Specifications

Installation and Operation Manual Chapter 1 Introduction
MiTOP-E1/T1 Ver. 1.0 Functional Description 1-5
PDV
t
t
Packets Leaving MiTOP-E1T1
Packets Arriving
Figure 1-6. Packet Delay Variation
PDVT (Jitter) Buffer
MiTOP-E1/T1 is equipped with a Packet DVT (Delay Variation Tolerance) buffer.
The PDVT buffer or jitter buffer is filled by the incoming packets and emptied out
to fill the TDM stream.
• A jitter buffer overrun usually occurs when MiTOP-E1/T1 loses its clock
synchronization
• A jitter buffer underrun occurs when no packets are received for more than
the configured jitter buffer size, or immediately after an overrun.
When the first packet is received, or immediately after an underrun, the buffer is
automatically filled with conditioning pattern up to the PDVT level in order to
compensate for the underrun. Then MiTOP-E1/T1 processes the packet
(packetization delay) and starts to empty out the jitter buffer to the TDM side.
See
Figure 1-7 for the illustration of the PDVT buffer operation.
The PDVT (jitter) buffer is designed to compensate for a network delay variation
of up to:
• 256 ms (E1, framed T1)
• 340 ms (unframed T1).
Packets arriving from the PSN side are stored in the jitter buffer before being
transmitted to the TDM side, adding a delay to the TDM traffic. The delay time is
equal to the jitter buffer size configured by the user.
PDVT (Jitter) Buffer Depth
Normal Operation
(No PDV)
Maximum Jitter Buffer Size
(2 PDVT + 2 PCT + 1 msec)
PVDT Buffer + Packet Creation Time
Figure
1-7. Jitter Buffer Operation