Method and apparatus for fault management of computer networks which utilizes a proxy or recruit network device to test the responsiveness of a network device. The reaction may be carried out in the presence of a catalyst. In some embodiments, a synchronization server software element may be responsible for maintaining synchronization for a plurality of clients, including software elements or devices. This radial symmetric wave can then interfere with a second portion of the plane wave incident but with a different angle of incidence to produce a periodic spatially-varying intensity pattern with circular symmetry. When the pull on the cable is released, the elastic element restores to cause the sliding block to move until the ball reaches the third turning point, to lock the cable in position. Thus, the first valve 25 and second valve 27 are press-fitted to the valve shaft 29 and those components are swaged together so that the first and second valves are secured to the valve shaft, and oil is placed in a press-fitted portion.