Model Two
1-Host
Connects other computers to the internet and act as a gate way between the LAN
and the global one.
2-IP address
Each computer connected to the internet has a unique address which enables any
other computer to locate it and communicate with it. The IP address is composed
of 4 numbers (4 bytes). Ex. 198.200.17.50.
3-DNS, Domain Name Server
Translates a domain name (cnn.com) into an IP address.
4-URL, Uniform Resource Locater
| URL |
http: |
//www. |
cnn.com |
|
Uniform resource locater/ |
Hyper text transfer protocol/ |
World wide web/ |
Domain name |
5-System
System is an assembly of componenets connected together in an organized way.
The components are affected by being in the system and may cahnged if they
leave it.
6-System thinking
System thinking is a way of looking at the world and things by concentrating
on the whole rather than individual parts.
7-Benefits of system thinking
- Focus on the whole properties rather than the components.
- Pay greater attention to the ways components interact.
- Take multiple partial views of things.
- Look at things from many different perspectives.
8-What is the "internet"
It is a global network of computer networks.
9-Where the internet came from?
- Prehistory: ideas which led to the internet, or which inspired the
individuals who conceived and built the system.
- ARPA and ARPANE: The Advanced Research Project Agency, was a special
agency within the US Department of Defence, set up to fund and faster
advanced research in a number of areas, including computing. In 1966
the agency decided to construct a wide area network which would link
ARPA-funded research laboratories across the US. the ARPANET was
designed and built between 1967 and 1972.
- The internet as we know it today evoloved from the ARPANET.
The dirve was to find a way of linking different networks together
into a "network of networks".
- The World Wide Web: was invented in CERN in Geneva in 1989. The
technical infrastructure for the web was in existence by 1991. But it
was not until 1993 with the launch of the first big "browser" programs
the web took off.
- Usenet news: Global online conference "newsgroup" in which much of the
discussions that is hold in the internet take place.
- The Open Source Movement: Social movement consists mainly of expert
programmers who share a particular view regarding intellectual property
and who have evolved a distinctive way of developing software.
10-Time sharing
The computer passes control from one program to the other in a "circular"
manner so every user thinks the computer is serving him only.
11-Decentralization
Means that nodes communicate with their neighbors with no central control.
12-Redundancy / distributed
Means that have more connections than you stricly needed for a normal
comunications, will enable decentralized network to function under faulty
situation.
13-Analog communication
A physical connection has to be established between the communicating
points. "Ciruit-switching" the switched connection should remain active
until communication is done.
14-Digital communication
No direct physical connection between the communication points. The sender's
message converted into sequences of 0s and 1s. Sequences of 0s and 1s is
broken into equal pieces called packets. Packets are transmitted to the
reciever one after another. Packets are collected at the recieving end to
assemble the original message. This is called packet-switching.
15-IMPs
Interferance Message Processors, a small computer that is inserted between
each host and the network of transmission lines, they act as the host interface
to the network. They are linked together to form a sub-network of IMPs.
16-Advantages of IMPs
*Free host computer from the routing load such as:
- dividing the message into packets.
- routing the packets.
- Gathering the packets.
*Same routing routing programs at each site since we have identical devices.
17-NWG
The Network Working Group, it is a name given to a group of graduated
students from two universities which sit together to discuss what application
would be built on the ARPANET.
18-RFC
Request for Comments, are technical notes written by the NWG to exchange ideas
on the design of the host software for the ARPANET.
19-Benefits of RFC
- They promoted cooperative and open work methods.
- They are timely documents containing information that comprise the consensus
of the network developers.
- RFCs present an accurate trace on how internet software evolved.
20-Why internet protocols?
- Provide rules that govern how computers communicate.
- Give the meaning to the bit flowing between the IMPs.
- Concerned with passsing messages.
- Specify the format that a message must take, and the way in which computers
must exchange a message within the context os a particular activity.
21-SMTP
Simple mail transfer protocol, used to send and recieve messages.
22-FTP
File transfer protocol, used to transfer files between computers.
