WHAT IS A NETWORK OR IP ADRRESS?

 WHAT IS A NETWORK OR IP ADDRESS? 

  NETWORK ADRRESS 

   -Addresses are vital in network communication just as they are for locating places in the actual world. They may not be the typical home number, block number, or zip codes that we use, but the same concept is utilized to determine the address of a device on a network.

WHAT IS A NETWORK (IP) ADRRESS?

- A network address is a set of numbers called octets that identifies any network device like computer printer camera router switch and etc.) which will generally refer to as a host in a network. It is more commonly known as internet protocol address. It can be compared to the physical addresses that we use for our homes with uniquely identifies it from the rest of the homes in our neighborhood town city province country and the whole wide    world, but unlike home addresses.

 IPv4

 - IPv4 address It is the precise version or type of IP address that we have all come to recognize and accept. Similarly, when we talk about IP addresses, we can't help but think of internet addresses. So, anytime we talk about IP addresses, we talk about IPv4 addresses that are used on the internet to help us comprehend what they are.

An IP address is a series of four sets of numbers called an "octets". For easier readability, we write this set of octets in what we call a "dotted decimal" notation: e.g., 192.168.1.120 or 74.125.224.72 (Google.com). Each octet in the series is a decimal value of 8 bits of binary number or 1 byte 00000000 is equal to 11111111 is equal to 255. So each will have a value range of 0-255 only. Having this is in mind, it would mean that there will only be a little less than 4.3 billion possible IP addresses available for each network host worldwide. 

 FIGURE: Showing the different IP address ranges for each class and the binary equivalent of each octet. 

- How exactly does and IP address able to give a unique identity to a host in a network so that it can be located. As mentioned earlier, an IP address, unlike a physical home address, does not refer to any specific geographic location. Rather, it points to what particular network group a specific host belongs to, regardless of geographic location. A certain scheme has to be made in order for ip addresses to first identify which network a host belongs to, and second, identify the specific host itself. For this reason, the ip address was first divided into two parts:  the net ID and the host ID.

 - The net id is indicated by the first three high order beads of the first octet and is categorized into different classes. The 3 most common classes are classes A, B, and C classes D and E are really used especially among end-users like you and me. Let's look at how the first three high order bits of an ip address is determines the classes. Keep in mind that although you are used to looking at ip address is dotted-decimal format, you need to understand that these numbers are operated in their binary format.  

From the below, we can see the different IP address ranges corresponding to the network classes it is associated with. These classes determine the network group to which a host belongs to. This information is important, especially for networks administrators, to be able to manage the networks properly.

 

  - This Figure on the right side : Summary of max number of possible networks and hosts per IP address or network class.

Classifying IP addresses allows for easy searching through different network. It also allows for effective management of hosts in a particular network. Generally, class A IP addresses are assigned to organizations with a large number of host connecting to the network, class B is for medium-sized network of organizations, while class C is usually for networks run by small organizations or offices. Thus, allocation of IP addresses is done according to the size of network, which is determined by the number of hosts. 

RESERVED IP ADDRESSES 

 - In some organizations, not all computers are directly connected to the Internet. Usually, these computers are connected through a local network and only connect to the Internet through one computer (usually a proxy or a gateway). In such cases, there is no need to reserve an IP address for the computers in this kinds of networks. For this reason, certain IP address blocks are reserved for each network class to make sure that this addresses do not conflict with IP addresses used in the internet.

FIGURE: Showing reserved IP address blocks for each network class.

Looking closely at the class C block, you will notice that this is commonly found if you are using routers like in small offices or even at home. Computers connected or members of this network will not be able to connect to the internet and less through the gateway address but can communicate among themselves. A gateway is a node that serves as the access point on a network — typically a router.

SUBNETTING AND SUBNET MASKS

 - From the start of this lesson, we've always been talking about how network administrators can create different networks within a network (subnet). Realistically, by now, we would have almost depleted most of the ip addresses available through the IPv4 addressing. But network administrators manage to conserve and optimize the use of these addresses by creating logical networks that does not necessarily need Internet- routable IP addresses. They do this by using subnet masks.

