Load balancing of client connections across a network using server based algorithms

In a communications network, a system comprising:

• A) a plurality of application servers having different network addresses but sharing a common host name, each said application server including circuitry for communicating over the network with a plurality of clients in transactions consisting of clients' requests and the application server's responses thereto, for measuring delays between requests and respective responses, for determining, as a function of the measured delays, performance-cost estimates representing the estimated increase that adding a further client will cause in the average number of said plurality of clients that are waiting for responses, and for transmitting the network performance-cost estimates over the network;
• and
• B) a domain-name server that includes circuitry for receiving the performance-cost estimates from the application servers, for receiving over the network DNS queries specifying the common host name, for making a choice among the application servers as a function of the performance-cost estimates respectively received therefrom, and for responding to such DNS queries by sending as the DNS response thereto the chosen application server's network address.