internet infrastructure

Possibly to most important foundation block of Internet Infrastructure is the Network. Without a network connection no data can pass over the Internet.

The Internet: Computer Network Hierarchy
Every computer that is connected to the Internet is part of a network. For example, you may use a modem to connect to an Internet Service Provider(ISP). When you connect to your ISP, you become part of their network. The ISP may then connect to a larger network and become part of their network. The Internet is simply a network of networks. DNS is an Internet service that translates domain names/hostnames to IP addresses and IP addresses to their associated domain names/host names. DNS helping each visitor refer to the desired website only by typing its alpha-numeric name (domain name) in the browser instead of its real numeric system name (IP address).


Internet Protocol: IP Addresses
A typical IP address might be 216.27.22.162. Every machine on the Internet has a unique identifying number, called an IP Address. The IP stands for Internet Protocol, which is the language that computers use to communicate over the Internet. A typical IP address is make it easier for us humans to remember, IP addresses are normally expressed in decimal format. The four numbers in an IP address are called octets, because they each have eight positions when viewed in binary form. If you add all the positions together, you get 32, which is why IP addresses are considered 32-bit numbers.

The octets serve a purpose other than simply separating the numbers. They are used to create classes of IP addresses that can be assigned to a particular business, government or other entity based on size and need. The octets are split into two sections: Network and Host. The Network section always contains the first octet. It is used to identify the network that a computer belongs to. Host sometimes referred to as Node is identifies the actual computer on the network. The Host section always contains the last octet.

IP address structure and classification

Class A
Class A addresses are assigned to networks with a very large number of hosts. The high-order bit in a class A address is always set to 0. The next seven bits (completing the first octet) complete the network ID. The remaining 24 bits (the last three octets) represent the host ID. This allows for 126 networks and 16,777,214 hosts per network.

Class B
Class B addresses are assigned to medium-sized to large-sized networks. The two high-order bits in a class B address are always set to binary 1 0. The next 14 bits (completing the first two octets) complete the network ID. The remaining 16 bits (last two octets) represent the host ID. This allows for 16,384 networks and 65,534 hosts per network.

 

Class C
Class C addresses are used for small networks. The three high-order bits in a class C address are set to binary 1 1 0. The next 21 bits (completing the first three octets) complete the network ID. The remaining 8 bits (last octet) represent the host ID. This allows for 2,097,152 networks and 254 hosts per network.

Class D
Class D addresses are reserved for IP multicast addresses. The four high-order bits in a class D address are always set to binary 1 1 1 0. The remaining bits are for the address that interested hosts recognize. Microsoft supports class D addresses for applications to multicast data to multicast-capable hosts on an internetwork.


Class E
Class E is an experimental address that is reserved for future use. The high-order bits in a class E address are set to 1111.

The network ID cannot begin with the number 127. The number 127 in a class A address is reserved for internal loopback functions. For example, 127.0.0.1 is the common loopback address.

·         Loopback means the interface created and designated to test a local port or interface. It routes test messages from their source device back to the source without any processing or modification.

·         The loopback IP address is the address used to access itself. A loopback interface is also known as a virtual IP, which does not associate with hardware interface.

·         The loopback address is used to test network software without physically installing a Network Interface Card (NIC), and without having to physically connect the machine to a TCP/IP network.

Internet Protocol: Domain Name System
Although people can type address information like http://207.241.148.80/ into their Web browser to visit sites, being able to use proper names like http://www.hotmail.com/ is much more practical. When someone types a site's name into their browser, DNS looks up the corresponding IP address for that site, the data required to make the desired network connections between Web browsers and Web servers.

The DNS organizes its servers into a hierarchy. For the Internet, so-called root name servers reside at the top of the DNS hierarchy. The Internet root name servers manage DNS server information for the Web's top-level domains (like ".com" and ".uk"). Servers at the next lower level of the DNS hierarchy track second-level domain names and addresses (like "hotmail.com").

Hierarchy of domain names

ISP
Short for Internet Service Provider, it refers to a computer access to the Internet. The service provider usually provides a software package,username and password. You can then log on to the Internet and browse the World Wide Web and send and receive e-mail. ISPs also serve large companies, providing a direct connection from the company's networks to the Internet. ISPs.

An ISP is a company that provides individuals and other companies access to the Internet and other related services such as Web site building and virtual hosting. An ISP has the equipment and the telecommunication line access required to have a point-of-presence on the Internet for the geographic area served. The larger ISPs have their own high-speed leased lines so that they are less dependent on the telecommunication providers and can provide better service to their customers.


