计算机网络课后习题指导 陕西师范大学 Chapter 1 Computer Networks and the Internet PI.Design and describe an application-level protocol to be used between an automatic teller machine and a bank's centralized computer.Your protocol should allow a user's card and password to be anaccount withdrawal to be made (that is,money disbursed to the user).Your protocol entities should be able to handle the all-too-common case in which there is not enough money in the account to cover the withdrawal.Specify your protocol by listing the messages exchanged and the action taken by theautomatic teller machine or the bank's centralized computer on transmission and messaes Sketch the operation of your simple withdrawal with diagram similar to that in Figure 12.Explicitly state the assumptions made by your protocol about the underlying end-to-end transport service. 答：本题不止一个答案，很多协议都能解决这个问趣，下面是一个简单的例 子： HELO <userid> 2 now that there。card in the user all done ATM(p) Me purpose opn.) ERR 计算机网络课后习题指导 陕西师范大学 1 Chapter 1 Computer Networks and the Internet P1. Design and describe an application-level protocol to be used between an automatic teller machine and a bank’s centralized computer. Your protocol should allow a user’s card and password to be verified, the account balance (which is maintained at the centralized computer) to be queried, and anaccount withdrawal to be made (that is, money disbursed to the user). Your protocol entities should be able to handle the all-too-common case in which there is not enough money in the account to cover the withdrawal. Specify your protocol by listing the messages exchanged and the action taken by theautomatic teller machine or the bank’s centralized computer on transmission and receipt of messages. Sketch the operation of your protocol for the case of a simple withdrawal with no errors, using a diagram similar to that in Figure 1.2. Explicitly state the assumptions made by your protocol about the underlying end-to-end transport service. 答：本题不止一个答案，很多协议都能解决这个问题，下面是一个简单的例 子：