CCS#7 MTP congestion and overload handling in different STP architectures

This paper describes CCS 7 MTP congestion and overload handling mechanisms for different STP architectures. An analysis of MTP Level 2 and Level 3 congestion mechanisms is performed, investigating, in particular, the congestion handling mechanisms based on the measurement of congestion thresholds at Level 2 buffers. The dependence on the implementation is investigated considering different architectures of some existing STP systems: in particular, centralized, hybrid and distributed Level 3 STP architectures are examined. Care is given in analysing possible treatments and message processing at different levels of the considered architectures. Finally, some problems related to congestion handling, which are not investigated in depth in the CCITT models, are analysed. In order to overcome some problems related to STP internal congestion, two proposals are suggested: first, the congestion of the communication processor between level 2 and 3 processors should activate level 2 congestion mechanism; second, level 3 overload handling should incorporate internal overload handling procedures based on the exchange of level 3 congestion messages and a policy of message discard and priority