d notification; in AML represented by events of operation classes OFFER, INVIT, C and U_REPORT). The logical network may instantiate hundreds to thousands of such chains in parallel, each chain dedicated to one particular transaction (or call). In order to minimize delays and save processing capacity, associations within a chain should not be released until the call setup procedure is finished. On the other hand, a chain should not be retained longer then necessary, since each SE2 element occupies some resources that might be needed by other transactions/calls. The master of a chain decides when the chain is no longer needed, and only it can make the first release of an association in the chain. When a slave notices that its uplink associa- tion is released, it automatically releases the downlink association. This creates a chain-reaction of association releases that quickly eliminates the chain from the DC-plane. 5.6 Relaying in Protocol Networks A relay chain (within a particular discrimination level) is completely transparent to the protocol element in which a particular service element exists. This fact can be used to restructure the allocation of service elements, and to add or remove serv- ice elements with a minimum of impact to other elements on the chain. The config- uration of a relay chain must be known by the level 2 integrators. When a chain is defined, the Int2 of each SE1 elements that can be included in the chain stores information about which SE2 elements it handles, and about it's partner (SE1 ele- ments) on the downlink side. The SE1 element that has no downlink information knows that it is a chain terminator. The SE1 element that has no SE2 elements knows that it is the master. Two kinds of functional modifications of the chain can be done: A new SE2 element is added or removed from an existing slave SE1 element. This is a minor change, and concerns only the master and the actual SE1 ele- ment. To implement the change requires configuration data changes only in the slave's Int2. A new SE1 elem