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Questions on Chapter 5

This article discusses the efficiency of slotted ALOHA and polling-based multiple access in broadcast channels. It also covers subnet addressing and IP datagram routing in interconnected LANs.

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Questions on Chapter 5

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  1. Questions on Chapter 5 Ying Zhang

  2. Question 1 • The efficiency of ALOHA • When there are N active nodes the efficiency of slotted ALOHA is Np(1-p)^{N-1}, find the value p that maximizes the expression • Using the value of p found in (a), find the efficiency of slotted ALOHA by letting N approach infinity.

  3. solution

  4. Maximum efficiency of pure ALOHA • Show that the maximum efficiency of pure ALOHA is 1/(2e)

  5. solution

  6. Question2 • Consider a broadcast channel with N nodes and a transmission rate of R bps. Suppose the broadcast channel uses polling for multiple access. Suppose the amount of time from when a node completes transmission until the subsequent node is permitted to transmit(that is, the polling delay) is t_poll. Suppose that within a polling round, a given node is allowed to transmit at most Q bits. What is the maximum throughput of the broadcast channel?

  7. Question 3 • Consider three LANs interconnected by two routers below. • A) redraw the diagram to include the adapters • B) Assign IP addresses to all of the interfaces. For Subnet 1 use addresses of the form 111.111.111.xxx; for subnet 2 uses addresses of the form 122.222.222.xxx; and for Subnet 3 use addresses of the form 133.133.133.xxx • c) assign MAC addresses to all the adapters

  8. D. consider sending an IP datagram from Host A to Host F. Suppose all of the ARP tables are up to date. Enumerate all the steps as done for the single router example

  9. subnet1 subnet3 router router subnet2

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