referrals are outside the scope of this
   specification.

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RFC 2651                  The CIP Architecture               August 1999

2. Related Documents

   This document is one of three documents. This document describes the
   fundamental concepts and framework of CIP.

   The document "MIME Object Definitions for the Common Indexing
   Protocol" [CIP-MIME] describes the MIME objects that make up the
   items that are passed by the transport system.

   Requirements and examples of several transport systems are specified
   in the "CIP Transport Protocols" [CIP-TRANSPORT] document.

   A second set of document describe the various specifications for
   specific index types.

3. Architecture

3.1 CIP in the Information Retrieval World

3.1.1 Information Retrieval in the Abstract

   In order to better understand how CIP fits into the information
   retrieval world, we need to first understand the unifying abstract
   features of existing information retrieval technology. Next, we
   discuss why adding indexing technology to this model results in a
   system capable of query routing, and why query routing is useful.

   An abstract view of the client/server data retrieval process includes
   data sets and data access protocols. An individual server is
   responsible for handling queries over a fixed domain of data. For the
   purposes of CIP, we call this domain of data the dataset. Clients
   make searches in the dataset and retrieve parts of it via a data
   access protocol. There are many data access protocols, each optimized
   for the data in question. For instance, LDAP and Whois++ are access
   protocols that reflect the needs of the directory services
   application domain. Other data access protocols include HTTP and
   Z39.50.

3.1.2 Indexing Information Facilitates Query Routing

   The above description reflects a world without indexing, where no
   server knows about any other server. In some cases (as with X.500
   referrals, and HTTP redirects) a server will, as part of its reply,
   implicate another server in the process of resolving the query.
   However, those servers generate replies based solely on their local
   knowledge. When indexing information is introduced into a server's
   local database, the server now knows not only answers based on the

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RFC 2651                  The CIP Architecture               August 1999

   local dataset, but also answers based on external indices. These
   indices come from peer servers, via an indexing protocol. CIP is one
   such indexing protocol.

   Replies based on index information may not be the complete answer.
   After all, an index is not a replicated version of the remote
   dataset, but a possibly reduced version of it. Thus, in addition to
   giving complete replies from the local dataset, the server may give
   referrals to other datasets. These referrals are the core feature
   necessary for effective query routing. When servers use CIP to pass
   indices from server to server, they make a kind of investment. At the
   cost of some resources to create, transmit and store the indices,
   query routing becomes possible.

   Query Routing is the process of replicating and moving a query closer
   to datasets which can satisfy the query. In some distributed systems,
   widely distributed searches must be accomplished by replicating the
   query to all sub-datasets. This approach can be wasteful of resources
   both in the network, and on the servers, and is thus sometimes
   explicitly disabled. Using indexing in such a system opens the door
   to more efficient distributed searching.

   While CIP-equipped servers provide the referrals necessary to make
   query routing work, it is always the client's responsibility to
   collate, filter, and chase the referrals it receives. This gives the
   end-user (or agent, in the case that there's no human user involved
   in the search) greatest control over the query resolution process.
   The cost of the added client complexity is weighed against the
   benefits of total control over query resolution. In some cases, it
   may also be possible to decouple the referral chasing from the client
   by introducing a proxy, allowing existing simple clients to make use
   of query routing. Such a proxy would transparently resolve referrals
   into concrete results before returning them to the simple-minded
   client.

3.1.3 Abstracting the CIP index object

   As useful as indices seem, the fact remains that not all queries can
   benefit from the same type of index. For example, say the index
   consists of a simple list of keywords. With such an index, it is
   impossible to answer queries about whether two keywords were near one
   another, or if a keyword was present in a certain context (for
   instance, in the title).

   Because of the need for application domain specific indices, CIP
   index objects are abstract; they must be defined by a separate
   specification. The basic protocols for moving index objects are
   widely applicable, but the specific design of the index, and the

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gt;.

   [scrocker]
              Crocker, S., "Renumbering Considered Normal", 2006, <http:
              //www.arin.net/meetings/minutes/ARIN_XVIII/PDF/wednesday/
              Renumbering_Crocker.pdf>.

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Appendix A.  Embedded IP addresses

   This Appendix lists common places where IP addresses might be
   embedded.  The list was adapted from
   [I-D.chown-v6ops-renumber-thinkabout].
      Provider based prefix(es)
      Names resolved to IP addresses in firewall at startup time
      IP addresses in remote firewalls allowing access to remote
      services
      IP-based authentication in remote systems allowing access to
      online bibliographic resources
      IP address of both tunnel end points for IPv6 in IPv4 tunnel
      Hard-coded IP subnet configuration information
      IP addresses for static route targets
      Blocked SMTP server IP list (spam sources)
      Web .htaccess and remote access controls
      Apache .Listen. directive on given IP address
      Configured multicast rendezvous point
      TCP wrapper files
      Samba configuration files
      DNS resolv.conf on Unix
      Any network traffic monitoring tool
      NIS/ypbind via the hosts file
      Some interface configurations
      Unix portmap security masks
      NIS security masks
      PIM-SM Rendezvous Point address on multicast routers

Authors' Addresses

   Brian Carpenter
   Department of Computer Science
   University of Auckland
   PB 92019
   Auckland,   1142
   New Zealand

   Email: brian.e.carpenter@gmail.com

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   Randall Atkinson
   Extreme Networks
   PO Box 14129
   Suite 100, 3306 East NC Highway 54
   Research Triangle Park,   NC 27709
   USA

   Email: rja@extremenetworks.com

   Hannu Flinck
   Nokia Siemens Networks
   Linnoitustie 6
   Espoo,   02600
   Finland

   Email: hannu.flinck@nsn.com

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