hello,
If you have a look at the earlier definition of updatelocationarg
in the first GSMMAP specs it will answer all your questions:
UpdateLocationArg ::= SEQUENCE {
imsi IMSI,
locationInfo LocationInfo,
vlrNumber ISDN-AddressString,
lmsid [10] IMPLICIT LMsId OPTIONAL}
mscnumber has been added by a different person which apparently like
tagging even if it is not required. He also added vlr-capabilities.
When updating the specifications you have to keep the old values with the
same tag for backward compatibility but you can add any new value with the
tag you like.
cheers.
--------------------------------------------------------------------------
Salim Mounir Alaoui Ph.D.
[EMAIL PROTECTED]
Computer Science Dept. [EMAIL PROTECTED]
[EMAIL PROTECTED]
Florida Institute of Technology
Melbourne, Florida
Voice: 321 733 7191
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On Thu, 18 Jul 2002, Bancroft Scott wrote:
> On Thu, 18 Jul 2002, tong wrote:
>
> > HI all
> >
> > again GSM-MAP
> > example:
> > UpdateLocationArg ::= SEQUENCE {
> > msi MSI,
> > msc-Number [1] ISDN-AddressString,
> > vlr-Number ISDN-AddressString,
> > lmsi [10] LMSI OPTIONAL,
> > extensionContainer ExtensionContainer OPTIONAL,
> > ... ,
> > vlr-Capability [6] VLR-Capability OPTIONAL }
> >
> > 1 why encode 1,6,10,not continuously?
>
> I don't follow the question. Please rephrase.
>
> > 2 the order of context why not from small to big ? in this example is 1,10,6.
>
> I don't know (but see my guess below). Perhaps someone who was involved
> in the writing of GSM-MAP can give you some insight.
>
> > 3 why some subtype(vlr-Number) not have context tag?
>
> Some components are not taged because tags are required only when the type
> would be ambiguously defined without it. A better question would be, "Why
> does msc-Number have a tag, for it is not required by ASN.1?". I suspect
> that whomever wrote the ASN.1 module thought that by adding tags where
> they aren't required by ASN.1 it would somehow help them in manually
> writing an encoder/decoder. Another possibility is that somewhere else in
> GSM-MAP these components are tagged as you see above, and the person who
> defined UpdateLocationArg thought that it would make the definition more
> consistent if they were tagged the same here.
>
> > 4 msc-Number not have OPTIONAL,so must presence,and so use context tag is
>absolutely unneeded ?
>
> Correct. As far as ASN.1 goes, there is no need for the tag on
> msc-Number. Note that it is required by encoders/decoders since it was
> specified in the definition of the UpdateLocationArg type.
>
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