ent is inserted or removed from the chain. This is a major change, compared to the previous ones. Besides the master, this concerns the SE1 elements on the uplink and downlink sides of the point in the chain where the new SEl-element is inserted. The simplest way is, of course, to insert the new SE1 element at the end of the chain. Inlinking can be performed when the new element becomes initiated into the network. It immediately sends a mes- sage to the previous chain terminator, providing its SE1 identity. If the new SE1 will be used frequently by the master, it might have to be inserted higher up in the chain. In that case, it must send a message to the uplink element, also defin- ing itself as the downlink element, and to the downlink element, identifying itself as the uplink element. Insertion of a new SE1 element in the chain also affects configuration data in Int1s, since Int1 does the translation between SE1 identities and SAPIs, and han- dles associations between SE1 elements. 5.6.3 Protocol Conversion In general, the relaying mechanism that was described in the previous section does not hinder allocation of service elements in the master. However, the master then becomes a protocol element that is affected both by modifications to the exter- nal protocol, and by internal restructuring of the implementation of that protocol. Since these types of changes occur more or less independently, it is not a good approach to allocate service elements in the master. A better approach is to dedicate a master to handle only the protocol conversion that must be performed between the external protocol and the internal structure of service elements. An even better approach is to separate the master into one part that terminates external events (external OPH), another part that handles the internal events (internal OPH) and a transaction handler, see Fig. 5.43. 5 Protocol Network Modelling external interface External protocol element [io1,102} Master eo1Req Transact.handler {io3} External Transaction Internal eo1Cnf speci