A big cause of delay and jitter across WAN links is serialization delay or the time that it takes to put a packet on a wire. For example, a 1500 byte FTP packet takes approximately 214 ms to be fed onto a 56 Kbps circuit. For optimal voice performance, the maximum serialization delay should be close to 10 ms. Therefore, a voice packet to wait for a large data packet over a slow circuit. The solution to this problem is to fragment the large data packet into smaller pieces for propagation. If a smaller voice packet comes in, it can be squeezed between the data packet fragments and be transmitted within a short period of time.

The following sections discuss some of the common fragmentation techniques: