1.In multipoint networks , there are tree persistence methods when a station finds achannel busy.in the 1-persistent method,after the station finds the line idle,it sends its frameimmediately.this method has the () chance of collision because two or more stations may find the line() and send their frames immediately. In the nonpersistent method , a station that has a frame to sen() the line . lf the line is idle , it sends immediately lf the line is not idle , it waits a(请作答此空)amount of time and then senses the line again.The nonpersistent approach ( ) the chance of collisionbecause it is unlikely that two or more stations will wait the same amount of time and retry to sendsimultaneously The p-persistent approach combines the advantages of the other two strategies . ltreduces the chance of collision and improves efficiency.
random
big
medium
small
2.We have already covered the topic of network addresses. The first (71)in a block(in classes A,B,andC) defines the network address. ln classes A,B,and c if the hostid is all ls, the address is called a directbroadcast address. lt is used by a. (72) to send a packet to all hosts in a specific network. All hosts willaccept a packet having this type of destination address. Note that this address can be used only as a( address in an iP packet, Note also that this special address also reduces the number of availablehostid for each netid in classes A,B,andIn classes A,B,and C, an address with all ls for the netid and hostid (32 bits) defines a (74) address inthe current network.A host that wants to send a message to every other host can use this address as adestination address in an lP packet. However, a router will block a packet having this type ofaddress toconfine the broadcasting to the (75)network, Note that this address belongs to classE.
source
destination
local
remote
3.0SPF is a link-state routing protocol, lt is designed to be run internal to a single ()system, Each OSPF router maintains an identical () describing the autonomous system's topology.From this database, a routing table is calculated by constructing a shortest-path ()。 OsPF recalculates(74)traffic.OSPFroutes quickly in the face of topological changes, utilizing a minimum of routingprovides support for equal-cost multipath, An area routing capability is provided, enabling anadditional level of routing protection and a reduction in routing protocol ()。
protocol
network
broadcast
multipath
4.The Hypertext Transfer Protocol , the Web's () protocol , is at the heart of the Web.HTTP is implemented in two programs : a () program and a server program .The client program andserver program executing on different end systems , talk to each other by (请作此空) HTTP messagesHTTp defines how Web clients request Web pages from servers and how servers transfer web pages toclients . when a user () a web page , the browser sends http request messages for the objects in thepage to the server . The server () the requests and responds with http response messages that containthe objects .
exchanging
8changing
declining
removing
5.CSMA, although more efficient than ALOHA or slotted ALOHA, still has one glaringinefficiency. lf the medium is busy, the station will wait for a random amount of time. When two framescolide, the medium remains () for the duration of transmission of both damaged frames. The use ofrandom delays reduces the probabilityof (). For () frames, compared to propagation time, theamount of wasted capacity can be considerable. This waste can be reduced if a station continues to listento the medium while (清作答此空) .The maximum utilization depends on the length of the frame and onthe () time; the longer the frames or the shorter the propagation time, the higher the utilization.
colliding
Bforwarding
transmitting
receiving
6.Together with the network layer,the transport layer is the heart of the protocol ().Thenetwork layer provides end-to-end () delivery using datagrams or virtual circuits.The transport layerbuilds on the network layer to provide data transport from a process on a () machine to a process on adestination machine with a desired level of reliability that is independent of the physical (请作答此空)currently in use.lt provides the abstractions that applications nedd to use the network..Without the ()layer,the whole concept of layered protocols would make little sense.
traffic
connection
lines
networks
7.Currently 94% of Web users use either Internet Explorer or Firefox, but recently somenew (71) have been developed that are beginning to attract attention. The browser Opera is becomingvery (72) because of its speed, it is currently the world's fastest browser, and because it is muchsmaller (73)existing browsers (it can almost fit on a single diskette). lt can also (74) the last Webpage you visited, so the next time you surf, you can start where you left off, And like the big two, youcan get it for free; the catch is that you have to watch blinking ads in one corner, or pay $40 for the ad.free (75)of opera.
