1.
No sooner had we gone to sleep when we were awake and in the cloned bodies of director Lan Trant and his wife Lyn
2.
Over time, a LAN, a WAN, a telephone and mobile radio service, video surveillance and now, SAP had been developed to support the work
3.
Centralized IT supported the LAN, the WAN, and the communications systems, while SAP was all decentralized
4.
This arrangement is most often used in place of a real LAN, to allow
5.
Note that this network could just be a LAN, or it
6.
wireless access point is to a wired LAN as a wireless router is to the Internet
7.
become part of the LAN - other computers on the LAN won't distinguish between
8.
There was one to log on to the PC, a LAN
9.
the LAN was intact and had not been damaged by the
10.
The driver pressed the accelerator harder and the aging sedan raced along the wide highway, paying scant attention to the few other cars and lorries, as it passed through the village of Tseng Lan Shue to the T junction which either went right to Clear water Bay or left to Sai Kung and the restricted High Island reservoir and Mount Hallows, west of Long Harbour and east of the Tolo Channel
11.
LAN - : A small isolated network at one office or physical location
12.
computers are connected to a LAN, but may also be connected to the Internet or a
13.
The eventual solution to this problem was the local area network (LAN)
14.
A LAN is a group of computers connected by a shared medium, usually a cable
15.
A LAN is limited to a local area by the electrical properties of the cables used to construct them and by the relatively small number of computers that can share a single network medium
16.
Some technologies, such as fiber optics, have extended the range of LANs to several kilometers, but it isn’t possible to use a LAN to connect computers in distant cities, for example
17.
In most cases, a LAN is a baseband, packet-switching network
18.
• Star bus A star bus topology is one method for expanding the size of a LAN beyond a single star
19.
The number of hubs that a single LAN can support is dependent on the protocol it uses
20.
Sometimes what users mean when they refer to a network is actually an internetwork, and at other times, what may seem to be an internetwork is actually a single LAN
21.
Strictly speaking, a LAN or a network segment is a group of computers that share a network cable so that a broadcast message transmitted by one system reaches all of the other systems, even if that segment is actually composed of many pieces of cable
22.
For example, on a typical 10Base-T Ethernet LAN, all of the computers are connected to a hub using individual lengths of cable
23.
Regardless of that fact, this arrangement is still an example of a network segment or LAN
24.
Individual LANs can be connected using several different types of devices, some of which simply extend the LAN while another creates an internetwork
25.
A typical WAN connection consists of two routers, one at each LAN site, connected using a long-distance link such as a leased telephone line
26.
Any computer on one of the LANs can communicate with the other LAN by directing its traffic to the local router, which relays it over the WAN link to the other site
27.
Unlike a LAN, which is nearly always privately owned and operated, an outside service provider (such as a telephone company) is nearly always involved in a WAN connection because private organizations don’t usually own the technologies needed to carry signals over such long distances
28.
A MAN has three features that differentiate it from both a LAN and a WAN:
29.
• A MAN’s size is usually between that of a LAN and a WAN
30.
Most of today’s desktop operating systems are capable of providing some of the services traditionally ascribed to NOSs since many small-office/home-office (SOHO) LAN implementations take advantage of the fact
31.
While it is relatively easy to learn enough about a LAN technology to purchase the appropriate equipment, installing the cable (or other medium) is much more difficult because you must be aware of all the specifications that affect the process
32.
When building a LAN, the standard for the data link layer protocol you intend to use contains specifications for the types of cable you can use and the guidelines for installing them
33.
On a coaxial network, such as a thin or thick Ethernet LAN, a stand-alone repeater enables you to extend the maximum bus length past 185 meters (for thin Ethernet) or 500 meters (for thick Ethernet)
34.
Using multiple hubs on a single LAN is possible by connecting them together to form a hierarchical star network, as shown in Figure 4-1
35.
Of the five segments permitted on a 10BaseT LAN, only three of these can be mixing segments
36.
A bridge is another device used to connect LAN cable segments, but unlike hubs, bridges operate at the data link layer of the OSI model and are selective about the packets that pass through them
37.
The segments are still considered to be part of the same LAN, however
38.