23-Telnet
Used for logging into remotr hosts.
24-HTTP
Hypertext transfer protocol, used to transmit information on the WWW.
25-NNTP
Network new transfer protocol, used to trnasmit network news.
26-NCP
Network contril protocol, enabled different hosts on the network to
communicate.
27-E-mail
Is one of the most important application develped on the ARPANET. It was
developed in 1970. It is a method of machine-to-machine message exchange.
The first e-mail was written by Ray Tomlinson (a hacker).
- In 1970 ARPANET community formalized an e-mail protocol.
- In 1975 a revised e-mail protocol has been introduced in RFC 680.
- Final revision of the e-mail protocol was done in 1977, since this date
this protocol remained unchnaged.
28-Building blocks for internet
- Gateways.
- TCP (Transmission Control Protocol).
- IP (Internet Protocol).
29-Other packet switching networks
- British NPL network.
- Cyclades network in France.
- Aloha packet-radio network in Hawaii.
- SATNET Satellite network.
30-How to connect incompatible networks
To connect incompatible networks together:
- Using computers known as Gateways between different networks.
- Making hosts responsible for end-to-end transmission of packets, with error
correction and retransmission if necessary.
- Devising the protocols necessary for performing the previous two tasks.
31-How internet works
Interent works by breaking long messages into smaller chunks called packets.
32-Packets
Packet: is a string of bits divided into different segments.
33-Payloads
Payloads: core of the packet, a data segment.
34-Header and trailers
Headers and trailers: extra information added to the data by different
protocol layers. By SMTP, TCP, IP and Etherent.
35-Application layer
This is where the user interact with the network.
- SMTP: Simple mail transfer protocol, used to send and recieve electronic
mail.
- HTTP: Hypertext transfer protocol, allows you to get pages from the WWW.
- FTP: File transfer protocol, used to transfer files between computers.
36-Transport layer
This is where TCP resides, its job is to ensure the reliability and integrity
of messages.
TCP: Transmission control protocol:
- Deals with assembly and disassembly of packets.
- Error detection, correction and retransmission if necessary.
- Flow control, regulate the transmission rate.
- Sequencing, it ensures that packets are stored out into the same order as they
were transmitted.
37-Network layer
Is responsible for figuring out how to get packets to their destination.
IP: Internet protocol, handle addressing of packets.
38-Link layer
Is responsible for communicating with the hardware which connects your machine
to the internet.
PPP: Point-to-point protocol, governs the transmission of IP packets over serial
lines.
39-Usenetnews
It is a way of exchanging news and opinions. It is a program that enabled people
to post articles to a shared location which can be read by many other people that
have access to that shared location.
- each location is called a news group.
- each news group will be restricted to a certain subject.
- usenet was emerged from the community of researches and programmers who
used UNIX OS.
40-UNIX
UNIX, is a multi-user time sharing OS. It allows more than one user to work on the
machine at the sametime by sharing the CPU time.
- It was created at Bell labs for AT&T company.
- It was written by Ken Thompson and Denis Ritchie.
41-Properties of UNIX
Two main properties distinguish UNIX from other OS:
- Existence of Kernel within UNIX OS.
- Final stages of UNIX is written in "C" which is a hhigh level language
that is easy to understand and use compared to Assembly Language which
was difficult to understand and machine specific.
42-Kernel
Is an isolated small piece of code that can be easily placed in another
machine which will then run UNIX.
43-UUCP
UNIX-TO-UNIX copy program, enables users of UNIX to import new UNIX programs
and releases as well as exchange some common discussions through a phone
line.
44-Fidonet
One of the first programs that was mainly connecting PC home users. It allows
them to recieve and store information, and at the end of the day send it to
other nodes in the network through a phone line.
45-Open source movement
- Was established by Richard Stallman.
- Its main idea is to have the software and its source code available for
programmers and developers to benifit from and improve in a cooperative manner.
46-Copeyleft
Enforce people using such free software to make it available to others, even
if they did significant improvements.
47-Linux
- It was developed by Linus Travolds.
