How the Internet Works? ( TCP/IP, DNS, HKIX … ) CSC1720 – Introduction to Internet Essential...

How the Internet How the Internet Works?Works?( TCP/IP, DNS, HKIX … )( TCP/IP, DNS, HKIX … )

CSC1720 – Introduction to CSC1720 – Introduction to InternetInternet

Essential MaterialsEssential Materials


All copyrights reserved by C.C. Cheung All copyrights reserved by C.C. Cheung 2003.2003.

22

How computers send How computers send data?data?

Channel

ProtocolConnection

method

Address



33

OutlineOutline

Internet HardwareInternet Hardware– Modem, Wired, Hubs, SwitchesModem, Wired, Hubs, Switches

Basic Internet StructureBasic Internet Structure– Postal service analogyPostal service analogy

Internet SoftwareInternet Software– IP address, SubnetsIP address, Subnets– Network ProtocolNetwork Protocol– DNS, WINS and DomainsDNS, WINS and Domains

HKIX and HARNETHKIX and HARNET



44

Communication Communication ChannelChannel

what kind of media?

Telephone line (Twist pair, Optical fiber)Telephone line (Twist pair, Optical fiber)– Modulator-Demodulator (Modulator-Demodulator (ModemModem))– Digital Subscriber Line (Digital Subscriber Line (DSLDSL))

Cable modemCable modem Satellite, MicrowaveSatellite, Microwave Wireless connection (IR, RF)Wireless connection (IR, RF)



55

Twisted pairTwisted pair RJ45 connectorRJ45 connector Coaxial cableCoaxial cable BNC connectorBNC connector Fiber optic cableFiber optic cable Different cabling lengthDifferent cabling length

– Optic > coaxial > Twisted pairOptic > coaxial > Twisted pair

Different mediumDifferent medium



66

Use ModemUse Modem

Telephone lineAnalog data

Digital data - 10101010101

Modulation / De-modulationModulation / De-modulation E.g. CU Dialup Pool (56kbps max.)E.g. CU Dialup Pool (56kbps max.)



77

Use Digital Subscriber Use Digital Subscriber Line (DSL)Line (DSL)

Traditional phone line

ADSL modem

Why ADSL?



88

Why ADSL?Why ADSL?

AAsymmetric symmetric DSLDSL– A slower upstream A slower upstream

(upload) can trade off (upload) can trade off a faster downstream a faster downstream (download) speed.(download) speed.

– 128 to 640 kbps 128 to 640 kbps (upstream)(upstream)

– 1.5M to 5M bps 1.5M to 5M bps (downstream)(downstream)

E.g. PCCW - E.g. PCCW - NetvigatorNetvigator



99

Use Cable ModemsUse Cable Modems

Use coaxial cable to carry TV Use coaxial cable to carry TV signal and High speed Internet signal and High speed Internet accessaccess



1010

Satellite & Satellite & MicrowaveMicrowave Satellite systemsSatellite systems

– Use satellites orbiting above the Earth Use satellites orbiting above the Earth to relay signals from one part of a WAN to relay signals from one part of a WAN to another, cause 0.5 to 5 sec delays.to another, cause 0.5 to 5 sec delays.

MicrowaveMicrowave– Costly to install but cheaper than Costly to install but cheaper than

satellite.satellite.– It is very useful for connecting It is very useful for connecting

networks that are separated by a networks that are separated by a barrier, such as a highway or a lake.barrier, such as a highway or a lake.



1111

Use Cellular Phone / Use Cellular Phone / PalmPalm Mobile computingMobile computing Latest technology – BluetoothLatest technology – Bluetooth

– A wireless technologyA wireless technology



1212

Using A Computer To Using A Computer To Interconnect NetworksInterconnect Networks

Special-purpose Special-purpose computers are used computers are used to interconnect to interconnect networks.networks.– Using standard Using standard

hardware (CPU, hardware (CPU, memory, and network memory, and network interfaces)interfaces)

– Running special-Running special-purpose softwarepurpose software



1313

Network Interface CardNetwork Interface CardNICNIC

Physically connects a computer to the Physically connects a computer to the transmission medium on a network.transmission medium on a network.

