Section 2(iii) in Regulation on Quality of Service of Dial-Up and Leased Line Internet Access Service, 2001
(iii)'Grade Of Service (GOS)' means the ratio of blocked calls and calls offered on a circuit group link connecting two nodes in a pubic switched network. It is measured during Time Consistent Busy Hour (TCBH). Busy Hour is defined as the 60 minutes period during the day when the traffic is the highest for a given number of days. For this purpose, ITU recommends taking traffic (Erlangs) measurements at 15 minutes interval by suitable man-machine commands, to establish the Busy Hour. For establishing the time consistency of the Busy Hour, the measurements are to be taken over a period of 90 days.
