A method is disclosed for simulating a load on an application server in a network. The method intercepts data packets of a request from a sender to a receiver. The data packets to be intercepted can be selected according to specified criteria, such as communications protocol or port and address information of the sender and/or receiver. A simulation session can begin and end based on a specified period of time or after a specified number of data packets have been received. The intercepted data packets are stored in a buffer and the time of arrival of the data packets is recorded. The data packets are held in the buffer for a user specified delay time. Upon expiration of the delay time, the data packets are forwarded to the receiver. Alternately, the method can operate bi-directionally, or by intercepting and delaying data packets of a response of the receiver sent to the sender.