What is device driver?What is device driver?– NIC comes with different drivers for NIC comes with different drivers for

different types of operating systems.different types of operating systems.– A driver is the software that allows the A driver is the software that allows the

operating system to communicate with the operating system to communicate with the network interface card.network interface card.

What is the major difference between What is the major difference between an expensive, 3Com, and a cheap, an expensive, 3Com, and a cheap, Filand, NIC?Filand, NIC?



1414

Hardware/Physical/MAC Hardware/Physical/MAC (Media Access Control) (Media Access Control) addressaddress

When a NIC is When a NIC is manufactured, manufactured, the card is given the card is given a unique a unique hardware hardware address.address.

It never changes.It never changes.



1515

RoutersRouters

Interconnecting computers are Interconnecting computers are called routers by using the same called routers by using the same protocol.protocol.– Determining where to send packetsDetermining where to send packets

Router



1616

HubsHubs

A network cable connects a A network cable connects a computer via a network computer via a network card to a hub.card to a hub.

Provides a central location.Provides a central location.



1717

PortsPorts

A hub A hub contains contains sockets or sockets or ports.ports.

Some LED Some LED indicates indicates information information transferred transferred through through the port.the port.



1818

Ethernet RepeaterEthernet Repeater

A repeater is a device that strengthens A repeater is a device that strengthens and retransmits signals on a network.and retransmits signals on a network.



1919

Network ArchitectureNetwork Architecture

It refers how information transfers on It refers how information transfers on networks.networks.

Ethernet Ethernet – It the most popular architecture used to build It the most popular architecture used to build

networks.networks.– Least expensive and easiest to setupLeast expensive and easiest to setup

Token-ring architectureToken-ring architecture– It was developed by IBM in 1984.It was developed by IBM in 1984.– They are popular found in large organizations, They are popular found in large organizations,

such as banks and insurance companies.such as banks and insurance companies. Others: ARCnet, AppleTalk, …Others: ARCnet, AppleTalk, …



2020

Ethernet & Token RingEthernet & Token Ring

Ethernet, Fast Ethernet, Gigabit Ethernet, Fast Ethernet, Gigabit Ethernet (transmit data at 1Gbps).Ethernet (transmit data at 1Gbps).



2121

Postal ServicesPostal Services

You have to write a complete address You have to write a complete address on the envelope specifying the on the envelope specifying the countrycountry, , statestate, , citycity, , districtdistrict, , streetstreet, , and so on.and so on.

After put the letter put into the After put the letter put into the mailbox, it will be delivered (routed) to mailbox, it will be delivered (routed) to its destination in a hierarchical way.its destination in a hierarchical way.

HK Post Office knows the letter is sent HK Post Office knows the letter is sent to US, without concerning the actual to US, without concerning the actual address to be routed within US.address to be routed within US.



2222

Basic Internet Basic Internet StructureStructure The Internet works in a similar way as The Internet works in a similar way as

postal services.postal services. Roughly speaking, you may consider US, Roughly speaking, you may consider US,

UK, HK, China and so on, as individual UK, HK, China and so on, as individual networks connecting to each other.networks connecting to each other.– Each network is further divided into smaller Each network is further divided into smaller

sub-networks such as CUHK, HKU, UST, and so sub-networks such as CUHK, HKU, UST, and so on.on.

CUHK has its academic departments, etc.CUHK has its academic departments, etc.

The different pieces of the Internet are The different pieces of the Internet are connected by a set of computers connected by a set of computers (Gateways)(Gateways)– Translates between protocolsTranslates between protocols



2323

Basic Internet Basic Internet StructureStructure (depicted) (depicted)



2424

Postage over the Postage over the InternetInternet When delivering information via the When delivering information via the

Internet, the information is split into small Internet, the information is split into small units called data packets (1500 byte each)units called data packets (1500 byte each)

When a packet is sent from US to a When a packet is sent from US to a particular host in CUHK.particular host in CUHK.

