I have a buffer below. Could somebody tell me how they decoded the extension additions
using PER?
 
I mean that from "conferenceID" , how can I know only "callIdentifier" is present and 
other
optional such as "h245SecurityMode", "tokens","cryptoTokens","fastStart" are absent? 
since Hex "09 00 11 00" is between "conferenceID" and "callIdentifier", what are these
 Hex"09 00 11 00" doing here?

Connect-UUIE is defined in H225 specification.
Connect-UUIE ::= SEQUENCE
{
     protocolIdentifier ProtocolIdentifier,
     h245Address                TransportAddress    OPTIONAL,
    destinationInfo             EndpointType,
    conferenceID                ConferenceIdentifier,
    ...,
    callIdentifier              CallIdentifier,
   h245SecurityMode     H245Security         OPTIONAL,
   tokens                             SEQUENCE OF ClearToken OPTIONAL,
   cryptoTokens                  SEQUENCE OF CryptoH323Token OPTIONAL,
   fastStart                 SEQUENCE OF OCTET STRING OPTIONAL
}

Below is ASN.1 decoding for Connect-UUIE
ASN.1:  value H323-UserInformation ::=  
ASN.1:  { 
ASN.1:    h323-uu-pdu  
ASN.1:    { 
ASN.1:      h323-message-body connect :  
ASN.1:        { 
ASN.1:          protocolIdentifier { 0 0 8 2250 0 2 }, 
ASN.1:          h245Address ipAddress :  
ASN.1:            { 
ASN.1:              ip 'C0A80196'H, 
ASN.1:              port 1037 
ASN.1:            }, 
ASN.1:          destinationInfo  
ASN.1:          { 
ASN.1:            vendor  
ASN.1:            { 
ASN.1:              vendor  
ASN.1:              { 
ASN.1:                t35CountryCode 181, 
ASN.1:                t35Extension 0, 
ASN.1:                manufacturerCode 21324 
ASN.1:              }, 
ASN.1:              productId '4D6963726F736F6674AE204E65744D656574696E67AE00'H, 
ASN.1:              versionId '332E3000'H 
ASN.1:            }, 
ASN.1:            terminal  
ASN.1:            { 
ASN.1:            }, 
ASN.1:            mc FALSE, 
ASN.1:            undefinedNode FALSE 
ASN.1:          }, 
ASN.1:          conferenceID 'DC3164503C21D41180CE00C04FA0C74A'H,   
//Question???????????????????????
ASN.1:          callIdentifier                                                         
                          // Question????????????????????????
ASN.1:          { 
ASN.1:            guid 'DB3164503C21D41180CE00C04FA0C74A'H 
ASN.1:          } 
ASN.1:        } 
ASN.1:    } 
ASN.1:  }

Here is the Hex
02 C0 06 00 08 91 4A 00 02 00 C0 A8 01 96 04 0D 
22 C0 B5 00 53 4C 16 4D 69 63 72 6F 73 6F 66 74 
AE 20 4E 65 74 4D 65 65 74 69 6E 67 AE 00 03 33
2E 30 00 00 DC 31 64 50 3C 21 D4 11 80 CE 00 C0
4F A0 C7 4A 09 00 11 00 DB 31 64 50 3C 21 D4 11
80 CE 00 00 C0 4F A0 C7 4A  

Thanks

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