CSCS 311 Data Communications and Networking Lecture 5

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CSCS 311 Data Communications and Networking Lecture 5

CSCS 311 Data Communications and Networking Lecture 5

Data Communications and Networking Lecture 5 Lecture Focus: Network Devices

Data Communications and Networking Lecture 5 Lecture Focus: Network Devices

Data Communications and Networking Network Devices: Computer networking devices are units that mediate data

Data Communications and Networking Network Devices: Computer networking devices are units that mediate data in a computer network. Computer networking devices are also called network equipment, Intermediate Systems (IS) or Inter. Working Unit (IWU). Units which are the last receiver or generate data are called hosts or data terminal equipment (DTE).

Data Communications and Networking Network Devices: Repeater A repeater connects two segments of your

Data Communications and Networking Network Devices: Repeater A repeater connects two segments of your network cable. When a signal travels along a cable, it tends to lose strength. It receives a signal and before it becomes too weak, electrically amplifies the signals to proper amplitude and regenerates the original signal and rebroadcast it to the other segments. It does not connect two LANs. It connects two segments of the same LAN. Works on OSI layer 1 (Physical). Repeaters require a small amount of time to regenerate the signal. This can cause a propagation delay which can affect network communication when there are several repeaters in a row. Many network architectures limit the number of repeaters that can be used in a row.

Data Communications and Networking Network Devices: Repeaters can be separate devices or they can

Data Communications and Networking Network Devices: Repeaters can be separate devices or they can be incorporated into a concentrator. They are used when the total length of your network cable exceeds the standards set for the type of cable being used. A good example of the use of repeaters would be in a LAN using a star topology with unshielded twisted-pair cabling. The length limit for unshielded twisted-pair cable is 100 meters. The most common configuration is for each workstation to be connected by twisted-pair cable to a multi-port active concentrator. The concentrator regenerates all the signals that pass through it allowing for the total length of cable on the network to exceed the 100 meter limit.

Data Communications and Networking Network Devices: Repeater Attenuation refers to the degradation of signal

Data Communications and Networking Network Devices: Repeater Attenuation refers to the degradation of signal strength (amplitude) that occurs in transmissions over long distances. Shortening the transmission distance or using repeaters can help solve this problem. Segment B 500 M Segment A 500 M Repeater

Data Communications and Networking Network Devices: Repeater

Data Communications and Networking Network Devices: Repeater

Data Communications and Networking Network Devices: Hub (Concentrator) A hub is actually a multi-port

Data Communications and Networking Network Devices: Hub (Concentrator) A hub is actually a multi-port Repeater. It is used to create connections between stations of star topology. Twisted-pair wire is run from each workstation to a central concentrator. A computer wanting to send a message in the network sends a message to the hub, which, in turn, broadcasts the message to all other computers. When using a hub, every attached device shares the same broadcast domain and the same collision domain. Only one computer connected to the hub is able to transmit at a time. It provides bandwidth which is shared among all the objects, compared to switches, which provide a dedicated connection between individual nodes. Works on OSI layer 1.

Data Communications and Networking Network Devices: Hub (Concentrator) A concentrator is a device that

Data Communications and Networking Network Devices: Hub (Concentrator) A concentrator is a device that provides a central connection point for cables from workstations, servers, and peripherals. Hubs are multi-slot concentrators into which can be plugged a number of multi-port cards to provide additional access as the network grows in size. Some concentrators are passive, that is they allow the signal to pass from one computer to another without any change. Most concentrators are active, that is they electrically amplify the signal as it moves from one device to another. Active concentrators are used like repeaters to extend the length of a network.

Data Communications and Networking Network Devices: Hub (Concentrator) Concentrators are: Usually configured with 8,

Data Communications and Networking Network Devices: Hub (Concentrator) Concentrators are: Usually configured with 8, 12, or 24 RJ-45 ports Often used in a star or star-wired ring topology Sold with specialized software for port management Usually installed in a standardized metal rack that also may store net modems, bridges, or routers A hub simply replicates what it receives on one port onto all the other ports

Data Communications and Networking Lecture 5 Network Devices: Switch A device used to connect

Data Communications and Networking Lecture 5 Network Devices: Switch A device used to connect several computers to form a network A switch has several ports. The number generally is 8, 12, 16, 24, 32, or 48 Each computer in a network is connected to one of those ports. A computer wanting to send a message in the network sends a message to the switch, which, in turn, sends message to the destination. An intelligent device: Unlike hub, the message is not broadcasted The switch filters and forwards data packets across a network. More expensive than hub, but better in performance Works on OSI layer 2. Switch provides a dedicated connection between individual nodes.

Data Communications and Networking Lecture 5 Network Devices: Switch The switch is an advanced

Data Communications and Networking Lecture 5 Network Devices: Switch The switch is an advanced form of the hub similar in functions but the advanced switches has a switching table in them Switch stores the MAC address of every attached computer and the data is only sent to the destined computer by looking up the MAC address, unlike the hubs where data is sent to all ports.

Data Communications and Networking Lecture 5 Network Devices: Switch A network switch can utilize

Data Communications and Networking Lecture 5 Network Devices: Switch A network switch can utilize the full throughput potential of a networks connection for each device making it a natural choice over a standard hub. Suppose you have a network of 5 PCs and a server all connected with 10 Mbps UTP (unshielded twisted-pair) cable. Using a hub, the throughput (10 Mbps) would be shared between each device With a switch each device could utilize the full 10 Mbps connection.

Data Communications and Networking Lecture 5 Network Devices: Bridge A device which connects two

Data Communications and Networking Lecture 5 Network Devices: Bridge A device which connects two LANs Connects LANs using the same protocols A bridge allows you to segment a large network into two smaller, more efficient networks. If you are adding to an older wiring scheme and want the new network to be up-to-date, a bridge can connect the two. Controls broadcast to the network Works on OSI layer 2. A bridge reads the outermost section of data on the data packet, to tell where the message is going. It reduces the traffic on other network segments, since it does not send all packets. Bridges can be programmed to reject packets from particular networks.

Data Communications and Networking Lecture 5 Network Devices: Bridge A bridge monitors the information

Data Communications and Networking Lecture 5 Network Devices: Bridge A bridge monitors the information traffic on both sides of the network so that it can pass packets of information to the correct location. Most bridges can "listen" to the network and automatically figure out the address of each computer on both sides of the bridge. The bridge can inspect each message and, if necessary, broadcast it on the other side of the network. The bridge manages the traffic to maintain optimum performance on both sides of the network. You might say that the bridge is like a traffic cop at a busy intersection during rush hour. It keeps information flowing on both sides of the network, but it does not allow unnecessary traffic through. Bridges can be used to connect different types of cabling, or physical topologies. They must, however, be used between networks with the same protocol.

Data Communications and Networking Lecture 5 Network Devices: Bridge Bridging occurs at the data

Data Communications and Networking Lecture 5 Network Devices: Bridge Bridging occurs at the data link layer of the OSI model, which means the bridge cannot read IP addresses, but only the outermost hardware address of the packet. Bridges forward all broadcast messages. Bridges do not normally allow connection of networks with different architectures. Only a special bridge called a translation bridge will allow two networks of different architectures to be connected.

Data Communications and Networking Lecture 5 Network Devices: Bridge The hardware address is also

Data Communications and Networking Lecture 5 Network Devices: Bridge The hardware address is also called the MAC (media access control) address. To determine the network segment a MAC address belongs to, bridges use one of: Transparent Bridging - They build a table of addresses (bridging table) as they receive packets. If the address is not in the bridging table, the packet is forwarded to all segments other than the one it came from. This type of bridge is used on Ethernet networks. Source Route Bridging - The source computer provides path information inside the packet. This is used on Token Ring networks.

Data Communications and Networking Lecture 5 Network Devices: Gateway A device which connects two

Data Communications and Networking Lecture 5 Network Devices: Gateway A device which connects two LANs Connects LANs using different protocols It connects two different and possibly incompatible networks. It can translate information between different network data formats or network architectures. It can translate TCP/IP to Apple. Talk so computers supporting TCP/IP can communicate with Apple brand computers. Works on OSI layers 4 to 7. Most gateways operate at the application layer, but can operate at the network or session layer of the OSI model. Gateways will start at the lower level and strip information until it gets to the required level and repackage the information and work its way back toward the hardware layer of the OSI model.