The packet is first delivered to Hong Kong,The packet is first delivered to Hong Kong, then is further transmitted to CUHK,then is further transmitted to CUHK, then is further transmitted to the appropriate then is further transmitted to the appropriate

department,department, finally arrived to the specific host.finally arrived to the specific host.

The data is reassembled at the destination.The data is reassembled at the destination. The data packet is continuously being The data packet is continuously being

switched from the source to destination.switched from the source to destination. The Internet is said to be Packet Switching The Internet is said to be Packet Switching

Network.Network.



2525

Packet Switching Packet Switching NetworkNetwork



2626

Packet switching Packet switching exampleexample

Figure 16.1 An example internet with four networks connected by routers.

Figure 16.2 Cars from two roads merging onto another road are analogous to packets from two networks merging onto a third network.



2727

IP addressIP address

Each host in the Internet is assigned Each host in the Internet is assigned to a specific and unique number for ito a specific and unique number for identification.dentification.

This number is called the IP address This number is called the IP address of the specific host.of the specific host.

This number is divided into 4 parts fThis number is divided into 4 parts for improving the readability.or improving the readability.

The range of each number is betweeThe range of each number is between 0 and 255.n 0 and 255.– E.g. 0.0.0.0E.g. 0.0.0.0– 255.255.255.255255.255.255.255

For example, the host “orchid.cse.cFor example, the host “orchid.cse.cuhk.edu.hk” has its IP address of “uhk.edu.hk” has its IP address of “137.189.91.60”137.189.91.60”



2828

Network Number / Network Number / Host NumberHost Number IP addresses are split into 2 partsIP addresses are split into 2 parts

– A network number + a host numberA network number + a host number For example, 137.189 is the network numbFor example, 137.189 is the network numb

er of CUHK, 91.60 is the host number of ther of CUHK, 91.60 is the host number of the host “orchid.cse.cuhk.edu.hk”e host “orchid.cse.cuhk.edu.hk”

Network numbers are assigned by a centrNetwork numbers are assigned by a central authority, the Internet Corporation for Aal authority, the Internet Corporation for Assigned Names and Numbers (ICANN).ssigned Names and Numbers (ICANN).



2929

Network ClassesNetwork Classes

There are 5 classes of IP addressThere are 5 classes of IP address Class A comprises networks 1.0.0.0 to 127.Class A comprises networks 1.0.0.0 to 127.

255.255.255, the network address is in first 255.255.255, the network address is in first quad. It allows roughly 16 million hosts pequad. It allows roughly 16 million hosts per network.r network.

Class B comprises network 128.0.0.0 to 19Class B comprises network 128.0.0.0 to 191.255.255.255, the network address is in th1.255.255.255, the network address is in the first two quads. It allows for 16,382 netwe first two quads. It allows for 16,382 networks with up to 64K hosts.orks with up to 64K hosts.



3030

Network ClassesNetwork Classes

Class C comprises networks Class C comprises networks 192.0.0.0 to 223.255.255.255, with 192.0.0.0 to 223.255.255.255, with the network number contained in the network number contained in the first three quads. It allows about the first three quads. It allows about 2 million networks with up to 254 2 million networks with up to 254 hosts in each network.hosts in each network.

Class D and E are falling into the Class D and E are falling into the range of 224.0.0.0 to 254.0.0.0 range of 224.0.0.0 to 254.0.0.0 which are reserved for multicast which are reserved for multicast address and for special purpose use.address and for special purpose use.



3131

SubnetSubnet

The Internet is structured hierarchically. CUHK coThe Internet is structured hierarchically. CUHK consists of many academic departments and adminnsists of many academic departments and administrative bodies.istrative bodies.

IP allows you to subdivide a network into several IP allows you to subdivide a network into several subnets. E.g. CSE and CSC are two subnets inside subnets. E.g. CSE and CSC are two subnets inside CUHK.CUHK.

Each subnet is identified by a subnet number.Each subnet is identified by a subnet number. E.g. we have a different way to interpret the IP adE.g. we have a different way to interpret the IP ad

dress 137.189.91.60dress 137.189.91.60– 137.189 refers to the network number of CUHK,137.189 refers to the network number of CUHK,– 91 refers to the subnet number of CSE,91 refers to the subnet number of CSE,– 60 refers to the host number of “orchid”.60 refers to the host number of “orchid”.



