From help-files :
Special RSVP classifier CONFIG_NET_CLS_RSVP The Resource Reservation Protocol (RSVP) permits end systems to request a minimum and maximum data flow rate for a connection; this is important for real time data such as streaming sound or video. Say Y here if you want to be able to classify outgoing packets based on their RSVP requests. This code is also available as a module called cls_rsvp.o ( = code which can be inserted in and removed from the running kernel whenever you want). If you want to compile it as a module, say M here and read Documentation/modules.txt