Temporary state preservation for a distributed file service

• US 5,606,719 A
• Filed: 06/07/1995
• Issued: 02/25/1997
• Est. Priority Date: 05/26/1988
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Digital Equipment Corporation (HP Inc.)
• Inventors: Phillips, Dennis E., Nichols, William G.
• Primary Examiner(s): Coleman, Eric
• Application Number:
  US08/473,138
• Time in Patent Office: 629 Days
• Field of Search: 395/876, 395/800
• US Class Current: 710/56
• CPC Class Codes: H04L 69/00 Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass networks security protocols H04L9/40; wireless communication networks H04W

Abstract

A distributed digital data processing system includes a server and a client that transmit messages over a virtual circuit in a network, the virtual circuit being defined by server virtual circuit information and client virtual circuit information. The server includes a server memory and a server interface. The server includes a server memory and a server interface. The server memory stores server virtual circuit control information and the server interface engages in message transfers over said network using the server virtual circuit control information in said server memory. The client includes a client memory, a client interface, and a purging mechanism. The client memory stores client virtual circuit control information that the client interface uses in connection with message transfers engaged by it over the virtual circuit. The purging mechanism enables the server memory to purge server virtual circuit control information relating to a virtual circuit if said virtual circuit has not been used for a predetermined period of time, thereby freeing up the memory space for server virtual circuit control information relating to other virtual circuits.

Claims

1. A distributed digital data processing system including a server and a client that transmit messages over a network,

A. said server including:

i. server memory means for storing server message transfer control information, said server message transfer control information including server virtual circuit control information and server sessions control information;

ii. server interface means for engaging in message transfers over said network using the server message transfer control information in said server memory means;

B. said client including;

i. client memory means for storing client message transfer control information, said client virtual circuit control information and client sessions control comprising;

ii. client interface means comprising;

(a) client message transfer means for engaging in message transfers over said network using the client message transfer control information in said client memory means;

(b) virtual circuit information control means for conditioning client virtual circuit control information in said client memory means and for enabling said client message transfer means to engage in an exchange of messages to enable said server interface means to condition server virtual circuit control information in said server memory means, said client virtual circuit control information and said server virtual circuit control information jointly serving to define a virtual circuit;

(c) session information control means for conditioning client session control information in said client memory means in connection with client virtual circuit control information in said client memory means, and for enabling said client message transfer means to engage in an exchange of messages to enable said server interface means to condition server session control information in said server memory means in connection with server virtual circuit control information in said server memory means, said server session control information and said client session control information jointly serving to define a session defined in connection with a virtual circuit;

(d) session timing means for determining when a virtual circuit has had no sessions defined in connection with the virtual circuit for a predetermined period of time; and

(e) means responsive to a positive determination by said session timing means in connection with a virtual circuit for enabling said client message transfer means to transfer a message to enable said server interface means to eliminate said server virtual circuit control information relating to said virtual circuit.

2. A system as defined in claim 1 wherein:

A. said client virtual circuit control information includes session number identification means for identifying the number of sessions defined in connection with the virtual circuit and an active sessions flag;

B. said session information control means conditioning said active sessions flag to a set condition when defining a session over the virtual circuit and to a clear condition when closing the last session defined over the virtual circuit;

C. said session timing means includes;

i. timer means for identifying the end of a predetermined timing interval;

ii. timer control means responsive to the clearing of said active sessions flag for starting said timer means; and

iii. determination means for generating a positive determination if said active sessions flag is set in response to the timing out of said timer means.

3. A distributed digital data processing system including a server and a client that transmit messages over a network,

A. said server including:

i. server memory means for storing server message transfer control information, said server message transfer control information including server virtual circuit control information and server session control information;

ii. server interface means for engaging in message transfers over said network using the server message transfer control information in said server memory means;

B. said client including;

i. client memory means for storing client message transfer control information, said client message transfer control information including client virtual circuit control information including session number identification means for identifying the number of sessions defined in connection with the virtual circuit and an active sessions flag, and client session control information;

ii. client interface means comprising;

(a) client message transfer means for engaging in message transfer over said network using the client message transfer control information in said client memory means;

(b) virtual circuit information control means for conditioning client virtual circuit control information in said client memory means and for enabling said client message transfer means to engage in an exchange of messages to enable said server interface means to condition server virtual circuit control information in said server memory means, said client virtual circuit control information and said server virtual circuit control information jointly serving to define a virtual circuit;

