Although they will help us out in many situations, wrappers should not be always used. First and foremost, there are many protocols not very well suited for being wrapped, at least not with the techniques described in this work. Some of the most representative are listed in section 3.7.
Although this point has already been mentioned, it demands being repeated as much as possible: Very heavily loaded systems, as well as systems where high availability is the top priority and can not afford facing a DoS attack, are particularly bad candidates for using wrappers. Wrappers add extra work to the CPU and extra load to the system RAM, and in some cases this will cause more harm than good.