3232

Subnet example in Subnet example in CUHKCUHK



3333

Subnet MaskSubnet Mask

252 252 254 = 1111 1100 254 = 1111 1100 1111 1111 11101110



3434

Dynamic Host Dynamic Host Configuration Protocol Configuration Protocol (DHCP)(DHCP) A Protocol for assigning dynamic IP A Protocol for assigning dynamic IP

address to devices on a network.address to devices on a network. It is built on client and server models.It is built on client and server models.

– Server is the machine running DHCPD.Server is the machine running DHCPD.– Client can be any network devices.Client can be any network devices.

Advantage?Advantage?EliminatesEliminates manual manual configuration of network configuration of network parameters and parameters and utilizesutilizes the the use of IP addressuse of IP address



3535

IP RoutingIP Routing

The process of transmitting a data packet froThe process of transmitting a data packet from the source to the destination via a series of im the source to the destination via a series of intermediate stations is called “Routing”.ntermediate stations is called “Routing”.

IP routing works as follow:IP routing works as follow:– Each data packet is labeled with IP address of the Each data packet is labeled with IP address of the

destination hostdestination host

137.189.90.184137.189.90.184 1500 bytes Data here 1500 bytes Data here



3636

IP PacketIP Packet

Includes Header, payload, dataIncludes Header, payload, data



3737

Packets Are Not The Same Packets Are Not The Same SizeSize

Packets may be any size up to the Packets may be any size up to the maximum.maximum.– Can be as small as a single Can be as small as a single

keystrokekeystroke– Can be larger, depending on Can be larger, depending on

applicationapplication



3838

IP RoutingIP Routing

For example, when a packet is routing to For example, when a packet is routing to “orchid.cse.cuhk.edu.hk” (137.189.91.6“orchid.cse.cuhk.edu.hk” (137.189.91.60), the network number is extracted as 137.0), the network number is extracted as 137.189 which is the network number of CUHK.189 which is the network number of CUHK. The packet is then sent to HK and then to The packet is then sent to HK and then to CUHK.CUHK.

Inside CUHK, the subnet number is examiInside CUHK, the subnet number is examined and it is 91 which is the subnet numbened and it is 91 which is the subnet number of CSE. Then it is sent to CSE.r of CSE. Then it is sent to CSE.

Inside CSE, the host number is examined aInside CSE, the host number is examined and it is 60 which is the host number of orcnd it is 60 which is the host number of orchid. Finally, it is routed to the destination.hid. Finally, it is routed to the destination.



3939

IP enough for routing?IP enough for routing?

A single packet is limited in length, uA single packet is limited in length, usually 1-1500 bytes.sually 1-1500 bytes.

Network may lose packets, or damagNetwork may lose packets, or damage the data in transit.e the data in transit.

Packets may arrive out of sequence Packets may arrive out of sequence (different routing path).(different routing path).

TCP is used to solve the problems.TCP is used to solve the problems.



4040

Protocol and Protocol and AddressingAddressing To communicate over the Internet, the coTo communicate over the Internet, the co

mputers must:mputers must:– use a use a common languagecommon language or a or a protocolprotocol to to

govern the exchange of messages.govern the exchange of messages.– have a way to have a way to addressaddress one another. one another.

ProtocolProtocol::– specifies exact format, order of messages specifies exact format, order of messages

sent and received among network entities, sent and received among network entities, and actions taken on message and actions taken on message transmission and receipt.transmission and receipt.

Addressing:Addressing:– defines where to deliver the messages. defines where to deliver the messages.



