Lecture 2 - Networking Lecture 2 - Networking DevicesDevices

RepeatersRepeaters HubsHubs CollisionsCollisions BridgesBridges RoutersRouters

What are internetworking What are internetworking devices?devices?

Internetworking devices are Internetworking devices are products used to connect products used to connect networks. As computer networks networks. As computer networks grow in size and complexity, so do grow in size and complexity, so do the internetworking devices used the internetworking devices used to connect them.to connect them.

The purposes of having The purposes of having devicesdevices

First, they allow a greater number of First, they allow a greater number of nodes to be connected to the network. nodes to be connected to the network.

Second, they extend the distance over Second, they extend the distance over which a network can extend. which a network can extend.

Third, they localize traffic on the network. Third, they localize traffic on the network. Fourth, they can merge existing Fourth, they can merge existing

networks.networks. Fifth, they isolate network problems so Fifth, they isolate network problems so

that they can be diagnosed more easily. that they can be diagnosed more easily.

What internetworking devices What internetworking devices operate at the physical layer (layer operate at the physical layer (layer 1) of the OSI model?1) of the OSI model?

A repeater can provide a simple A repeater can provide a simple solution if either of these two problems solution if either of these two problems exists.exists.

When signals first leave a transmitting When signals first leave a transmitting station, they are clean and easily station, they are clean and easily recognizable. However, the longer the recognizable. However, the longer the cable length, the weaker and more cable length, the weaker and more deteriorated the signals become as deteriorated the signals become as they pass along the networking media.they pass along the networking media.

Location of RepeaterLocation of Repeater

HubHub

Multi-port repeaters are often Multi-port repeaters are often called hubs. Hubs are very called hubs. Hubs are very common internetworking devices. common internetworking devices. Generally speaking, the term hub Generally speaking, the term hub is used instead of repeater when is used instead of repeater when referring to the device that serves referring to the device that serves as the center of a star topology as the center of a star topology network.network.

What is the disadvantage What is the disadvantage associated with using a associated with using a repeater?repeater?

it can't filter network traffic. Data, it can't filter network traffic. Data, sometimes referred to as bits, sometimes referred to as bits, arriving at one port of a repeater arriving at one port of a repeater gets sent out on all other portsgets sent out on all other ports

data gets passed along by a data gets passed along by a repeater to all other LAN segments repeater to all other LAN segments of a network regardless of whether of a network regardless of whether it needs to go there or noit needs to go there or no

What problem could occur as a What problem could occur as a result of too much traffic on a result of too much traffic on a network?network?

if segments of a network are only if segments of a network are only connected by non-filtering devices such as connected by non-filtering devices such as repeaters, this can result in more than one repeaters, this can result in more than one user trying to send data on the network at user trying to send data on the network at the same timethe same time

If more than one node attempts to transmit If more than one node attempts to transmit at the same time, a collision will occur.at the same time, a collision will occur.

When a collision occurs, the data from each When a collision occurs, the data from each device impact and are damageddevice impact and are damaged

What internetworking device can What internetworking device can be used to filter traffic on the be used to filter traffic on the network?network?

One way to solve the problems of too One way to solve the problems of too much traffic on a network and too much traffic on a network and too many collisions is to use an many collisions is to use an internetworking device called a internetworking device called a bridge.bridge.

A bridge eliminates unnecessary A bridge eliminates unnecessary traffic and minimizes the chances of traffic and minimizes the chances of collisions occurring on a network by collisions occurring on a network by dividing it into segments dividing it into segments

At what layer of the OSI At what layer of the OSI model do bridges operate?model do bridges operate?

Because bridges operate at the data link layer, Because bridges operate at the data link layer, layer 2, they are not required to examine layer 2, they are not required to examine upper-layer information.upper-layer information.

How do bridges filter How do bridges filter network traffic? network traffic?

How are bridge data-How are bridge data-forwarding decisions forwarding decisions limited?limited?

Although bridges use tables to Although bridges use tables to determine whether or not to determine whether or not to forward data to other segments of forward data to other segments of the network, the types of the network, the types of comparisons and decisions they comparisons and decisions they make are relatively low level, make are relatively low level, simple onessimple ones

What types of network What types of network traffic problems is a bridge traffic problems is a bridge incapable of solving? incapable of solving?

Bridges work best where traffic Bridges work best where traffic from one segment of a network to from one segment of a network to other segments is not too great. other segments is not too great.

However, when traffic between However, when traffic between network segments becomes too network segments becomes too heavy, the bridge can become a heavy, the bridge can become a bottleneck and actually slow down bottleneck and actually slow down communication.communication.

How many addressing How many addressing schemes are there in schemes are there in networking? networking?

You have already learned what one You have already learned what one of these addressing schemes is. It of these addressing schemes is. It is the MAC address. is the MAC address.

The second addressing scheme in The second addressing scheme in networking makes use of what is networking makes use of what is called the IP address. called the IP address.

How do IP addresses differ How do IP addresses differ from MAC addresses? from MAC addresses?

Like MAC addresses, every IP address is Like MAC addresses, every IP address is unique. No two IP addresses are ever alike. unique. No two IP addresses are ever alike.

However, while MAC addresses are However, while MAC addresses are physical addresses that are actually hard-physical addresses that are actually hard-coded into the NIC card and occur at the coded into the NIC card and occur at the data link layerdata link layer

IP addresses are implemented in software IP addresses are implemented in software and occur at the network layer of the OSI and occur at the network layer of the OSI model.model.

What are routers? What are routers?

Routers are another type of Routers are another type of internetworking device. internetworking device.

These devices pass data packets These devices pass data packets between networks based on network between networks based on network protocol or layer 3 information. protocol or layer 3 information.

Routers have the ability to make Routers have the ability to make intelligent decisions as to the best intelligent decisions as to the best path for delivery of data on the path for delivery of data on the network. network.

What network problems What network problems can routers help resolve?can routers help resolve?

The problem of excessive The problem of excessive broadcast traffic can be solved by broadcast traffic can be solved by using a router. using a router.

Routers are able to do this, Routers are able to do this, because they do not forward because they do not forward broadcast frames unless broadcast frames unless specifically told to do sospecifically told to do so

How do routers differ from How do routers differ from bridges?bridges?

Routers differ from bridges in several Routers differ from bridges in several respects. First, bridging occurs at the respects. First, bridging occurs at the data link layer or layer 2,while routing data link layer or layer 2,while routing occurs at the network layer or layer 3 of occurs at the network layer or layer 3 of the OSI model.the OSI model.

Second, bridges use physical or MAC Second, bridges use physical or MAC addresses to make data forwarding addresses to make data forwarding decisions. Routers use a different decisions. Routers use a different addressing scheme that occurs at layer addressing scheme that occurs at layer three three

How do routers work? How do routers work?

Routers are used to connect two or Routers are used to connect two or more networks. For routing to be more networks. For routing to be successful, each network must successful, each network must have a unique network numberhave a unique network number

The port where a router connects to The port where a router connects to network A would have an IP address network A would have an IP address of A5. of A5.

The IP address of the The IP address of the router's second interface router's second interface would be B5.would be B5.

The router would determine to send The router would determine to send the data from network A to network the data from network A to network B out its port with the IP address B5. B out its port with the IP address B5.