Re: [ASN.1] how to decode the extension additions in CHOICEusing PER?

[Louw Jansen van Rensburg]

Hi,

I've got the same problem.... did anyone answer yet?

Thanx

Louw

Louw Jansen van Rensburg

School for Electrical & Electronic Engineering 
Potchefstroom University for Christian Higher Education
Potchefstroom
South Africa

Tel:+27 (0) 18 299 1961
Cel:          082 782 1373
Fax:+27 (0)18 299 1977

e-mail: [EMAIL PROTECTED]


>>> [EMAIL PROTECTED] 02/08/01 06:57PM >>>
Could someone tell me how to decode the extension additions in CHOICE using PER? Below 
is a buffer, could someone show me how they decoded it?  Thanks, bing.

---- Abstract Syntax Notation 1   (ASN1) ----
ASN.1:        forwardLogicalChannelParameters  
ASN.1:        { 
ASN.1:          dataType data :  
ASN.1:            { 
ASN.1:              application t120 : separateLANStack : NULL, 
ASN.1:              maxBitRate 0 
ASN.1:            }, 
ASN.1:          multiplexParameters h2250LogicalChannelParameters :  
ASN.1:            { 
ASN.1:              sessionID 0 
ASN.1:            } 



Hex:
**10 18 30 01 00 00 00 80 03 00 00 00 **  break down these Hex in bits as follows:

0               Indicates that no extension addition in 
*forwardLogicalChannelParameters*
0               Indicates that optional *portNumber* is absent in  
*forwardLogicalChannelParameters*
0               Indicates that no extension addition in *DataType*
100                     Indicates that *data* has been chosen in *DataType*
0               Indicates that no extension addition in *DataApplicationCapability*
0               Indicates that no extension addition in *application*

0001                    Indicates that *t120* has been chosen in *application*
1               Indicates that extension addition is present in 
*DataProtocolCapability*
000             QUESTION: are these three bits padding 
bits????????????????????????????????
 
QUESTION: from rest Hex (30 01 00 00 00 ), how can I know *separateLANStack* has been 
chosen???????
QUESTION: how did *maxBitRate = 0* decode using PER? Here maxBitRate is INTEGER 
(0..4294967295) 

        
H245 specification:

        forwardLogicalChannelParameters SEQUENCE
        {
                portNumber      INTEGER (0..65535) OPTIONAL,
                dataType        DataType,
                multiplexParameters     CHOICE
                {
                        h222LogicalChannelParameters    H222LogicalChannelParameters,
                        h223LogicalChannelParameters    H223LogicalChannelParameters,
                        v76LogicalChannelParameters     V76LogicalChannelParameters,
                                ...,
                        h2250LogicalChannelParameters   H2250LogicalChannelParameters,
                        none    NULL  -- for use with Separate Stack when
                                  -- multiplexParameters are not required
                                  -- or appropriate

                },
                ...,
                forwardLogicalChannelDependency LogicalChannelNumber OPTIONAL,
                        -- also used to refer to the primary logical channel when 
using video redundancy coding
                replacementFor  LogicalChannelNumber OPTIONAL

        },

DataType                ::=CHOICE
{
        nonStandard     NonStandardParameter,
        nullData        NULL,
        videoData       VideoCapability,        
        audioData       AudioCapability,
        data            DataApplicationCapability,
        encryptionData  EncryptionMode,
        ...,
        h235Control     NonStandardParameter,
        h235Media       H235Media,
        multiplexedStream       MultiplexedStreamParameter
}


        DataApplicationCapability       ::=SEQUENCE
{
        application     CHOICE
        {
                nonStandard     NonStandardParameter,
                t120    DataProtocolCapability,
                dsm-cc  DataProtocolCapability,
                userData        DataProtocolCapability,
                t84     SEQUENCE
                {
                        t84Protocol     DataProtocolCapability,
                        t84Profile      T84Profile
                },
                t434    DataProtocolCapability,
                h224    DataProtocolCapability,
                nlpid   SEQUENCE
                {
                        nlpidProtocol   DataProtocolCapability,
                        nlpidData       OCTET STRING
                },
                dsvdControl     NULL,
                h222DataPartitioning    DataProtocolCapability,
                ...,
                t30fax  DataProtocolCapability,
                t140    DataProtocolCapability,
                t38fax  SEQUENCE
                {
                        t38FaxProtocol  DataProtocolCapability,
                        t38FaxProfile   T38FaxProfile
                },
                genericDataCapability   GenericCapability
        },
        maxBitRate      INTEGER (0..4294967295),        -- units 100 bit/s
        ...
}

DataProtocolCapability  ::=CHOICE
{
        nonStandard     NonStandardParameter,
        v14buffered     NULL,
        v42lapm NULL,   -- may negotiate to V.42bis
        hdlcFrameTunnelling     NULL,
        h310SeparateVCStack     NULL,
        h310SingleVCStack       NULL,
        transparent     NULL,
        ...,
        segmentationAndReassembly       NULL,
        hdlcFrameTunnelingwSAR  NULL,
        v120            NULL,   -- as in H.230
        separateLANStack        NULL,
       v76wCompression          CHOICE
        {
                transmitCompression             CompressionType,       
                receiveCompression      CompressionType,       
                transmitAndReceiveCompression   CompressionType,       
                ...
        },
        tcp                     NULL,
        udp                     NULL
}