4141

Protocol and AddressingProtocol and AddressingTCP/IP modelTCP/IP model



4242

Protocol and Protocol and AddressingAddressing Internet has a large collections of protocolInternet has a large collections of protocol

s organized in a layering model. s organized in a layering model. – ApplicationApplication: enables the user, whether human : enables the user, whether human

or software, to access the network.or software, to access the network.– TransportTransport: responsible for source-to-destinatio: responsible for source-to-destinatio

n (end-to-end) data transfer.n (end-to-end) data transfer.– NetworkNetwork: responsible for routing packets from : responsible for routing packets from

source-to-dest across multiple networks. source-to-dest across multiple networks. – Data linkData link: responsible for data transfer betwee: responsible for data transfer betwee

n neighboring network elements.n neighboring network elements.– PhysicalPhysical: coordinates the functions required to : coordinates the functions required to

transmit a bit stream over a physical medium. transmit a bit stream over a physical medium.



4343

Protocol and Protocol and AddressingAddressing

L5 data L5 data

Lower layer adds header to the data from upper layer. Lower layer adds header to the data from upper layer. Header includes addressing and other fields.Header includes addressing and other fields.



4444

Protocol Stack - Open Protocol Stack - Open Systems Interconnection Systems Interconnection (OSI) model(OSI) model



4545

Protocol and Protocol and AddressingAddressing

TCP/IP Protocol Suite.TCP/IP Protocol Suite.



4646

What is TCP/IP?What is TCP/IP?

““TCP would be in charge of the breaking TCP would be in charge of the breaking up the up the packetspackets and messages then reasse and messages then reassembling them at the destination, and the IP mbling them at the destination, and the IP would be responsible for transmitting the would be responsible for transmitting the individual individual packetspackets. For example: the TCP p. For example: the TCP protocol would split up the letter and place rotocol would split up the letter and place it into multiple envelops, while the IP protit into multiple envelops, while the IP protocol would be in charge of addressing the ocol would be in charge of addressing the envelop and making sure it arrived at its penvelop and making sure it arrived at its proper destination.” roper destination.”

– – from “Where Wizards Stay Up Late”from “Where Wizards Stay Up Late”



4747

TCP/IPTCP/IP

A protocol is a collection of rules for formatting, oA protocol is a collection of rules for formatting, ordering, and error-checking data sent across a nerdering, and error-checking data sent across a network.twork.

In 1974, Vincent Cerf and Robert Kahn developed In 1974, Vincent Cerf and Robert Kahn developed the Transmission Control Protocol (TCP) which wthe Transmission Control Protocol (TCP) which was further split into the Internet Protocol (IP) and as further split into the Internet Protocol (IP) and TCP in 1978.TCP in 1978.

In 1982, DoD adopted TCP/IP as the standard proIn 1982, DoD adopted TCP/IP as the standard protocol in the Internet.tocol in the Internet.

Because the significance of TCP/IP in the history Because the significance of TCP/IP in the history of the Internet, Cerf and Kahn are considered to bof the Internet, Cerf and Kahn are considered to be the Father of the Internet.e the Father of the Internet.



4848

Transmission Control Transmission Control Protocol - TCPProtocol - TCP Basic functionsBasic functions

– Decompose a lengthy data into Decompose a lengthy data into multiple packets for transmissionmultiple packets for transmission

– Error detection, ensure validityError detection, ensure validity– Packet loss? Packet loss?

No problem, packet retransmissionNo problem, packet retransmission



4949

TCP breaks the information into multiple TCP breaks the information into multiple packets.packets.

Each packet is associated with a sequence Each packet is associated with a sequence number for identification.number for identification.

137.189.90.184 Number 1137.189.90.184 Number 1 Data here Data here137.189.90.184 Number 2137.189.90.184 Number 2 Data here Data here 137.189.90.184 Number 3137.189.90.184 Number 3 Data here Data here

Each packet is individually routed in the InEach packet is individually routed in the Internet, and arrive in random order.ternet, and arrive in random order.

The data is reassembled in the correct ordThe data is reassembled in the correct order according to the sequence number.er according to the sequence number.

Sequence NumbersSequence Numbers



5050

Packet RetransmissionPacket Retransmission

A packet may be lost during the transmissiA packet may be lost during the transmission across the Internet (host down, link failon across the Internet (host down, link failure, … )ure, … )

When the destination host has been waitiWhen the destination host has been waiting for a particular packet for a certain timng for a particular packet for a certain time (timeout), it will request the source host e (timeout), it will request the source host to retransmit the packet.to retransmit the packet.