(c) session information control means for conditioning client session control information in said client memory means in connection with client virtual circuit control information in said client memory means, and for enabling said client message transfer means to engage in an exchange of messages to enable said server interface means to condition server session control information in said server memory means in connection with server virtual circuit control information in said server memory means, said server session control information and said client session control information jointly serving to define a session defined in connection with a virtual circuit, said session information control means conditioning said active sessions flag to a set condition when defining a session over the virtual circuit and to a clear condition when closing the last session defined over the virtual circuit;

(d) session timing means including;

I. timer means for identifying the end of a predetermined timing interval;

II. timer control means responsive to the clearing of said active sessions flag for starting said timer means; and

III. determination means for generating a positive determination if said active sessions flag is set in response to the timing out of said timer means; and

(e) means responsive to a positive determination by said session timing means in connection with a virtual circuit for enabling said client message transfer means to transfer a message to enable said server interface means to eliminate said server virtual circuit control information relating to said virtual circuit.

4. A client for use in a distributed digital data processing system including a server, the client and server transmitting messages over a network, the server including server memory means for storing server message transfer control information, said server message transfer control information including server virtual circuit control information and server session control information and server interface means for engaging in message transfers over said network using the server message transfer control information in said server memory means, said client including:

A client memory means for storing client message transfer control information, said client message transfer control information including client virtual circuit control information and client session control information;

B. client interface means comprising;

i. client message transfer means for engaging in message transfers over said network using the client message transfer control information is said client memory means;

ii. virtual circuit information control means for conditioning client virtual circuit control information in said client memory means and for enabling said client message transfer means to engage in an exchange of messages to enable said server interface means to condition server virtual circuit control information in said server memory means, said client virtual circuit control information and said server virtual circuit control information jointly serving to define a virtual circuit;

iii. session information control means for conditioning client session control information in said client memory means in connection with client virtual circuit control information in said client memory means, and for enabling said client message transfer means to engage in an exchange of messages to enable said server interface means to condition server session control information in said server memory means in connection with server virtual circuit control information and said client session control information jointly serving to define a session defined in connection with a virtual circuit;

iv. session timing means for determining when a virtual circuit has had no sessions defined in connection with the virtual circuit for a predetermined period of time; and

v. means responsive to a positive determination by said session timing means in connection with a virtual circuit for enabling said client message transfer means to transfer a message to enable said server interface means to eliminate said server virtual circuit control information relating to said virtual circuit.

5. A system as defined in claim 4 wherein:

A. said client virtual circuit control information includes session number identification means for identifying the number of sessions defined in connection with the virtual circuit and an active sessions flag;

B. said session information control means conditioning said active sessions flag to a set condition when defining a session over the virtual circuit and to a clear condition when closing the last session defined over the virtual circuit;

C. said session timing means includes;

i. timer means for identifying the end of a predetermined timing interval;

ii. timer control means responsive to the clearing of said active sessions flag for starting said timer means; and

iii. determination means for generating a positive determination if said active sessions flag is set in response to the timing out of said timer means.

6. A client for use in a distributed digital data processing system including a server, the client and server transmitting messages for storing server message transfer control information, said server message transfer control information including server virtual circuit control information and server session control information and server interface means for engaging in message transfers over said network using the server message transfer control information in said server memory means said client including:

A. client memory means for storing client message transfer control information, said client message transfer control information including client virtual circuit control information including session number identification means for identifying the number of sessions defined in connection with the virtual circuit and an active sessions flag, and client session control information;

B. client interface means comprising;

i. client message transfer means for engaging in message transfers over said network using the client message transfer control information in said client memory means;

ii. virtual circuit information control means for conditioning client virtual circuit control information in said client memory means and for enabling said client message transfer means to engage in an exchange of messages to enable said server interface means to condition server virtual circuit control information in said server memory means, said client virtual circuit control information and said server virtual circuit control information jointly serving to define a virtual circuit;

iii. session information control means for conditioning client session control information in said client memory means in connection with client virtual circuit control information in said client memory means, and for enabling said client message transfer means to engage in an exchange of messages to enable said server interface means to condition server session control information in said server memory means in connection with server virtual circuit control information in said server memory means, said server session control information and said client session control information jointly serving to define a session defined in connection with a virtual circuit, said session information control means conditioning said active sessions flag to a set condition when defining a session over the virtual circuit and to a clear when closing the last sessions defined over the virtual circuit;

iv. session timing means including;

(a) timer means for identifying the end of a predetermined timing interval;

(b) timer control means responsive to the clearing of said active sessions flag for starting said timer means; and

(c) determination means for generating a positive determination if said active sessions flag is set in response to the timing out of said timer means; and

v. means responsive to a positive determination by said session timing means in connection with a virtual circuit for enabling said client message transfer means to transfer a message to enable said server interface means to eliminate said server virtual circuit control information relating to said virtual circuit.