readers2
machines
techniques
browsers
8.0SPF is a link-state routing protocol, lt is designed to be run internal to a single ()system, Each OSPF router maintains an identical () describing the autonomous system's topology.From this database, a routing table is calculated by constructing a shortest-path ()。 OsPF recalculatesroutes quickly in the face of topological changes, utilizing a minimum of routing ()traffic, OSPFprovides support for equal-cost multipath, An area routing capability is provided, enabling anadditional level of routing protection and a reduction in routing protocol (75).
flow
state
4traffi
stream
9.Traditional network layer packet forwarding relies on the information provided bynetwork layer ()protocols, or static routing, to make an independent (本题) decision at each hopwithin the network, The forwarding () is based solely on the destination () IP address, All packets forthe same destination follow the same path across the network if no other equal-cost paths exist.Whenever a router has two equal-cost () toward a destination, the packets toward the destinationmight take one or both of them, resulting in some degree of load sharing.
switch
hop
host
cunstomer
10.The lnternet is based on connectionless end-to-end packet service, whichtraditionally provided best-effort means of data() using the Transmission Control Protocol/InternetProtocol suite. Although the(请作此空) design gives the Internet its flexibility and robustness, itspacket dynamics also make it prone to congestion problems,especially at ( ) that connect networks ofwidely different bandwidths.The initial Qos function set was for internet hosts.One major problem withexpensive wide-area () links is the excessive overhead due to small Transmission Control Protocolpackets created by applications such as telnet and rlogin, The Nagle (), which solves this issue,isnow supported by all lp host implementations.
connectionless
connection
connection-oriented
connotation
11.Secure shell (SsH) is a cryptographic network protocol for () remote login and other secure network services over an() network.The standard ( ) port for ssH is 22. The best known example application is for remotelogin to computer systems by users.SSH provides a secure channel over an insecured network in a () architecture, connecting an ssH clientapplication with an ssH server. Common applications include remote command-line login and remotecommand execution, but any network service can be secured with ssH. The protocol specification distinguishes between two major versions, referred to as s$H-1 and ssH-2.The most visible application of the protocol is for access to shell accounts on(请作答此空)operatingsystems, but it sees some limited use on Windows as well. in 2015, Microsoft announced that they wouldinclude native support for SSH in a future release.
Windows
Unix-like
MS-DOS
Graphical
12.
private
common
publi
external
13.0pen shortest Path First (OSPF) was designed as an () gateway protocol, for use in an autonomous system such as a local areanetwork (LAN). lt implements Dijkstra's algorithm, also known as the ( ) path first algorithm. As alink-state routing protocol it was based on the link-state algorithm developed for the ARPANET in 1980and the ls-ls routing protocol. OsPF was first standardised in 1989 as RFc 1131, which is now known asOSPF version 1.Routing protocols like OSPF calculate the shortest route to a destination through thenetwork based on an algorithm. The first routing protocol that was widely implemented, the ()calculated the shortest route based on hops, that is the number of routers that an lP packet had totraverse to reach the destination host. RlP successfully implemented dynamic routing, where routingtables change if the network topology changes. But RlP did not adapt its routing according to changingnetwork conditions, such as data-transfer rate. Demand grew for a dynamic routing protocol that couldcalculate the fastest route to a destination. () was developed so that the shortest path through anetwork was calculated based on the cost of the route, taking into account bandwidth, delay and loadTherefore OSPF undertakes route cost calculation on the basis of link-cost parameters, which can beweighted by the administrator. OSPF was quickly adopted because it became known for reliablycalculating routes through large and complex local area networks.As a link state routing protocol, OsPfmaintains link state(请作北空) , which are really network topology maps, on every router on which itis implemented. The state of a given route in the network is the cost, and OSPF algorithm allows everyrouter to calculate the cost of the routes to any given reachable destination. Unless the administratorhas made a configuration, the link cost of a path connected to a router is determined by the bit rate (1Gbit/s, 10 Gbit/s, etc) of the interface. A router interface with OSPF will then advertise its link cost toneighbouring routers through multicast, known as the hello procedure. All routers with OSPFimplementation keep sending hello packets, and thus changes in the cost of their links become known toneighbouring routers. The information about the cost of a link, that is the speed of a point to pointconnection between two routers, is then cascaded through the network because OSPF routers advertisethe information they receive from one neighbouring router to all other neighbouring routers. Thisprocess of flooding link state information through the network is known as synchronisation. Based onthis information, all routers with OSPF implementation continuously update their link state databaseswith information about the network topology and adjust their routing tables.OsPF has become apopular dynamic routing protocol. Other commonly used dynamic routing protocols are the RlP and theBorder Gateway Protocol (BGP). Today routers support at least one interior gateway protocol toadvertise their routing tables within a local area network. Freguently implemented interior gatewayprotocols besides OSPF are Rlp, is-ls, and the proprietary interior Gateway Routing Protocol (lGRP) byCisc
table
databases
maps
topology
14.
unique
observable
particular
ordinary
15.A management domain typically contains a large amount of managementinformation. Each individual item of ()information is an instance of a managed object type. Thedefinition of a related set of managed (72) types is contained in a Management Information Base (MlB)module. Many such MlB modules are defined, For each managed object type it describes, a MlB (73)defines not only the semantics and syntax of that managed object type, but also the method ofidentifying an individual instance so that multiple (74) of the same managed object type can bedistinguished. Typically, there are many instances of each managed object (75)within a managementdomain
Arotation
switch
management
transmission
16.Traditional network layer packet forwarding relies on the information provided bynetwork layer () protocols, or static routing, to make an independent () decision at each hop withinthe network, The forwarding () is based solely on the destination () IP address. All packets for thesame destination follow the same path across the network if no other equal-cost paths exist, Whenever arouter has two equal-cost (本题) toward a destination, the packets toward the destination might takeone or both of them, resulting in some degree of load sharing.
loan
Bload
content
constant
17.A management domain typically contains a large amount of managementinformation. Each individual item of (71) information is an instance of a managed object type. Thedefinition of a related set of managed (72) types is contained in a Management information Base (MlB)module. Many such MlB modules are defined. For each managed object type it describes, a MlB ()defines not only the semantics and syntax of that managed object type, but also the method ofidentifying an individual instance so that multiple (74) of the same managed object type can bedistinguished. Typically, there are many instances of each managed object (75)within a managementdomain
connection
window
module
destination
18.The File Transfer Protocol (FTP) is a standard network protocol used for the transferof computer () between a client and server on a computer network.FTp is built on a () modelarchitecture using separate control and data connections between the client and the server. FTp usersmay authenticate themselves with a(请作答此空)sign-in protocol, normally in the form of a usernameand password, but can connect anonymously if the server is configured to allow it. For securetransmission that protects the username and password, and encrypts the content, FTp is often securedwith SSL/TLS (FTPS) or replaced with ssH File Transfer Protocol (SFTP).The first FTP client applicationswere () programs developed before operating systems had graphical user interfaces, and are stilshipped with most Windows, Unix, and Linux operating systems. Many FTP clients and automationutilities have since been developed for desktops, servers, mobile devices, and hardware, and FTp hasbeen incorporated into productivity applications, such as HTML editors.FTP may run in () mode,which determines how the data connection is established. in both cases, the client creates a Tcp controlconnection from a random, usually an unprivileged, port N to the FTp server command port 21.in activemode, the client starts listening for incoming data connections from the server on port M. it sends theFTP command PORT M to inform the server on which port it is listening. The server then initiates a datachannel to the client from its port 20, the FTp server data port.in situations where the client is behind afirewall and unable to accept incoming Tcp connections, passive mode may be used. in this mode, theclient uses the control connection to send a PAsy command to the server and then receives a server lfaddress and server port number from the server, which the client then uses to open a data connectionfrom an arbitrary client port to the server IP address and server port number received.Both modes wereupdated in September 1998 to support lPv6. Further changes were introduced to the passive mode atthat time, updating it to extended passive mode.