There is no need to retransmit all data pacThere is no need to retransmit all data packets. Instead, only the missing packet, whikets. Instead, only the missing packet, which is identified by the sequence number, nch is identified by the sequence number, needs to be retransmitted.eeds to be retransmitted.



5151

Error detection - Error detection - ChecksumsChecksums Transmission errors occur even if a data packTransmission errors occur even if a data pack

et is received by the destination successfully.et is received by the destination successfully. How to ensure the data is correctly received?How to ensure the data is correctly received?

– A method to detect possible transmission errors.A method to detect possible transmission errors.– At the destination, checksum is recalculated baseAt the destination, checksum is recalculated base

d on the received data.d on the received data.– The attached checksum and the newly calculated The attached checksum and the newly calculated

checksum are compared. Mismatch means there ichecksum are compared. Mismatch means there is transmission errors occurred.s transmission errors occurred.



5252

IPv6 (IP version 6)IPv6 (IP version 6)

Major changes:Major changes:– More addressesMore addresses

IP address size IP address size from 32 bits to 128 from 32 bits to 128 bitsbits

– Simplified IP Simplified IP headersheaders

Reduction of Reduction of header fields in IP header fields in IP packetpacket

– Added security Added security featuresfeatures



5353

IPX/SPX ProtocolIPX/SPX Protocol

IPX/SPX makes up the IPX/SPX makes up the protocol suite that is used to protocol suite that is used to transfer information on transfer information on networks running the Novell networks running the Novell NetWare operating system.NetWare operating system.

Internetwork Packet Internetwork Packet Exchange (IPX) - Transfer Exchange (IPX) - Transfer information between devices.information between devices.

Sequenced Packet Exchange Sequenced Packet Exchange (SPX) - An extension of the (SPX) - An extension of the IPX protocol.IPX protocol.



5454

NetBEUI ProtocolNetBEUI Protocol

NetBNetBIOS IOS EExtended xtended UUser ser IInterfacenterface– Is a network protocol used on small Is a network protocol used on small

local area networks.local area networks.– A very small and efficient protocol, A very small and efficient protocol,

use little computer resources.use little computer resources. NetBIOSNetBIOS

– NetNetwork work BBasic asic IInput/nput/OOutput utput SSystemystem– Develop by IBM and allow computers Develop by IBM and allow computers

to communicate with each other on to communicate with each other on a network.a network.



5555

Why DNS?Why DNS?

What is DNS?What is DNS?– Domain Name SystemDomain Name System

IP address is difficult to remember.IP address is difficult to remember.– 137.189.92.1 is which machine?137.189.92.1 is which machine?

Names are given to each computer on Names are given to each computer on the Internet for the convenience of the Internet for the convenience of human users.human users.

Besides IP addresses, all internet Besides IP addresses, all internet applications allow users to use applications allow users to use computer names.computer names.



5656

Computer names on Computer names on the NETthe NET How does it look like?How does it look like?

– DNS administrators is responsible to DNS administrators is responsible to name computers/group in their own name computers/group in their own subnet.subnet.

– Each level of responsibility is called Each level of responsibility is called a domain.a domain.

Domains are separated by “dots”Domains are separated by “dots”– cse.cuhk.edu.hkcse.cuhk.edu.hk– www.intel.comwww.intel.com



5757

Domain name and Host Domain name and Host namename Each domain can create or change wEach domain can create or change w

hatever belongs to it.hatever belongs to it.– CUHK can create any new domain, cseCUHK can create any new domain, cse– CSE can buy a new computer and name CSE can buy a new computer and name

it as – robin, orchid, any other name.it as – robin, orchid, any other name. Two computers may have the same Two computers may have the same

name if they are in different domains.name if they are in different domains.– orchid.cse.cuhk.edu.hkorchid.cse.cuhk.edu.hk– orchid.ie.cuhk.edu.hkorchid.ie.cuhk.edu.hk



5858

Domain Name System Domain Name System (DNS)(DNS)

Each node in the Each node in the tree hastree has– a a labellabel - a string - a string

with a maximum with a maximum of 63 characters.of 63 characters.

