CHAPTER 3

NETWORKS
Networks provide the ability to connect people and equipment no matter where they are in the world.

VOICE NETWORK COMPUTER NETWORK VIDEO NETWORK

The Internet is considered a "network of networks" because it is literally made up of thousands of networks that are connected to each other.

Here are other uses of a network and the Internet:
Sharing music and video files
Research and on-line learning
Chatting with friends
Planning vacations
Purchasing gifts and supplies

CATEGORIES:

PERIPHERALS
it doesnt communicate directly on the network. instead,it relies on its connected host to perform all network operations.
cameras, sacnners, and local attached prinetrs.

HOSTS
send and receive user traffic.it has an IP network address.
personal computers and network attached printers.

NETWORK DEVICES
connect other devices, mainly hosts. these devices move and control network traffic.
hubs,swithces and routers.

NETWORK MEDIA
provides connections between hosts and network devices. it can be wired, such as copper and fiber optic or use wireless technologies.

COMPUTER ROLE IN NETWORK

ALL CONNECTED TO THE SWITCH

file access client/ file server
store the file, the client accesses with client sofware such as windows explorer.

web server/ browser client
runs server software and cleints use their browser software, such as Windows internet to access web pages.

email server/ email client
runs server software and clients use their mail client software, such as microsoft outlook to access.

PEER-TO-PEER NETWORKS
many computers function as the servers and clients on the network. This type of network is called a peer-to-peer network.

ADVANTAGES:
easy to set up
less complexity
lower cost
can be used for simpel tasks, such as transferring files and sharing printers.

DISADVANTAGES:
no centralized administration
not as secure
not scalable
all devices may act both clients and servers which can slow their performance.

NETWORK TOPOLOGIES
When networks are installed
PSYSICAL TOPOLOGY MAP
created to record where each host is located and how it is connected to the network.
shows where the wiring is installed and the locations of the networking devices that connect the hosts.

LOGYCAL TOPOLOGY MAP
groups hosts by how they use the network
Host names, addresses, group information and applications can be recorded on it.

SURCE, CHANNEL and DESTINATION

MESSAGE SIGNAL SIGNAL MESSAGE
MESSAGE----TRANSMITTER-----TRANSMISSION MEDIUM-----RECEIVER----MESSAGE DESTINATION

RULES OF COMMUNICATION
Message format
Message size
Timing
Encapsulation
Encoding
Standard message pattern

MESSAGE ENCODING
emite una idea------la cuenta a otro------el otro por fin se imagina la idea contada
SOURCE ENCODED--------------------DESTINATION DECODED

MESSAGE FORMATTINGH

DESTINATION: physcial hardware address
SOURCE: physcial hardware address
START FLAG: start of message indicator
RECIPIENT: destination identifier
SENDER: source indentifier
ENCAPSULATED: data bits
END OF FRAME: end of message indicator

MESSAGE SIZE
Too short or long messages cant be delivered,they need to be divided in small pieces.

MESSAGE TIMING

Access Method
Hosts on a network need an access method to know when to begin sending messages and how to respond when errors occur.

Flow control
Source and destination hosts use flow control to negotiate correct timing for successful communication.

Response Timeout
Hosts on the network also have rules that specify how long to wait for responses and what action to take if a response timeout occurs.

MESSAGE PATTERNS

UNICAST: A one-to-one message pattern
MULTICAST: When a host needs to send messages using a one-to-many pattern,
BROADCAST: If all hosts on the network need to receive the message at the same time

Protocols
In a wired environment, a local network is defined as an area where all hosts must "speak the same language" or in computer terms "share a common protocol".

SATANDARIZATION OF PROTOCOLS

Standards are beneficial to networking in many ways:
Facilitate design
Simplify product development
Promote competition
Provide consistent interconnections
Facilitate training
Provide more vendor choices for customers

Ethernet, has become more common than the others. It has become a de facto standard.

PHYSICAL ADDRESSING

Every Ethernet network interface has a physical address assigned to it when it is manufactured. This address is known as the Media Access Control (MAC) Address. The MAC address identifies each source and destination host on the network.

ETHERNET COMUNICATION

The format for Ethernet frames specifies the location of the destination and source MAC addresses, and additional information including:
Preamble for sequencing and timing
Start of frame delimiter
Length and type of frame
Frame check sequence to detect transmission errors

HIERACHICAL DESIGN OF ETHERNET
In networking, hierarchical design is used to group devices into multiple networks that are organized in a layered approach.

It has three basic layers:
Access Layer - to provide connections to hosts in a local Ethernet network.
Distribution Layer - to interconnect the smaller local networks.
Core Layer - a high-speed connection between distribution layer devices.

LOGYCAL ADDRESSING

The IP address is known as a logical address because it is assigned logically based on where the host is located.

The IP address, or network address, is assigned to each host by a network administrator based on the local network.