encrypt
decryption
clear-text
secure
19.Currently 94% of Web users use either Internet Explorer or Firefox, but recently somenew (71) have been developed that are beginning to attract attention. The browser Opera is becomingvery (72) because of its speed, it is currently the world's fastest browser, and because it is muchsmaller (73)existing browsers (it can almost fit on a single diskette). it can also (74) the last Webpage you visited, so the next time you surf, you can start where you left off. And like the big two, youcan get it for free, the catch is that you have to watch blinking ads in one corner, or pay $40 for the ad.free (75)of opera.
version
8revision
software
book
20.0pen Shortest Path First (OSP:) was designed as an () gateway protocol, for use in an autonomous system such as a local areanetwork (LAN). lt implements Dijkstra's algorithm, also known as the ( ) path first algorithm. As aink-state routing protocol it was based on the link-state algorithm developed for the ARPANET in 1980and the ls-s routing protocol. OsPF was first standardised in 1989 as RFc 1131, which is now known asOSPF version 1.Routing protocols like OsPF calculate the shortest route to a destination through thenetwork based on an algorithm. The first routing protocol that was widely implemented, the(请作答此空) , calculated the shortest route based on hops, that is the number of routers that an lP packet had totraverse to reach the destination host. RlP successfully implemented dynamic routing, where routingtables change if the network topology changes. But Rlp did not adapt its routing according to changingnetwork conditions, such as data-transfer rate. Demand grew for a dynamic routing protocol that couldcalculate the fastest route to a destination. () was developed so that the shortest path through anetwork was calculated based on the cost of the route, taking into account bandwidth, delay and loadTherefore OSPF undertakes route cost calculation on the basis of link-cost parameters, which can beweighted by the administrator. OSPF was quickly adopted because it became known for reliablycalculating routes through large and complex local area networks.As a link state routing protocol, OSPFnaintains link state () , which are really network topology maps, on every router on which it isimplemented. The state of a given route in the network is the cost, and OsPF algorithm allows everyrouter to calculate the cost of the routes to any given reachable destination. Unless the administrator1as made a configuration, the link cost of a path connected to a router is determined by the bit rate (Gbit/s, 10 Gbit/s, etc) of the interface. A router interface with OsPF will then advertise its link cost toneighbouring routers through multicast, known as the hello procedure. All routers with OSPFimplementation keep sending hello packets, and thus changes in the cost of their links become known toneighbouring routers. The information about the cost of a link, that is the speed of a point to pointconnection between two routers, is then cascaded through the network because OSPF routers advertisethe information they receive from one neighbouring router to all other neighbouring routers. Thisprocess of flooding link state information through the network is known as synchronisation. Based onthis information, all routers with OsPF implementation continuously update their link state databaseswith information about the network topology and adjust their routing tables.OsPF has become apopular dynamic routing protocol. Other commonly used dynamic routing protocols are the RiP and theBorder Gateway Protocol (BGP). Today routers support at least one interior gateway protocol toadvertise their routing tables within a local area network. Frequently implemented interior gatewayprotocols besides OSPF are RlP, ls-lS, and the proprietary interior Gateway Routing Protocol (lGRP) bycisco.
OSPF
RIP
IS-IS
EIGRP
21.Secure shell (ssH) is a cryptographic network protocol for(请作此空)remote login and other secure networkservices over an () network,The standard ( ) port for $sH is 22. The best known example application isfor remote login to computer systems by users.SSH provides a secure channel over an insecured network in a ( ) architecture, connecting an sSH clientapplication with an sSH server, Common applications include remote command-line login and remotecommand execution, but any network service can be secured with SSH. The protocol specification distinguishes between two major versions, referred to as ssH-1 and ssH-2The most visible application of the protocol is for access to shell accounts on () operating systems, butit sees some limited use on Windows as well. in 2015, Microsoft announced that they would includenative support for SSH in a future release
secure
insecure
sftp
sCp
22.IP multicasting is a set of technologies that enable efficient delivery ofdata to many locations on a network, Rather than making multiple copiesof a message intended to be distributed to multiple recipients at the () of origin of a message.multicasting initially sends just one () and does not copy it to the individual recipients until it reachesthe closest common point on the network, thereby () the bandwidth consumed. Network performanceis significantly () because it isn't bogged down with the processing and transmission of several largedata files; each receiving computer doesn't have to () the transmitting server for the file.
