The usual way to ensure reliable delivery is to provide the (71) with some feedback about what is happening at the other end of the line. Typically, the protocol calls for the receiver to send back special (72) flame bearing positive or negative (73) about the incoming frames. If the sender receives a positive acknowledgement about a frame, it knows the frame. has arrived safely. On the other hand, a negative acknowledgement means that' something has gone wrong, and the frame. must be transmitted again.

A．n additional complication comes from the possibility that hardware troubles may cause a flame to (74) completely. In this case, the receiver will not react at all, since it has no any reason to react. It should be clear that a protocol in which the sender transmits a frame. and then waits for an acknowledgement, positive or negative, will hang forever if a frame. is ever lost due to, for example, (75) hardware.

A．receiver

B．controller

C．sender

D．customer

[单选题] The usual way to ensure reliable delivery is to provide the （71） with some feedback about what is happening at the other end of the line. Typically, the protocol calls for the receiver to send back special （72） frame. bearing positive or negative （7

[单选题]（）is the way to deliver goods for different shippers in the same truck, by the most economic route.A . Joint DistributionB . United DistributionC . Multiple DeliveryD . Joint Delivery

[单选题]（ ） transport is a reliable and cost effective way totransport goods in a l

[单选题]D．eveloping reliable software on time and within(31)represents a difficult endeavor for many organizations.Usually business solutions have three main aspects:people,(32), and technology. The main reason for failing software projects has little to do

[单选题]Developing reliable software on time and within (66) represents a difficultendeavor for many organizations.Usually business solutions have three main aspects：people， (67) ，and technology.Themaion reason for failing software projects has little to do

[单选题]D．eveloping reliable software on time and within(1)represents a difficult endeavor for many organizations.Usually business solutions have three main aspects: people,(2), and technology. The maion reason for failing software projects has little to do

[单选题]_________[A] available[B] reliable[C] identifiable[D] suitable

[单选题]Pipeline is able to deliver the products based on the advantages of low rate of loss and damage, minimal climatic effects and reduced labor cost. Do you agree? （）A . Yes, I do.B . No, I do think so.C . I don’t find it hereD . I can’t find

[单选题]They went on ________ as usualA．workB．workedC．worksD．working

[单选题]_________[A] deliver [B] carry [C] perform. [D] apply