Lecture #3 - Uses of Networks. Lecture #3 - Uses of Networks. Network Architecture - Network Network Architecture - Network

HardwareHardwareprof. Boyanovprof. Boyanov

C o n t e n t s C o n t e n t s TerminologyTerminology Application of the Computer NetworksApplication of the Computer Networks Network HardwareNetwork Hardware Network TypesNetwork Types

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Text book of the courseText book of the course

Our new Bible:Our new Bible:

Introduction - Introduction - TerminologyTerminology

prof. Boyanovprof. Boyanov

Computer Network:Computer Network:interconnected autonomous computersinterconnected autonomous computers

explicit addressing and namingexplicit addressing and naming virtualvirtual

explicit allocation / reallocationexplicit allocation / reallocation memorymemoryexplicit remote managementexplicit remote management

Distributed System:Distributed System:interconnected autonomous computersinterconnected autonomous computers

transparent addressingtransparent addressing virtualvirtualtransparent allocation and reallocationtransparent allocation and reallocation

uniprocessoruniprocessortransparent executiontransparent execution

Application of the Application of the Computer NetworksComputer Networks

Enterprise Networks (Intranets) Enterprise Networks (Intranets) Public NetworksPublic Networks Personal UsePersonal Use

Social AspectsSocial Aspects

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Resource SharingResource Sharing - many computers in - many computers in different placesdifferent places

High ReliabilityHigh Reliability - duplication of data, - duplication of data, hardware resources, fault-tolerancehardware resources, fault-tolerance

Low Cost/Performance RatioLow Cost/Performance Ratio - cheaper - cheaper workstations than mainframes; application workstations than mainframes; application of the of the client-server modelclient-server model

Scalability and FlexibilityScalability and Flexibility - system - system grows with the enterprise grows with the enterprise

Enterprise Networks Enterprise Networks (“(“IntranetsIntranets”)”)

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Public NetworksPublic Networks

2 preconditions2 preconditions: cheap and compact home : cheap and compact home computers and communication technologiescomputers and communication technologies

Electronic commercial and banking, Electronic commercial and banking, entertainment, public and social services, entertainment, public and social services, mass media etc.mass media etc.

Person-to-person communicationPerson-to-person communication Instances: WWW, E-mail, electronic Instances: WWW, E-mail, electronic

newspapers, on-line TV/Radio, newsgroups, newspapers, on-line TV/Radio, newsgroups, videoconferencing etc. videoconferencing etc.

Personal UsePersonal Use Moving all the services at home - Moving all the services at home -

shopping, banking, health, shopping, banking, health, TV/radio/cinema/news-papers etc.TV/radio/cinema/news-papers etc.

On-line information - “Browsing”, On-line information - “Browsing”, “Surfing”, searching machines.“Surfing”, searching machines.

Personal contacts and communication.Personal contacts and communication.

Social IssuesSocial Issues Formal (Legislative) Regulation of service Formal (Legislative) Regulation of service

providing (incl. taxes, QoS/protection of providing (incl. taxes, QoS/protection of customer rights, registration of customer rights, registration of sites/addressing etc.)sites/addressing etc.)

Electronic Payments and Security IssuesElectronic Payments and Security Issues Advertisement (incl. Internet, Advertisement (incl. Internet,

“spaming”/“bombing”)“spaming”/“bombing”) Information CorrectnessInformation Correctness Public control (illegal sex, trade, crimes)Public control (illegal sex, trade, crimes)

Clinton’s Communication Decency Act - 1996

Network HardwareNetwork Hardware Main Taxonomy Dimensions:Main Taxonomy Dimensions:

transmission technologytransmission technology

network range (scale, size)network range (scale, size) Transmission TechnologyTransmission Technology

broadcast networksbroadcast networks

point-to pointpoint-to point

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Broadcast NetworksBroadcast Networks Single communication channel shared by Single communication channel shared by

all the machines in the networkall the machines in the network Short messages (packets) with addressing Short messages (packets) with addressing

fieldfield Target machine interprets current Target machine interprets current

message; the rest ignore itmessage; the rest ignore it Special bits in the address field indicate the Special bits in the address field indicate the

transmission mode: transmission mode: broadcastbroadcast (to all the (to all the machines); machines); multicastmulticast (to group of (to group of machines)machines)

Point-to-point Point-to-point NetworksNetworks

Many connections between pairs of Many connections between pairs of machinesmachines

Packets visit 0, 1, 2 … intermediate Packets visit 0, 1, 2 … intermediate machines reaching the target onemachines reaching the target one

Alternative routes Alternative routes -- routing algorithms routing algorithms

Basically for large networksBasically for large networks

Network RangeNetwork Range Physical SizePhysical Size

Data Flow Machines & Multicomputers Data Flow Machines & Multicomputers are are Distributed SystemsDistributed Systems but notbut not Computer Computer NetworksNetworks

