Networks

Ing. Ludmila Kunderová

ludmila.kunderova@mendelu.cz

Department of Informatics

Office Q 2.40

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Networks

Module „Networks“ includes• The theoretical part (lessons)• The practical part (exercises)

Topics of the module „Networks“1. Network infrastructure

2. Network architecture

3. Internet services

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Networks

The aim of lessons– To introduce to the basics and essential

principles of data communication, networks, networking and network services

The aim of exercises– To gain basic skill in usage of network utilities

and tools for network services

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Introduction and Basic Terms• Network – series of points (nodes) interconnected by

communication path• Communication path – physical and logical environment

enabling the data transmission. Communication path is created with the transmitter and receiver that controls the data transmission through the transmission medium

• Network nodes – devices interconnected within network in order to be able to communicate with other network nodes. Network nodes are or user-end computers or network peripherals (printers, scanners …) or intermediate devices (repeaters, network switches, network HUBs, network routers, gateways ….)

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Components of the network infrastructure•User-end devices

– Computers

• PC machines

• Servers

– Network peripheral devices

•Network devices– HUBs

– Switches

– Routers

•Transmission media Networks - Network infrastructure 5

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Networks - – Network infrastructure • HUB is a device where data signal arrives from one or

more directions and is forwarded out in one or more other directions (multiport repeater)

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Networks – Network infrastructure • Switch is a device that selects the path for sending of the data

unit (data packet) to its next destination („intelligent HUB“)

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• Router is a device that determines the next network point to which a packet should be forwarded toward its destination. The router is connected to at least two networks and decides which way to send each packet

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Router for small LAN Router for medium LAN

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 WAP device Back-panel of the WAP

Wireless Access Point oWAP allows mobile users to connect to a central network node without using any wires .  oIt is useful for mobile workstations, since there is no wiring involved. oWireless access is specified by standards 802.11b/g/n.

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Networks - Network infrastructure • Transmission medium is the physical environment that guide the

signal or enable the penetration of signal. The transmission medium may be:

– Twisted pair

– Coaxial cable

– Optical fibre cable

– Air space (wireless transmission)

• Signal works as the data bearer. It is an electrical pulse or electromagnetic wave that is used to convey data from one place to another.

– Analog signal is the sine wave continually changing its value.

– Digital signal is the sequence of pulses changing value from one to other level at once.

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• Twisted pair (UTP) – Two insulated copper wires arranged

in regular spiral pattern– 4 pairs are bundled together into a

cable by wrapping them in a tough protective coat.

• Coaxial Cable– One physical channel that carries the

signal surrounded (after a layer of insulation) by another concentric physical channel, both running along the same axis.

– The outer channel serves as a groundInner conductorInsulationOuter shielding conductorOuter sheath

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• Optical Fiber Cable– It transmits light pulses along a glass fiber.

– It carries much more information than conventional copper wire.

– It is not subject to electromagnetic interference and the need to retransmit signals.

– There is one central core made up of best glass material best possible refraction.

– The core is covered by another glass material that has lower refraction rate to keep light inside of core. This second layer is covered by a plastic jacket.

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Networks – Network infrastructure • Air space

– Electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation – infinite and continuous.

– Frequency ranges proper for wireless data transmission are:

• Radio frequencies in the range about 30 MHz to 1 GHz.

• Microwave frequencies in the range about 2 to 40 GHz.

• Infrared (IR) frequencies - higher than those of microwaves, but lower than those of visible light.

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Radio and Microwave technologies

•Terrestrial transmission

•Satellite transmission

•Mobile networks

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Radio Transmission characteristics•Radio waves – frequency to 300 GHz can penetrate through the walls

•Lower frequency waves can travel on the ground up to 1000 km over the earth‘s surface

•Upper frequency waves reaches ionosphere and are refracted back to the earth

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Microwave Transmission characteristics•Frequency 300 MHz to 300GHz

•Waves can travel trough the obstacles

•Usually performed in wireless networks LAN (Wi-Fi technology) and WAN (WIMAX technology)

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Mobile Network •Transmissions use the microwave frequencies

•Hierarchical Structure of the Mobile Network:

