5.9. Short-Haul Modems

While some maybe not consider a short-pull modem to be a genuine network gadget, it is a gadget that your network may require to give point-to-point availability between a workstation or terminal and another gadget. Short- haul modems (called line drivers) empower you to interface two far off RS-232C gadgets to each other. Standard RS-232C links are constrained in separation to 15 to 30 meters. Short- haul modems permit the same association with keep running far as 5 miles utilizing basic phone grade twisted pair wiring.

Short- haul modems can frequently be impeccable arrangements when a PC needs terminal access to a remote gadget. For instance, a client may need to get to a terminal on a PBX phone framework, which utilizes a RS-232C port. You have two choices to give this remote access:

a)   Install normal modems on every end and utilize a phone association with interface from the workstation to the PBX.

b)  Use two short- haul modems and run a contorted pair link between the two focuses.

Contingent upon how much of the time access is required and how far off the gadget is, either approach can be great. By and large, short- haul modems are favoured when the two gadgets frequently or dependably should be associated, and running a twisted pair wire between the areas is not restrictively costly or troublesome. Short- haul modems are genuinely modest, at about $100 each.

In most short-pull modem frameworks, two sets of wire interface every short- haul modem, albeit one-set variations exist. With the two-set assortment, one set is utilized to transmit data and the other to get data. Most short-pull modems are full duplex, permitting transmission to occur in both bearings all the while.

To attach two gadgets utilizing short-haul modems, you utilize a standard RS-232C link to interface every gadget to its short-haul modem. At that point you wire the twisted pair wire to the short-pull modem, utilizing the directions that accompany the modem. At long last, most short- haul modems require outside power, so you have to connect them to an electrical plug. Figure 5.9 demonstrates a case of a short- haul modem association.

Figure 5.9. Short- haul modem association

On the off chance that you often do RS-232C interfacing, you ought to put resources into a gadget called a breakout box. This is a little gadget that has two RS-232C connectors on every end. In the container, each of the RS-232C pin signals is spoken to with a light-transmitting diode (LED). Uncommon patch posts and switches in the breakout box empower you to reconfigure the RS-232C association on the fly. Breakout boxes can be important for accomplishing RS-232C correspondences between two gadgets that aren't conveying. They can indicate what is really happening with the signals and empower you to attempt diverse link designs progressively. When you utilize the breakout box to make sense of how to make the gadgets impart, a lasting link can then be made to those particulars.

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5.8. Firewalls

Firewalls are equipment gadgets that authorize your network security strategies. Firewalls regularly are introduced with routers. Case in point, firewalls are once in a while introduced with routers to make internetwork associations. In many routers intended for little office or home office utilize, a firewall is a piece of the router itself. Gear for bigger networks still keeps these obligations in discrete bits of hardware, be that as it may.

A firewall is an equipment gadget (which can be a PC set up for the undertaking that runs firewall programming or a devoted firewall gadget that contains a PC inside it) that sits between two networks and upholds network security strategies. For the most part, firewalls sit between an organization LAN and the Internet, yet they can likewise be utilized between LANs or WANs.

There are essentially two diverse sorts of firewalls:

a)   A network-based firewall works at layer 3 and for the most part executes a strategy called packet filtering, where bundles between networks are looked at against an arrangement of tenets modified into the firewall before the parcels are permitted to cross the limit between the two networks. Parcel sifting principles can permit or deny bundles in view of source or destination address, or in view of TCP/IP port.

b)  An application-based firewall as a rule in a proxy role between the 2 networks, such that no network activity passes straightforwardly between the two networks. Rather, the firewall (normally called a proxy firewall) goes about as a proxy for the clients of one network to connect with services on the other network. This proxy collaboration is typically done utilizing a strategy called network address translation (NAT), where the network addresses on the inner network are not specifically presented to the outer network. In the application-based model, the proxy firewall deals with interpreting the locations so that the associations can happen.