entity
procession
volume
message
23.In multipoint networks , there are tree persistence methods when a station finds achannel busy.in the 1-persistent method,after the station finds the line idle,it sends its frameimmediately.this method has the () chance of collision because two or more stations may find the line and send their frames immediately. in the nonpersistent method , a station that has a frame to send(请作答此空) the line . lf the line is idle , it sends immediately lf the line is not idle , it waits a( )amount of time and then senses the line again.The nonpersistent approach ( ) the chance of collisionbecause it is unlikely that two or more stations will wait the same amount of time and retry to sendsimultaneously The p-persistent approach combines the advantages of the other two strategies . ltreduces the chance of collision and improves efficiency.
overhears
hears
listens
senses
24.We have already covered the topic of network addresses. The first (71)in a block(in classes A,B,andC) defines the network address. in classes A,B,and c,if the hostid is all ls, the address is called a directbroadcast address, lt is used by a. () to send a packet to all hosts in a specific network. All hosts wilaccept a packet having this type of destination address. Note that this address can be used only as a(73) address in an lp packet. Note also that this special address also reduces the number of availablehostid for each netid in classes A,B,and3，In classes A,B,and c, an address with all ls for the netid and hostid (32 bits) defines a (74) address inthe current network,A host that wants to send a message to every other host can use this address as adestination address in an liP packet, However, a router will block a packet having this type ofaddress toconfine the broadcasting to the (75)network, Note that this address belongs to class:
router
switch
Bhu
firewal
25.We have already covered the topic of network addresses. The first (71)in a block(in classes A,B,andC) defines the network address. in classes A,B,and c if the hostid is all ls, the address is called a directbroadcast address. lt is used by a. (72) to send a packet to all hosts in a specific network. All hosts wilaccept a packet having this type of destination address, Note that this address can be used only as a(73) address in an lP packet, Note also that this special address also reduces the number of availablehostid for each netid in classes A,B,andIn classes A,B,and C an address with all ls for the netid and hostid (32 bits) defines a () address in thecurrent network,A host that wants to send a message to every other host can use this address as adestination address in an Ip packet. However, a router will block a packet having this type ofaddress toconfine the broadcasting to the (75)network, Note that this address belongs to classE.
unicast
multicast
broadcast
anycast
26.IP multicasting is a set of technologies that enable efficient delivery of data to manylocations on a network, Rather than making multiple copies of a message intended to be distributed tomultiple recipients at the(请作答此选顶) of origin of a message, multicasting initially sends just oneIand does not copy it to the individual recipients until it reaches the closest common point on thenetwork, thereby () the bandwidth consumed. Network performance is significantly () because itisn' t bogged down with the processing and transmission of several large data files; each receivingcomputer doesn'thave to () the transmitting server for the file.
point
bottom
hea
sight
27.Secure shell (ssH) is a cryptographic network protocol for () remote login and other secure network services over an() network.The standard ( ) port for ssH is 22. The best known example application is for remotelogin to computer systems by users.SSH provides a secure channel over an insecured network ina(请作此空)architecture, connecting anSSH client application with an ssH server, Common applications include remote command-line login andremote command execution, but any network service can be secured with SsH. The protocol specification distinguishes between two major versions, referred to as $$H-1 and SsH-2.The most visible application of the protocol is for access to shell accounts on () operating systems, butit sees some limited use on Windows as well. in 2015, Microsoft announced that they would includenative support for $SH in a future release.
client-server
8browser-server
connectionless
P2P
28.Currently 94% of Web users use either internet Explorer or Firefox, but recently somenew (71) have been developed that are beginning to attract attention. The browser Opera is becomingvery (72) because of its speed, it is currently the world's fastest browser, and because it is muchsmaller (73) existing browsers it can almost fit on a single diskette). it can also (74) the last Webpage you visited, so the next time you surf, you can start where you left off. And like the big two, youcan get it for free; the catch is that you have to watch blinking ads in one corner, or pay $40 for the ad.free (75)of opera.