 Subnet masks are used to set or assign a logical network within a network. What happens is that, depending on the network class, we borrow certain bits of the IP address that is set for the hosts. This way, administrators are able to extend the network size by creating logical or subnetworks equivalent to as many as the number of beats it borrowed from the host ID side of the IP address.

Before we move forward, let us take a look at automatic subnet mask per network class to help us understand more about subnetting. whenever a particular host is assigned an ip address it also acquires an automatic or default subnet mask; i.e.,

• Class A - 255.0.0.0     ( 11111111.00000000.00000000.0000000)
• Class B - 255.255.0.0   ( 11111111.11111111.00000000.00000000)
• Class C - 255.255.255.0 ( 11111111.11111111.11111111.00000000)

Based on the subnet mass please given above you can also see that if you look at the binary conversion of the subnet mass it follows that wherever you have a bite of once, it will also indicate the network class.

Moving on, let's take an example of how to create a sibnetwork using a subnet mask. Let's say we have the class C IP address.

  

IP Address : 192.168.123.0.  —  11000000.10101000.01111011.00000000

Subnet :  255.255.255.0   —   11111111.11111111.11111111.00000000

11000000.10101000.01111011.00000000

 - From the example given above, you can see that applying a default subnet mask for a class C network, where all bits are set to 1s, simply comes up with the same IP address giving it the impression of being absolute. What happens if we do apply for example a subnet mass of 255.255.255.192? Doing so would mean that we will be borrowing some binary bits from the host portion of the IP address, Thus: 

IP ADDRESS:192.168.123.0      — 11000000.10101000.01111011.00000000

SUBNET: 255.255.255.255.192. — 11111111.11111111.11111111.11000000

 - Looking at the binary conversion of the subnet mask above, the first two binary digits of the last octet becomes part of the network address as it comes out of being part of the whole series of ones. With the subnet given above, the administrator is effectively telling that the system that you want to use the first two bits of the last octet to indicate the network ID. this will now allow him or her to have four logical networks for the 192.168.123.0 block of IP address. The four network addresses then will be:

• 192.168.123.0-62
• 192.168.123.65-126
• 192.168.123.129-190
• 192.168.123.193-254

WHAT IS AN OSI LAYER?

 

WHAT IS AN OSI?                             

                             -An Open Systems Interconnection (OSI) model is a fundamental framework used to understand how computer networks function. It is a 7-layer architecture with each layer having specific functionality to perform. All these 7 layers work collaboratively to transmit the data from one person to another across the globe.

 WHAT ARE THE 7 LAYERS OF AN OSI?

• PHYSICAL
• DATA LINK
• NETWORK
• TRANSPORT
• SESSION
• PRESENTATION
• APPLICATION

ARE THEY IMPORTANT?

             

             - Yes of course, the OSI layers is important because it helps to determine the required hardware and software to build a network. Understand and communicate the process followed by components communicating across a network. Perform troubleshooting, by identifying which network layer is causing an issue and focusing efforts on that layer. Understand new technologies as they are developed. Compare primary functional relationships on various network layers.

WHAT ARE THE FUNCTIONS OF OSI LAYERS?

1. PHYSICAL LAYER

                -The lowest layer of the OSI reference model is the physical layer. It is responsible for the actual physical connection between the devices. The physical layer contains information in the form of bits. It is responsible for transmitting individual bits from one node to the next. When receiving data, this layer will get the signal received and convert it into 0s and 1s and send them to the Data Link layer, which will put the frame back together.  

Functions of the Physical Layer

• Bit synchronization: The physical layer provides the synchronization of the bits by providing a clock. This clock controls both sender and receiver thus providing synchronization at the bit level.
• Bit rate control: The Physical layer also defines the transmission rate i.e. the number of bits sent per second.
• Physical topologies: Physical layer specifies how the different, devices/nodes are arranged in a network i.e. bus, star, or mesh topology.
• Transmission mode: Physical layer also defines how the data flows between the two connected devices. The various transmission modes possible are Simplex, half-duplex and full-duplex.

