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For each blank, choose the best answer from the four choices and write down on the answer sheet. (11) is a protocol that a host uses to inform a router when it joins Or leaves an Internet multicast group. (12) is an error detection code that most data communication networks use. (13) is an interior gateway protocol that uses a distance vector algorithm to propagate routing information. (14) 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. (15) is an identifier of a web page.

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(56) is a one-way function that takes an arbitrarily long piece of plaintext and from it computes a fixed-length bit string. (57) 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. (58) is an approach preferred by cable TV providers. In this solution the fiber terminates at an opto-electrical converter and the final segment is a shared coaxial cable. (59) is a device used to connect two separate network that use different communication protocol. (60) is a digital-to-digital polar encoding method in which the signal level is always either positive or negative.

A. Router
B. Gateway
C. Bridge
D. hub

(56) is a one-way function that takes an arbitrarily long piece of plaintext and from it computes a fixed-length bit string. (57) 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. (58) is an approach preferred by cable TV providers. In this solution the fiber terminates at an opto-electrical converter and the final segment is a shared coaxial cable. (59) is a device used to connect two separate network that use different communication protocol. (60) is a digital-to-digital polar encoding method in which the signal level is always either positive or negative.

A. RTP
B. RTTP
C. FTP
D. NNTP

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.

A. reapers
B. relays
C. packages
D. modems

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. A socket is basically an end point of a communication link between two applications. Sockets that extend over a network connect two or more applications running on (31) computers attached to the net-work. A socket (32) two addresses: (33) . Sockets provide a (34) communication channel between one or more systems. There are (35) sockets separately using TCP and UDP.

A. message and packet
B. packet and frame
C. stream and datagram
D. flow and block

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