For the economic planning of an alternate routing network the number of circuits in a high-usage group should be determined so that the annual charges for the whole network arrangement are at a minimum. This is done under the constraint that given requirements for the grade of service are fulfilled. In the optimum arrangement, the cost per erlang of carrying a marginal amount of traffic over the high-usage route or over the alternative route is the same.
ITU-T E.522-1993 Referenced Document
ITU-T E.500 Traffic Intensity Measurement Principles - Series E: Overall Network Operation Telephone Service Service Operation and Human Factors Quality of Service Network Management and Traffic Engineering - Traffic Engineering - Measurement and Recording of Traffic*， 1998-04-19 Update
ITU-T E.502 Traffic Measurement Requirements for Digital Telecommunication Exchanges Series E: Overall Network Operation Telephone Service Service Operation and Human Factors Traffic Engineering - Measurement and Recording of Traffic Study Group 2*， 2001-02-01 Update
ITU-T E.506 Forecasting International Traffic - Telephone Network and ISDN - Quality of Service@ Network Management and Traffic Engineering (Study Group II) 18 pp
ITU-T E.521 CALCULATION OF THE NUMBER OF CIRCUITS IN A GROUP CARRYING OVERFLOW TRAFFIC
ITU-T E.522 NUMBER OF CIRCUITS IN A HIGH-USAGE GROUP