Wireshark-bugs: [Wireshark-bugs] [Bug 8165] Filter s1ap.eNB_UE_S1AP_ID exists with multiple case
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From: bugzilla-daemon@xxxxxxxxxxxxx
Date: Mon, 14 Jan 2013 14:59:39 +0000

Comment # 3 on bug 8165 from 
Hi Evan,

Looking at the ASN.1 code in the spec, this is happening because they define
two different data structures to hold the xxx-UE-S1AP-ID parameter. If they are
sent individually, they use fully uppercase:

MME-UE-S1AP-ID ::= INTEGER (0..4294967295)
ENB-UE-S1AP-ID ::= INTEGER (0..16777215)

If they are sent as a pair, they use the first letter in lowercase:

UE-S1AP-ID-pair ::= SEQUENCE{
    mME-UE-S1AP-ID        MME-UE-S1AP-ID,
    eNB-UE-S1AP-ID        ENB-UE-S1AP-ID,
    iE-Extensions        ProtocolExtensionContainer { {UE-S1AP-ID-pair-ExtIEs}
} OPTIONAL,
    ...
}

Not sure if this is just 3GPP's thing or a general ASN.1 practice, but if you
look through the spec (any 3GPP spec), they define all top-level parameters as
first letter uppercase, and all fields of a data structure as being first
letter lowercase. Since this particular parameter exists at both levels, it
ends up with two different cases.

I would guess this probably happens in other places in the 3gpp spec's too, but
the S1AP ID's are the only specific example I have.

I'm hesistant to make a suggestion on how to handle this in Wireshark since I'm
not familiar with the code base, but I think it does merit some attention to
correct it.

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