Note:

1. Hub, Repeater, Modem, and Cables are Physical Layer devices. 
2. Network Layer, Data Link Layer, and Physical Layer are also known as Lower Layers or Hardware Layers.

2. DATA LINK

           -The data link layer is responsible for the node-to-node delivery of the message. The main function of this layer is to make sure data transfer is error-free from one node to another, over the physical layer. When a packet arrives in a network, it is the responsibility of the DLL to transmit it to the Host using its MAC address. 
The Data Link Layer is divided into two sublayers:  

1. Logical Link Control (LLC)
2. Media Access Control (MAC)

The packet received from the Network layer is further divided into frames depending on the frame size of the NIC(Network Interface Card). DLL also encapsulates Sender and Receiver’s MAC address in the header. 

The Receiver’s MAC address is obtained by placing an ARP(Address Resolution Protocol) request onto the wire asking “Who has that IP address?” and the destination host will reply with its MAC address.  

Functions of the Data Link Layer

• Framing: Framing is a function of the data link layer. It provides a way for a sender to transmit a set of bits that are meaningful to the receiver. This can be accomplished by attaching special bit patterns to the beginning and end of the frame.
• Physical addressing: After creating frames, the Data link layer adds physical addresses (MAC addresses) of the sender and/or receiver in the header of each frame.
• Error control: The data link layer provides the mechanism of error control in which it detects and retransmits damaged or lost frames.
• Flow Control: The data rate must be constant on both sides else the data may get corrupted thus, flow control coordinates the amount of data that can be sent before receiving an acknowledgment.
• Access control: When a single communication channel is shared by multiple devices, the MAC sub-layer of the data link layer helps to determine which device has control over the channel at a given time.

Note:

1. Packet in the Data Link layer is referred to as Frame. 
2. Data Link layer is handled by the NIC (Network Interface Card) and device drivers of host machines. 
3. Switch & Bridge are Data Link Layer devices.

3. NETWORK LAYERS

The network layer works for the transmission of data from one host to the other located in different networks. It also takes care of packet routing i.e. selection of the shortest path to transmit the packet, from the number of routes available. The sender & receiver’s IP addresses are placed in the header by the network layer. 

Functions of the Network Layer 

• Routing: The network layer protocols determine which route is suitable from source to destination. This function of the network layer is known as routing.
• Logical Addressing: To identify each device on Internetwork uniquely, the network layer defines an addressing scheme. The sender & receiver’s IP addresses are placed in the header by the network layer. Such an address distinguishes each device uniquely and universally.

Note:

1. Segment in the Network layer is referred to as Packet. 
2. Network layer is implemented by networking devices such as routers and switches.  

4 TRANPORT LAYER

        -The transport layer provides services to the application layer and takes services from the network layer. The data in the transport layer is referred to as Segments. It is responsible for the end-to-end delivery of the complete message. The transport layer also provides the acknowledgment of the successful data transmission and re-transmits the data if an error is found.

At the sender’s side: The transport layer receives the formatted data from the upper layers, performs Segmentation, and also implements Flow and error control to ensure proper data transmission. It also adds Source and Destination port numbers in its header and forwards the segmented data to the Network Layer. 

Note: The sender needs to know the port number associated with the receiver’s application. 

Generally, this destination port number is configured, either by default or manually. For example, when a web application requests a web server, it typically uses port number 80, because this is the default port assigned to web applications. Many applications have default ports assigned. 

At the receiver’s side: Transport Layer reads the port number from its header and forwards the Data which it has received to the respective application. It also performs sequencing and reassembling of the segmented data. 

Functions of the Transport Layer 

• Segmentation and Reassembly: This layer accepts the message from the (session) layer, and breaks the message into smaller units. Each of the segments produced has a header associated with it. The transport layer at the destination station reassembles the message.
• Service Point Addressing: To deliver the message to the correct process, the transport layer header includes a type of address called service point address or port address. Thus by specifying this address, the transport layer makes sure that the message is delivered to the correct process.

