White Pages Requirements Working Group P. Faltstrom draft-ietf-wnils-whois-mesh-02.txt BUNYIP INFORMATION SYSTEMS, inc Expires: 12 April 1996 R. Schoultz KTHNOC C. Weider BUNYIP INFORMATION SYSTEMS, inc 20 October 1995 How to interact with a Whois++ mesh Status of this Memo This document is an Internet-Draft. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), it areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress". To learn the current status of any Internet-Draft, please check the "1id-abstracts.txt" listing contained in the Internet- Drafts Shadow Directories on ds.internic.net (US East Coast), nic.nordu.net (Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim). 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. 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. 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. 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. 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. 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 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. The algorithm used by the server 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: ServerList := OriginalServers; OriginalServers := {}; while ServerList is not empty do: Server := ServerList[1]; send Polled-For-Query to Server; Answer := answer from Server; append Answer to OriginalServers; remove Server from ServerList; end; done; done; display AnswerList to user; The Directory of Servers A second way of finding the correct server to query is to use a separate service we call the Directory of Servers. Authors Addresses Patrik Faltstrom BUNYIP INFORMATION SYSTEMS, inc Suite 300 310 Ste Catherine Street West Montreal, Quebec CANADA H2X 2A1 Rickard Schoultz KTHNOC, SUNET/NORDUnet/Ebone Operations Centre S-100 44 STOCKHOLM SWEDEN Chris Weider BUNYIP INFORMATION SYSTEMS, inc Suite 300 310 Ste Catherine Street West Montreal, Quebec CANADA H2X 2A1 References [Deutsch94] Deutsch P., Schoultz R., Faltstrom P., Weider C., Architecture of the Whois++ service, August 1995. RFC 1835 [Weider94] Weider C., Fullton J., Spero S., Architecture of the WHOIS++ Index Service: Internet Draft, July 1994. < URL:ftp://ds.internic.net/internet-drafts/ draft-ietf-wnils-whois-03.txt >