These 2 methods fragment a byte array into smaller byte arrays (given a fragmentation size), and re-assemble a number of smaller byte arrays into a larger one. The first method takes a byte array and a fragmentation size as parameters, and returns a vector of byte arrays that correspond to the fragmented byte buffers. If the fragmentation size is greater than the original buffer's size, the original buffer is returned in as the only element in the vector. The second method takes a vector of fragments (byte arrays) and concatenates them into a larger byte array, which is returned. These methods are used in the fragmentation layer (FRAG, cf. 7.2.4).