Local Area Networks (LANs)Local Area Networks (LANs) Metropolitan Area NetworksMetropolitan Area Networks Wide Area Networks (WANs)Wide Area Networks (WANs) Internetworks (connection of more than Internetworks (connection of more than

one network - The Internet) one network - The Internet)

fine grain parallel com-puters; many functional units

perform any instruction

message passing sys-tems; short and fast com-

munication busses

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Local Area Networks Local Area Networks (LANs)(LANs)

Up to 1-2 km physical range (room, Up to 1-2 km physical range (room, building, campus)building, campus)

Private owned (companies, branches, Private owned (companies, branches, laboratories, small institutions)laboratories, small institutions)

Connect PCs, workstations, disk stores, Connect PCs, workstations, disk stores, printers and other peripherals printers and other peripherals

Main characteristics:Main characteristics:sizesizetransmission technologytransmission technologytopologytopology 16

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Size of the LANsSize of the LANs Small, technologically restricted sizeSmall, technologically restricted size

Bounded and known transmission timeBounded and known transmission time

Simple network management due to the Simple network management due to the

limited transmission time limited transmission time

Transmission Transmission Technology of the LANsTechnology of the LANs

Usually based on a single cable attaching Usually based on a single cable attaching

all the components of the networkall the components of the network

Communication speed 10 - 100 Mb/S, 1+ Communication speed 10 - 100 Mb/S, 1+

Gb/sGb/s

Communication delay 10 - 100 Communication delay 10 - 100 S S (1 (1 s = s =

1010-6-6 S) S)

Topology of the LANsTopology of the LANs

Topology is the graph of the connectivity of the Topology is the graph of the connectivity of the network componentsnetwork components

Typical topology of LANs is bus or ringTypical topology of LANs is bus or ring Bus topology is based on linear cableBus topology is based on linear cable Arbitration management - time-sharing control: Arbitration management - time-sharing control:

1 master machine at any instant is allowed to 1 master machine at any instant is allowed to transmit; conflict requests resolvationtransmit; conflict requests resolvation

Centralized or Distributed arbitrationCentralized or Distributed arbitration EthernetEthernetTMTM (IEEE 802.3) standard: bus-based, (IEEE 802.3) standard: bus-based,

distributed arbitration based on collision distributed arbitration based on collision detection and random delay for next attemptdetection and random delay for next attempt

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Topology of the LANs - Topology of the LANs - ring topologyring topology

Network ring forms necklace of the Network ring forms necklace of the

workstationsworkstations

Bit-slice propagation of the packetsBit-slice propagation of the packets

IBM IBM Token RingToken Ring (IEEE 802.5) standard (IEEE 802.5) standard

operates at 4-16 Mb/Soperates at 4-16 Mb/S

Local area networksLocal area networks•Local area networks (LANs) are physically relatively

small. They are usually spanning one km or less. •Usually, every device on the LAN essentially shares the

same transmission cable. This is called shared media access.•Ethernet LAN technology (IEEE 802.3) has today the

largest installed base. It has several types of cabling - Thick coaxial (10-base-5) with AUI connectors and transceivers, thin coaxial (10-base-2) with BNC connectors, and unshielded twisted pair (UTP or 10-base-T) with RJ-45 jacks. •Each station on an Ethernet has an Ethernet network

interface card (NIC), which has a special hardware address, assigned to guarantee link layer uniqueness, even across vendors.•Ethernet is mostly used with speeds 10 Mbps and 100 Mbps.

Local area networksLocal area networks• Ethernet media access control allows any station on the network try to transmit at any time, which may produce collisions when several stations transmit at one time. • Media access mechanism identifies collisions and allows each station to have adequate access to common channel.• In Ethernet this mechanism is called carrier sense multiple access with collision detection (CSMA/CD).• Another quite a popular LAN technology is the Token Ring specified in IEEE 802.5 with basic speed of 4 Mbps. • The media access in Token Ring is based on token passing mechanism.• Other IEEE 802.x standards are 802.4 Token Bus (5 and 10 Mbps) used in Manufacturing Automation Protocol (MAP) systems, and 802.6 Metropolitan Area Network (MAN), which is also called DQDP (Distributed Queue Dual Bus) and has speed 100 Mbps.

Metropolitan Area Metropolitan Area NetworksNetworks

Bigger version of LANs using similar Bigger version of LANs using similar technology - common broadcast media technology - common broadcast media that connects all the computersthat connects all the computers

Options: voice and image Options: voice and image communications (incl. cable TV)communications (incl. cable TV)

No switching elements; 1 - 2 cablesNo switching elements; 1 - 2 cables DQDB (Distributed Queue Dual Bus - DQDB (Distributed Queue Dual Bus -

IEEE 802.6) Standard: 2 unidirectional IEEE 802.6) Standard: 2 unidirectional buses with 2 head-ends (for each bus) buses with 2 head-ends (for each bus) to initiate the transmission activity in to initiate the transmission activity in each direction.each direction. 1/4

Wide Area Networks Wide Area Networks (WANs)(WANs)

WAN covers large geographic area (country, WAN covers large geographic area (country, continent)continent)

Connects different types of machines - Connects different types of machines - ““hostshosts” via communication ” via communication subnetsubnet

Separation of the services: hosts run Separation of the services: hosts run application programs and subnet performs application programs and subnet performs the connection tasksthe connection tasks

Subnet consists of Subnet consists of transmission linestransmission lines and and switching elementsswitching elements (“ (“routersrouters”: ”: specialized in connecting 2 or more specialized in connecting 2 or more switching lines)switching lines)

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WANs & Routers WANs & Routers

Router is specialized switching element in Router is specialized switching element in the WAN subnet. the WAN subnet.

