Problems with circuit switching Many data sessions are low duty factor(bursty), (message transmission time)/(message interarrival time)<<1 Same as:(message arrival rate)*(message transmission time)<< 1 The rate allocated to the session must be large enough to meet the delay requirement. This allocated capacity is idle when the session has nothing to send If communication is expensive then circuit switching is uneconomic to meet the delay requirements of bursty traffic Also, circuit switching requires a call set-up during which resources are not utilized If messages are much shorter than the call set-up time then circuit switching is not economical (or even practical) More of a problem in high-speed networksProblems with circuit switching • Many data sessions are low duty factor (bursty), (messag e transmission time)/(messag e interarrival time) < < 1 Same as: (message arrival rate) * (message transmission time) << 1 • The rate allocated to the session must be large enough to meet the delay requirement. This allocated capacity is idle when the session has nothing to send • If communication is expensive, then circuit switching is uneconomic to meet the delay requirements of bursty traffic • Also, circuit switching requires a call set-up during which resources are not utilized. If messages are much shorter than the call set-up time then circuit switching is not economical (or even practical) – More of a problem in high-speed networks Eytan Modiano Slide 11