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Format of s1ap.m_TMSI


I'm trying to filter s1ap communication for a certain M-TMSI. So a1ap.m_TMSI looks like what I'm searching for.

M-TMSI format is a hex 4Byte number .... (i.e.: 0x21de4747)

How can I search for this or do I misunderstand m_TMSI in wireshark....?

Error: "s1ap.m_TMSI==0x021de4747" isn't a valid display filter: "0x021de4747" is not a valid byte string.

asked 12 Feb '15, 23:24

dibu's gravatar image

accept rate: 0%

One Answer:


Try instead:

s1ap.m_TMSI == 21:de:47:47

answered 13 Feb '15, 03:00

Pascal%20Quantin's gravatar image

Pascal Quantin
accept rate: 30%

sometimes solutions are real simple ....


... confusing: filter notation of technical parameter M-TMSI depends on packet you want to get the information from.....

s1ap.m_TMSI==21:de:47:47 --> thats's what I've been looking for ...

nas_eps.emm.m_tmsi == 0x21de4747 --> when I realized that I didn't see all of the packets .....

(13 Feb '15, 03:41) dibu

This is a side effect of the S1AP dissector being automatically generated from the ASN.1 specification where M-TMSI is defined as OCTET STRING (SIZE (4)). This could be easily fixed but would break backward compatibility.

(13 Feb '15, 05:25) Pascal Quantin