Services Provided by Transport Layer 

1. Connection-Oriented Service
2. Connectionless Service

1. Connection-Oriented Service: It is a three-phase process that includes

• Connection Establishment
• Data Transfer
• Termination/disconnection

In this type of transmission, the receiving device sends an acknowledgment, back to the source after a packet or group of packets is received. This type of transmission is reliable and secure.

2. Connectionless service: It is a one-phase process and includes Data Transfer. In this type of transmission, the receiver does not acknowledge receipt of a packet. This approach allows for much faster communication between devices. Connection-oriented service is more reliable than connectionless Service.

Note:  

1. Data in the Transport Layer is called Segments. 
2. Transport layer is operated by the Operating System. It is a part of the OS and communicates with the Application Layer by making system calls. 
3. The transport layer is called as Heart of the OSI model. 
4. Device or Protocol Use : TCP, UDP  NetBIOS, PPTP

5 SESSION LAYER

This layer is responsible for the establishment of connection, maintenance of sessions, and authentication, and also ensures security.

Functions of the Session Layer

• Session establishment, maintenance, and termination: The layer allows the two processes to establish, use, and terminate a connection.
• Synchronization: This layer allows a process to add checkpoints that are considered synchronization points in the data. These synchronization points help to identify the error so that the data is re-synchronized properly, and ends of the messages are not cut prematurely and data loss is avoided.
• Dialog Controller: The session layer allows two systems to start communication with each other in half-duplex or full-duplex.

Note:

1. All the below 3 layers(including Session Layer) are integrated as a single layer in the TCP/IP model as the ????pplication Layer”. 
2. Implementation of these 3 layers is done by the network application itself. These are also known as Upper Layers or Software Layers. 
3. Device or Protocol Use :  NetBIOS, PPTP.

For example:-

Let us consider a scenario where a user wants to send a message through some Messenger application running in his browser. The “Messenger” here acts as the application layer which provides the user with an interface to create the data. This message or so-called Data is compressed, encrypted (if any secure data), and converted into bits (0’s and 1’s) so that it can be transmitted.  

Communication in Session Layer

6. Presentation Layer – Layer 6

The presentation layer is also called the Translation layer. The data from the application layer is extracted here and manipulated as per the required format to transmit over the network. 

Functions of the Presentation Layer

• Translation: For example, ASCII to EBCDIC.
• Encryption/ Decryption: Data encryption translates the data into another form or code. The encrypted data is known as the ciphertext and the decrypted data is known as plain text. A key value is used for encrypting as well as decrypting data.
• Compression: Reduces the number of bits that need to be transmitted on the network.

Note: Device or Protocol Use:  JPEG, MPEG, GIF

7.  Application Layer – Layer 7

At the very top of the OSI Reference Model stack of layers, we find the Application layer which is implemented by the network applications. These applications produce the data, which has to be transferred over the network. This layer also serves as a window for the application services to access the network and for displaying the received information to the user. 

Example: Application – Browsers, Skype Messenger, etc. 

Note: 1. The application Layer is also called Desktop Layer.  

          2.  Device or Protocol Use :  SMTP

Functions of the Application Layer

The main functions of the application layer are given below.

• Network Virtual Terminal: It allows a user to log on to a remote host.
• FTAM- File transfer access and management: This application allows a user to
  access files in a remote host, retrieve files in a remote host, and manage or
  control files from a remote computer.
• Mail Services: Provide email service.
• Directory Services: This application provides distributed database sources
  and access for global information about various objects and services.

Note: OSI model acts as a reference model and is not implemented on the Internet because of its late invention. The current model being used is the TCP/IP model.  

What is the Flow of Data in OSI Model?

When we transfer information from one device to another, it travels through 7 layers of OSI model. First data travels down through 7 layers from the sender’s end and then climbs back 7 layers on the receiver’s end.

