egulatory guidelines (which should be based on fair, reasonable, and non-discriminatory approaches) for establishing proper interconnection (e.g. referent interconnection offer) in order to facilitate effective and expeditious interconnection. In all cases the concrete details of the interconnection agreement needs to be mutually decided by both interconnecting telecom operators, but in a time limited manner. Alternatively, if both parties fail to establish an agreement within a predefined time frame then an interconnecting agreement may be prescribed by the authority (e.g. national regulatory agency), for the benefit of the customers which require affordable and available ICT services which end-to-end traffic may span across two or more networks and hence across several POIs. Every interconnection is based on a bilateral agreement. In order to have effective interconnection, one possibility is to establish an interconnect exchange, which will pro- vide interconnection ports to different telecom service providers and at the same time will reduce the number of needed POIs. In such case all interconnections may continue as before (between two connecting peer operators), but any required increase in the number of ports is done through the interconnect exchange. 7.3 Interconnection and QoS Table 7.3 KPIs for TDM interconnection. Key Performance Indicators (KPI) Description POI congestion This refers to number of failed call requests over the POI VS. total number of calls (e.g. benchmark threshold may be set at <0.5%). Subscriber This parameter refers to the ratio between actual seizures at the attempts-seizure success interconnection and the total number of call attempts. ratio Inter-operator POI Gives comparative performance indicators of particular efficiency inter-operator POI with respect to the other inter-operator POIs. Time-frame for activation The time limit for providing POI connectivity (one benchmark for of a new POI this KPI is 90 d). Time-frame for POI This is time frame for enhancement of capacity of th