HTTP  (Hypertext Transfer Protocol)

HTTP stands for Hypertext Transfer Protocol. It is an TCP/IP based communication protocol which is used to deliver virtually all files and other data, collectively called resources, on the World Wide Web. These resources could be HTML files, image files, query results, or anything else.Every Web server on the Internet conforms to the hypertext transfer protocol (HTTP). The Hypertext Transfer Protocol (HTTP) is an application-level TCP/IP based protocol with the lightness and speed necessary for distributed, collaborative, hypermedia information systems (internet).

There are three important things about HTTP of which you should be aware:

·         HTTP is connectionless: After a request is made, the client disconnects from the server and waits for a response. The server must re-establish the connection after it process the request.

·         HTTP is media independent: Any type of data can be sent by HTTP as long as both the client and server know how to handle the data content. How content is handled is determined by the MIME specification.

·         HTTP is stateless: This is a direct result of HTTP's being connectionless. The server and client are aware of each other only during a request. Afterwards, each forgets the other. For this reason neither the client nor the browser can retain information between different request across the web pages.

The diagram shows where HTTP Protocol fits in communication:

UNBOUND MEDIA

Unbound Media is based on air and implementations including microwave, laser, infrared and radio
Microwaves travels at high frequency than radio waves and provide through put as a wireless network media. Micro wave transmission requires the sender to be inside of the receiver.

Following are the types of Microwaves.
· Terrestrial Micro waves
· Satellite Micro waves

1. Terrestrial Micro waves:
Terrestrial Micro waves are used are used to transmit wireless signals across a few miles. Terrestrial system requires that direct parabolic antennas can be pointed to each other. These systems operate in a low Giga Hertz range. two types of antennas are used for terrestrial microwave communication are parabolic dish and horn antenna.

A parabolic dish antenna is good at catching a wide range of signal waves and directing them to a common point. Every wave that is parallel to the line of sight reflects back to the focus on a common point.

a horn antenna looks like a gigantic scoop that broadcasts the assembled signals that are deflected outward in a series of narrow parallel beams by the curve head. signals are received in a manner similar to the parabolic dish antenna and are deflected down into the stem.





2. Satellite Micro waves
The main problem with aero wave communication is the curvature of the earth, mountains & other structure often block the line of side. Due to this reason, many repeats are required for long distance which increases the cost of data transmission between the two points. This problem is recommended by using satellites.

Satellite micro wave transmission is used to transmit signals through out the world. These system use satellites in orbit about 50,000 Km above the earth. Satellite dishes are used to send the signals to the satellite where it is again send back down to the receiver satellite. These transmissions also use directional parabolic antenna’ with in line of side.

In satellite communication micro wave signals at 6 GHz is transmitted from a transmitter on the earth through the satellite position in space. By the time signal reaches the satellites becomes weaker due to 50,000 Km distance. The satellite amplifies week signals and transmits it back to the earth at the frequency less than 6 GHz.
 

other information.......

WiFi:
Fairly recently the IEEE 802.11 standard became more popular as it suites mobile computing devices really well. The IEEE 802.11 standard is another term for WiFi essentially is wireless networking. This standard allows two computers that have wireless NICs to communicate with one another with no strings (wires) attached. This standard makes use of radio waves that are transmitted through the air to communicate. Speeds of either 54 Mbps or 108 Mbps are supported but higher speeds are in the pipeline.

IEEE (Institute of Electrical and Electronics Engineers).
The IEEE describes itself as "the world's largest technical professional society; promoting the development and application of electro technology and allied sciences for the benefit of humanity, the advancement of the profession, and the well-being of our members." One of the technologies they have developed is known as Ethernet 802 standard which governs local area networks (wired LANs). Ethernet governs the way in which Data Communications are done across the spectrum.

Difference Between 3G And 4G
4G speeds are meant to exceed that of 3G. Current 3G speeds are topped out at 14Mbps downlink and 5.8Mbps uplink. To be able to qualify as a 4G technology, speeds of up to 100Mbps must be reached for a moving user and 1Gbps for a stationary user. So far, these speeds are only reachable with wired LANs.

different:
1. 3G stands for 3rd generation while 4G stands for 4th generation
2. 3G technologies are in widespread use while 4G compliant technologies are still in the horizon
3. 4G speeds are much faster compared to 3G
4. 3G is a mix of circuit and packet switching network while 4G is only a packet switching network

Cellular phone
is a device that can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile phone operator, allowing access to the public telephone network. By contrast, a cordless telephone is used only within the short range of a single, private base station.
In addition to telephony, modern mobile phones also support a wide variety of other services such as text messaging, MMS, email, Internet access, short-range wireless communications (infrared, Bluetooth), business applications, gaming and photography. Mobile phones that offer these and more general computing capabilities are referred to as smartphones.

