14th week: internet infrastructure

Internet infrastructure

Hierarcy of networks

In order to connect to internet, we need:

¨       Computer

¨       Web browser

¨       Internet access (ISP)

All of this look so easy, what you need to do is just find a computer, connect to a WIFI or internet, click on the web browser which installed in it…that’s all.But the exactly policy and procedures to bring to internet is quite complicated.

Internet protocol (IP)

§      provide a common layer over dissimilar network

§      move packets among “host” computer thru gateways

§      each computer assign a unique IP address

§      IP address consist of 32 bits (shown as 4 octets of numbers from 0-225 represented in decimal form instead of binary)

·         168.212.226.204

·         10101000.11010100.11100010.11001100

§      consists of 2 part:

·         Identifying the network

·         Identifying the node/host

§      Class of addresses will part it into network add part and node part.

§      All nodes on a given network share the same network prefix have a unique host number

class	Class A	Class B	Class C	Class D	Class E
Binary add	0	10	110	1110	1111
Decimal no	1 to 126	128 to 191	192 to 223	224 to 239	240 to 255
Identify network	First octet, first 8 bits	First 2 octet, first 16 bits	First 3 octet, first 24 bits	support multicasting	experimentation
example	102.168.212.226	102.168.212.226	102.168.212.226	102.168.212.226

§      So where is the decimal no of 127?

§      Number 127 is for loopback, used for internal testing on local machine

Domain name system (DNS)

©       Domain name is alphabetic that we usually use to search on internet (or we commonly call it website name)

©       Internet service that translates domain names like www.yahoo.com into numerical IP address like 204.62.131.129

©       Moe.gov.my

©       Why we use DNS? = domain names are alphabetic (easier to remember)

Internet servise provider (ISP)

ª       Or IAPs (Internet access providers)

ª       Is an organization that provides access to the internet

ª       Two type: community-owned and non-profit, privately owned and for-profit

ª       User can access ISP to connect the internet via using wires, wireless or fiber-optic connections.

Hypertext transfer protocol (HTTP)

ª       An application protocol for distributed, collaborative, hypermedia information system.

ª       Foundation of data communication for the World Wide Web.

ª       Hypertext = multi-linear set of objects, building a network by using logical link or hyperlinks between the nodes (text or words).

ª       HTTP is the protocol to exchange or transfer hypertext.

Hypertext transfer protocol secure (HTTPS)

ª       Combination of HTTP and SSL/TLS protocol.

ª       From the name we know that it is in secure.

ª       It provides encrypted communication:  prevent eavesdropping, securely identify web server communicating.

ª       Primarily used for e-payment transactions, e-mail and sensitive transaction in corporate information system.

ª       Now, widespread use for protecting page authenticity on all type of websites, securing accounts, keeping user communication, identity and browsing history private.

12th week:unbounded / unguided media

Different between bounded and unbounded media

·        Bounded media are those that use cables for transmitting electricity or light;

·        Unbounded media does not require cabling and includes satellite, microwave and radio transmission.

·        Wireless connections, including 802.11b and 802.11a, are examples of unbounded media.

·        Today, bounded media continue to be more common than unbounded.

Unbounded media / unguided media

-         Translate electromagnetic wave without physical conductor.

-         Signal = broadcasting thru air/water

-         Available for anyone who has a device capable of receiving them

-         2 type of microwave:

1.         Terrestrial Microwave

§  Require line-of-sight transmission and reception equipment

§  The taller the antennas, the longer the sight distance

§  The higher, the stronger

§  So…Usually built on hills / mountains

§  One way direction signal

§  Install system(repeater) with antennas to increase distance

§  2 type of antennas

1.         Parabolic dish

o   Same as it’s name, in a dish shape

o   good at catching a wide range of signal waves

o   directing to a common point(focus)

o   Every wave parallel to the line of sight reflects back to the focus on a common point

2.      Horn

o   looks like a gigantic scoop

o   broadcasts the assembled signals that are deflected outward in a series of narrow parallel beams by the curve head

o   signals are received in a manner are deflected down into the stem

2.      Satellite microwave

§  same principle as terrestrial microwave

§  acting as a super tall antenna and repeater

§  single bounce

§  capability = anywhere on earth

§  high quality communication without huge investment in ground-based infrastructure

§  same speed as earth

§  Geosynchronous satellite = orbit speed is based on distance from the planet

§  Minimum 3 satellites to provide full global transmissions

§  earth à satellite = uplink

§  satellite à earth = downlink

Something you might do not know….

