- Entry:
- TDU
- Event:
- Topology database update for a TG
- Modules Generating Entry:
- ISTTRIAT
This trace record is issued when a TG record is created
or updated when a TDU is received for a TG and the information in
the TDU about that TG is more recent than the information already
in the TGREC. 
- Byte (hex)
- Contents
- 00–02
- Record ID: C"TDU"
- 03
- Action
- C"C" Create TG record
- C"I" TG became inoperative
- C"O" TG became operational
- 04
- Status byte from the CV47
- 05
- Flag byte from the CV4680
- 06
- Flag byte
- Bit
- Meaning
- 111. ....
- TG type from TGREC
- B'000'
- Endpoint TG
- B'001'
- Intermediate routing TG
- B'010'
- Interchange TG
- B'011'
- Intersubnet TG
- B'100'
- Branch extender TG
- ...1 ....
- Garbage collection indicator from TGREC
- .... 1...
- Adjacent node's HPRTT value from TGREC
- .... .11.
- Local node's HPR/HPRTT values from TGREC
- 07
- Number of days left before TGREC is garbage collected
- 08–0F
- CPNAME of the adjacent node sending the TDU. The CPNAME is not network qualified. This is the node that forwarded the TDU and is not necessarily the originator of the TDU information.
- 10–13
- Current FRSN (flow reduction sequence number)
- 14–17
- Last FRSN previously sent from the adjacent node that forwarded this TDU
- 18–1B
- Resource sequence number from CV47
- 1C–1F
- First word of timestamp for trace entry