There is little information on the requirements analysis process as it applies to networking. However, there are some excellent preparatory materials that are of a more general systems engineering nature that will provide an overview of the requirements analysis process. The following books are recommended:
The Art of Systems Architecting, 2nd edition, by Mark W. Maier and Eberhardt Rechtin, CRC Press, June 2000
Requirements Engineering: A Good Practice Guide, by Ian Sommerville and Pete Sawyer, John Wiley & Sons, April 1997
Enterprise System Architectures: Building Client Server and Web Based Systems, by Mark Goodyear, CRC Press, September 1999
Systems Engineering: Coping with Complexity, by Stuart Arnold, Peter Brook, Ken Jackson, and Richard Stevens, Prentice Hall, June 1998