Radio frequency (RF) 

is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals. RF usually refers to electrical rather than mechanical oscillations, although mechanical RF systems do exist

Uplink and downlink
In satellite telecommunication, a downlink is the link from a satellite down to one or more ground stations or receivers, and an uplink is the link from a ground station up to a satellite. Some companies sell uplink and downlink services to television stations, corporations, and to other telecommunication carriers. A company can specialize in providing uplinks, downlinks, or both.
The following table shows the main frequency bands used for satellite links.

Frequency Band	Downlink	Uplink
C	3,700-4,200 MHz	5,925-6,425 MHz
Ku	11.7-12.2 GHz	14.0-14.5 GHz
Ka	17.7-21.2 GHz	27.5-31.0 GHz

CABLING

Cable is the medium through which information usually moves from one network device to another. There are several types of cable which are commonly used with LANs. In some cases, a network will utilize only one type of cable, other networks will use a variety of cable types. The type of cable chosen for a network is related to the network's topology, protocol, and size. Understanding the characteristics of different types of cable and how they relate to other aspects of a network is necessary for the development of a successful network.

The following sections discuss the types of cables used in networks.

• Unshielded Twisted Pair (UTP) Cable
• Shielded Twisted Pair (STP) Cable
• Coaxial Cable
• Fiber Optic Cable

Unshielded twisted pair (UTP) is the most popular and is generally the best option for school networks

Unshielded twisted pair

The quality of UTP may vary from telephone-grade wire to extremely high-speed cable. The cable has four pairs of wires inside the jacket. Each pair is twisted with a different number of twists per inch to help eliminate interference from adjacent pairs and other electrical devices. The tighter the twisting, the higher the supported transmission rate and the greater the cost per foot. 

Categories of Unshielded Twisted Pair

Category	Speed	Use
1	1 Mbps	Voice Only (Telephone Wire)
2	4 Mbps	LocalTalk & Telephone (Rarely used)
3	16 Mbps	10BaseT Ethernet
4	20 Mbps	Token Ring (Rarely used)
5	100 Mbps (2 pair)	100BaseT Ethernet
	1000 Mbps (4 pair)	Gigabit Ethernet
5e	1,000 Mbps	Gigabit Ethernet
6	10,000 Mbps	Gigabit Ethernet

Unshielded Twisted Pair Connector

The standard connector for unshielded twisted pair cabling is an RJ-45 connector. This is a plastic connector that looks like a large telephone-style connector. A slot allows the RJ-45 to be inserted only one way. RJ stands for Registered Jack, implying that the connector follows a standard borrowed from the telephone industry. This standard designates which wire goes with each pin inside the connector.

RJ-45 connector

Shielded Twisted Pair (STP) Cable

Although UTP cable is the least expensive cable, it may be susceptible to radio and electrical frequency interference. If you must place cable in environments with lots of potential interference, or if you must place cable in extremely sensitive environments that may be susceptible to the electrical current in the UTP, shielded twisted pair may be the solution. Shielded cables can also help to extend the maximum distance of the cables.

Shielded twisted pair cable is available in three different configurations:

1. Each pair of wires is individually shielded with foil.
2. There is a foil or braid shield inside the jacket covering all wires.
3. There is a shield around each individual pair, as well as around the entire group of wires.

Coaxial Cable

Coaxial cabling has a single copper conductor at its center. A plastic layer provides insulation between the center conductor and a braided metal shield. The metal shield helps to block any outside interference from fluorescent lights, motors, and other computers.

Coaxial cable

Although coaxial cabling is difficult to install, it is highly resistant to signal interference. In addition, it can support greater cable lengths between network devices than twisted pair cable. The two types of coaxial cabling are thick coaxial and thin coaxial.

Thin coaxial cable is also referred to as thinnet. 10Base2 refers to the specifications for thin coaxial cable carrying Ethernet signals. The 2 refers to the approximate maximum segment length being 200 meters. In actual fact the maximum segment length is 185 meters. Thin coaxial cable has been popular in school networks, especially linear bus networks.

Thick coaxial cable is also referred to as thicknet. 10Base5 refers to the specifications for thick coaxial cable carrying Ethernet signals. The 5 refers to the maximum segment length being 500 meters. Thick coaxial cable has an extra protective plastic cover that helps keep moisture away from the center conductor. This makes thick coaxial a great choice when running longer lengths in a linear bus network. One disadvantage of thick coaxial is that it does not bend easily and is difficult to install.