A)beyond
S0
than
as
29.0pen Shortest Path First (OSPF) was designed as an () gateway protocol, for use in an autonomous system such as a local areanetwork (LAN). lt implements Diikstra's algorithm, also known as the ( ) path first algorithm. As alink-state routing protocol it was based on the link-state algorithm developed for the ARPANET in 1980and the ls-ls routing protocol. OSPF was first standardised in 1989 as RFc 1131, which is now known asOSPF version 1.Routing protocols like OSPF calculate the shortest route to a destination through thenetwork based on an algorithm. The first routing protocol that was widely implemented, the ()calculated the shortest route based on hops, that is the number of routers that an lP packet had totraverse to reach the destination host. RlP successfully implemented dynamic routing, where routingtables change if the network topology changes. But RlP did not adapt its routing according to changingnetwork conditions, such as data-transfer rate. Demand grew for a dynamic routing protocol that couldcalculate the fastest route to a destination.(清作答比字)was developed so that the shortest paththrough a network was calculated based on the cost of the route, taking into account bandwidth, delayand load. Therefore OSPF undertakes route cost calculation on the basis of link-cost parameters, whichcan be weighted by the administrator. OSPF was quickly adopted because it became known for reliablycalculating routes through large and complex local area networks.As a link state routing protocol, OSPFmaintains link state ( ) , which are really network topology maps, on every router on which it isimplemented. The state of a given route in the network is the cost, and OSPF algorithm allows everyrouter to calculate the cost of the routes to any given reachable destination. Unless the administratorhas made a configuration, the link cost of a path connected to a router is determined by the bit rate (?Gbit/s, 10 Gbit/s, etc) of the interface. A router interface with OsPF will then advertise its link cost toneighbouring routers through multicast, known as the hello procedure. All routers with OSPFimplementation keep sending hello packets, and thus changes in the cost of their links become known toneighbouring routers. The information about the cost of a link, that is the speed of a point to pointconnection between two routers, is then cascaded through the network because OSPF routers advertisethe information they receive from one neighbouring router to all other neighbouring routers. Thisprocess of flooding link state information through the network is known as synchronisation. Based onthis information, all routers with OSPF implementation continuously update their link state databaseswith information about the network topology and adjust their routing tables.OsPF has become apopular dynamic routing protocol. Other commonly used dynamic routing protocols are the RlP and theBorder Gateway Protocol (BGP). Today routers support at least one interior gateway protocol toadvertise their routing tables within a local area network. Frequentlyimplemented interior gatewayprotocols besides OSPF are RlP, is-lS, and the proprietary interior Gateway Routing Protocol (lGRP) byCisco.
RIP
IGRP
OSPF
BGP
30.work ( ) ,systems that effectively isolate an organization's internal network structurefrom an(清作答此空)network, such as the INTERNET is becoming increasingly popular. These firewallsystems typically act as application-layer () between networks, usually offering controlled TELNET, FTPand SMTP access. With the emergence of more sophisticated () layer protocols designed to facilitateglobal information discovery , there exists a need to provide a general () for these protocols totransparently and securely traverse a firewall.
exterior
Internal
center
middle
31.work(请作答此空),systems that effectively isolate an organization's internal networkstructure from an () network, such as the INTERNET is becoming increasingly popular. These firewallsystems typically act as application-layer ( ) between networks, usually offering controlled TELNET, FTPand SMTP access. With the emergence of more sophisticated () layer protocols designed to facilitateglobal information discovery , there exists a need to provide a general () for these protocols totransparently and securely traverse a firewall.
safequards
firewalls
routers
switches
32.work ( ) ,systems that effectively isolate an organization's internal network structurefrom an () network, such as the INTERNET is becoming increasingly popular. These firewall systemstypically act as application-layer ( ) between networks, usually offering controlled TELNET, FTP andSMTP access. With the emergence of more sophisticated ( ) layer protocols designed to facilitate globalinformation discovery , there exists a need to provide a general(请作答此字) for these protocols totransparently and securely traverse a firewall.
