Decode TP4(COTP) inside CLNP

Question

Why there is no way to force wireshark to decode perfectly normal TP4 transport layer (it's called COTP in wireshark terms) packets inside CLNP network layer? All I see is "Data" and there is no way to "Decode as" or apply any other dissector. On wireshark wiki it states: "CLNP: COTP uses CLNP as its underlying network protocol." And yes, this is the case.

Example (don't see how to attach actual pcap):

15:14:34.065889 CLNP, length 65
Data PDU, hlen: 60, v: 1, lifetime: 2.5s, Segment PDU length: 65, checksum: 0x0000(unverified)
Flags [Segmentation permitted]
source address (length 20): 39.356f.0000.0001.0000.0001.0001.0000.0011.0000.00
dest   address (length 20): 39.356f.0000.0001.0000.0001.0001.0000.0022.9685.00
Data Unit ID: 0x64c0, Segment Offset: 0, Total PDU Length: 65
  Priority Option #205, length 1, value: 0x0
  undecoded non-header data, length 5
  0x0000:  0465 8d8e 15

Answer 1

OMG, thanks god we have source code:

static gboolean always_decode_transport = FALSE;

And I this leads to option inside CLNP protocol preferences that says:

"Always try to decode NSDU as transport PDUs"

Check it and it works! I really wonder why it's not checked by default, people use CLNP for something else?