SWITHCES

An Ethernet switch is a device that is used at the Access Layer. Like a hub, a switch connects multiple hosts to the network. A switch can forward a message to a specific host. When a host sends a message to another host on the switch, the switch accepts and decodes the frames to read the physical (MAC) address portion of the message.

CHAPTER 2 resume

To perform a specific task, a special type of computer program, known as an operating system (OS)is required,which controls input and output functions.
In addition, the entered data is manipulated inside of the computer, stored in RAM and processed by the CPU. This internal manipulation and processing is also controlled by the OS. All computerized devices, such as servers, desktops, laptops or handhelds, require an OS in order to function.

PURPOSE OF AN OPERATING SYSTEM

A user interacts with the computer system through an application, such as
word processor
spreadsheet
computer game or instant messaging program
Application programs are designed for a specific purpose, such as word processing, and know nothing of the underlying electronics.

The portion of the OS code that interacts directly with the computer hardware is known as the kernel

The portion that interfaces with the applications and user, is known as the shell

The CLI, the user interacts directly with the system in a text-based environment by entering commands on the keyboard at a command prompt.

The GUI interface allows the user to interact with the system in an environment that uses graphical images, multimedia, and text.

REDIRECTOR
To work with resources that are not directly connected to the computer system, a special piece of software must be added that allows a device to send and receive data from the network.
May either be an integral part of the OS or may need to be installed separately as a network client. When installed, the operating system becomes a network operating system (NOS).

OPERATING SYSTEM REQUIERMENTS
These resources are specified by the manufacturer and include such things as:
Amount of RAM
Hard disk space required
Processor type and speed
Video resolution

Choosing an appropriate OS requires many factors to be considered before deciding which one to use in a given environment.

SECURITY
SUPPORT
POLITICS
COST
AVAILABILITY
RESOURCES
PLATFROM
USE

Types of OS:
Microsoft Windows: XP, Vista, 2003 Server
UNIX-Based: IBM AIX, Hewlett Packard HPUX, and Sun Solaris
BSD - Free BSD
Linux-Based (Many varieties)
Macintosh OS X
Non-Unix Proprietary: IBM OS/400, z/OS

There are several operating systems released under a different type of licensing scheme known as the GNU Public License (GPL).

Windows XP, Mac OS X and UNIX are all examples of commercial OS software.

OS selection

determine the user requiermentes
determine choices and OS
technicaland financial resources available
other restrictions
implement selected OS

OS installation Methods:
CLEAN INSTALL
is done on a new system or in cases where no upgrade path exists between the current OS and the one being installed.

UPGRADE
With an upgrade, system configuration settings, applications and data are preserved. It simply replaces the old OS files with the new OS files.

MULTI-BOOT
It is possible to install more than one OS on a computer to create a multi-boot system.

VIRTUALIZATION
It enables multiple copies of an OS to be run on a single set of hardware, thus creating many virtual machines.

PREPARING OS FOR INSTALLATION

A pre-installation checklist helps ensure that the installation process is successful.

1. Verify that all hardware is certified to work with the selected OS.

2. Verify that the hardware resources meet or exceed the published minimum requirements.

3. Confirm that the appropriate installation medium is available. Due to the file size of current operating systems, they are usually available on both CD and DVD medium.

4. If the OS is to be installed on a system that already contains data: (a) Use system diagnostic tools and utilities to ensure the current OS installation is in good condition, free of malicious or damaging files and codes; (b) Complete a full backup of all important files.

5. If performing a clean-install, verify that all application software is available for installation.
BEFORE IT
One of the techniques available to help protect data is to divide the hard drive into multiple partitions
it's also necessary to determine the type of file system to use.

CONFIFURING FOR A NETWORK
3 parts to the IP configuration, which must be correct for the computer to send and receive information:
IP address - identifies the computer on the network.

Subnet mask - is used to identify the network on which the computer is connected.

Default gateway - identifies the device that the computer uses to access the Internet or another network.

COMPUTER NIC default gateway IP INTERNET


MANUAL IP CONF
network adm.

DYNAMIC IP CONF
server---------- ip adress----------subnet mask-------def gateway-----host

computer naming
A computer name provides a user friendly name, making it easier for users to connect to shared resources such as folders and printers on other computers.

NETWORK NAME AND ADDRESS PLANNING helps them to find you in case.

PATCHES
A patch is a piece of program code that can correct a problem or enhance the functionality of an application program or OS.

Patches to operating systems can be installed in different ways, depending on the OS and the needs of the user. Options for downloading and installing updates include:

Automatic installation
a computer automatically accesses a manufacture'sweb site bightly to check for any OS updates to install.

Prompt for Permission
the suer is available to decide not to install it based on reports of poor computer performance after installation.

Manual
to correct known functionality and security issues within and operating system