framework
internetwork
computer
Application
33.Together with the network layer,the transport layer is the heart of the protocol ().Thenetwork layer provides end-to-end ( delivery using datagrams or virtual circuits.The transport layerbuilds on the network layer to provide data transport from a process on a () machine to a process on adestination machine with a desired level of reliability that is independent of the physical 0 currently inuse.lt provides the abstractions that applications nedd to use the network..Without the(请作答此空laver,the whole concept of lavered protocols would make little sense
network
transport
link
physical
34.Together with the network layer,the transport layer is the heart of the protocol ().Thenetwork layer provides end-to-end (请作答此空) delivery using datagrams or virtual circuits.The transportlayer builds on the network layer to provide data transport from a process on a ( machine to a processon a destination machine with a desired level of reliability that is independent of the physical 0 currentlin use.lt provides the abstractions that applications nedd to use the network..Without the 0 layer thewhole concept of lavered protocols would make little sense.
packet
data
command
recor
35.Together with the network layer,the transport layer is the heart of the protocol(请作答此空).The network layer provides end-to-end () delivery using datagrams or virtual circuits.Thetransport layer builds on the network layer to provide data transport from a process on a ( machine to aprocess on a destination machine with a desired level of reliability that is independent of the physical 0currently in use.lt provides the abstractions that applications nedd to use the network.Without the 0layer,the whole concept of layered protocols would make little sense.
transport
network
hierarchy
service
36.The internet is based on connectionless end-to-end packet service, whichtraditionally provided best-effort means of data () using the Transmission Control Protocol/InternetProtocol Suite. Although the () design gives the Internet its flexibility and robustness, its packetdynamics also make it prone to congestion problems,especially at(请作北空) that connect networksof widely different bandwidths.The initial Qos function set was for internet hosts.One major problemwith expensive wide-area( ) links is the excessive overhead due to small Transmission ControlProtocol packets created by applications such as telnet and rlogin.The Nagle ( ), which solves thisissue,is now supported by all lP host implementations
hosts
switches
routers
computers
37.The Internet is based on connectionless end-to-end packet service, whichtraditionally provided best-effort means of data () using the Transmission Control Protocol/internetProtocol Suite. Although the () design gives the internet its flexibility and robustness, its packetdynamics also make it prone to congestion problems,especially at () that connect networks of widelydifferent bandwidths.The initial Qos function set was for internet hosts.One major problem withexpensive wide-area(请作答此空) links is the excessive overhead due to small Transmission ControlProtocol packets created by applications such as telnet and rlogin.The Nagle ( ), which solves thisissue,is now supported by all lp host implementations.
interconnection
network
internet
web
38.The Hypertext Transfer Protocol , the Web's (请作答此空) protocol , is at the heart ofthe Web. HTTP is implemented in two programs : a () program and a server program . The clientprogram and server program executing on different end systems , talk to each other by () HTTPmessages . HTTP defines how Web clients request Web pages from servers and how servers transfer webpages to clients . when a user () a web page , the browser sends http request messages for the objects inthe page to the server . The server () the requests and responds with http response messages thatcontain the objects
transport-layer
application-layer
network-layer
link-layer
39.The Hypertext Transfer Protocol , the Web's () protocol , is at the heart of the WebHTTP is implemented in two programs : a () program and a server program . The client program andserver program executing on different end systems , talk to each other by () HTTP messages . HTTPdefines how Web clients request Web pages from servers and how servers transfer web pages to clientswhen a user (请作答此空) a web page , the browser sends http request messages for the objects in thepage to the server . The server () the reguests and responds with http response messages that containthe objects .
sends
requests
receives
abandons
40.CSMA, although more efficient than ALOHA or slotted ALOHA, still has one glaringinefficiency. lf the medium is busy, the station will wait for a random amount of time. When two framescollide, the medium remains () for the duration of transmission of both damaged frames. The use otrandom delays reduces the probability of().For (请作答此空)frames, compared to propagation timethe amount of wasted capacity can be considerable. This waste can be reduced if a station continues tolisten to the medium while () .The maximum utilization depends on the length of the frame and on the() time; the longer the frames or the shorter the propagation time, the higher the utilization.