If, for example, you have a LAN that is experiencing diminished performance because of high levels of traffic, you can split it into two segments by inserting a bridge at the midpoint
39.
In the previous sections, you learned how repeaters, hubs, and bridges can connect network segments at the physical and data link layers of the OSI model, creating a larger LAN with a single collision domain
40.
To make communications between the networks in the two offices possible, each must connect its LAN to a router, and the two routers are linked by the WAN connection
41.
Here, routers are needed because one single LAN may be unable to support the number of workstations required
42.
The traditional network configuration uses multiple LANs connected by routers to form a network that is larger than would be possible with a single LAN
43.
This is necessary because each LAN is based on a network medium that is shared by multiple computers, and there is a limit to the number of systems that can share the medium before the network is overwhelmed by traffic
44.
A virtual LAN (VLAN) is a group of systems on a switched network that functions as a subnet and communicates with other VLANs through routers
45.
Layer 3 switches are optimized for use on LAN and metropolitan area network (MAN) connections, not WANs
46.
The cables are wired straight through (that is, without the crossover) on a normal Ethernet LAN because the hub is responsible for performing the crossover
47.
• A traveling salesperson can walk into the home office with a laptop in hand, and as soon as the computer is within range of the wireless network, it connects to the LAN, downloads new e-mail, and synchronizes the user’s files with copies stored on a network server
48.
• Dynamic topology Unlike cabled networks, in which the LAN topology is meticulously planned out before the installation and remains static until deliberate changes are made, the topology of a wireless LAN changes frequently, if not continuously
49.
Mobility is an integral part of the wireless network design, and a wireless LAN protocol must be able to compensate for systems that enter and leave the area in which the medium can operate
50.
11 wireless LAN is the basic service set (BSS)
51.
A wireless LAN could use any one of the three media, all of which interface with the same MAC layer
52.
The router or bridge located at each terminus of the WAN link is connected to the local LAN and to whatever hardware is used to make the physical layer connection to the WAN
53.
When you design, build, and maintain a LAN, you are working with equipment that you (or your organization) owns and controls completely
54.
LAN technicians are often tinkerers by trade
55.
On a LAN, when you want to increase the bandwidth available to users, you can upgrade to a faster protocol or add network connection components such as bridges, switches, and routers
56.
The result of this expense is that WAN bandwidth is far more expensive than LAN bandwidth
57.
It usually is not practical to use a WAN link in the same way you would use a LAN connection
58.
For example, an employee working at home or on the road can dial in to a server at the office and connect to the LAN to access e-mail and other network resources
59.
In the same way, a small LAN connection may be sufficient for a small branch office to connect to the corporate headquarters for the same purposes
60.
When a user on one LAN performs an operation that requires access to the other LAN, the server automatically dials in to a server on the other network, establishes the connection, and begins routing traffic
61.
There are also stand-alone routers that perform in the same way, enabling users to connect to a remote LAN or the Internet as needed
62.
Figure 7-2 The CSU/DSU provides the interface between a LAN and a leased line
63.
Figure 7-5 Frame-relay connections use a FRAD to connect a LAN to the cloud
64.
ATM is both a LAN and WAN protocol and is a radical departure from the other lower-layer protocols examined in this book
65.
Thus, the same cells generated by a workstation can travel to a switch that connects the LAN to an ATM carrier service, through the carrier’s ATM cloud, and then to a workstation on the destination network
66.
6 Mbps ATM LAN solution intended for desktop use has been eclipsed by Fast Ethernet, which runs at 100 Mbps and is far more familiar to the majority of network administrators
67.
Many enterprise backbones run over ATM, largely because administrators find that its Q05 capabilities and support for voice, data, and video make it a better performer than traditional LAN protocols
68.
This process transmits the LAN data to the POP first and then repackages it into cells
69.
This way, the LAN data is converted to ATM cells at each site before it is transmitted over the WAN
70.
• AAL-5 Also called Simple and Efficient Adaptation Layer (SEAL), AAL-5 provides both connection-oriented and connectionless services and is most commonly used for LAN traffic
71.