– a a domain namedomain name - - a sequence of a sequence of labels separated labels separated by dots.by dots.



5959

How does DNS How does DNS work?work? DNS server = DNS service?DNS server = DNS service?



6060

Domain Example - Domain Example - CUHKCUHK



6161

IP vs Domain NameIP vs Domain Name



6262

Most Common Most Common hostnamehostnameFigure 18.1 The fifty most common names assigned to computers on the Internet in 2000.



6363

Top Level DomainsTop Level Domains

The Internet Corporation for Assigned Names The Internet Corporation for Assigned Names and Numbers (ICANN) define the and Numbers (ICANN) define the Top Level Top Level DomainsDomains..



6464

ISO 3166 Country ISO 3166 Country CodesCodes Partial listPartial list Full listFull list



6565

Windows Internet Windows Internet Naming Service (WINS)Naming Service (WINS) Like DNS, WINS Like DNS, WINS

also resolves also resolves names and IP names and IP addresses except addresses except that the look up that the look up by WINS is by WINS is specific for specific for Windows Windows computers.computers.– DynamicDynamic– Win2k use DNS to Win2k use DNS to

replace WINSreplace WINS



6666

HKIXHKIX

HHong ong KKong ong IInternet enternet eXXchangechange– http://http://www.hkix.netwww.hkix.net

Operated by Operated by Information Technology Services Information Technology Services CentreCentre (ITSC) of CUHK (ITSC) of CUHK

interconnect the Internet Access interconnect the Internet Access Providers (IAPs) in Hong Kong Providers (IAPs) in Hong Kong – No need to route via US for local No need to route via US for local

connections.connections.



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HARNETHARNET

Why?Why? Connect 7 UConnect 7 U

niversities.niversities. Manage by tManage by t

he Joint Unihe Joint Universities Coversities Computer Centmputer Centre (JUCC) re (JUCC)



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HARNET configurationHARNET configuration

Try this link: Try this link: http://http://www.cuhk.edu.hk/hkix/harnetwww.cuhk.edu.hk/hkix/harnet//



6969

HARNET in CUHKHARNET in CUHK

HARNET connect to US is 12M and a connection oHARNET connect to US is 12M and a connection of 5M to HKT as backup.f 5M to HKT as backup.

Our connection to HARNET is dual 12Mbps.Our connection to HARNET is dual 12Mbps. With the following additional connections:With the following additional connections:

– a secondary link to Hong Kong Telecom Netplus which ia secondary link to Hong Kong Telecom Netplus which is 2Mbps inbound and 10Mbps outbound shared with ots 2Mbps inbound and 10Mbps outbound shared with other projects, Internet services for CUHK alumni and Schher projects, Internet services for CUHK alumni and SchoolNet; oolNet;

– a third link provided by UUNET (Worldcom) which is 2Ma third link provided by UUNET (Worldcom) which is 2Mbps inbound & outbound; and bps inbound & outbound; and

– a direct ATM/155Mbps connection to Hong Kong Interna direct ATM/155Mbps connection to Hong Kong Internet eXchange (HKIX), which was set up and is operated bet eXchange (HKIX), which was set up and is operated by ITSC of CUHKy ITSC of CUHK



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SummarySummary

What should be considered if you What should be considered if you install or update a network?install or update a network?– PlanPlan: the size, the budget: the size, the budget– DetermineDetermine: the network design: the network design– SelectSelect: the transmission media: the transmission media– ChooseChoose: the network hardware, devices: the network hardware, devices– InstallInstall: the network OS, drivers: the network OS, drivers– ConfigureConfigure: server & client computers: server & client computers– TestTest: the final network: the final network– MaintainMaintain: the network reliability, admin: the network reliability, admin



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ReferencesReferences

Computer Networks – A. S. TanenbaComputer Networks – A. S. Tanenbaum (Prentice Hall)um (Prentice Hall)

The End.The End. Thank you for your patience!Thank you for your patience!

How the Internet Works? ( TCP/IP, DNS, HKIX … ) CSC1720 – Introduction to Internet Essential...

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