计算机网络英文版复习知识教材课程.ppt

Transport Layer Problem 2 -- P34 Transport Layer Problem 2 -- P34 Transport Layer Solution 2 -- P34 a)TCP slowstart is operating in the intervals [1,6] and [23,26] b)TCP congestion advoidance is operating in the intervals [6,16] and [17,22] c)After the 16th transmission round, packet loss is recognized by a triple duplicate ACK. If there was a timeout, the congestion window size would have dropped to 1. Transport Layer Solution 2 -- P34 d)After the 22nd transmission round, segment loss is detected due to timeout, and hence the congestion window size is set to 1. e)The threshold is initially 32, since it is at this window size that slowtart stops and congestion avoidance begins. f)The threshold is set to half the value of the congestion window when packet loss is detected. When loss is detected during transmission round 16, the congestion windows size is 42. Hence the threshold is 21 during the 18th transmission round. Transport Layer Solution 2 -- P34 g)The threshold is set to half the value of the congestion window when packet loss is detected. When loss is detected during transmission round 22, the congestion windows size is 26. Hence the threshold is 13 during the 24th transmission round. i)The congestion window and threshold will be set to half the current value of the congestion window (8) when the loss occurred. Thus the new values of the threshold and window will be 4. Transport Layer Solution 2 -- P34 H)During the 1st transmission round, packet 1 is sent; packet 2-3 are sent in the 2nd transmission round; packets 4-7 are sent in the 3rd transmission round; packets 8-15 are sent in the 4th transmission round; packets15-31 are sent in the 5th transmission round; packets 32-63 are sent in the 6th transmission round; packets 64 – 96 are sent in the 7th transmission round. Thus packet 70 is sent in the 7th transmission round. The Network Layer Virtual-Circuit Networks Datagram Networks longest prefix match Router Fabric IP MTU、Fragment CIDR DHCP