Whereas paging suffers from the problem of internal fragmentation due to the fixed size pages, a segmented scheme can allocate each process exactly the memory it needs (or very close to it - segment sizes are often constrained to be multiples of some small unit such as 16 bytes.) However, the problem of external fragmentation now comes back, since the available spaces between allocated segments may not be of the right sizes to satisfy the needs of an incoming process. Since this is a more difficult problem to cope with, it may seem, at first glance, to make segmentation a less-desirable approach than paging.