tutorial-2-solution.pdf - The network core v v mesh of interconnected routers packet-switching hosts break application-layer messages into packets �

# tutorial-2-solution.pdf - The network core v v mesh of...

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Introduction v mesh of interconnected routers v packet-switching: hosts break application-layer messages into packets § forward packets from one router to the next, across links on path from source to destination § each packet transmitted at full link capacity The network core 1-1
Introduction Packet-switching: store-and-forward v takes L / R seconds to transmit (push out) L -bit packet into link at R bps v store and forward: entire packet must arrive at router before it can be transmitted on next link one-hop numerical example: § L = 7.5 Mbits § R = 1.5 Mbps § one-hop transmission delay = 5 sec more on delay shortly … 1-2 source R bps destination 1 2 3 L bits per packet R bps v end-end delay = 2 L / R (assuming zero propagation delay)
Q1 a) At time t 0 the sending host begins to transmit. At time t 1 = L/R 1 , the sending host completes transmission and the entire packet is received at the router (no propagation delay). Because the router has the entire packet at time t 1 , it can begin to transmit the packet to the receiving host at time t 1 . At time t 2 = t 1 + L/R 2 , the router completes transmission and the entire packet is received at the receiving host (again, no propagation delay). Thus, the end-to-end delay is L/R 1 + L/R 2 .

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