Firewalls come in all shapes and sizes, and range in expense from as meagre as a couple of hundred dollars to a great many dollars. Truth be told, nowadays, you can even discover little individual firewalls for home utilize that cost under $200 for equipment based gadgets, or around $40 for firewall programming that can be introduced on a home PC.

Diverse firewall gadgets have diverse components, and might envelop both network-based and application-based procedures to ensure the network. Firewalls additionally typically serve as a review point for the activity between the two networks, utilizing logging and reporting instruments to help the manager identify and manage improper network movement.

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5.7. Gateways

Gateways are application-particular interfaces that connect each of the seven layers of the OSI model when they are disparate at any or all levels. For example, on the off chance that you have to associate a network that utilizes one of the OSI networking models to one utilizing IBM's Systems Network Architecture (SNA) model, utilize an gateway. Gateways can likewise make an interpretation of from Ethernet to Token Ring, albeit more straightforward arrangements than gateways exist in the event that you need such an interpretation. Since gateways must interpret a lot, they have a tendency to be slower than different arrangements, especially under overwhelming burdens.

The essential use for gateways today is for taking care of email. POP3 and SMTP are two cases of conventions that are taken care of by gateways. Most email frameworks that can associate with unique frameworks either utilize a PC set up as a gateway for that errand or let the email server hold the gateway tasks itself.

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5.6. Routers

Generally as bridges are fundamentally more wise repeaters, routers are more smart bridges. Routers work at the network (layer 3) of the OSI model, and they are significantly more smart than bridges in sending approaching bundles off to their destination. Since routers work at the network layer, an association over a router requires just that the higher layers utilize the same conventions. The router can interpret from any of the protocols at layers 1 through 3 to some other conventions at layers 1 through 3 (gave the router has been arranged and intended to do as such). Routers can interface both comparable and disparate networks. They are frequently utilized for wide area network (WAN) cables.

Routers really turn into a node on the network, and having their own network addresses. Different nodes send parcels to the router, which then inspects the substance of the bundles and advances them properly. Thus, routers frequently have quick microchips, for the most part of the reduced instruction set computer (RISC) sort and memory incorporated with them to perform this work. Routers can likewise decide the briefest course to a destination and use it. They can perform different traps to augment network data transfer capacity and progressively conform to changing issues or movement designs on a network.

Routers shape the foundation of the Internet. When you utilize the TRACERT command to follow the course from a node to a destination, a large portion of the locations that show up for the bounces are really distinctive routers, every one sending the parcel to the following until it achieves its destination.

Figure 5.6. A network utilizing routers

Routers must be set to work effectively. They need the locations appointed to each of their ports, and different network protocol settings must be arranged. Routers are generally designed in one of two ways:

a)   Most routers incorporate a RS-232C port. You can associate a terminal or computer with terminal emulation software to this port and program the router in content mode.

b)  Most routers have network based programming that empowers you to program the router, regularly utilizing graphical tools or a straightforward web interface.

The technique you utilize relies on upon the router and your security needs. (You might need to debilitate network-based router software so that unapproved clients can't change the router's arrangement.) Figure 5.6 demonstrates a case of a network that utilizes routers.

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5.5. Bridges

Bridges are, more or less, more wise renditions of repeaters. Bridges can associate two network portions together, however they have the aptitude to pass activity starting with one fragment then onto the next just when that movement is bound for the other section. Bridges are utilized to section networks into smaller pieces. Some bridges can traverse distinctive networking frameworks and media, for example, from coaxial Thin Ethernet to twisted pair Token Ring.

As you may review, repeaters work at the physical (layer 1) of the OSI networking model. Bridges work one layer higher, at the data-join (layer 2). Bridges inspect the media access control (MAC) location of every parcel they experience to figure out if they ought to forward the bundle to the next network. Spans contain address data about all the parts of your network, through either a static steering table that you program or a dynamic, learning-tree framework that finds every one of the devices and locations on the network consequently.

You ought to utilize connects just on smaller networks, or in situations where you would some way or another utilize a repeater, however would profit by keeping traffic on one fragment from being transmitted on the other portion pointlessly. Regularly, routers or switches offer arrangements that perform better and make less issues, so look at these different alternatives before picking a bridge.