Advantages of OSI Model

OSI Model defines the communication of a computing system into 7 different layers. Advantages of OSI Model include:

• It divides network communication into 7 layers which makes it easier to understand and troubleshoot.
• It standardizes network communications, as each layer has fixed functions and protocols.
• Diagnosing network problems is easier with the OSI model.
• It is easier to improve with advancements as each layer can get updates separately.

WHAT ARE THE OTHER NETWORK DEVICES?

                          OTHER NETWORK DEVICES

"Aside from the three common communication devices, there are also other devices that help connect through the network."

networking has many components that make it work more efficiently. Devices, when combined, will enable a faster transmission of data. here are the other devices that make up a network.

THE BRIDGE

The bridge is used to divide larger networks into smaller sections. It is also located between two physical network segments and manages the flow of data between the two. By looking at the physical address of the devices connected to each segment, bridges can forward the data if the destination address is on another interface, or block it from crossing if verified that it is on the interface from which it came.

THERE ALSO DIFFERENT TYPES OF BRIDGE

Transparent Bridge - derives its name from the fact that the devices on the network are unaware of its existence. a transparent bridge does nothing except black or forward data based on the mac address.

Source Route Bridge - is used in token ring networks. the source route bridge derives its name from the fact that the entire path to be taken by the packet through the network is embedded within the packet.

Translational Bridge - is used to convert one network data format to another for example from the token ring to ethernet and vice versa.

THE NETWORK CARD

It is also called the Network Interface Card, is a device that enables computers to connect to the network.

To install or configure a network interface, you will need drivers of the device. You might also need to configure it, although many devices are now plug and play. Most network cards are now software configured. Many of these so
ftware configuration utilities also include testing capabilities. The drivers and software configuration utilities supplied with the cards are often not the latest available, so it is best practice to log on the Internet and download the latest drivers and associated software.

THE MODEM

a short for modulator or demodulator, is a device that converts the digital signals generated by a computer into analog signals that can travel over conventional phone lines.

The modem converts the signal back at the receiving end it converts it into a format the computer can understand.

 a modem can be used as a means to connect to an ISP, or as a mechanism for dialing up to a LAN. a modem can also be internal ad in expansion cards or external devices that connect to the serial or USB port of a system. it can also be PCMCIA cards designed for use in laptops or proprietary devices design for use on other devices such as portables and handhelds.

THE TRANSCEIVER

The transceiver is responsible for placing signals onto the network media and detecting incoming signals traveling through the same wire.

The term transceiver does describe a separate network device, but it can also be technology built and embedded in devices such as network cards and modems. In a network environment a transceiver gets its name from being both a transmitter and a receiver of signals does the name transceivers.

It is logical that the technology would found in network cards. Although transceivers are found in network cards, they can be external devices as well. In terms of network transceivers can be shipped as a model or chip type.

CHIP TRANSCEIVER are small and are inserted into a system board or wire directly on a circuit board. MODULE TRANSCEIVER are external to the network and are installed and function similar to other computer peripherals or they can also function as a stand alone devices. 

Several types of the transceivers are RF transceivers, fiber optic transceivers, Ethernet transceivers wireless (WAP) transceivers and more. Each of these media types are different though the function of the transceiver remains the same. Each type of the transceiver used has different characteristics, such as the number of ports available to connect to the network and whether it function as a full duplex communication if supported.

THE FIREWALL

It is a networking device that can be either hardware or software-based. It controls access to your organization's network. This controlled access is designed to protect data and sources from outside the threat. 

A typical firewall is placed at entry or exit points of the network. For example placing a firewall between an internal network and the internet. when in place it control access in and out of that point. The firewall is configured on the server to allow or permit certain type of network traffic. In a small offices and in regular home use a firewall is commonly installed on the local system and configure to control traffic.

Hardware firewalls are used in networks of all sizes today. Hardware firewalls are often dedicated network devices that can be implemented with very little configuration and protect all system behind the firewall from outside sources. Hardware firewalls are readily available and often combined with other devices today. For example, many broadband routers and wireless access points have built-in firewall functionally in such case the router or WAP might have a number of ports available to plug system into.

