TCP/IP host name resolution for machines on several domains

• US 5,777,989 A
• Filed: 12/19/1995
• Issued: 07/07/1998
• Est. Priority Date: 12/19/1995
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: McGarvey, John Ryan
• Primary Examiner(s): MARCELO, MELVIN C
• Application Number:
  US08/574,488
• Time in Patent Office: 931 Days
• Field of Search: 370/254-258, 370/392, 370/475, 395/200.11, 395/200.79
• US Class Current: 370/254
• CPC Class Codes: H04L 61/4511 using domain name system [DNS]
• CPC Class Codes: H04L 61/4552 Lookup mechanisms between a plurality of directories; Synchronisation of directories, e.g. metadirectories

Abstract

This invention deals with an enhancement to the name resolution capabilities of existing TCP/IP networks. More specifically, it allows a host which is connected to a private network to be located through a connection to a different private network or a public network, such as the internet. This is achieved by allowing the host to be configured with more than one primary domain name server. This can be done using existing TCP/IP communications protocol and does not require a change to any code outside of the host. The host can also define one or more alternate domain name servers for each of the primary domain name servers. The definition of multiple primary and secondary domain name servers for each host allows the name of the host to be located, without a degradation in performance, if it is located or defined in any of the primary domain name servers.

Claims

1. In a TCP/IP communications network containing more than one domain and having at least one local TCP/IP host, said local TCP/IP host being connected to multiple of said more than one domains and configured to use a primary domain name server and zero or more alternate domain name servers for each of the multiple connected domains, said local TCP/IP host having a name resolver program, a method for host address resolution comprising

sending a name resolution query for a specified name originating with an application program concurrently to each of the primary domain name servers by the name resolver program;

if a positive reply to the name resolution query is received from any of the primary domain name servers, returning the resolved host address information in the reply from the resolver program to the application program.

2. The method for host address resolution of claim 1, further including:

if a reply is not received from each primary domain name server within a specified period of time, determining if an alternate domain name server

is available for any of the domains from which no reply was received;

if there is an alternate domain name server available for any of the domains that did not reply, sending the name resolution query for the specified name to each such alternate domain name server; and

if no alternate domain name servers are available, returning a first negative reply received from said domain name servers by said resolver program to said application program.

3. The method for host address resolution of claim 2, wherein:

said specified name is a short name;

said local TCP/IP host is configured with a domain name to use in resolution of said short name; and

said name resolver program concatenates said short name with said configured domain name prior to sending the name resolution query to the domain name servers.

4. The method for host address resolution of claim 2, wherein:

said specified name is a short name;

said local TCP/IP host is configured with a list of domain names to use in resolution of said short name;

said name resolver program concatenates said short name to the configured domain name at the top of said list of domain names prior to sending the name resolution query to the domain name servers; and

if no positive reply is received from any domain name server, and if at least one negative reply is received, said name resolver program concatenates said short name with the configured domain name next in said list of domain names and resends said name resolutions query.

5. A TCP/IP communications network comprising:

two or more hosts;

two or more domains;

each of said domains containing a primary domain name server;

means for initiating a name resolution query from one of said hosts for a specified name, said name resolution query being sent concurrently to said primary domain name server in each of said domains.

6. The TCP/IP communications network as claimed in claim 5, further comprising:

means for sending said name resolution query for said specified name to an alternate domain name server for each primary domain name server when no reply is received within a specified period of time.

7. The TCP/IP communications network as claimed in claim 5, further comprising:

means for returning a negative response to the name resolution query if there are no alternate domain name servers available for said domain and a positive response is not received within a specified period of time.

8. In a TCP/IP communications network containing a plurality of domains and one or more local hosts which may be connected to multiple domains, an address resolution system for one or more of the domains, said system including:

a primary domain name server for each said domain including a database having entries which correlate host names to addresses;

means for concurrently sending a name resolution query for a specified name to each of said primary domain name servers; and

means for returning a host address if the specified name in the name resolution query is contained within the database at any of said primary domain name servers.

9. The address resolution system of claim 8, including:

a timer mechanism for determining if one or more domain name servers have failed to reply to said name resolution query within a specified time; and

means for transmitting said name resolution query to an alternate domain name server if no reply to said name resolution query has been received by the expiration of said specified time.

10. A host computer connected to a plurality of domains using a TCP/IP protocol, each domain containing a primary domain name server and zero or more secondary domain name servers, said host computer comprising:

means for transmitting a name resolution query from said host computer concurrently to each of said primary domain name servers;

timer means for detecting if any of said primary domain name servers fail to reply to said name resolution query within a specified time interval;

means for resending said name resolution query to each said primary domain name server a predetermined number of times if said each primary domain server fails to reply within said specified time interval; and

means for resending said name resolution query to each said secondary domain name server if said primary domain name server for said domain fails to reply after said predetermined number of times.