Data Communications and Networking Network Devices: Router is used for sending data from a

Data Communications and Networking Network Devices: Router is used for sending data from a particular station of a LAN to remote station of another LAN. It routes data packets between two networks by choosing best shortest path (route) for data transfer based on source and destination address. It is similar to a super intelligent bridge Acts as store-and-forward message system Protocols of all the LANs should be same Unlike a gateway, it cannot interface different protocols. They can connect networks with different architectures such as Token Ring and Ethernet. Works on OSI layer 3 (Network layer). The router can direct traffic to prevent head-on collisions, and is smart enough to know when to direct traffic along back roads and shortcuts.

Data Communications and Networking Lecture 5 Network Devices: Router It reads the information in

Data Communications and Networking Lecture 5 Network Devices: Router It reads the information in each packet to tell where it is going. If it is destined for an immediate network it has access to, it will strip the outer packet, readdress the packet to the proper Ethernet address, and transmit it on that network. If it is destined for another network and must be sent to another router, it will re-package the outer packet to be received by the next router and send it to the next router. Although they can transform information at the data link level, routers cannot transform information from one data format such as TCP/IP to another such as IPX/SPX. Routers do not send broadcast packets or corrupted packets. If the routing table does not indicate the proper address of a packet, the packet is discarded.

Data Communications and Networking Network Devices: Router While bridges know the addresses of all

Data Communications and Networking Network Devices: Router While bridges know the addresses of all computers on each side of the network, routers know the addresses of computers, bridges, and other routers on the network. Routers can even "listen" to the entire network to determine which sections are busiest -- they can then redirect data around those sections until they clear up. If you have a school LAN that you want to connect to the Internet, you will need to purchase a router. In this case, the router serves as the translator between the information on your LAN and the Internet. It also determines the best route to send the data over the Internet.

Data Communications and Networking Network Devices: Routers can: Direct signal traffic efficiently Route messages

Data Communications and Networking Network Devices: Routers can: Direct signal traffic efficiently Route messages between any two protocols Route messages between linear bus, star, and star-wired ring topologies Route messages across fiber optic, coaxial, and twisted-pair cabling A router is a key device in the internet communication and WAN communication system. A router has software called routing table: Source and destination addresses are stored in this table. Router finds the IP address of the next hop (next router) and the data is sent toward it and so on.

Data Communications and Networking Network Devices:

Data Communications and Networking Network Devices:

Data Communications and Networking Lecture 5 Some Hybrid Network Devices: Multilayer Switch A switch

Data Communications and Networking Lecture 5 Some Hybrid Network Devices: Multilayer Switch A switch which, in addition to switching on OSI layer 2, provides functionality at higher protocol layers. Protocol Convertor A hardware device that converts between two different types of transmissions, such as asynchronous and synchronous transmissions. Bridge Router (Brouter) Combines router and bridge functionality and are therefore working on OSI layers 2 and 3 (Network and Data Link). Bridge for network transport protocols that are not routable Router for routable protocols

Data Communications and Networking Lecture 5 Some other Network Devices: Hardware or software components

Data Communications and Networking Lecture 5 Some other Network Devices: Hardware or software components that typically sit on the connection point of different networks, e. g. between an internal network and an external network Proxy Computer network service which allows clients to make indirect network connections to other network services Firewall A piece of hardware or software put on the network to prevent some communications forbidden by the network policy Network Address Translator Network service provided to convert internal to external network addresses and vice versa

Data Communications and Networking Lecture 5 Hardware to establish network or dial up connections:

Data Communications and Networking Lecture 5 Hardware to establish network or dial up connections: Hardware or software components that typically sit on the connection point of different networks, e. g. between an internal network and an external network Multiplexer Device that combines several electrical signals into a single signal Network Card A piece of computer hardware to allow the attached computer to communicate with the network Line Driver A device to increase transmission distance by amplifying the signal.