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5.4. Repeaters

A repeater is a gadget that amplifies the expanse of a specific network run. It takes a frail network signal in on one side, amplifies the signal, and after that sends it out its other side. You regularly see repeaters on Thin Ethernet networks, yet they are accessible for almost any network association. For example, on the off chance that you have to run a 100Base-T Cat-5 link longer than 100 meters, a repeater empowers you to twofold that space.

Repeaters work at the physical layer of the OSI networking model. They don't have the insight to comprehend the signals they are transmitting. Repeaters just intensify the signal coming in either side and rehash it through their other side. (Keep in mind that they additionally open up any commotion on the link!) Repeaters are utilized to associate just the same kind of media, for example, 10Base-2 Thin Ethernet to 10Base-2 Thin Ethernet, or from Token Ring twisted pair to Token Ring twisted pair. By and by, repeaters are typically utilized with 10Base-2 networks (Thin Ethernet), which are talked about in Chapter 4.

Repeaters do have a little measure of insight that can be valuable. They can isolate one of their associations from the other when there is an issue. For instance, consider two fragments of Thin Ethernet that are associated utilizing a repeater. If one of those fragments is out of order; the repeater permits the great section to keep working inside itself. Clients on the great fragment will be not able interface with assets on the out of order portion, however they can at present utilize the great section without inconvenience. (However, recollect that this capacity does you great if your servers are on the broken portion and your workstations are on the great section!) Figure 5.4 demonstrates a network expansion utilizing repeaters.

Figure 5.4. Utilizing repeaters to augment network length (10Base-2 Thin Ethernet appeared)

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5.3.1. Large Switches or Small Switches?

Bigger switches that can have hundreds of associations inside a solitary suspension are usually more intense than their smaller 24-port kin, and they have a tendency to have more inherent repetition, for example, excess power supplies in the unit etc. Be that as it may, now and then it's simpler and less costly to construct a network utilizing smaller 24-port switches. You can essentially buy an additional 24-port unit as a hot-swap backup (a backup unit that can be immediately swapped into take the position of a fizzled unit) that you can physically execute immediately. The main genuine inconvenience to this methodology is that the excess is not automatic. On the off chance that one 24-port switch fizzles, you'll have to move its associations with the backup switch. Conversely, a bigger unit can change to excess components consequently. As usual, consider such exchange offs painstakingly for your specific organization and its needs.

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5.3. Switches

Switches, as their name infers, can change associations starting with one port then onto the next, and they can do as such quickly. They are association oriented and powerfully switch among their different ports to make these associations. Think about a train yard, with numerous trains coming in on some tracks and leaving on different tracks. The yard director arranges the track "switches" to happen so the trains can get to their destination. A network switch is much similar to the yard director, aside from that the switch coordinates bundles instead of trains and uses Ethernet wiring as opposed to prepare tracks to transport its freight.

Since switches structure coordinated associations between any two ports, all the ports coming into a switch are not part of a solitary collision domain. In this sense, the switch goes about as a kind of super bridge (bridges are talked about in the following segment).

Switches are frequently used to associate various hubs to a much speedier spine. For instance, assume that you have 10 hubs, each with 24 workstation nodes associated. On the off chance that you basically associate every one of the hubs together on a typical spine, each of the 240 workstations would share a solitary crash area, which could hurt execution a considerable amount. Rather, a greatly improved methodology is to introduce a 12-port switch and associate every hub to one of the ports on the switch. For example, it is normal to utilize 100Base-T Ethernet for workstation associations, however 1000Base-T (or some other quicker network association) for the spine. This permits all the movement being produced by each of the 10 hubs to keep on running at around a 100 Mbps association rate to the servers, despite the fact that every one of the hubs are sharing the spine. Figure 5.3 shows this methodology.

Figure 5.3. A network fabricated utilizing hubs and switches

Switches are cheap and are blazingly quick. For LAN associations, switches bode well than hubs, mostly in view of their expense and their relative straightforwardness. Truth be told, obtaining bridges has gotten to be troublesome, as switches now overwhelm the business sector.

