For each blank，choose the best answer from the four choices and write down on the answer sheet．

  (66) is a protocol that a host uses to inform. a router when it joins or leaves an Internet multicast group．

  (67) is an error detection code that most data communication networks use．

  (68) is an interior gateway protocol that uses a distance vector algorithm to propagate routing information．

  (69) is a transfer mode in which all types of information are organized into fixed form. cells on an asynchronous or non -periodic basis over a range of media.

  (70) is an identifier of a web page.

(78)

(79)

(76)

(77)

(71) is a one -way function that takes an arbitrarily long piece of plaintext and from it computes a fixed-length bit string.

  (72) is a protocol that most USENET machines now use it to allow news articles to propagate from one machine to another over a reliable connection.

  (73) is an approach preferred by cable TV providers. In this solution the fiber terminates at an optoelectrical converter and the final segment is a shared coaxial cable.

  (74) is a device used to connect two separate network that use different communication protocol.

  (75) is a digital-to-digital polar encoding method in which the signal level is always either positive or negative.

(73)

(74)

(71)

(72)

In the following essay, each blank has four choices. Choose the most suitable one from the four choices and write down in the answer sheet.

 Open Shortest Path First(OSPF) is a(66)routing algorithm that(67)work done on the OSI IS-IS intradomain routing protocol. This routing, as compared to distance-vector routing, requires(68)processing power. The Dijkstra algorithm is used to calculate(69)OSPF routing table updates only take place when necessary,(70)at regular intervals.