Data Communications and Networking Hub, Switch, and Router similarities and differences A router is

Data Communications and Networking Hub, Switch, and Router similarities and differences A router is a more sophisticated network device than either a switch or a hub. Like hubs and switches, network routers are typically small, box-like pieces of equipment that multiple computers can connect to. Each features: A number of "ports" that provide the connection points for these computers, A connection for electric power, and A number of LED lights to display device status.

Data Communications and Networking Hub, Switch, and Router similarities and differences Traditional routers are

Data Communications and Networking Hub, Switch, and Router similarities and differences Traditional routers are designed to join multiple area networks (LANs and WANs). On the Internet or on a large corporate network, for example, routers serve as intermediate destinations for network traffic. These routers receive TCP/IP packets, look inside each packet to identify the source and target IP addresses, then forward these packets as needed to ensure the data reaches its final destination.

Data Communications and Networking Hub, Switch, and Router similarities and differences Routers for home

Data Communications and Networking Hub, Switch, and Router similarities and differences Routers for home networks (often called broadband routers) also can join multiple networks. These routers are designed specifically to join the home (LAN) to the Internet (WAN) for the purpose of Internet connection sharing. In contrast, neither hubs nor switches are capable of joining multiple networks or sharing an Internet connection. A home network with only hubs and switches must designate one computer as the gateway to the Internet, and that device must possess two network adapters for sharing, one for the home LAN and one for the Internet WAN. With a router, all home computers connect to the router equally, and it performs the equivalent gateway functions.

Data Communications and Networking Hub, Switch, and Router similarities and differences Hubs are not

Data Communications and Networking Hub, Switch, and Router similarities and differences Hubs are not designed to work on high speed business networks involving database connectivity because they are not full duplex. If you were to use the software with a hub you would definitely experience data losses. You would experience more crashes whenever traffic is high.

Data Communications and Networking Hub, Switch, and Router similarities and differences Hubs are only

Data Communications and Networking Hub, Switch, and Router similarities and differences Hubs are only half duplex - each client can only send OR receive data at a particular time. A switch can operate at full duplex allowing your computers to send and receive at the same time.

Data Communications and Networking Hub, Switch, and Router similarities and differences Switches also route

Data Communications and Networking Hub, Switch, and Router similarities and differences Switches also route traffic directly between ports instead of broadcasting traffic across all ports. This basically means that each port on a switch gets dedicated bandwidth instead of shared bandwidth. When transferring large files between multiple computers, this can make a big difference in how well your LAN operates. A hub shares the total bandwidth among all users, while a switch provides a dedicated line at full bandwidth between every two devices transmitting to each other. In the 1990 s, switches were much more costly than hubs, and devices were carefully evaluated based on the traffic requirement. By the turn of the century, switches became much less expensive, and the popularity of hubs began to wane. In a small home or office, a hub is generally sufficient. However, if many users are always sending large files to each other, the switch is the better choice.

Data Communications and Networking Hub, Switch, and Router similarities and differences Switches control the

Data Communications and Networking Hub, Switch, and Router similarities and differences Switches control the flow of network traffic based on the address information in each packet. A switch learns which devices are connected to its ports (by monitoring the packets it receives), and then forwards on packets to the appropriate port only. This allows simultaneous communication across the switch, improving bandwidth. This switching operation reduces the amount of unnecessary traffic that would have occurred if the same information had been sent from every port (as with a hub). Switches and hubs are often used in the same network; the hubs extend the network by providing more ports, and the switches divide the network into smaller, less congested sections.

Data Communications and Networking Hub, Switch, and Router similarities and differences In a small

Data Communications and Networking Hub, Switch, and Router similarities and differences In a small network (less than 30 users), a hub (or collection of hubs) can easily cope with the network traffic generated and is the ideal piece of equipment to use for connecting the users. When the network gets larger (about 50 users), you may need to use a switch to divide the groups of hubs, to cut down the amount of unnecessary traffic being generated. If there is a hub or switch with Network Utilization LEDs, you can use the LEDs to view the amount of traffic on the network. If the traffic is constantly high, you may need to divide up the network using a switch. When adding hubs to the network (to add more users), there are rules about the number of hubs you can connect together. Switches can be used to extend the number of hubs that you can use in the network.