Also, most new networks shun hubs for a 100 % switched approach. Indeed, it's essentially difficult to buy hubs any more, since producers commonly offer just switches. (You may at present have the capacity to buy little hubs, with four to eight ports, however even in these little applications, switches are best and very little more costly.)

It's critical that you comprehend the contrast amongst hubs and switches, in light of the fact that you may at present experience hubs introduced in existing networks. For new networks, you will utilize switches solely. Doing as such drastically decreases the open door for network parcel impacts, which are more probable in a hub plan.

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5.2. Hubs and Concentrators

Intelligent LAN concentrators generally just called concentrators or, much all the more essentially, hubs are utilized to associate network nodes to network spines. Nodes are associated with hubs in a physical star design (links fan out from the hub to every node); whether they are utilized for a star topology or a ring topology network (these topologies are talked about in Chapter 4). A straightforward network may comprise of only a hub or two; smaller networks mostly don't require a network spine.

Hubs are accessible for almost any network media sort, with the higher-end units utilizing replaceable modules to bolster numerous media sorts. For instance, you can buy a top of the line hub suspension that can house both Ethernet and Token Ring modules.

You can buy hubs in an assortment of sizes, going from those that backing just 2 workstations to those that bolster more than 100 workstations. Numerous network designers use stackable hubs, which more often than not bolster 24 node associations each. These hubs are frequently utilized in performance with switches, which are talked about in the following segment.

Hubs have two critical properties:

a)   Hubs echo all data from every port to the various ports on the hub. Despite the fact that hubs are cabled in a star design, they really perform electrically (coherently) more like a bus topology section in this admiration. On account of this reverberating, no sifting or rationale strikes counteract crashes between bundles being transmitted by any of the associated nodes.

b)  Hubs can consequently partition (in this connection, remove) a difficult node from alternate nodes—essentially, closing down that node. Such dividing happens if a link short is distinguished, if the hub port is getting over the top parcels that are flooding the network, or in the event that some different significant issue is identified for a given port on the hub. Routine apportioning keeps one failing connection from bringing on issues for the majority of alternate associations.

Hubs are turning out to be a great deal more refined. They regularly have various progressed integrated elements, including the accompanying:

a)   Built-in administration, where the hub can be midway overseen over the network, utilizing SNMP or other network administration conventions and software.

b)  Autosensing of various association speeds. For instance, Ethernet hubs that can consequently identify and run every node at either 10 Mbps (10Base-T) or 100 Mbps (100Base-T) are basic.

c)   Speedy uplinks that associate the hub to a spine. These typically work at 10x the essential rate of the hub. (For instance, for a 100 Mbps hub, the uplink ports may keep running at 1 Gbps.)

d)  Integrated bridging and steering capacities, which make it pointless to utilize separate gadgets to perform connecting and directing.

e)   Integrated switching, where nodes on the hub can be exchanged rather than shared.

At the point when buying a hub, it's imperative to know what number of nodes you need to associate, the amount of data transmission each requires, and what kind of network spine is being utilized. Spines can be anything from shared 10 Mbps Thin Ethernet, to 100 Mbps 100Base-TX, to high-speed spines. Your decision of a backbone technology relies on upon the aggregate sum of data transfer capacity that you require and the different other network outline criteria that you should meet.

Figure 5.2. A typical hub arrangement

Every hub is a different collision domain, or a zone of the network in which impacts can happen. Associating all hubs together in some design normally results in a bigger collision domain, surrounding every one of the hubs. The special case to this guideline is a setup where all the different hubs are associated with a switch (see the following section), which keeps every hub in its own particular collision space. Figure 5.2 demonstrates a case of a network utilizing hubs.

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5.1. Network Interface Cards

To the extent networking is concerned, the network interface card (NIC) is a standout amongst the most vital PC gadgets. Every PC on the network (counting servers and clients) requires one, and it is the NIC that gives the association between the PC and the network's physical medium, (for example, copper or fibre optic link).