SwitchingSwitching is the process of: is the process of:1) receiving data on the incoming channel[s]; 1) receiving data on the incoming channel[s];

2) interpreting it;2) interpreting it;

3) choosing an outgoing line and 3) choosing an outgoing line and

4) forwarding the data on it.4) forwarding the data on it. Typical structure of WAN: hosts connected Typical structure of WAN: hosts connected

by LANs; LANs connected by the subnetby LANs; LANs connected by the subnet

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WANs & SubnetsWANs & Subnets Subnet consists of routers and connection linesSubnet consists of routers and connection lines The subnet lines are based on cables The subnet lines are based on cables

(telephone lines) that connects pairs of routers (telephone lines) that connects pairs of routers ((point-to-pointpoint-to-point network) in a connected graph. network) in a connected graph. ExceptionException: : wirelesswireless//satellitesatellite based subnets based subnets are of broadcast type (for WANs specialized in are of broadcast type (for WANs specialized in broadcasting communication)broadcasting communication)

Non connected routers communicate via Non connected routers communicate via intermediate routers in intermediate routers in store-and-forwardstore-and-forward modemode

Subnet topology - usually irregularSubnet topology - usually irregular 1/6

Wide area networksWide area networksWide area network (WANWide area network (WAN) is a concept ) is a concept

that is used in context of geographically that is used in context of geographically large networks (1 - 50 km span). large networks (1 - 50 km span).

Generally, WANs consist of site specific Generally, WANs consist of site specific LANs and teleoperator backbones which are LANs and teleoperator backbones which are used to interconnect the LANs. used to interconnect the LANs.

This trunk capacity is provided to WANs as:This trunk capacity is provided to WANs as:– Basic analogue telephone connection with modemsBasic analogue telephone connection with modems– Digital ISDN connection with terminal adapters (TA)Digital ISDN connection with terminal adapters (TA)– PDH based connection with direct router support or using Frame PDH based connection with direct router support or using Frame

Relay (FR)Relay (FR)– SDH based connection with ATM.SDH based connection with ATM.

Wide area networksWide area networksBasic telephone networks support switched 64 kbps Basic telephone networks support switched 64 kbps

connections with either analogue modem or digital connections with either analogue modem or digital ISDN subscriber lines.ISDN subscriber lines.

ISDN Basic Rate InterfaceISDN Basic Rate Interface (BRI) (BRI) consists of two consists of two bearer (B) channels and a 16 Kbps signaling (D) bearer (B) channels and a 16 Kbps signaling (D) channel (called as 2 B + D).channel (called as 2 B + D).

ISDN Primary Rate InterfaceISDN Primary Rate Interface (PRI) (PRI) is a high- is a high-bandwidth version of the BRI, also called as 30 B + D.bandwidth version of the BRI, also called as 30 B + D.

Serial Line Internet Protocol (SLIP)Serial Line Internet Protocol (SLIP) and and Point-Point-to-Point Protocolto-Point Protocol

(PPP)(PPP) are used with the basic analogue and digital are used with the basic analogue and digital telephone interfaces as the transport layer for an telephone interfaces as the transport layer for an Internet link. Internet link.

SLIP/PPP connections are temporary links over SLIP/PPP connections are temporary links over standard serial phone links between end user and standard serial phone links between end user and terminal server.terminal server.

Wireless NetworksWireless Networks

Preconditions: mobile computers Preconditions: mobile computers ++ digitaldigital wireless communications wireless communications

Application: portable office, Application: portable office, transportation business, emergency transportation business, emergency services, police/ military, etc. services, police/ military, etc.

Features:Features: easy installation, portabilityeasy installation, portabilitylow capacity (1-2 Mb/S), low security, low capacity (1-2 Mb/S), low security,

high error rate + radio pollutionhigh error rate + radio pollution Wired-Wireless Networking ConvergenceWired-Wireless Networking Convergence TendenciesTendencies

Laptops, PDAsbinary coded radio transmission orCDPD (Cellular Digital Packet Data)

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InternetworksInternetworks Internetwork = Communication Internetwork = Communication

between LANs, MANs and WANs with between LANs, MANs and WANs with different internal standardsdifferent internal standards

Compatibility requires Compatibility requires gatewaysgateways Typical architecture: collection of LANs Typical architecture: collection of LANs

connected by a WAN: connected by a WAN: (WAN (WAN differs from the subnet just by differs from the subnet just by presence of hosts besides the routers)presence of hosts besides the routers)

The InternetThe Internet = biggest internetwork = biggest internetwork connecting universities, public and connecting universities, public and private offices, persons etc. private offices, persons etc.

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