Wireless technology

·        Technology that does not require any wires. (unbounded media)

·        The distances involved may be short such as a few meters as in television remote control

·        Long like thousands or millions of kilometers for radio communications.

Wifi

·        developed to be used for mobile computing devices

·        Transmit data use radio wave

·        IEEE802.11 – standard for implementing wifi

·        IEEE802.11b standard provides a transmit data size up to 11Mbps (Megabyte per second)

·        IEEE802.11a standard provides throughput rates up to 54Mbps

Radio frequency[RF] and cellular phones

·        Cellular phone is one of the wireless devices make use of RF

·        Cell phones work by sending signals to (and receiving them from) nearby cell towers (base stations) using RF waves

·        This is a form of electromagnetic energy that falls between FM radio waves and microwaves

·        RF waves are a form of non-ionizing radiation

·        RF waves are different from stronger (ionizing) types of radiation such as x-rays, gamma rays, and ultraviolet (UV) light, which can break the chemical bonds in DNA.

·        At very high levels, RF waves can heat up body tissues. (This is the basis for how microwave ovens work.)

·        But the levels of energy given off by cell phones are much lower, and are not enough to raise temperatures in the body.

Designation	Frequencies	Free-space Wavelengths
Very Low Frequency	9 kHz - 30 kHz	33 km - 10 km
Low Frequency	30 kHz - 300 kHz	10 km - 1 km
Medium Frequency	300 kHz - 3 MHz	1 km - 100 m
High Frequency	3 MHz - 30 MHz	100 m - 10 m
Very High Frequency	30 MHz - 300 MHz	10 m - 1 m
Ultra High Frequency	300 MHz - 3 GHz	1 m - 100 mm
Super High Frequency	3 GHz - 30 GHz	100 mm - 10 mm
Extremely High Frequency	30 GHz - 300 GHz	10 mm - 1 mm

By Mhui

10th week: cabling

It’s been a long time....from the previous update....fuhhhh.. =)

We got camp…..holidays…..tournament…..

Dr.Dayang also gt her stuff to buzy………….

And here only come a new update….=))

Cabling

-          Not same with wireless, microwave and satellite.

-          Is the medium through which information usually moves from 1 network device to other.

-          common used with LANs.

-          Some cases, a network will utilize only 1 type of cable, other networks will use a variety of cable types

Types of Cables

1.   Unshielded Twisted Pair (UTP) Cable

©      Got four pairs of wires inside jacket.

©      Each pair is twisted with different number of twists per inch to help eliminate interference from adjacent pairs and other electrical devices.(reduce the interrupt from other call)

©      The standard connector for unshielded twisted pair cabling is an RJ-45 connector

Disadvantages

~  It may be susceptible to radio and electrical frequency interference.

2.  Shielded Twisted Pair (STP) Cable

©      consists of 2 individual wires wrapped in a foil shielding to help provide a more reliable data communication.

©      suitable for environments with electrical interference

©      extra shielding can make the cables quite bulky.

©      often used on networks using Token Ring topology.

3.  Coaxial Cable

©      has a single copper conductor at its center.

©      metal shield helps to block any outside interference from fluorescent lights, motors, and other computers

©      plastic layer provides insulation between the center conductor and a braided metal sheild

©      The most common type of connector is the Bayone-Neill-Concelman (BNC) connector

©      Different types of adapters are available: T-connector, barrel connector, and terminator.

4.  Fiber Optic Cable

©      consists a center glass core surrounded by several layers of protective materials

©      It transmits light rather than electronic signals eliminating the problem of electrical interference.

©      ideal for certain environments that contain a large amount of electrical interference..

©      able to transmit signals over much longer distances than coaxial and twisted pair.

Summary of Ethernet Cabling

Cable & Topology

By Mhui

6th week: topology

What is network topology?

-is the study of the arrangement or mapping of the elements (links, nodes, etc.) of a network, especially:

- logical (virtual) and

- physical (real)

-interconnections between nodes

Logical topology

Is…….

the mapping of the flow of data between the nodes in the network determines the logical topology of the network

Physical topology

Any given node in the LAN will have one or more links to one or more other nodes in the network and the mapping of these links and nodes onto a graph results in a geometrical shape that determines the physical topology of the network.

Types/classification

1.  Linear Bus

©      creates a network by connecting 2 or more hosts to a length of coaxial backbone cabling.

©      consists of a main run of cable (with terminator at each end)

©      all nodes connected to the linear cable.

©      Example: Think of the data as water; in this respect, the terminator must be placed in order to prevent the water from flowing out of the network.

©      The bus topology is regarded as one of the major network topologies of the networking world.