long
short
big
small
41.CSMA, although more efficient than ALOHA or slotted ALOHA, still has one glaringinefficiency. lf the medium is busy, the station will wait for a random amount of time. When two framescollide, the medium remains () for the duration of transmission of both damaged frames. The use ofrandom delays reduces the probability of (). For () frames, compared to propagation time, theamount of wasted capacity can be considerable, This waste can be reduced if a station continues to listento the medium while () .The maximum utilization depends on the length of the frame and on the(诗青作答此空) time; the longer the frames or the shorter the propagation time, the higher the utilization.
propagation
transmission
colliding
listening
42.We have already covered the topic of network addresses. The first (71)in a block(in classes A,B,and) defines the network address. in classes A,B,and c if the hostid is all ls, the address is called a directbroadcast address, lt is used by a, (72) to send a packet to all hosts in a specific network, All hosts wilaccept a packet having this type of destination address. Note that this address can be used only as a(73) address in an lP packet. Note also that this special address also reduces the number of availablehostid for each netid in classes A,B.andIn classes A,B,and C, an address with all ls for the netid and hostid (32 bits) defines a (74) address inthe current network.A host that wants to send a message to every other host can use this address as adestination address in an lp packet. However, a router will block a packet having this type ofaddress toconfine the broadcasting to the () network. Note that this address belongs to class
neighbor
next
remote
local
43.We have already covered the topic of network addresses. The first () in a block (inclasses A,B,and) defines the network address. In classes A,B,and c,if the hostid is all ls, the address is called a directbroadcast address, lt is used by a, (72) to send a packet to all hosts in a secific network. All hosts wilaccept a packet having this type of destination address. Note that this address can be used only as a(73) address in an lp packet. Note also that this special address also reduces the number of availablehostid for each netid in classes A.B.andIn classes A,B,and C, an address with all ls for the netid and hostid (32 bits) defines a (74) address inthe current network.A host that wants to send a message to every other host can use this address as adestination address in an lP packet. However,a router wil block a packet having this type ofaddress toconfine the broadcasting to the (75)network. Note that this address belongs to classE.
datagram
function
address
service
44.Traditional network layer packet forwarding relies on the information provided bynetwork layer () protocols, or static routing, to make an independent () decision at each hop withinthe network. The forwarding (本题) is based solely on the destination () IP address. All packets for thesame destination follow the same path across the network if no other equal-cost paths exist. Whenever arouter has two equal-cost () toward a destination, the packets toward the destination might take oneor both of them, resulting in some degree of load sharing.
connection
transmission
broadcast
unicas
45.in multipoint networks , there are tree persistence methods when a station finds achannel busy.in the 1-persistent method,after the station finds the line idle,it sends its frameimmediately.this method has the () chance of collision because two or more stations may find the line(清作答此空) and send their frames immediately. in the nonpersistent method , a station that has aframe to send ( ) the line . lf the line is idle , it sends immediately lf the line is not idle , it waits a ( )amount of time and then senses the line again.The nonpersistent approach ( ) the chance of collisionbecause it is unlikely that two or more stations will wait the same amount of time and retry to sendsimultaneously The p-persistent approach combines the advantages of the other two strategies . ltreduces the chance of collision and improves efficiency.
idle
busy
useful
unusable
46.We have already covered the topic of network addresses. The first (71)in a block(in classes A,B,andC) defines the network address. in classes A,B,and c,if the hostid is all ls, the address is called a directbroadcast address. lt is used by a. () to send a packet to all hosts in a specific network. All hosts willaccept a packet having this type of destination address, Note that this address can be used only as a(73) address in an lP packet, Note also that this special address also reduces the number of availablehostid for each netid in classes A,B,andC.In classes A,B,and C, an address with all ls for the netid and hostid (32 bits) defines a (74) address inthe current network.A host that wants to send a message to every other host can use this address as adestination address in an lP packet. However,a router will block a packet having this type ofaddress toconfine the broadcasting to the (75)network, Note that this address belongs to classE.
router
switch
hu
firewall