Transfer packets can arrive with different delays in TCP/IP-based networks. Because these delays cause interruptions, packets entering the data stream must be verified. The jitter buffer provides temporary storage for IP packets. It can balance out IP packet delays to a certain degree.

IP packets enter the jitter buffer in the order in which they arrive. Each packet contains a time stamp, which is stored in the RTP header of the packet. The actual order is determined using the packet time stamps. The jitter buffer ensures that packets leave in the right order and in sync. An average time (average delay) defines how long packets, which arrive at the expected time, are held in the jitter buffer. Packets which arrive later than expected are held for a shorter period in the jitter buffer; packets which arrive earlier than expected are held longer. If a packet arrives so late that it can no longer be assigned, it is lost. In theory, packets can also arrive so early that they cannot be assigned. This is, however, rarely the case in practice.

Figure 4 Jitter buffer functionality illustrates the jitter buffer functionality.

If one or two packets are lost during voice transmission, this is not an immediate problem. However, the delay should be as short as possible, as delays which are too long compromise voice quality when making calls.

To ensure data integrity, the number of packets lost during data transfer should be kept to a minimum. Delays, on the other hand, do not play a major role here.