Showing posts from April 26, 2009

Frame Relay Voice-Adaptive Traffic Shaping(FR-VATS) (Bc=minCIR/100)

在QoS 2.2 Vol.2 P.7-72的slide中出現了一段"Bc to minCIR / 100"的內容,我翻遍了整本教材也完全沒有提到這個公式的由來,所以我特地去翻了一下Cisco官網的內容,後來在以下網址中找到一段相關的敘述,原來是Cisco IOS在PVC上為了因應Voice的特性因此選定Tc = 10ms,避免過大的延遲。
Configuring Frame Relay Traffic Shaping on 7200 Routers and Lower Platforms
Configurable Parametersframe relay cirThe average rate you want to send traffic out on a given PVC in bps. This is generally higher than the guaranteed rate but less than the access rate (AR). It equals the guaranteed rate only if:The service provider does not allow you to send above guaranteed rate.The physical line rate on the interface is same as the guaranteed rate.There are Voice (voice over IP [VOIP] or voice over Frame Relay [VOFR]) packets on this PVC, therefore you cannot afford dropped packets for quality or service.The value of the CIR is 56000 bps is by default.frame relay mincirThe actual guaranteed rate obtained from service provider in bps. This value should be the minimum rate you should drop to in the event of…