rfc1914.txt

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Network Working Group                                       P. Faltstrom
Request for Comments: 1914              Bunyip Information Systems, Inc.
Category: Standards Track                                    R. Schoultz
                                                                  KTHNOC
                                                               C. Weider
                                        Bunyip Information Systems, Inc.
                                                           February 1996


                  How to Interact with a Whois++ Mesh

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.

1. Overview

   In the Whois++ architecture [Deutsch94],[Weider94], mesh traversal is
   done by the client, since each server 'refers' the client to the next
   appropriate server(s). The protocol is simple. The client opens a
   connection to a  server, sends a query, receives a reply, closes the
   connection, and after parsing the  response the client decides which
   server to contact next, if necessary.

   So, the client needs to have an algorithm to follow when it interacts
   with the Whois++ mesh so that referral loops can be detected, cost is
   minimised, and appropriate servers are rapidly and effectively
   contacted.



















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RFC 1914          How to Interact with a Whois++ Mesh      February 1996


2. Basic functionality

   Each Whois++ client should be configured to automatically send
   queries to a specific Whois++ server. The deault Whois++ server can
   vary depending on which template is desired, and the location of the
   client with respect to the WHOIS++ index mesh,  but as a rule the
   server should be as local as possible.

                        A
                       / \
                      B   C
                     / \   \
           Z -----> D   E   F
                   / \
                  G   H

       Fig 1: The client Z is configured to first query server D

   After getting responses from a server, the client can act in several
   ways. If the number of hits is greater than zero, the response is
   just presented to the user. If the client gets one or many servers-
   to-ask answers, the client should be able to automatically resolve
   these pointers, i.e. query these servers in turn.

                        A
                       / \
                      B   C
                     / \   \
           Z <----- D   E   F
             \     / \
              --> G   H

   Fig 2: The client Z gets a "servers-to-ask G" response from D and
             therefore may automatically queries server G.

3. How to navigate in the mesh

   A client can use several different strategies when traversing or
   navigating around in the mesh. The automatic way of doing this is to
   just "expand the search" (described in 3.1) and a second method is to
   use the "Directory of Servers" (described in 3.2).

3.1. Expansion of searches

   If the number of hits is zero, or if the user in some way wants to
   expand the search, it is recommended for the client to issue a
   'polled-by' and 'polled-for' query to the server. The client can then
   repeat the original query to the new servers indicated.



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RFC 1914          How to Interact with a Whois++ Mesh      February 1996


                        A
                       / \
              /-----> B   C
             /       / \   \
           Z <----- D   E   F
                   / \
                  G   H

 Fig 3: The client Z gets a "polled-by B" response from D and therefore
                           queries server B.

   The client must always keep track of which servers it has queried
   because it must itself detect loops in the mesh by not querying the
   same server more than once.

                        A
                       / \
                   /- B   C
                  /  / \   \
           Z <---/  D   E   F
                   / \
                  G   H

  Fig 4: The client Z gets a "servers-to-ask D" response from B but Z
    does not query D because the server D has already been queried.

   So, the default expansion of a query by a client causes increasingly
   more comprenhensive index servers to be queried; the forward
   knowledge contained in the index server mesh allows rapid pruning of
   these larger trees.

   All loop detection and elimination is done in the client, rather than
   in the server mesh. This decision was made because loop detection and
   elimination are quite difficult to build into the mesh if we are to
   continue to allow each server to participate in multiple hierarchies
   within the mesh.

3.1.1. Optimising the mesh

   If organization A tends to use organization B's WHOIS++ server
   frequently, for example if A is cooperating in a project with B, A
   may wish to make B's server locally available by creating a local
   index server which retrieves the centroid for both organizations.
   When A's client then expands a query which is looking for someone at
   B, the client can much more rapidly resolve the query, as it does not
   have to find the top level servers for the tree to which A and B both
   belong.




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RFC 1914          How to Interact with a Whois++ Mesh      February 1996


                        A
                       / \
                      B   C
                     / \   \
           Z        D   --> F
                   / \
                  G   H

           Fig 5: The server B gets a centroid from server F

                        A
                       / \
                      B   C
                     / \   \
           Z <----> D   --- F
                   / \
                  G   H

  Fig 6: The client queries server D, gets zero hits back, expands the
             search and gets a "polled-by B" response back.

                        A
                       / \
                 /--> B   C
                /    / \   \
           Z <-/    D   --- F
                   / \
                  G   H

    Fig 7: The client Z queries server B and gets "servers-to-ask F"
                             response back.

                        A
                       / \
                      B   C
                     / \   \
                    D   --- F <-----> Z
                   / \
                  G   H

       Fig 8: The client Z queries server F and gets the answer.

   The example given in Fig 5-8 shows that the algorithm works even
   though the Whois++ mesh is not a tree. There are many reasons why a
   given index server mesh might be 'short-circuited'. For example, in
   the case of a multinational company, the Swedish branch of Acme Inc.,
   is polled both by the national server in Sweden and the headquarters
   server in the USA. By querying the Swedish server, one finds all



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RFC 1914          How to Interact with a Whois++ Mesh      February 1996


   persons working at the Swedish branch of Acme Inc., but by querying
   the Acme Inc.  server in the USA, you will find all employees in the
   company, including those in Sweden.

   Note that the location of a server does not implicitly narrow the
   search, i.e. you have to specify all information when sending a query
   to a server. In the example above, one can see that by just querying
   a server for companies in the USA, you will not implicitly only get
   hits from records in the states, because the Acme Inc. server in the
   states has polled a server in Sweden. So, in this case you have to
   explicitly include "country=USA" in the query if you are only
   interested in those records.

   Although the WHOIS++ index service has been designed to make searches
   at any location in the index mesh quite effective and efficient,
   blindly expanding the query can incur an exponentially growing cost
   in resources, and, as charging for responses is implemented in parts
   of the WHOIS++ index service mesh, growing cost, automatic expansion
   is not recommended. More sophisticated clients  should also be
   configurable to "cut off" some servers from a search, i.e. a
   blacklist of servers. This might be needed when searching for records
   and one server might have a very high cost (in dollars) so one might
   want to explicitly forbid the client to send queries to that server.

3.1.2. The algorithm used by the client

   By following this algorithm a client finds all records in a mesh
   which the first Whois++ server queried belongs to.

   The algorithm for the client follows:

      Query := data to search for;
      QueriedServers := {};
      AnswerList := {};
      OriginalServers := { known servers to this client };
      while OriginalServers is not empty do:
            ServerList = OriginalServers;
            while ServerList is not empty do:
                  Server := ServerList[1];
                  if Server is not in QueriedServers then do:
                        send Query to Server;
                        Answer := answer from Server;
                        append ServersToAsk to ServerList;
                        remove Server from ServerList;
                        append Answers to AnswerList;
                  end;
            done;
            if query should be expanded then do:



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