System for distributing load over multiple servers at an internet site

• US 7,146,417 B1
• Filed: 09/12/2001
• Issued: 12/05/2006
• Est. Priority Date: 11/03/1995
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Kersey, Edward C., Coile, Brantley W., Howes, Richard A., Tenereillo, Peter A.
• Primary Examiner(s): Vaughn, William
• Assistant Examiner(s): BLAIR, DOUGLAS B
• Application Number:
  US09/954,523
• Time in Patent Office: 1,910 Days
• Field of Search: 709/203, 709/224, 709/226, 709/227
• US Class Current: 709/224
• CPC Class Codes: H01R 2201/04 for network, e.g. LAN connectors
• CPC Class Codes: H01R 31/005 Intermediate parts for distributing signals
• CPC Class Codes: H04L 2101/663 Transport layer addresses, e.g. aspects of transmission control protocol [TCP] or user datagram protocol [UDP] ports
• CPC Class Codes: H04L 41/00 Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
• CPC Class Codes: H04L 61/00 Network arrangements, protocols or services for addressing or naming
• CPC Class Codes: H04L 61/2514 between local and global IP addresses
• CPC Class Codes: H04L 61/2564 for a higher-layer protocol, e.g. for session initiation protocol [SIP]
• CPC Class Codes: H04L 63/0254 Stateful filtering
• CPC Class Codes: H04L 67/1001 for accessing one among a plurality of replicated servers
• CPC Class Codes: H04L 67/1008 based on parameters of servers, e.g. available memory or workload monitoring of computer activity G06F11/30
• CPC Class Codes: H04L 67/1017 based on a round robin mechanism
• CPC Class Codes: H04L 69/40 for recovering from a failure of a protocol instance or entity, e.g. service redundancy protocols, protocol state redundancy or protocol service redirection management of faults, events, alarms or notifications in data switching networks H04L41/06
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

Disclosed is a system and method for distributing connections among a plurality of servers at an Internet site. All connections are made to a single IP address and a local director selects the server from among the plurality of servers which is to receive the connection. Thus, the DNS server is not relied upon to distribute connections, and the connection distribution scheme is not avoided when DNS is bypassed. In one embodiment, a session distribution scheme is implemented such that connections are distributed to the server in the group of servers which has the fewest connections of the group. In other embodiments, other session distribution schemes which route connections based on the predicted response times of the servers or according to a round robin scheme are used.

Claims

1. A system for distributing connections from clients on an external network to a plurality of servers on an internal network, the system comprising:

a client interface to the external network, the client interface being operative to receive and send packets to and from a remote client;

a server interface to the internal network, the server interface being operative to receive and send packets to and from a plurality of servers, the plurality of servers being operative to establish a connection with the remote client and the system being configured to monitor connections established between the plurality of servers and clients on the external network;

a plurality of predicted responsiveness indicators, each of the plurality of predictive responsiveness indicators being associated with at least one of the plurality of servers, the predicted responsiveness indicators being operative to predict the response time of each of the plurality of servers based at least in part on a previous time stamp of a response time measurement, a current time stamp, and an aging factor applied to a difference between the previous time stamp and the current time stamp gathered at the system in the course of monitoring connections established between the plurality of servers and clients on the external network, the predicted response time for each of the plurality of servers being a function of the number of client connections to a particular server, the predicted responsiveness indicators being stored within the system in a manner that the predicted responsiveness indicators may be accessed; and

a predicted responsiveness comparator which is operative to access and compare the predicted responsiveness indicators and to determine which servers from among the plurality of servers is associated with a predicted responsiveness indicator which measures a best predicted response time, the predicted responsiveness comparator being further operative to select a pointer to a server which has a predicted responsiveness that is the best predicted responsiveness among the predicted responsiveness of the plurality of servers;

whereby the server which has a predicted responsiveness which is the best predicted responsiveness is selected to handle the next connection from a client.

2. A system as recited in claim 1, wherein the predicted responsiveness indicators are periodically updated.

3. A system as recited in claim 1, wherein the predicted responsiveness indicators include the number of connections to each of the plurality of servers.

4. A system as recited in claim 1, wherein the predicted responsiveness indicators include the predicted response time of each of the plurality of servers.

5. A system for distributing connections from clients on an external network to a plurality of servers on an internal network, the system comprising:

means for receiving and sending packets to and from a remote client;

means for receiving and sending packets to and from a plurality of servers, the plurality of servers being operative to establish a connection with the remote client;

means for monitoring connections established between the plurality of servers and clients on the external network, the means for monitoring connections comprising means for gathering response time data at the system in the course of monitoring connections between the plurality of servers and clients on the external network;

means for predicting the response time of each of the plurality of servers based at least in part on a previous time stamp of a response time measurement, a current time stamp, and an aging factor applied to a difference between the previous time stamp and the current time stamp gathered at the system in the course of monitoring connections established between the plurality of servers and clients on the external network, the predicted response time for each of the plurality of servers being a function of the number of client connections to a particular server; and

means for comparing the predicted response time of each of the plurality of servers to select a pointer to a server which has a best predicted response time of the plurality of servers;

whereby the server that has the best predicted response time is selected to handle the next connection from a client.

6. The system as recited in claim 5, further comprising:

means for periodically updating the predicted responsiveness indicators.

7. A system as recited in claim 5, wherein the predicted responsiveness indicators include the number of connections to each of the plurality of servers.

8. A system as recited in claim 5, wherein the predicted responsiveness indicators include the predicted response time of each of the plurality of servers.

10. A method as recited in claim 5, further comprising:

periodically updating the predicted responsiveness indicators.

11. A method as recited in claim 5, wherein the predicted responsiveness indicators include the number of connections to each of the plurality of servers.

12. A method as recited in claim 5, wherein the predicted responsiveness indicators include the predicted response time of each of the plurality of servers.

9. A method for distributing connections from clients on an external network to a plurality of servers on an internal network, the method comprising:

receiving and sending packets to and from a remote client;

receiving and sending packets to and from a plurality of servers, the plurality of servers being operative to establish a connection with the remote client;

monitoring connections established between the plurality of servers and clients on the external network, the means for monitoring connections comprising means for gathering response time data at the system in the course of monitoring connections between the plurality of servers and clients on the external network;

predicting the response time of each of the plurality of servers based at least in part on a previous time stamp of a response time measurement, a current time stamp, and an aging factor applied to a difference between the previous time stamp and the current time stamp gathered at the system in the course of monitoring connections established between the plurality of servers and clients on the external network, the predicted response time for each of the plurality of servers being a function of the number of client connections to a particular server; and

means for comparing the predicted response time of each of the plurality of servers to select a pointer to a server which has a best predicted response time of the plurality of servers;

whereby the server that has the best predicted response time is selected to handle the next connection from a client.