Data Communications and Networking An interesting scenario I have two pc's sharing one cable

Data Communications and Networking An interesting scenario I have two pc's sharing one cable connection. I installed a router but the hardware firewall was killing me. I was told that a Hub was the same thing as a router, minus the firewall, so i picked up a hub. Now my hub let me connect LAN but not over the internet. I don’t have a printer to share so no worries there. Is there something I'm doing wrong? Or is perhaps a switch the way to go?

Data Communications and Networking An interesting scenario Log into the router using your browser,

Data Communications and Networking An interesting scenario Log into the router using your browser, and DISABLE the router's firewall. I was told that a Hub was the same thing as a router, minus the firewall. . . Whoever told that doesn't know what he is talking about. Routers are designed specifically to join the home (LAN) to the Internet (WAN). Neither hubs nor switches are capable of joining multiple networks or sharing an Internet connection.

Data Communications and Networking An interesting scenario A router is a layer 3 device.

Data Communications and Networking An interesting scenario A router is a layer 3 device. A hub is a layer 1/2 device. A layer 2 device (if not smart) is just a special cable. It doesn't care unless you overload. Overload starts somewhere near 35% of bandwidth. Switches and routers are about 70% bandwidth. If you try to exceed that you end up with what looks to be a network hardware problem. Some games might require a great deal of bandwidth. Along with the game there is always broadcast traffic to mix in.

Data Communications and Networking An interesting scenario They go up in terms of "intelligence":

Data Communications and Networking An interesting scenario They go up in terms of "intelligence": hub (brainless) switch (rudimentary) router (quite intelligent) (and lastly there was "very intelligent" - gateway) A hub does not analyze the traffic at all; just passes it on to anything connected. A switch just analyzes some info about all the computers/devices plugged into it. (Specifically MAC addresses) A router analyzes info about this and other "nearby" networks. It can "route" the traffic onto the next network (e. g. your ISP)

Data Communications and Networking Some Definitions Hop On larger networks, the trip from one

Data Communications and Networking Some Definitions Hop On larger networks, the trip from one switch point to another in the network is called a hop. Latency The time a switch takes to figure out where to forward a data unit is called its latency. The price paid for having the flexibility that switches provide in a network is this latency. Switches are found at the backbone and gateway levels of a network where one network connects with another and at the sub -network level where data is being forwarded close to its destination or origin. The former are often known as core switches and the latter as desktop switches.

Data Communications and Networking Some Definitions Crossover cable Two computers can be connected directly

Data Communications and Networking Some Definitions Crossover cable Two computers can be connected directly together in an Ethernet with a crossover cable. A crossover cable doesn't have a collision problem. It hardwires the Ethernet transmitter on one computer to the receiver on the other. Most 100 BASE-TX Ethernet Adapters can detect when listening for collisions is not required with a process known as auto-negotiation and will operate in a full duplex mode when it is permitted. The result is a crossover cable doesn't have delays caused by collisions, data can be sent in both directions simultaneously, the maximum available bandwidth is 200 Mbps, 100 Mbps each way, and there are no other PC's with which the bandwidth must be shared.

Data Communications and Networking Some Definitions Crossover cable

Data Communications and Networking Some Definitions Crossover cable

Data Communications and Networking Important Question Although hubs and switches both glue the PCs

Data Communications and Networking Important Question Although hubs and switches both glue the PCs in a network together, a switch is more expensive and a network built with switches is generally considered faster than one built with hubs. Why?

