Internet Service Providers (ISPs)

Most companies obtain IP address blocks from ISPs. ISPs connect our data network to the Internet. ISPs have their own set of internal data networks to manage Internet connectivity and to provide related services.

ISP Tiers

ISPs are designated by a hierarchy based on their level of connectivity to the Internet backbone. Each lower tier obtains connectivity to the backbone through a connection of a higher tier ISP.

Tier 1

Tier 1 ISPs are at the top of ISP hierarchy. They are directly connected to Internet Backbone. The primary advantages for customers of Tier 1 ISPs are reliability and speed. There are less opportunities for failure or traffic bottlenecks as Tier 1 ISP customers are only one connection away from Internet.

Tier 2

Tier 2 ISPs get their internet services from Tier 1 ISPs. So, the internet bandwidth and reliability are lower than Tier 1 ISPs.

Tier 3

Tier 3 ISPs purchase their internet services from Tier 2 ISPs. Generally, the internet bandwidth and reliability are lower Tier 1 and Tier 2 ISPs.

IP Addresses

The networking devices need IP addresses to communicate with each other on the network. There are two types of IP addresses versions: IP Version 4 (IPv4) and IP Version 6 (IPv6).

IPv4 Address

                   In IPv4 address, the host can communicate in one of three different ways:

    Unicast: The process of sending a packet from one host to an individual host

   Broadcast: The process of sending a packet from one host to all hosts in the network

   Multicast: The process of sending a packet form one host to selected group of hosts

                   There are three types of addresses in IPv4 network range.

   Network address: A special network that refers to the network

   Broadcast address: A special address used to send data to the all hosts in the network

   Host address: The unicast address assigned to the end device in the network

Subnet Mask

                   The subnet mask is a 32-bit values used with IPv4 address that specifies the network portion of the address to the network device. The subnet mask uses 1s and 0s to indicate which bits of the IPv4 address are network bits and which bits are hosts bits.

OSI Model and TCP/IP Model

OSI Model

                     The Open System Interconnection (OSI) Model provides an abstract description of the network communication process. International Organization for Standard (ISO) develops it to provide a road map for non-proprietary protocol development. The OSI model is just a reference model and many of OSI protocols are no longer in use. There are seven layers in OSI Model. Those are as follows:

Layer 7 -  Application

                        Performs services for the application used by the end users.

Layer 6 -  Presentation

                       Provides data format information to the application.

Layer 5 -  Session

                      Manages session between users.

Layer 4 -  Transport

                     Defines data segments and numbers them at the source, transfers the data, and reassembles the data at the destination.

Layer 3 -  Network

                    Creates and addresses packets for end-to-end delivery through intermediary devices in other network.

Layer 2 - Data Link

                    Creates and addresses frames for host-to-host delivery on the local LANs and between WAN devices.

Layer 1 - Physical

                    Transmits binary data over media between devices. Physical layer protocols define media specifications.

Network Protocols

Network Protocols are machine languages used to communicate the devices on the network. For devices to communicate on a network, they must follow different protocols that perform the many tasks to be complicated. The protocols define the followings:

Ø  The format of the message, such as how much data to put into each segment

Ø  The way intermediary devices share information about the path to the destination

Ø  The method to handle update messages between intermediary devices

Ø  The process to initiate and terminate communications between hosts
The examples of Network Protocols are as follows:

Hypertext Transfer Protocol (HTTP):  HTTP is a common protocol that controls the wa that a web server and web client interact.

Transport Protocol: Transmission Control Protocol (TCP) is the transport protocol that manages the individual conversions between a web server and web client. TCP divides the HTTP messages into smaller pieces, called segment, to be sent to the destination client. It also controls the size and rate of messages exchanged between the server and the client.

      Internet Protocol (IP): IP takes the formatted segments from TCP, encapsulates them into packets, assign the appropriate addresses, and select the best path to the destination client.

Network Access Protocols: Network access protocols describe two primary functions: data-link management and the physical transmission of data on the media. Data-link management protocols take the packets from IP and format them to be transmitted over the media. The physical media controls how the signals are sent over the media and how they are interpreted by the receiving clients.

Short Description of Networking Devices

Desktop Computer

A common computer used in a home or offices.

Laptop

A portable computer.

IP Phone

A digital telephone that carries voice at data over networks instead of analog phone lines.

LAN Media

Local-area network media, usually copper cable.

Wireless Media

Depicts local-area network wireless access.

Switch

The most common devices for interconnecting local-area networks

Router

A device that helps direct message between networks

Firewall

A device that provides security network.

Server

A common computer dedicated to provide application services to end users on a network. Server stores information to share with its clients.

The things we need to check when buying computers

- System Model and Generation
- Processor
- RAM
 - Graphic
- Network Interface Card (NIC)
- Hard Disk
 - And the most important is price.