tted and interpreted. The result of this analysis will be described in terms of message and operation specifications, using AML syntax for specifications and data types (based on ASN. 5 Protocol Network Modelling 5.5.3 The Integrator Protocol The message specification of the integrator MessTrain message looks as shown in Fig. 5.34. The syntax used for the message specification is ASN. 1. However, since no general encoding methods have been used in EIA553, all data types are AML types. AML types are distinguished from ASN.1 types by the $-sign. Basically, AML types are encoded in the smallest number of bits possible. Type information is never encoded and length information is encoded only if the type is not length- constrained. Read more about AML types in Appendix 2. Service access McsMessTrain control Broadcast data handling - OvhMessTrain MscSdu OvhSdu MessTrain specification T1T2 ::= $BITSTR SIZE (2) Integrator partOfOvhMessTrain T1T2 ::= '11'B mscOneOnly T1T2 ::= '00'B mscFirst T1T2 ::= '01'B FOCCsdu mcsNotFirst T1T2 ::= '10'B DCC ::= $BITSTR SIZE (2) P ::= $BITSTR SIZE (12) MessTrain ::= $SEQ{$SEQ OF Ovh, $SEQ OF Msc} Ovh ::= SSEQ{{partOfOvhMessTrain},DCC,O OvhSdu $BITSTR SIZE (24) Msc ::= $SEQ{PartOfMscMessTrain,DCC,MscSduFragm,P} PartOfMscMessTrain ::= T1T2 {mscOneOnly, mscFirst,mcsNotFirst} MscSduFragm :: $BITSTR SIZE (24) Fig. 5.34 The message specification for the integrator 1. The integrator receives a sequence of FOCCsdu that represents the MessTrain every 800 ms. After discrimination, part of the data is distributed to the broad- cast data-handling element as sequence of OvhSdu, and another part to the serv- ice access control element as a sequence of MscSdu. The MessTrain consists of a number of messages of two types, Ovh and Msc, in that order. The Ovh includes the OvhSdu, the Msc a fragment of the MscSdu (MscSduFragm). 3. The discrimination method used includes a discrimination identifier, called T1T2 in the MessTrain protocol. This parameter has four values, encoded in two bits, but actually two 