A hefty portion of the new motherboards accessible for computers and servers have the network interface incorporated with the motherboard. More established PCs or new PCs that don't give built-in network interfaces will need that a NIC be added to it (unless you purchase your network clients and servers with a NIC as their standard equipment arrangement, which can be incorporated on the motherboard or a different card in a expansion slot). Figure 5.1 demonstrates a PCI NIC from 3Com, which gives the RJ-45 female port for the CAT 5 twisted pair link that associates the PC to a hub or switch.

Figure 5.1.      Network interface cards give the association between the computer & the network wiring.

Not just does the NIC give the PC an association with the network, yet it additionally handles an imperative data- exchange capacity. Data goes in parallel on the computer’s bus framework; the network medium requests a serial transmission. The transceiver (a transmitter and recipient) on the NIC can move data from parallel to serial, and the other way around. This is much the same as vehicles proceeding onward a multi-path superhighway that should all converge into one path of traffic.

Network interface cards likewise supply the fundamental tending to framework used to get data starting with one PC then onto the next on the network. This equipment or MAC address is smouldered into a ROM chip on the NIC. It is alluded to as the MAC address in light of the fact that the Media Access Control (MAC) layer is really a sub-layer of the OSI model's Data Link layer.

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5. Network Hardware

On the off chance that network wiring constitutes the sensory system of a network, the gadgets talked about in this chapter characterize the different organs. These network gadgets; hubs, repeaters, routers, etc. are liable of moving data starting with one network link then onto the next. Every gadget has diverse properties and jobs. A decent network outline utilizes the right gadget for each of the different uses the network must satisfy.

It is vital that you comprehend essential segments that go into structuring a network, and also the work each performs.

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4.3.2. Wireless Network Caveats

Before you introduce a wireless network, you ought to know about the accompanying:

a)   The major standards work at various data rates. 802.11b works at 11 Mbps; 802.11g and 802.11a both work at up to 54 Mbps and 802.11n works at 65 or 150 Mbps.

b)  The particulars of the home and other introduced gear may meddle with a wireless network. This is most affirmed with 802.11b and 802.11g, which work at 2.4 GHz—the same recurrence the as most of wireless phones furthermore close to the recurrence where microwave ovens work. For instance, when I set up an 802.11b network at my home quite a long while back, I continued getting dropped associations, and I couldn't utilize my wireless telephone anyplace close to the remote network associations since it brought about discernable impedance. 802.11n/a works at 5 GHz, which might be less subject to obstruction in a home that has impedance in the 802.11b/g recurrence.

c)   A wireless network conceivably opens you to security dangers. Individuals with wireless network cards introduced in their notebook PCs can look around searching with the expectation of free associations. More probable is that your neighbours might have the capacity to "hitch a free ride" on your Internet association through your home network on the off chance that you don't secure it when you introduce it (this is more basic than you might suspect).

d)  This field is keeping on developing quickly, and an answer bought today may not be perfect with proportionate equipment accessible in a few years.

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4.3.1. Wireless Standards

Three essential wireless principles are in wide utilize: 802.11b, 802.11a, 802.11g, and 802.11n. It's unnatural, yet in this specific case, 802.11n is a more progressed and quicker standard than 802.11a. 802.11g is basically an advance to 802.11b and utilizes the same frequencies to transmit data.

The 802.11n standard is currently top of the market, and numerous great and generally cheap arrangements utilize this standard. You can even buy units that join a 802.11n remote access point (WAP), which is kind of like a remote hub, with a router expected to share a home's high data transmission Internet association among various PCs. The pleasant thing about such mix units is that you don't have to pay extra for Internet service for numerous PCs, since the router makes it show up as though one and only PC were on the association.

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4.3. Wireless Networking

By a wide margin, the most famous home networking alternative is to utilize wireless connections. A significant number of organizations including NETGEAR, Linksys, and D-Link offer wireless home networking gear.

