●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 SD

● A glue that holds the whole Internet together is the network layer protocol,(71). Unlike most older network layer protocols, it was designed from the beginning with internetworking in mind. Its job is to provide a -(72) way to transport datagrams from source to destination, without regard to whether these machines are on the same network or whether there are other networks in between them.

Communication in the Internet works as follows. The (73)layer takes data streams and breaks them up into datagrams. Each datagram is transmitted through the Internet, possibly being fragmented into smaller units as it goes. When all the pieces finally get to the destination machine, they are reassembled by the

(74) layer into the original datagram. This datagram is then handed to the transport layer, which inserts it into the receiving process' input stream.

An IP datagram consists of a header part and a text part. The header has a (75) part and a variable length optional part.

(71) A. IP (Internet Protocol)

B. IP (Interworking Protocol)

C. TCP (Transport Control Protocol)

D. TCP (Transfer Communication Protocol)

(72) A. best-quality

B. quality-guaranteed

C. connection-oriented

D. best-efforts

(73) A. data link

B. transport

C. network

D. application

(74) A. data link

B. transport

C. network

D. application

(75) A. 40-byte fixed

B. 64-byte fixed

C. 20~64 bytes variable

D. 20-byte fixed

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．HDLC

B．Frame. Relay

C．X.25

D．X.21

VRP平台上，设置Serial接口数据链路层的封装类型为HDLC的命令是()。

A.encapsulation hdlc

B.link-protocol hdlc

C.hdlc enable

D.link-protocol ppp

● The TCP protocol is a __（72）__ layer protocol．

（72） A． physical B． network C． transport D． application

● TCP/IP （71） layer protocols provide services to the application （72） running on a computer. The application layer does not define the application itself, but rather it defines （73） that applications need—like the ability to transfer a file in the case of HTTP. In short, the application layer provides an （74） between software running on a computer and the network itself. The TCP/IP application layer includes a relatively large number of protocols, with HTTP being only one of those. The TCP/IP （75） layer consists of two main protocol options—the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP).

A. If using IS-IS as the PE-CE routing protocol, no redistribution is required.

B. If using static routes between the CE and PE routers, no redistribution of other VPN routes is required.

C. If the PE-CE protocol is not BGP, redistribution of other VPN routes from MP-BGP is required.

D. If RIP is the routing protocol that is used between the PE-CE routers, no redistribution is required, but any other protocol will require redistribution.

E. If using OSPF or EIGRP as the PE-CE routing protocol, redistribution is not required, but any other protocol or static route will require redistribution.

In data communication, data link is those parts of two data terminal equipments that are controlled by a protocol along with the(71) data circuit, which together enable data(72). So-called protocol means, in short, a set of rules that determines the behavior. of functional units in achieving communication.Data circuit, however, consists of a pair of(73) transmission channels that provides a means of two-way data transmission. Between data switching exchanges, the data circuit may or may not include data circuit-terminating equipment (DCE), depending on the type of(74) used at the data switching exchange. Between a data station and a data switching exchange or data concentrator, the data circuit includes the DCE at the data station end, and may include equipment(75) to a DCE at the data switching exchange or dam concentrator location.

A．handshaking

B．interconnecting

C．linkage

D．joining

The TCP protocol is a （72）layer protocol．

A.physical

B.network

C.transport

D.application

TCP/IP is a communication protocol, which provides many different networking services. The TCP/IP Internet protocol suite is formed from two standards: the TCP （Transmission Control Protocol） and the IP（Internet Protocol）.

（72） means it is on the transport layer.

A.ISO

B.IP

C.OSI

D.TCP

The Simple Network Management Protocol (SNMP)is an(71)protocol that facilitates the exchange of management information between(72). It is part of the Transmission Control Protocol/Internet Protocol (TCP/IP) protocol suite. SNMP enables network(73)to manage network performance, find and sole network problems, and plan for(74). An SNMP-man-aged network consists of three key components: managed devices,(75), and network-management systems.

A．Physical Layer

B．Link Layer

C．Network Layer

D．Transport Layer

Microsoft's COM is a software architecture that allows applications to be built from binary software components. COM is the underlying(71)that forms the foundation for higher-level software services, like those provided by OLE. COM defines a binary standard for function calling between components, a way for components to dynamically discover the interfaces implemented by other components, and a mechanism to identify components and their interfaces uniquely.

OLE is a compound(72)standard developed by Microsoft. OLE makes it possible to create(73)with one application and link or embed them in a second application. Embedded objects retain their original format and(74)to the application that created them. Support for OLE is built into the Windows and MacOS Operating Systems. A(75)compound document standard developed mainly by Apple and IBM is called OpenDoc.

A．architecture

B．structure

C．procedure

D．protocol

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.

An 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