题目内容
In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet. Spread spectrum simply means that data is sent in small pieces over a number of the (16) frequencies available for use at any time in the specified range. Devices using (17) spread spectrum(DSSS) communicate by (18) each byte of data into several parts and sending them concurrently on different (19) . DSSS uses a lot of the available (20) , about 22 megahertz(MHz).
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Networks can be interconnected by different devices in the physical layer networks can be connected by (1) or hubs. Which just move the bits from one network to an identical network. One layer up we find bridges and switches which operate at data link layer. They can accept (2) examine the MAC address and forward the frames to a different network while doing minor protocol translation in the process in me network layer, we have routers that can connect two networks, If two networks have (3) network layer, the router may be able to translate between the packer formats. In the transport layer we find transport gateway, which can interface between two transport connections Finally, in the application layer, application gateways translate message (4) . As an example, gateways between Internet e-mail and X.400 e-mail must (5) the e-mail message and change various header fields.
简述养老保险的两种制度种类的内容。
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 (36) routing algorithm that (37) work clone on the OSI IS-IS intradomain routing protocol. This routing, as compared to distance-vector routing, requires (38) processing power. The (39) algorithm is used to calculate routes. OSPF routing table updates only take place when necessary, (40) at regular intervals.
For each blank, choose the best answer from the four choices and write down on the answer sheet. (21) is a six bytes OSI layer 2 address which is burned into every networking device that provides its unique identity for point to point communication. (22) is a professional organization of individuals in multiple professions which focuses on effort on lower-layer protocols. (23) functions with two layers of protocols. It can connect networks of different speeds and can be adapted to an environment as it expands. (24) is the popular LAN developed under the direction of the IEEE802.5. (25) is the popular backbone technology for transmitting information at high speed with a high level of fault tolerance which is developed under the direction of ANSI.
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