At the point when utilizing the most recent innovation, wireless networks keep running at an entirely quick clasp. They begin at 11 Mbps (more than sufficient for home use), and numerous variations go up to 54 Mbps. In any case, distinctive components in your home may restrain the remote network's pace or usefulness. For instance, a machine might be the wellspring of electrical impedance, or something in the dividers may confine the signal quality between rooms or floors. Ensure that you can return or trade the hardware on the off chance that it doesn't work appropriately in your home. 

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4.2.2. Power line Networks

Some organizations offer equipment that gives you a chance to network PCs through a home's electrical wiring. The network hardware transmits its data through the electrical wiring, and all that is required is to connect an unique adapter to an accessible outlet close to every PC.

Realize that electrical cable networks are liable to electrical clamour from different sorts of apparatus in the home. (One analyst, actually, had his electrical cable network crash each time his fridge's compressor starts.) However, in the event that this methodology bodes well in your home, try it out. Simply make certain to spare your receipts and guarantee you can give back the hardware on the off chance that it doesn't work in your home.

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4.2.1. Phone line Networks

It's conceivable to utilize a home's current phone cables to give a network association between PCs in a home. This alternative gets to be appealing if there are phones near to every PC. Intel, D-Link, 3Com, and different organizations offer telephone line network units for the home.

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4.2. Phone line and Power line Networking Options

It is cleared in the previous section bears rehashing: The toughest element of introducing a home network is the wiring. Many of the people are not qualified to introduce network wiring, nor would they like to begin making holes in their dividers and attempting to make sense of how to lay wiring through their home (or under their house). Numerous organizations have turned out with option network alternatives that wipe out the requirement for introducing network wiring, including telephone line and electrical cable networks.

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4.1. Standard Network Hardware

Previously, it wasn't feasible for home networks to utilize networking hardware intended for businesses, since business network gear was excessively costly and was intended to bolster just bigger networks. A 24-port Ethernet hub would be too much for a home with a few PCs!

Nowadays, business network hardware is accessible in all shapes and sizes, and low-end arrangements intended for business use will regularly work pleasantly in many homes. Little Ethernet hubs or switches that can financially bolster two to four PCs are promptly accessible for around $10 to $30.

In the event that you consider every one of the components that you would require for a small network, you'll see that you truly don't require all that much:

a)   Central hub or switch: You can introduce this hub in a suitable area, for example, where the home's phone cabling is found, wardrobe, storage room, or cellar. You will require an accessible electrical plug for the hub in whatever area you select.

b)  Network interface card: Each PC require a network interface card (NIC) that backings the kind of network that you are introducing. Most present day PCs accompany integrated 10/100/1000Base-T Ethernet cards. In the event that your PC doesn't have one of these cards, it's normally simple and reasonable to buy and introduce a standard NIC. The expense for a decent Ethernet NIC is around $3 to $10. Likewise, there are great Ethernet interfaces that can associate with a PC's USB port, and these are also cheap and function admirably.

c)   Cabling: You should have the capacity to link the network. This could be the hardest piece of network setup, contingent upon the real area of the PCs and the simplicity with which you can run network link to every area. In the event that you aren't happy with running the link yourself, a electrician or phone wiring professional ought to have the capacity to carry out the work for you. The expense of expert wiring is about $100 to $150 per network link run, and this cost ought to incorporate all connectors, link, and additional items, (for example, divider plates and jacks).

d)  Operating System: The OS on most home PCs— usually Windows XP or Windows 7, yet maybe Windows 8 or Windows 10—is impeccably equipped for taking care of the greater part of the networking responsibilities that you'll require for a home network. In the event that you design the OS for a decentralized network, you'll have the capacity to share printers and documents through the framework's inherent networking software. No extra programming is required.

These components are accessible independently, generally as you would buy them for a business. You can likewise buy home networking units, which incorporate the majority of the components that you require, alongside guidelines for setting up the home network.

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4. Home Networking

In spite of the fact that this book concentrates on business networking, little office and home office (SOHO) networking is developing in significance, and no prologue to networking would be finished without in any event of brief dialog of this point. This section gives a review of how various PCs in a home can be networked together.

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