- It was developed on cooperative development, the copyleft principle and
the efforts of Richard Stallman.
- It is considered as one of the best networking OS which is available free
of charge.
48-Vannevar Bush
In 1945 described in an article an information storage and retival machine that
he called Memex which looks like an early description of the web
49-Douglas Engelbart
Who invented many of the fundamentals of modern PCs such as computer mouse,
bit-mapped screens, had proposed a method for linking documents similar to the
web. Hypertext document is a document that has many links that can read some
text and then jump to another text based on some links.
50-Ted Nelson
Invented the Hyper concept. He worked on a Xanuda project (took more than 30
years) for constructing a global hypertext publishing system.
51-Bill Atkinson
Invented the Hypercard which was the first simple hypertext system for personal
computers. These cards have used "hot-spots" which if you click on, would
instantly cause a jump to another card. A collection of linked cards was called
a "stack". The key card in the stack is called the "Home card".
52-Hypertext system
Is a system that presents information in a simple format and maintains links
which points to other pages on different machines or other pages on the same
web page.
53-Hypermedia system
Is a simple extension of hypertext where text is not the only way to create links:
images, sound, animations and video can have links to another pages.
54-Characteristics of Hypertext system
- allow remote access.
- allow access of the same information from different types of computer systems.
- be non-centralized.
- allow users to add their own provate links to and from public information.
- allow access to existing data.
- allow live links to be made between dynamically changing data.
55-Browser
Is a cleint program which communicates with a server a nd provides a window
through which the user can see the set of linked hypertext documents or
resources.
56-Types of browsers
*Text based browsers:
Are for text only pages. They do not handle images. They are still in use
because:
- Smaller.
- Faster.
- Requires less RAM and resources.
- Can run on mobile phones.
*Graphical based browsers:
- Can handle all types of information including images. Ex. Mosia, Opera,
Netscape Navigator and Internet Explorer.
57-Protocols
For enabling different machines to talk to one another, Tim Berners Lee came up
with a set of rules or protocols:
- HTTP, Hypertext transfer protocol, specifies how information exchange
between machines on the web should be handled. It defines how the four stages
of a web transaction should be done. (Connection/Request/Reply/End)
- URL, Uniform resource locator, defines a uniform way of specify the location
and which information was held.
- HTML, Hypertext mark-up language, it represents a uniform way of structuring
web pages on the web. It consists os a set of setups for attaching tags into
text. A tag consists of "<", a directive and a "/>".
- Client-server model treats computers as two types;
* A set of client computers requesting some resources which could be files or
web pages from a server computer.
* A server computer which will respond to the client(s) request(s) based on
some common protocols.
58-Mosiac browser
- The first browser program to run on regular PCs.
- A GUI and hence very easy to use.
- Designed to interpret images embedded in web pages
59-Netscape Navigator
Is another browser written by Andreeson who with his team started from
scratch and wrote compltely new code so as not to violate copyright of the
original Mosiac code. This lead to more clean, secure and sophisticated
packge which was given free to regular users.
60-Internet Explorer
Microsoft boought the right of Mosiac and distributed it with its windows OS.
This created a kind of war between the two companies and resulted in a major
law suit against Microsoft.
61-Collaborative Hypertext
Is the process by which people are allowed to add their links to a hypertext
document and help each other in producing such a document.
62-W3C
World Wide Web Consortium, its objective is to lead the WWW to its full
potential by developing common protocols that promote its evolution.
- Universal access: which allow web to be available for all people regardless
of the software, hardware, network, language and culture.
- Semantic web: which enable computers to interpret and exchange information.
- Trust, that makes the web as truly collborative medium.
- Interoperability, which allow web products to communicate and work together
by adopting common open protocols.
- Evolvability, which makes the design simple, modular and compatible.
- Decentralization, which limits the number of central web facilities.
- Cooler multimedia, which develops a more user friendly web.
63-Markup language
64-SGML
65-XML
66-XML vs. HTML
67-DTD
68-Meta Data
69-XSL
70-Subject approach
71-Keyword approach
72-P2P network
