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____________________________________________________ DS34T101, DS34T102, DS34T104, DS34T108
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Field
Description
there is a failure of that direction of the bi-directional connection. This indication can be used to signal
congestion or other network related faults. Receiving remote failure indication may trigger fall-back
mechanisms for congestion avoidance. The R bit must be set after a preconfigured number of
consecutive packets are not received, and must be cleared once packets are once again received.
M
Defect Modifier failure.
These bits are set by CPU software
(Port[n]_cfg_reg.Tx_defect_modifier) for packets transmitted out
the Ethernet port.. This field is optional. When used it supplements the L-bit meaning.
FRG
Fragmentation field
This field is used for fragmenting multiframe structures into multiple packets in case of CESoPSN
structured with CAS bundles.
The field is used as follows:
00 = Indicates that the entire (unfragmented) multiframe structure is carried in a single packet.
01 = Indicates the packet carrying the first fragment.
10 = Indicates the packet carrying the last fragment.
11 = Indicates a packet carrying an intermediate fragment.
Length
Length field
Includes control word, payload and RTP header (if present) unless it is a UDP/IP packet. It is only
used when the total length of these fields is less than 64 bytes. Otherwise, it must be set to zero.
Sequence Number
TDM-over-Packet sequence number, defined separately for each bundle and incremented by one for
each TDMoP packet sent for that bundle. The initial value of the sequence number is random
(unpredictable) for security purposes, and the value is incremented in wrap-around manner separately
for each bundle. Used by the receiver to detect packet loss and restore packet sequence.
The HDLC payload type machine supports three different modes for this field: always zero,
incremented in wrap-around manner or incremented in wrap-around manner, but skips zero value.
For OAM packets, it uniquely identifies the message. Its value is unrelated to the sequence number of
the TDMoP data packets for the bundle in question. It is incremented in query messages, and
replicated without change in replies.
10.6.1.9 RTP Header
Figure 10-20. RTP Header Format
Table 10-16. RTP Header Fields
Field
Description
V
RTP version. Must be set to 2.
P
Padding bit. Must be set to 0.
X
Extension bit. Must be set to 0.
CC
CSRC Count. Must be set to 0.
M
Marker bit. Must be set to 0.
PT
Payload Type. One PT value MUST be allocated from the range of dynamic values for each direction
of the bundle. The same PT value MAY be reused for both directions of the bundle, and also reused
between different bundles.
SN
Sequence number. Identical to the sequence number in the control word.
TS
Timestamp. The RTP header can be used in conjunction with the following modes of timestamp
generation:
Absolute mode: the chip sets timestamps using the clock from the incoming TDM circuit. As
a consequence, the timestamps are closely correlated with the sequence numbers. The
timestamp is incremented by one every 125
s.
Differential (common clock) mode: The two chips at bundle edges have access to the same
high-quality network clock, and this clock source is used for timestamp generation.