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GPRS: PACKET SI STATUS Decoding Problem

asked 2019-06-18 09:30:23 +0000

Nalin gravatar image

updated 2019-06-18 10:16:27 +0000

grahamb gravatar image

While decoding 3GPP GPRS RLC/MAC Uplink Control Message “PACKET_SI_STATUS”, it is seen that for MESSAGE_TYPE decoding text is showing as Invalid message type. (ideally it should be any valid System Information type).

Can you please help to check this decoding issue.?

According to 3GPP spec, 44.060, Table 11.2.17b.2: PACKET SI STATUS information element details, SI MESSAGE TYPE is as mentioned below.

SI_MESSAGE_TYPE (8 bit field) This field is the binary representation of the message type of the indicated SI message (see 3GPP TS 24.007 and 3GPP TS 44.018).

But from decoded output, it seems this IE value is taken from 44.060 not from 44.018.

Example:

Wireshark decoder printing 0x03 as : .... 0000  0011 .... = MESSAGE_TYPE (DL): PACKET_MEASUREMENT_ORDER (3)

But Ideally it should be 0 0 0 0 0 0 1 1 SYSTEM INFORMATION TYPE 2ter

RAW data of PDU is:

40 34 9b 19 63 6c 69 81 30 32 0e 47 18 fb 18 43 2b 2b 2b 2b 2b 2b 2b

Decoded output:

SI_Message_List
    .... ...1 = SI_Message Exists: 1
    SI_Message[0]
        0001 1001 = MESSAGE_TYPE (DL): Invalid Message Type (25)
        01.. .... = MESS_REC: 1
    ..1. .... = SI_Message Exists: 1
    SI_Message[0]
        ...0 0011  011. .... = MESSAGE_TYPE (DL): Invalid Message Type (27)
        ...0 1... = MESS_REC: 1
    .... .1.. = SI_Message Exists: 1
    SI_Message[0]
        .... ..00  0110 10.. = MESSAGE_TYPE (DL): Invalid Message Type (26)
        .... ..01 = MESS_REC: 1
    1... .... = SI_Message Exists: 1
    SI_Message[0]
        .000 0001  0... .... = MESSAGE_TYPE (DL): PACKET_DOWNLINK_ASSIGNMENT (2)
        .01. .... = MESS_REC: 1
    ...1 .... = SI_Message Exists: 1
    SI_Message[0]
        .... 0000  0011 .... = MESSAGE_TYPE (DL): PACKET_MEASUREMENT_ORDER (3)
        .... 00.. = MESS_REC: 0
    .... ..1. = SI_Message Exists: 1
    SI_Message[0]
        .... ...0  0000 111. = MESSAGE_TYPE (DL): PACKET_TIMESLOT_RECONFIGURE (7)
        .... ...0  0... .... = MESS_REC: 0
    .1.. .... = SI_Message Exists: 1
    SI_Message[0]
        ..00 0111  00.. .... = MESSAGE_TYPE (DL): Invalid Message Type (28)
        ..01 .... = MESS_REC: 1
    .... 1... = SI_Message Exists: 1
    SI_Message[0]
        .... .000  1111 1... = MESSAGE_TYPE (DL): Invalid Message Type (31)
        .... .01. = MESS_REC: 1
    .... ...1 = SI_Message Exists: 1
    SI_Message[0]
        0001 1000 = MESSAGE_TYPE (DL): Invalid Message Type (24)
        01.. .... = MESS_REC: 1
    ...0 .... = Message List: 0
    .... 0... = ADDITIONAL_MSG_TYPE: 0
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Wireshark version?

grahamb gravatar imagegrahamb ( 2019-06-18 10:16:39 +0000 )edit

I think it is Version 2.4.5 (v2.4.5-0-g153e867ef1)

Nalin gravatar imageNalin ( 2019-06-19 07:42:29 +0000 )edit

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answered 2019-06-18 19:13:53 +0000

Pascal Quantin gravatar image

Hi Nalin,

thanks for the report. I pushed a fix here: https://code.wireshark.org/review/#/c...

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Thanks Pascal

Nalin gravatar imageNalin ( 2019-06-19 07:41:38 +0000 )edit

Note that Wireshark 2.4 hits end of life next month so updates will end. You should plan to upgrade.

grahamb gravatar imagegrahamb ( 2019-06-19 08:16:36 +0000 )edit

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Asked: 2019-06-18 09:30:23 +0000

Seen: 36 times

Last updated: Jun 18