– BTS – Base Transceiver Station

– BSC – Base Station Controller

– MSC – Mobile Switching Center

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• Wave lengths

– Infrared waves 300 GHZ – 430 THz

– Visible waves 430 THZ – 740 THz

• Waves cannot penetrate obstacles and are distorted by wind, rain and fog

• Sender and receiver must be in the line-of-sight

• Utilization of the light/infrared technologies is limited (point-to-point connections)

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Infrared and Visible Light Transmission characteristics

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Network categories •Local Area Network (LAN)•Metropolitan Area Network (MAN)•Wide Area Network (WAN)

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LAN•LANs are typically owned, controlled, and managed by a single person or organization. They also use certain specific connectivity technologies, primarily Ethernet.•LAN supplies networking capability to a group of computers in relatively short distances to each other such as in a building, in an organization or in an enterprise. •LANs are useful for sharing resources like servers, printers, or applications. A LAN consists of user-end devices (PCs, workstations, servers) and intermediate devices (switches, LAN routers, HUBs …) •LAN is often connects to other LANs, and to the Internet or to some other WAN

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WAN•WAN spans a large geographic area, such as a state or country. WANs often connect multiple smaller networks, such as LANs or MANs. •The most popular WAN in the world today is the Internet. Many smaller portions of the Internet, such as extranets, are also WANs. •WANs generally utilize different and much more expensive networking equipment than do LANs (WAN routers, WAN switches)•WAN technologies offer high-speed networking capabilities, therefore they are called high-speed transmission technologies

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MAN•MAN (Metropolitan Area Network) is a large computer network that spans a metropolitan area or campus.

•Its geographic scope falls between a WAN and LAN.

•MANs provide Internet connectivity for LANs in a metropolitan region, and connect them to wider area networks like the Internet.

•The MAN technologies are similar to the WAN technologies.

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Typical LAN topology

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Network Interface Card (NIC)

Network devices

LAN Equipment

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Typical WAN topology

WAN Equipment

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Essential HW and SW elements of the user-end system

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• A network operating system (NOS) is a computer operating system that is designed primarily to support workstation, personal computer that are connected on a LAN

• NOS implements protocol stacks as well as device drivers for network hardware (NIC).

• Network operating systems have existed for more than thirty years. – The UNIX® operating system was designed to support networking

from the early 80th´ years.– Novell NetWare became the first popular network operating system

for the personal computer. – Windows 95 and Windows for Workgroups were Microsoft's first

network operating system products.

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Networks – Network infrastructure • Network nodes are equipped with one or more network

interface cards (NICs) • The NIC creates the network interface for network

processes • Network node identifiers:

– Physical (associated with the NIC) - MAC address

– Logical (associated with the SW configuration) - IP address

– Symbolic - Domain name – for network applications

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Networks – Network infrastructureMAC address   • A MAC address is a 12-digit hexadecimal number (total 48 bits – 6

octets). The first three octets define the manufacturer, while the second three octets vary and identify the individual adapter.

• An example 00:40:96:E8:3A:77

IP address• IP Addresses (IPv4) uses a 32-bit number and it defines both network and

host address.• An IP address is written in "dotted decimal" notation, which is 4 sets of

numbers separated by period each set representing 8-bit number ranging from (0-255).

• An example of IPv4 address is 216.3.128.12

  

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MAC

IP

Host Domain Name

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• Domain name is the registered unique identifier of IP node based on DNS (Domain Name System)

• The fully qualified domain name (FQDN)

www.juice.com –www = Name of server (physical machine)–juice.com = domain name

juice =  sub domain of com (Second level domain name - SLD)

com= Top level domain name (TLD)

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Networks – Network infrastructureDNS Hierarchy

com

juice

www

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Domain Name System (DNS)Regional Internet Registry (RIR)

Regional Internet Registry (RIR)•African Network Information Centre (AfriNIC) for Africa

•American Registry for Internet Numbers (ARIN) for the United States, Canada, several parts of the Caribbean region, and Antarctica.

•Asia-Pacific Network Information Centre (APNIC) for Asia, Australia, New Zealand, and neighboring countries

•Latin America and Caribbean Network Information Centre (LACNIC) for Latin America and parts of the Caribbean region

•Réseaux IP Européens Network Coordination Centre (RIPE NCC) for Europe, Russia, the Middle East, and Central Asia

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Domain Name System (DNS)