RAD Data comm IPmux-11 - Manual (Page 25)

Installation and Operation Manual Chapter 1 Introduction
IPmux-11 Ver. 2.00 Functional Description 1-11
Table 1-4. TDMoMPLS Frame Structure
Field Length (Bytes) Field
7 Preamble
1 SFD
6 Destination MAC Address
6 Source MAC Address
2 Type
20 Outer label
3 EXP
1 Stacking bit
8 TTL
20 Inner label
3 EXP
1 Stacking bit
8 TTL
...
Payload
4 CRC
Packet Delay Variation
Packets are transmitted at set intervals. Packet Delay Variation is the maximum
deviation from the nominal time the packets are expected to arrive at the far end
device. IPmux-11 has a buffer that compensates for the deviation from the
expected packet arrival time to prevent IPmux-11 buffers from emptying out or
overflowing.
Packet Delay Variation is an important network parameter. Large PDV (exceeding
the jitter buffer configuration) will cause receive buffer underflows and errors at
the TDM level (see
Figure 1-9 ).
To compensate for large PDV, configure the PDVT (jitter) buffer to a higher value.
PDV
t
t
Packets Leaving IPmux-11
Packets Arriving
Figure 1-9. Packet Delay Variation
ETH
Layer
LLC
Layer
Note: IEEE 802.1p&Q VLAN
Tagging (additional 4 bytes if
enabled)
ETH
Layer
MPLS
Layer
The inner label field is used to
transfer a destination bundle
number.
Data
Layer