Data Communications and Networking Answer When a hub receives a packet of data at

Data Communications and Networking Answer When a hub receives a packet of data at one of its ports from a PC on the network, it transmits (repeats) the packet to all of its ports and, thus, to all of the other PCs on the network. If two or more PCs on the network try to send packets at the same time, a collision is said to occur. When that happens all of the PCs have to go though a routine to resolve the conflict. The process is prescribed as Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol. Each Ethernet Adapter has both a receiver and a transmitter. If the adapters didn't have to listen with their receivers for collisions, they would be able to send data at the same time they are receiving it (full duplex). Because they have to operate at half duplex (data flows one way at a time) and a hub retransmits data from one PC to all of the PCs, the maximum bandwidth is 100 Mhz and that bandwidth is shared by all of the PC's connected to the hub. The result is when a person using a computer on a hub downloads a large file or group of files from another computer the network becomes congested. In a 10 Mhz 10 Base-T network the affect is to slow the network to nearly a crawl. The affect on a small, 100 Mbps (million bits per scond), 5 -port network is not as significant.

Data Communications and Networking Answer A switch automatically divides the network into multiple segments,

Data Communications and Networking Answer A switch automatically divides the network into multiple segments, acts as a high-speed, selective bridge between the segments, and supports simultaneous connections of multiple pairs of computers which don't compete with other pairs of computers for network bandwidth. It accomplishes this by maintaining a table of each destination address and its port. When the switch receives a packet, it reads the destination address from the header information in the packet, establishes a temporary connection between the source and destination ports, sends the packet on its way, and then terminates the connection.

Data Communications and Networking Answer Picture a switch as making multiple temporary crossover cable

Data Communications and Networking Answer Picture a switch as making multiple temporary crossover cable connections between pairs of computers (the cables are actually straight-thru cables; the crossover function is done inside the switch). High-speed electronics in the switch automatically connect the end of one cable (source port) from a sending computer to the end of another cable (destination port) going to the receiving computer on a per packet basis. Multiple connections like this can occur simultaneously. And like a crossover cable between two PCs, PC's on an Ethernet switch do not share the transmission media, do not experience collisions or have to listen for them, can operate in a full-duplex mode, have bandwidth as high as 200 Mbps, 100 Mbps each way, and do not share this bandwidth with other PCs on the switch. In short, a switch is "more better. "

Data Communications and Networking Another Question What's the difference between a Hub, a Switch

Data Communications and Networking Another Question What's the difference between a Hub, a Switch and a Router? Answer In a word: intelligence.

Data Communications and Networking Answer Hubs, switches, and routers are all devices that let

Data Communications and Networking Answer Hubs, switches, and routers are all devices that let you connect one or more computers to other computers, networked devices, or to other networks. Each has two or more connectors called ports into which you plug in the cables to make the connection. A hub is typically the least expensive, least intelligent, and least complicated of the three. Its job is very simple: anything that comes in one port is sent out to the others. That's it. Every computer connected to the hub "sees" everything that every other computer on the hub sees. The hub itself is blissfully ignorant of the data being transmitted. For years, simple hubs have been quick and easy ways to connect computers in small networks.

Data Communications and Networking Answer A switch does essentially what a hub does but

Data Communications and Networking Answer A switch does essentially what a hub does but more efficiently. By paying attention to the traffic that comes across it, it can "learn" where particular addresses are. For example, if it sees traffic from machine A coming in on port 2, it now knows that machine A is connected to that port and that traffic to machine A needs to only be sent to that port and not any of the others. The net result of using a switch over a hub is that most of the network traffic only goes where it needs to rather than to every port. On busy networks this can make the network significantly faster.

Data Communications and Networking Answer A router is the smartest and most complicated of

Data Communications and Networking Answer A router is the smartest and most complicated of the bunch. A simple way to think of a router is as a computer that can be programmed to understand, possibly manipulate, and route the data its being asked to handle. For example, broadband routers include the ability to "hide" computers behind a type of firewall which involves slightly modifying the packets of network traffic as they traverse the device. All routers include some kind of user interface for configuring how the router will treat traffic. The really large routers include the equivalent of a full-blown programming language to describe how they should operate as well as the ability to communicate with other routers to describe or determine the best way to get network traffic from point A to point B. Most devices now are capable of both 10 mps (10 mega-bits, or million bits, per second) as well as 100 mbs and will automatically detect the speed. If the device is labeled with only one speed then it will only be able to communicate with devices that also support that speed. 1000 mbs or "gigabit" devices are starting to slowly become more common as well.