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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. MD
B. RSA
C. DES
D. MIB

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SDLC was invented by IBM to replace the older Bisynchronous protocol for wide area connections between IBM equipment. A varietion of the (71) protocol called NRM is essentially the same as SDLC. SDLC is (72) protocol like HDLC, Frame Relay or X.25.An SDLC network is made up of (73) that controls all communications, and (74) . It is capable of (75) operation, but almost all practical applications are strictly half duplex.

A. a primary station
B. one or more primary stations
C. a secondary station
D. one or more secondary stations

Frame Relay is simplified form of (51) , similar in principle to (52) , in which synchronous, frames of data are routed to different destinations depending on header information. Packets are routed throught one or more Virtual Circuits known as (53) . Most Virtual Circuits are (54) , which means that the network provider sets up all DLCI connections at subscription time. (55) are also part of the Frame Relay specification. They privide a link that only lasts only as long as the session.

A. Datagram Switching
B. Datagram Routing
C. Packet Switching
D. packet Routing

Multipurpose Internet Mail Extension (MIME) is a (46) document messaging standard in the Internet enviroment, with MIME, users can send (47) Email messages that include audio, video, graph-ices, and text to any other user of a TCP/IP network. Richtext information can also be (48) into messages. It defines the fonts, formats, and (49) features of a document so the document can be easily (50) on many different types of systems.

A. color
B. size
C. design
D. layout

In low-speed network, it is usually adequate to wait for congestion to occur and then react to it by telling the source of packets to slow down. In high-speed networks, this approach often works poorly, because in the (61) between sending the notification and notification arriving at the source, thousands of additional (62) may arrive. In ATM network, a major tool for preventing (63) is (64) control. When a host wants a new virtual (65) , it must describe the traffic to be offered and the service expected.

A. flow
B. admission
C. traffic
D. time

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