LANs can be connected by using bridges,which operate in theA． physical layerB．data link la

A.When work PCs were connected to each other via Local Area Networks (LANs).

B.When work PCs were connected to each other via Internet.

C.When people showed their interest in work PCs.

D.When more and more businessmen noticed the potential market for work PCs.

●LANs can be connected by using bridges，which operate in the (67) .

(67) A．data-link layer

B．Physical layer

C．network layer

D．transport layer

LANs can be connected by using bridges, which operate in the

A．physical layer

B．data link layer

C．network layer

D．transport layer

LANs can be connected by using bridges, which operate in the(67).

A．data-link layer

B．Physical layer

C．network layer

D．transport layer

To compete in today’s fast-paced competitive environment, organizations are increasingly allowing contractors, partners, visitors and guests to access their internal enterprise network. These users may connect to the network through wired ports in conference rooms or offices, or via wireless access points. In allowing this open access for third parties, LANs become（）

And worms acquired from unprotected public networks． Hackers masquerading as internal users can take advantage of weak internal security to gain access to confidential information． A．damageable

B．susceptible

C．vulnerable

D．changeable

A.composed

B.combined

C.connecte

D.associated

● To compete in today’s fast-paced competitive environment, organizations arincreasinglyallowing contractors, partners, visitors andgueststoaccesstheirinternalenterprisnetworks.Theseusersmayconnect to the network through wired ports in conference rooms ooffices, or via wireless accesspoints.Inallowing this open access for third parties, LANs becom（71）.Third parties can introduce risk in a variety of ways from connecting with an infectelaptop to unauthorized access of network resources to （72）activity. For many organizationhowever, the operational complexity and costs to ensure safe third party network access havbeen prohibitive. Fifty-two percent of surveyed CISOs state that they currently use a moat ancastle’s security approach, and admit that defenses inside the perimeter are weak. Threats fromnternal users are also increasingly a cause for security concerns. Employees with maliciouintent can launch （73）of service attacks or steal （74）information by snooping thnetwork. As they access the corporate network, mobile and remote users inadvertently can infethe network with （75）and worms acquired from unprotected public networks. Hackemasquerading as internal users can take advantage of weak internal security to gain access tconfidential information.

nologies and products hold the promise of making the concept a reality. Most important of all these new technologies are (66) . The ultimate switched LAN, which is technically possible, now, exhibits the following characteristics:

1. High-speed yet cost-effective switching devices can be implemented on a wide scale, providing dedicated connections for individual users and supporting the aggregate (67) of all networked users.

2. The ability to deploy switching capabilities incrementally into the (68) base. Switching implementations support switching of individual users or groups so that existing users of shared media modules can continue to use the existing equipment until they can justify moving to dedicate switched LAN connections.

3. Support and enhancement of existing routed environments. Switching (69) routint, but rather can be introduced into the network without making any changes to the existing routing equipment or configuration.(70) play a critical role in the integration of switching into existing networks.

A．switch-based LANs

B．WANs

C．user services

D．LAN-BY-PHONE

llowing contractors, partners, visitors and guests to access their internal enterprise networks. These users may connect to the network through wired ports in conference rooms or offices, or via wireless access points. In allowing this open access for third parties, LANs become(171). Third parties can introduce risk in a variety of ways from connecting with an infected laptop to unauthorized access of network resources to(172)activity. For many organizations, however, the operational complexity and costs to ensure safe third party network access have been prohibitive. Fifty-two percent of surveyed CISOs state that they currently use a moat and castle's security approach, and admit that defenses inside the perimeter are weak. Threats from internal users are also increasingly a cause for security concerns. Employees with malicious intent can launch(173)of service attacks or steal(174)information by snooping the network. As they access the corporate network, mobile and remote users inadvertently can infect the network with(175) and worms acquired from unprotected public networks. Hackers masquerading as internal users can take advantage of weak internal security to gain access to confidential information.

A．damageable

B．susceptible

C．vulnerable

D．changeable

Most IP layer-based proxy mechanisms，such as network address translation (NAT)，only supportuni-directional proxy，from the internal network to external network(the Interned．The proxvestablishes the communication channel by (71) IP addresses．The IP addresses must be (72) ．These proxy mechanisms prevent applications that must establish return data channels from establishing their data channels，such as，multimedia applications．IP layer-based proxy mechanisms need additional software (73) for each application that uses (74) channels． SOCKS identifies communication targets through domain names，overcoming the restriction of Usina private IP addresses．SOCKS can use domain names to establish communication between separate LANs，with (75) IP addresses．

(66)

A．manufacturing

B．manipulating

C．conduct

D．implement