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Specially, this message has got two IEs with the same type, and they both are optional:

-- TransferToNumberRequest RETURN RESULT Parameters
TransferToNumberRequestRes ::= [PRIVATE 18] SET {
    digits-Destination                      [4] IMPLICIT Digits OPTIONAL,
    -- (Destination) M a
    -- O e, f
    digits-Carrier                          [4] IMPLICIT Digits OPTIONAL,

Given the nature of ASN.1 set type, the question is:

If there's only one IE with the tag value 4 appear in a BER-encoded PDU buffer, how can we judge its actual type (digits-Destination or digits-Carrier) ?

Thanks for any of your answers.

asked 11 Feb '14, 21:33

TB_BT's gravatar image

accept rate: 0%

If you look at the document ref ("M a") the first parameter is Mandatory in the specification. I don't remember if I had to make it optional in Wirehark for it to work properly or if that's a bug. This probably works for Wireshark as the tags are in a table and the mandatory parameter is found first. It might not work if there are 3 tags with the value of 4. I'm not sure to what extent ANSI MAP actually adhere to ASN1 specifications I haven't found a complete ASN1 document as you can for GSM MAP. The specification might say that each parameter may only occure once as well I suppose.

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answered 11 Feb '14, 22:20

Anders's gravatar image

Anders ♦
accept rate: 17%

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question asked: 11 Feb '14, 21:33

question was seen: 1,120 times

last updated: 11 Feb '14, 22:20

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