Coaxial Cable Connectors

The most common type of connector used with coaxial cables is the Bayone-Neill-Concelman (BNC) connector. Different types of adapters are available for BNC connectors, including a T-connector, barrel connector, and terminator. Connectors on the cable are the weakest points in any network. To help avoid problems with your network, always use the BNC connectors that crimp, rather screw, onto the cable.

Fig. 4. BNC connector

Fiber Optic Cable

Fiber optic cabling consists of a center glass core surrounded by several layers of protective materials. It transmits light rather than electronic signals eliminating the problem of electrical interference. This makes it ideal for certain environments that contain a large amount of electrical interference. It has also made it the standard for connecting networks between buildings, due to its immunity to the effects of moisture and lighting.

Fiber optic cable has the ability to transmit signals over much longer distances than coaxial and twisted pair. It also has the capability to carry information at vastly greater speeds. This capacity broadens communication possibilities to include services such as video conferencing and interactive services. The cost of fiber optic cabling is comparable to copper cabling; however, it is more difficult to install and modify. 10BaseF refers to the specifications for fiber optic cable carrying Ethernet signals.

The center core of fiber cables is made from glass or plastic fibers. A plastic coating then cushions the fiber center, and kevlar fibers help to strengthen the cables and prevent breakage. The outer insulating jacket made of teflon or PVC.

Fiber optic cable

There are two common types of fiber cables -- single mode and multimode. Multimode cable has a larger diameter; however, both cables provide high bandwidth at high speeds. Single mode can provide more distance, but it is more expensive.

VIDEO!!!!

Specification	Cable Type
10BaseT	Unshielded Twisted Pair
10Base2	Thin Coaxial
10Base5	Thick Coaxial
100BaseT	Unshielded Twisted Pair
100BaseFX	Fiber Optic
100BaseBX	Single mode Fiber
100BaseSX	Multimode Fiber
1000BaseT	Unshielded Twisted Pair
1000BaseFX	Fiber Optic
1000BaseBX	Single mode Fiber
1000BaseSX	Multimode Fiber

WEEK 6 :NETWORK TOPOLOGY

ASSALAMUALAIKUM & SALAM  SATU MALAYSIA

Hai kekawan...bejumpe lg kite pada minggu ini...ok seperti yang dijanjikan...dibawah ni sy telah updatekn nota pada minggu ni...pada minggu ni sy telah mempelajari mengenai network topology...JOMMM KITE 

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          Network Topology

         is the study of the arrangement or mapping of the elements (links, nodes, etc.) of a network, especially the physical (real) and logical (virtual) interconnections between nodes

         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

         Logical  Topology :

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

         We will discuss about logical topology later

         Types/Classification of physical topologies

        § Linear Bus

        § Star

        § Star-Wired Ring

        § Tree

       TYPES OF PHYSICAL TOPOLOGY:

linear bus

         A linear bus topology consists of a main run of cable with a terminator at each end.

         All nodes (file server, workstations, and peripherals) are connected to the linear cable.

         Ethernet and LocalTalk networks use a linear bus topology.

         TYPES OF PHYSICAL TOPOLOGY:

Linear Bus

Topologi "linear bus" terdiri daripada suatu kabel utama dengan suatu penamat (terminator) dikedua-dua hujungnya.

         Semua nod (seperti komputer pelayan, stesyen kerja dan peranti lain) disambung kepada kabel linear ini.

         Contoh rangkaian yang menggunakan topologi Linear Bus ini ialah Ethernet dan LocalTalk.

       TYPES OF PHYSICAL TOPOLOGY:

LINEAR BUS

LINEAR BUS

                                                                           

         Advantages of a Linear Bus Topology

         Easy to connect a computer or peripheral to a linear bus.

         Requires less cable length than a star topology.

     Disadvantages

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

·         A faulty cable or workstation will take the entire LAN down

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

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

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

         TYPES OF PHYSICAL TOPOLOGY:

Star

-     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 continue 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; however, it can also be used with coaxial cable or fiber optic cable.

         The protocols used with star configurations are usually Ethernet or LocalTalk

STAR

     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 monitoring

     Disadvantages

• ·         Requires more cable length than a linear topology.
• 
  
• ·         If the hub or concentrator fails, nodes attached are disabled.
• 
  
• ·         More expensive than linear bus topologies because of the cost of the concentrators.

         TYPES OF PHYSICAL TOPOLOGY:

Star-Wired

         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 a star-wired topology.

         TYPES OF PHYSICAL TOPOLOGY:

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

TREE

     Advantage

Point-to-point wiring for individual segments

     Disadvantages

• ·         Overall length of each segment is limited by the type of cabling used.
• 
  
• ·         If the backbone line breaks, the entire segment goes down.
• 
  
• ·         More difficult to configure and wire than other topologies.
• 
  

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