4343 X21 Network Hardware Tananbaum Ch1.2

4343 X22 Outline Network taxonomy Network software

4343 X23 Network Taxonomy There are two major ways to classify a network: –The size of the network –The transmission technology used by the network There is no defined taxonomy into which all computer networks can be classified, but these two network features are acceptable for general classifications.

4343 X24 Transmission Technologies There are two types of transmission technologies: –Broadcast –Point-to-point

4343 X25 Broadcast Networks uses a single communications channel the channel is shared information sent from any one machine on the network is received by all other machines on the network each piece of data received by a computer is checked to see if it is addressed to that computer

4343 X26 Broadcasting Broadcast networks allow data to be addressed to every machine on the network. This allows one machine to “broadcast” a message to all other machines. It is possible to “broadcast” to a subset of the machines on the network. This is known as “multicasting”.

4343 X27 Point-to-Point Point-to-point networks consist of a large number of individual connections between pairs of computers. The data travels through the network and is directed by machines along the way. Although these intermediate machines look at the data to see where it is going, they do not (should not) look at the data itself.

4343 X28 Point-to-Point (cont’d) As a general rule, point-to-point is used in larger networks while broadcasting is used in smaller, geographically localized networks. There are exceptions. Point-to-point is sometimes referred to as unicasting. This creates the list: –broadcasting –multicasting –unicasting

4343 X29 Network Size We can also classify networks based on their physical size. Different technologies may be used based on the size of the network. We can determine the type of network based on the physical distance that the network covers.

4343 X210 Network Size Chart Interprocessor Distance Processors located in same 1 mSquare Meter 10 mRoom 100 mBuilding 1 kmCampus 10 kmCity 100 kmProvince 1000 kmContinent 10,000 kmPlanet Personal Area Network Lan Area Network Metropolitan Area Network Wide Area Network The Internet

4343 X211 Personal Network A network meant for one person. A personal computer network: –a wireless keyboard and mouse –a networked printer –a PDA connection Devices to control pacemakers Remote controls for car stereos

4343 X212 Local Area Network (LAN) Usually privately-owned networks Confined to a building or several buildings on a campus or company location. Usually used to connect personal computers for data interchange and to share resources such as printers and server machines.

4343 X213 LANs LANs are distinguished by three characteristics: –size –transmission technology –topology

4343 X214 LANs - Size LANs are restricted in size based on the size of the campus or building. Knowing the size of the LAN allows the worse-case data transmission scenarios to be known ahead of time. This information can be used during LAN design to make decisions about the technology that will be used.

4343 X215 LANs - Transmission LANs are usually broadcast networks that are connected by a cable that attaches all of the computers together. LANs can run at speeds from 10Mbps to 10Gbps depending on the technology. LAN delays are usually small (microseconds) and few errors (scrambled data) occur.

4343 X216 LANs - Topologies A linear connection of computers with two distinct ends is known as a “bus network” One machine on the network becomes the “master” and is allowed to transmit a packet across the network. We have to resolve the problem of two computers wanting to be “master” at the same time.

4343 X217 Bus Network Transmission Transmitting data on a LAN may result in two “packets” of data colliding and being “lost”. We can resolve this problem using the IEEE standard known as Ethernet where if a collision is detected, the two computers just wait random amounts of time and retransmit.

4343 X218 LANs – Topologies (cont’d) The “ring” technology is a series of computers that are connected in a circle. Data can travel around the ring and is picked up by the computer it is addressed to. We still have to deal with determining who can transmit on the ring at any given point in time.

4343 X219 Ring Network Transmission One of the most famous ring transmission technologies is IBM’s Token Ring standard (IEEE 802.5) The token ring LAN can achieve speeds from 4 to 16 Mbps.

4343 X220 Local Area Networks Two broadcast networks (a) Bus (b) Ring

4343 X221 Metropolitan Area Network (MAN) MANs are usually large enough to cover a city. Best known example – a cable TV network. Originally intended for TV only, it quickly became used for computer networks once the cable companies determined that there was money to be made.

4343 X222 MANs - Topology The topology of a MAN usually results in a series of computers with a single entry point at the head end of the network. It is at the head end that the MAN would be connected to another network.

4343 X223 MAN based on cable

4343 X224 Wide Area Network (WAN) WANs are much larger than MANs, covering a whole country or other large geographical area. The user computers in a WAN are called hosts. Host computers on various LANs are connected via a communication subnet. The subnet consists of routers and transmission lines.

4343 X225 WAN – Subnet Routers A router is a specialized piece of switching hardware that is responsible for determining the direction that data packets should be sent. Routers are responsible for directing data down transmission lines from one LAN to another.

4343 X226 Wide Area Networks

4343 X227 Subnets (confusion) The word “subnet” also refers to network addressing. There is no other words to define the either the router-subnet or the addressing- subnet. I (and the book) will try to make it clear from context which “subnet” we are talking about.

4343 X228 Subnets Store-and-forward or Packet-switched –The message is broken down into smaller packets to send. –Each packet is sent out onto the network. –As a packet arrives at a router, it is stored there until the outgoing line is free. It is then sent on it’s way. –All the packets make take the same or different routes depending on if they are individually routed or not.

4343 X229 Subnets (cont’d) It is possible to have a broadcast subnet. The best example is a satellite system, where the data is broadcast to everyone. With a satellite, no routing occurs at the satellite – it simply acts as a big dish to bounce signals off of.

4343 X230 Wireless Networks Wireless networks can be divided into three main categories: –System Interconnection –Wireless LANs –Wireless WANs Lets take a look at these three categories…

4343 X231 System Interconnection We can use wireless technology to interconnect our system. –wireless mouse –wireless keyboard –wireless PDA Bluetooth is a wireless technology that would allow all sorts of digital devices to “talk” to each other just by being close.

4343 X232 Wireless LANs Computers and printers can connect to the network with a radio communication link. There is usually a (or some) central access point or base station where the radio connections are converted to wire connections. Computers may also be able to talk directly to one another if close enough together.

4343 X233 Wireless LANs (cont’d) The standard is IEEE It works on the same frequency as 2.4 GHz portable phones and Bluetooth. There are some compatibility issues between and Bluetooth that have to be worked out. Wireless is great for old homes you don’t want to wire and laptops that you want to be able to move around.

4343 X234 Wireless WANs Cell phone networks are a good example of wireless WANs. We are on our third generation of wireless WANs – there was analog voice, digital voice, and now digital voice and data. Distances are much greater than LANs, but bandwidth is much lower.

4343 X235 Home Networks Many of us have them already – multiple computers all connected. What about connections to phones, entertainment systems, appliances and other devices? How practical is a home network? Will people pay so that their toaster can talk to their fridge?

4343 X236 Internetworks A collection of interconnected networks is called an internetwork or internet. Connections are usually made through gateways that can provide the translation between the two different technologies. An internetwork is formed when distinct networks are connected.