1) (3 points) Remember the Ethernet LAN protocol (explained on pages 346-347 and
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1) (3 points) Remember the Ethernet LAN protocol (explained on pages 346-347 and in slides 17-20). Explairn why an address field is needed in the Ethernet LAN protocol 2) (2 points) How does the Ethernet protocol behave in a very heavily loaded network (one where there are lots of nodes attempting to send messages)? What behavior do you expect to see and why? 3) (2 points) In an Ethernet network, where there are collisions, are messages guaranteed to be delivered in some maximum amount of time? Explain your answer. 4) (1 point) Assume there is a wide area network with N nodes, where N >= 2. what is the smallest number of point- to-point communication links such that every node in the network is able to talk to every other node?Explanation / Answer
(1) Address field is of 6 byte(48-bit).Ethernet 802.3 uses 48-bit address(MAC address).This addresses can be local or global in type. Local addresses have no significance,it is required for ethernet installation.But global addresses are unique globally,every system that uses ethernet has a unique global address hardwired into that ethernet interface.So,by this address any ethernet interface can address other ethernet interfaces.Actually network layer is deployed upon this.
(2)In Ethernet LAN protocol,When a frame is ready to be transmitted,then it senses the carrier/medium.If idle then only transmits,else wait.Now if after sensing idle two or more frames have been transmitted,they will collide.Then a jam signal will be sent to the nodes that transmitted the frames.Then these node knows that collison happened,then it will restart counter and retransmit the frame again.
(3)It is not guaranteed that all frames to be transmitted in some maximum time.For collison what it does that
(1)Transmit jam signal for minimum packet time to ensure that all receivers detect the collision.(2)Then increment retransmission counter by 1.(3)check for the maximum number of transmission attempts.If reached, stop transmission.(4)else ,calculate and wait the random backoff period based on number of collisions.(5)repeat 1.
So,(1) what can happen that max attempt reached,then transmission will be stopped.
(2)It sense collision,wait,calculated back-off time,again sense collision.In this way it can be possible that max time for transmission may be over.
(4)A network with n node will be able to talk to each other if there is a path between every nodes in the network.that means connected.So,minimum number of edges(links) required so that the network is connected is (n-1)
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