While a competent Ethernet LAN administrator should be able to install the components of a Gigabit Ethernet backbone with little trouble, an ATM backbone is a completely different story
72.
When building a local area network (LAN), you can purchase virtually any computer and use it as a server
73.
You can connect the appliance directly to the LAN, using a standard Ethernet connection, enabling clients and servers alike to access its file system directly, or you can build a dedicated storage network, using Ethernet or Fibre Channel, enabling your servers to access the NAS and share files with network clients
74.
In a typical enterprise network containing an SAN, the servers have interfaces to both the data network (the LAN) and the storage network (the SAN)
75.
The LAN, therefore, is completely ordinary, containing client and server computers, and the storage devices are connected only to the SAN
76.
You can design each LAN separately, using standard hardware already mentioned, but then you must consider how you are going to connect the LANs into an internetwork and regulate the communications between them
77.
A network for a home or small office typically consists of a single LAN connecting anywhere from 2 to 16 computers
78.
The LAN might also have additional network devices attached to it, such as a network printer or a router providing a connection to the Internet or another office
79.
For network installations where cables are impractical or undesirable, you can also elect to install a wireless LAN
80.
Even the largest internetwork consists of individual LANs that require the same components as a stand-alone LAN, such as computers, NICs, cables, hubs, and switches
81.
For a large internetwork with more varied requirements, you can design each LAN separately, selecting protocols and hardware that best suit the physical environment and the requirements of the users, or you can create a uniform design suitable for all of the LANs
82.
The term backbone can refer to a LAN that connects other LANs (usually in the same building or campus) or to a network of wide area links that connect networks or internetworks at remote locations
83.
One of the most common configurations for a large internetwork that encompasses an entire building with multiple floors is to have a separate LAN connecting all of the network devices on each floor (which is the origin of the term horizontal network) and a backbone network running vertically between the floors, connecting all of the LANs
84.
When two computers on the same LAN communicate with each other, the traffic stays on that local network
85.
However, when the communicating computers are on different LANs, the traffic goes through the router connecting the source computer to the backbone and then to the LAN on which the destination computer is located
86.
Because the backbone is shared by the horizontal networks, it carries all of the internetwork traffic generated by each of the computers on every LAN
87.
Computers on that LAN can communicate with each other but not with the computers on other LANs, which can cut them off from vital network services
88.
You can, for example, use two routers on each LAN, both of which connect to the backbone network hub so that if one router fails, the other provides continued access to the rest of the network
89.
The distance that the backbone LAN must span and the environment in which it’s used can also affect the protocol selection
90.
Designing the individual LANs that make up the internetwork is similar to designing a single, stand-alone LAN, except you must work the backbone connections into the design
91.
This closet can serve as the location for the patch panel where all of the cable runs for the floor terminate, as well as the hub that connects all of the devices on the floor into a LAN and the router that connects the LAN to the backbone network
92.
If the distance between any of your wall plate locations and the data center exceeds 100 meters, you must either use fiber-optic cable (which supports longer segments) or place the hubs at the location of each LAN
93.
At the time of FDDI’s introduction, 10 Mbps thick and thin Ethernet were the dominant LAN technologies, and FDDI represented a major step forward in speed
94.
In most cases, systems use SLIP or PPP to provide Internet or WAN connectivity, whether or not the system is connected to a LAN
95.
LANs also use SLIP or PPP connections in their routers to connect to an ISP to provide Internet access to the entire network or to connect to another LAN, forming a WAN connection
96.
For LAN users, servers still fill the traditional file and printer sharing roles, but also provide application-related functions, such as access to databases
97.
Web, FTP, and e-mail are all services that can be as useful on a LAN, a smart phone, or a tablet as on the Internet
98.
A site is a collection of domain controllers that are assumed to be well connected, meaning that all of the systems are connected using the same relatively high-speed LAN technology
99.
Adding peer-to-peer networking to an already popular, user-friendly operating system such as Windows led to its rapid growth in the business local area network (LAN) industry and its eventual encroachment into NetWare’s market share
100.
The term is most often used in relation to protection from unauthorized users on the Internet, but a firewall can also protect a local area network (LAN) from users on other LANs, either local or wide area networks (WANs)
