 them. If the tags are not specified explicitly then ASN.1 will automatically tag the items in a SET. Fundamentals of EMS, NMS and OSS/BSS Type Definition: NodeInfo : = SET nodeName VisibleString, nodeState VisibleString, BladeNo INTEGER Value Assignment: MediaGateway NodeInfo : = { nodeName "MGW-10", nodeState "Offline" BladeNo 4 SET OF: Used for collection of variables of same type where order is insignificant. Type Definition: UserList : : = SET OF VisibleString Value Assignment: operators UserList : = { "Joe" "Patrick" "Dan" "Peter", ASN.1 supports explicit and implicit tagging. An advanced feature of ASN.1 that is not discussed here is the concept of modules. Module definitions are used for grouping ASN.1 definitions. 15.3 BER BER (basic encoding rules) is a transfer syntax discussed in this section. Encoding involves converting ASN.1 data to a sequence of octets for transfer. Though other methods of representing ASN.1 exist like packed encoding rules (PER), BER is suggested for OSI data transfer. BER has two subset forms called canonical encod- ing rules (CER) and distinguished encoding rules (DER). DER is suited for trans- fer of small encoded data values while CER is commonly used for large amount of data transfer. Information Handling There are three methods of encoding ASN.1 data to BER: Primitive, definite-length encoding: This method is employed with simple types and types derived from simple types using implicit tagging, excluding simple string type. The length of the value to be encoded needs to be known to perform this method of encoding. Constructed, definite-length encoding: This method is employed with simple string type, structured type, types derived from simple string, and structured type using implicit tagging and type derived from any type using explicit tagging. The length of the value to be encoded needs to be known to perform this method of encoding. Constructed, indefinite-length encoding: This method is employed with simple string type, structured type, types derived from simple string