After performance and tuning have been discussed in general in the previous chapters, this one will deal specifically with special aspects of these problem areas with respect to networks and distributed applications. Classical performance tools, of course, have initially been deployed for mainframe architectures. Although the basic philosophy remains the same, a number of specific features have to be observed with network applications. Because of these general similarities, the whole performance philosophy will not again be unrolled but instead reference is made directly to tools available on the market and their evaluation will be presented. Special emphasis is placed on WLAN applications later on.