--- title: "Traffic engineering goals; E.600 busy hours" subject: "Telecommunications" chapter: 6 key: "semester_8/telecommunications:traffic-engineering-busy-hour-e600" source: https://www.bctengineer.com/q/semester_8/telecommunications/traffic-engineering-busy-hour-e600 site: BCT Engineering --- # Traffic engineering goals; E.600 busy hours Telecommunications · Chapter 6: Telephone Traffic - Asked in: 2070 Asar, 3+3 marks - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/telecommunications/traffic-engineering-busy-hour-e600 - Whole chapter: https://www.bctengineer.com/md/semester_8/telecommunications/chapter-6 ## Question Explain the major tasks and goals of traffic engineering in telecommunication along with different types of busy hour defined by CCITT in its recommendation E.600. ## Short answer Major tasks include measurement, forecasting, modelling, dimensioning, performance evaluation, routing, and monitoring. Goals are target GoS, minimum cost, high utilisation, low delay, and overload protection. Busy hour (E.600) is the continuous 60-minute peak; peak busy hour varies daily; time-consistent busy hour uses a fixed start time each day with highest average traffic. ## Answer **Traffic engineering** is the use of probability theory and traffic measurements to find how much equipment (trunks, switches, channels, queues) a network needs to carry the expected traffic at an acceptable grade of service and at minimum cost. #### Major tasks of traffic engineering 1. **Traffic measurement:** record calls, holding times and busy-hour traffic on each route and switch. 2. **Traffic forecasting:** predict future demand from growth of subscribers and services. 3. **Modelling:** choose the right model (Erlang B, Erlang C, Engset, binomial) for each part of the network. 4. **Dimensioning:** compute the number of trunks, switching paths, registers and processors needed for a target GoS. 5. **Performance evaluation:** compute blocking, delay and server utilisation of existing equipment. 6. **Routing and overflow planning:** plan high-usage and final routes, alternate routing. 7. **Monitoring and network management:** detect congestion and overload and apply controls. #### Goals - Provide a target **grade of service** (e.g. GoS 0.01 or 0.02) so most calls succeed. - **Minimum cost:** avoid over-provisioning while keeping quality. - High **utilisation** of trunks and switching equipment. - Keep delays (dial tone delay, post-dialling delay) within limits. - Allow for growth and protect the network from overload. #### Busy hour as defined in CCITT Recommendation E.600 Equipment is dimensioned for the busy hour, not the daily average. E.600 defines: 1. **Busy hour:** the continuous 1-hour period lying wholly within the time interval concerned for which the traffic volume or the number of call attempts is greatest. 2. **Peak busy hour:** the busy hour of each individual day. It usually changes from day to day. 3. **Time-consistent busy hour:** the 1-hour period starting at the same time each day for which the average traffic volume or call-attempt count of the exchange or resource group is greatest over the days under consideration. ```text Traffic ^ peak busy hour (day 1) | __ | _____/ \____ ____ | / \______/ \ |____/ \___ +----+----+----+----+----+----+----+--> time 08 10 12 14 16 18 20 ``` In practice, traffic is read in quarter-hour intervals; the four consecutive quarter-hours with the highest total form the busy hour. The time-consistent busy hour is preferred for planning because one fixed hour is used every day. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What is the goal of traffic engineering? A. Maximise trunks B. Eliminate all blocking C. Only record calls D. Provide target GoS at minimum cost Answer: D. Balance service quality and cost. (Key point: Purpose) 2. Dimensioning means? A. Computing trunks, paths, processors for target GoS B. Measuring calls C. Forecasting growth only D. Routing Answer: A. Equipment is sized for the target GoS. (Key point: Dimensioning) 3. Why design for the busy hour? A. It is the average B. It is when traffic is greatest C. It is cheapest D. Calls are shortest Answer: B. Dimensioning for the busy hour keeps service acceptable. (Key point: Busy hour) 4. Time-consistent busy hour is? A. The busiest hour on each day B. Any hour of the day C. The same 1-hour period each day with greatest average traffic over days D. A 15-minute interval Answer: C. Peak busy hour varies daily; the time-consistent one is fixed. (Key point: Time-consistent busy hour) ## Related in Telecommunications - [E.600 busy hour, NTA duties and ITU sectors](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Ae600-busy-hour-nta-itu) — Telecommunications, chapter 7 - [Traffic numerical: 600 calls, 40 lost, 120 s](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Agos-600-calls-120s) — Telecommunications, chapter 6, asked 5× - [CCITT Q.40 transmission plan guidelines](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Accitt-q40-transmission-plan) — Telecommunications, chapter 2 - [Traffic engineering objectives; Engset formula](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Atraffic-objectives-engset) — Telecommunications, chapter 6 - [Importance and unit of traffic engineering](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Atraffic-engineering-importance-unit) — Telecommunications, chapter 6 - [Short note: Telephone traffic engineering](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Ashort-note-traffic-engineering) — Telecommunications, chapter 6, asked 2× ## Related in other subjects - [Traffic engineering; road user characteristics and HVE](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Ate-definition-road-user-hve) — Transportation Engineering II, chapter 1 - [Traffic engineering; road users and vehicular characteristics](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Ate-definition-road-users-vehicular) — Transportation Engineering II, chapter 1 - [Phases of EGS and its tasks](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Aegs-phases-tasks) — Engineering Geology II, chapter 1, asked 8×