Regarding INAP parameter Tags

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Regarding INAP parameter Tags

prabath weerasinghe
Hi All,

This is regarding INAP PDU encoding and decoding. I'm working on an INAP protocol implementation and was referring  ASN.1 specification. Here follows an excerpt from the spec for InitialDP.

InitialDPArg ::= SEQUENCE {
 serviceKey [0] ServiceKey,
 calledPartyNumber [2] CalledPartyNumber OPTIONAL,
 callingPartyNumber [3] CallingPartyNumber OPTIONAL,
 callingPartysCategory [5] CallingPartysCategory OPTIONAL,
 cGEncountered [7] CGEncountered OPTIONAL,
 iPSSPCapabilities [8] IPSSPCapabilities OPTIONAL,

As per the specification, serviceKey has the tag value of 0 and calledPartyNumber has a tag value of 2 an so on. When I checked a sample INAP pcap
INAP-Sample-PCAP , it was showing the tag values for serviceKey and calledPartyNumber as 80 and 82 in Hex. 
Could anyone please explain the reason for the difference ?  Is there any special way of encoding the tag value ?

Thanks and Regards,
Prabath Weerasinghe

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