©      Ethernet and LocalTalk networks use a linear bus topology

Advantages

      Easy to connect a computer or peripheral to a linear bus

      Requires less cable length than a star topology

Disadvantages

v  Entire network shuts down if there is a break in the main cable.

v  A faulty cable or workstation will take the entire LAN down.

v  Terminators are required at both ends of the backbone cable.

v  Difficult to identify the problem if the entire network shuts down.

v  Not meant to be used as a stand-alone solution in a large building.

2.  Star

©      A star topology creates a network by arranging 2 or more host machines around a central hub.

©      A star topology is designed with each node (file server, workstations, and peripherals) connected directly to a central network hub or concentrator

©      Data on a star network passes through the hub or concentrator before continuing to its destination.

©      The hub or concentrator manages and controls all functions of the network. It also acts as a repeater for the data flow.

©      This configuration is common with twisted pair cable.

©      usually Ethernet or LocalTalk use this

Advantages

      Easy to install, and wire.

      Easy to add new workstations

      No disruptions to the network when connecting or removing devices.

      Any non-centralised failure will have very little effect on the network

      Easy to detect faults and to remove parts.

      Centralized control

      Centralized network/hub monitoringges

Disadvantages

v  Requires more cable length than a linear topology.

v  If the hub or concentrator fails, nodes attached are disabled.

v  More expensive than linear bus topologies because of the cost of the concentrators.

3.  Star-Wired Ring

©      A star-wired topology may appear (externally) to be the same as a star topology.

©      Internally, the MAU (multistation access unit) of a star-wired ring contains wiring that allows information to pass from one device to another in a circle or ring

©      The Token Ring protocol uses this.

4.  Tree

©      A tree topology combines characteristics of linear bus and star topologies.

©      It consists of groups of star-configured workstations connected to a linear bus backbone cable.

©      Tree topologies allow for the expansion of an existing network, and enable schools to configure a network to meet their needs.

Advantages

      Point-to-point wiring for individual segments.

Disadvantages

v  Overall length of each segment is limited by the type of cabling used.

v  If the backbone line breaks, the entire segment goes down.

v  More difficult to configure and wire than other topologies.

Can refer to this website:

©     Click on the colour word =)

·        http://asiabizz.com/2232/various-types-of-computer-networks-and-network-topology/

·        http://errajib.hubpages.com/hub/Types-of-Networks

1.       A network interface controller (also known as a network interface card, network adapter, LAN adapter and by similar terms) is a computer hardware component that connects a computer to a computer network. Whereas network interface controllers were commonly implemented on expansion cards that plug into a computer bus, the low cost and ubiquity of the Ethernet standard means that most newer computers have a network interface built into the motherboard.

2.       A networking operating system (NOS)(also referred as the Dialoguer) is the software that runs on a server and enables the server to manage data, users, groups, security, applications, and other networking functions. The network operating system is designed to allow shared file and printer access among multiple computers in a network, typically a local area network (LAN), a private network or to other networks. The most popular network operating systems are Microsoft Windows Server 2003, Microsoft Windows Server 2008, UNIX, Linux, Mac OS X, and Novell NetWare.

3.       A network switch (or switching hub) is a computer networking device that connects network segments or network devices. The term commonly refers to a multi-port network bridge that processes and routes data at the data link layer (layer 2) of the OSI model. Switches that additionally process data at the network layer (layer 3) and above are often referred to as layer-3 switches or multilayer switches.The first Ethernet switch was introduced by Kalpana in 1990.

4.       A repeater is an electronic device that receives a signal and retransmits it at a higher level or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances.

5.       LocalTalk is a particular implementation of the physical layer of the AppleTalk networking system from Apple Computer. LocalTalk specifies a system of shielded twisted pair cabling, plugged into self-terminating transceivers, running at a rate of 230.4 kbit/s. CSMA/CA was implemented as a random multiple access method.

6.       Token ring local area network (LAN) technology is a local area network protocol which resides at the data link layer (DLL) of the OSI model. It uses a special three-byte frame called a token that travels around the ring. Token-possession grants the possessor permission to transmit on the medium. Token ring frames travel completely around the loop.Initially used only in IBM computers, it was eventually standardized with protocol IEEE 802.5.

7.       Ethernet has largely replaced competing wired LAN technologies. In the OSI reference system, Ethernet is at the Data Link layer. Systems communicating over Ethernet divide a stream of data into individual packets called frames. Each frame contains source and destination addresses and error-checking data so that damaged data can be detected and re-transmitted.

By Mhui