WHAT IS THE DIFFERENCE BETWEEN HUB, SWITCH AND, ROUTER ?

NETWORK COMMUNICATION DEVICES HUB, SWITCH AND ROUTER

•  Network basics required devices to provide connectivity and functionally. learning this network devices and how they operate our essential in setting up your own network. routers hubs and switches are network device terms that tend to be used interchangeably.
• The functions of the three devices of quite different from one another even though at times they are all integrated into a single device.                                                              
• Each device serves as a central connection for all of your network equipment and handles a data type known as frames a frame carries your data when a frame is received it is amplified and then transmitted onto the port of the destination pc the big difference between frames is in the method in which frames are being delivered.

                             WHAT IS HUB, SWITCH AND ROUTER?

                                    

   WHAT IS A HUB?

 a hub is a simple device that directs data packets to all devices connected to it. Basically I have does nothing except provide a pathway for the electrical signals and regenerate signal before it forwards it to all connected devices.

A message is forwarded along or broadcast to all of the hub's ports. It doesn't matter if the message is only for one port. The hub has no way of determining which port a message should be delivered to. Passing it along to each port guarantees that it reaches its proper destination. These add a lot of traffic to the network, which might lead to slow network response times.

It's 10 or 100 mbps have must share its bond with rich data transfer rate with each and every one of its ports. so when only one pc is broadcasting it will have access to the maximum available bandwidth.b however if multiple pieces are broadcasting that bandwidth will need to be divided among all of those systems which will degrade performance.

                                                                                     WHAT IS A SWITCH?

It is a similar to hubs, switches are the connectivity point of a wired network. Devicesare connected via twisted pair cabling one cable for each device. The difference between the two is on how the devices deal with the data that they receive. If a hub forwards the data it receives to all parts on the device as which forwards the data it receives only to the port that connects to the destination device. 

A switch keeps a record of the mac addresses or the   unique identity of the client devices connected to it. With this information stored in a switch it can identify which system is sitting on which port. Thus, when a message is received it knows exactly which port to send it the different from a hub, 10 or 100 mbps is which will allocate a full 10 or 100 mbps to each of its ports so it does not matter how many pieces transmitting users will always have access to the maximum amount of bandwidth. This is why switch is most considered to be much better choice than a hub. The network result of this measures is that switches can offer significant performance improvements over hub base networks particularly when network use is high.

                   WHAT IS A ROUTER?

Router are completely different devices. If a hub or switch is concerned with transmitting frames, the job of a router, as its name implies, is to route pockets to other networks until that packet ultimately reaches its destination. It can transmit through wired and wireless network. A router is typically connected to at least two networks commonly two local area networks or wide area networks or a LAN and its network internet the service providers network. 

Routers have a WAN port that connects to an internet connection provided by your Internet Service, Provider, the integrated switch allows users to easily create a LAN. This allows all the PCs on the land to have access to the internet windows file, and printer sharing services. Routers might have a single WAN port and a single LAN port and are designed to connect an existing LAN hub or switch to a WAN.  Switches and hubs can be connected to a router with multiple Pc ports to expand a LAN. When a router receives a packet of data it reads the header of the pocket to determine the destination address. Once it has determined the address it looks in its routing table to determine whether it knows how to reach the destination; does it forwards the pocket to the next hop on the route. the next hop might be the final destination or it might be another router. 

WHAT IS THE DIFFERENCE BETWEEN

 HUB, SWITCH, AND ROUTER? 

  

- The difference between the three main network communication devices a hub glues together a wired network segment.
- A switch can connect multiple wired segments more efficiently while a router can do those functions, plus route pockets between multiple LANs and/or so much more.
- Hubs simply broadcast data to all connected devices.
- Switches intelligently forward data packets to specific devices based on their MAC addresses.
- Routers forward data packets between different networks based on their IP addresses and make decisions about the best path for routing traffic.