Virtualization Technology

What is Virtualization technology ?

Virtualization is very useful for those who want to run multiple operating system on a single PC. It is very useful for IT administrators, software developers etc. For virtualization, Microsoft designed a software called Hyper-V. It is the machine virtualization technology which has been part of the last two releases of Windows Server.

What is Hyper-V technology ?

With the help of Hyper-V, users can run more than one 32-bit or 64-bit x86 operating system at the same time on the same computer. Instead of working directly with computer's hardware, operating system will run inside of a Virtual machine (VM). With the help of Hyper-V it is easy for developers to maintain multiple test environments and to provide a easy mechanism to switch between environments without paying on additional hardware costs. For general users, they can use Hyper-V to try out new operating system without risking changes to the PC which they are actively using.

Requirements of Hyper-V technology

Hyper-V requires a 64-bit system which has SLAT(Second Level Address Translation). It is a feature which is present in the current generation of 64-bit processors of Intel and AMD. Apart from the SLAT processors, users need a 64-bit version of Windows 8 operating system, minimum 4GB of RAM. Hyper-V supports both 32-bit and 64-bit operating systems in the Virtual Machines.

How Hyper-V works ?

Hyper-V allows memory needed by the virtual machines to be allocated and de-allocated dynamically. Users can specify minimum and maximum amount of memory and Hyper-V shares unused memory between virtual machines. Users can run 3 or 4 virtual machines on a machine which has 4GB of RAM. If users want to run more than 4 virtual machines at a time, they need more RAM. 

Windows provides two types of mechanisms with virtual machines. They are 

1) VM Console 

2) Remote Desktop Connection.

VM Console which is also known as VMConnect, is a console view of virtual machine. VM Console provides a single monitor view of the virtual machine with resolution up to 1600x1200 in 32-bit color. To get better experience, many of the users connect to the virtual machine using Remote Desktop Connection which is also called as RDC. With the help of RDC, virtual machine takes advantage of capabilities which were present on users computer. 

Users can add multiple hard disks to IDE or SCSI controllers which were available in the VM. They can use virtual hard disks or actual disks. One of the important feature in Hyper-V is the ability to take snapshots of a virtual machine while it is running. With the help of snapshot, users can save everything about the virtual machine which will be helpful to go back to a previous point if they occurs any problem in VM.

TCP/IP VS OSI MODEL

TCP/IP Model Vs OSI Model

This article is about TCP/IP model vs OSI model. It is meant to highlight the differences between the two set standards of the industry. TCP/IP model and the OSI model have been the two protocol suites on which the communication industry heavily relies on.

Both TCP/IP model and OSI model work in a very similar fashion. But they do have very subtle differences too. Knowing these differences is very crucial to learning computer networking. This article will try to show the comparison between TCP/IP model vs OSI model.

A Background

OSI reference model came into existence way before the TCP/IP model was created. Advance research project agency (ARPA) created an OSI reference model so that they could logically group the similarly working components of the network into various layers of the protocol. But after the advent of the Internet, there arose the need for a streamlined protocol suite, which would address the need of the ever-growing Internet. So the Defense Advanced Research Project Agency (DARPA) decided to create the TCP/IP protocol suite. This was going to address many, if not all the issues that had arisen with the OSI reference model.

TCP/IP Model Layers Explained

So  what does TCP/IP stand for? It is a suite of protocol which is named after its most significant pair of protocols. That is Transmission Control Protocol and Internet Protocol. TCP/IP are made up of layers. Each layer is responsible for a set of computer network related tasks. Every layer provides service to the layer above it. In all, there are four layers in the TCP/IP reference model.

Application Layer:-

 This is the topmost layer of the TCP/IP suite. This is responsible for coding of the packet data.

Transport Layer:- 

This layer monitors end-to-end path selections of the packets. It also provides service to the application layer.

Internet Layer:- This layer is responsible for sending packets through different networks.

Link Layer:- It is the closest layer to the network hardware. It provides service to Internet layer.OSI Model Layers Explained

In OSI reference model there seven layers of protocols.

 Again, in OSI reference model, each layer provides services to the layer above it. There are in all seven layers of in OSI. They are:-

Physical Layer:-

 It is the lower most layer of the OSI reference model. It is layer which is responsible for direct interaction of the OSI model with hardware. The hardware provides service to the physical layer and it provides service to the data link layer.

Datalink Layer:- There may be certain errors which may occur at the physical layer. If possible, these errors are corrected by the data link layer. The datalink layer provides the way by which various entities can transfer the data to the network.

Network Layer:- It does not allow the quality of the service to be degraded that was requested by the transport layer. It is also responsible for data transfer sequence from source to destination.

Transport Layer:- The reliability of the data is ensured by the transport layer. It also re transmits those data that fail to reach the destination.

Session Layer:- The sessions layer is responsible for creating and terminating the connection. Management of such a connection is taken care of by the sessions layer.

Presentation Layer:- This layer is responsible for decoding the context (syntax and semantics) of the higher level entities.

Application Layer: Whichever software application that implements socket programming will communicate with this layer. This layer is closest to the user.TCP/IP Model vs OSI Model

Sr. No.	TCP/IP Reference Model	OSI Reference Model
1	Defined after the advent of Internet	Defined before advent of internet
2	Service interface and protocols were not clearly distinguished before	Service interface and protocols are clearly distinguished
3	TCP/IP supports Internet working	Internet working not supported
4	Loosely layered	Strict layering
5	Protocol Dependent standard	Protocol independent standard
6	More Credible	Less Credible
7	TCP reliably delivers packets, IP does not reliably deliver packets	All packets are reliably delivered

The entire communication industry stands on the backbone of TCP/IP and OSI reference model. It is very vital to learn the above differences, if anyone wants to be an expert in the field of communication.

192.168.0.1(Why this is Default IP for Router)

Why is the default IP address for my router 192.168.0.1?


Someone at my office recently asked me why their wireless routers always had a default IP address of 192.168.0.1 and I really could not come up with a good answer! Being an IT guy myself, I was obviously irritated by the fact that I hadn’t really thought about something that’s in my face pretty much every day before.

So why do most routers use this IP address? Well, it’s pretty simple actually. The reason is that the IP address is a non-routable IP address. A non-routable IP address, also known as a private IP address, is not assigned to any one particular organization and does not need to be assigned by an Internet Service Provider.

Some will argue that all IP addresses are routable, it’s just specific IP address ranges are not publicly routed on the Internet. Instead, they are routed to a NAT gateway or a proxy server before being connected to the Internet.

Private IP addresses are used in most and small business networks because a ISP usually assigns only one IP address to a location. If there is more than one device that needs to connect to the Internet, a NAT (Network Address Translation) gateway is used to connect to the Internet.

Most of the time, the NAT device is also the router that gives out the private IP addresses to all the computers on the local network.

Officially, there are three private IP address ranges that have been defined by the IANA in RFC 1918:

IP address range	Number of Addresses	Class
10.0.0.0 – 10.255.255.255	16,777,216	Class A
172.16.0.0 – 172.31.255.25	1,048,576	Class B
192.168.0.0 – 192.168.255.255	65,536	Class C

Any private network in the world is using one of these three IP address ranges for their addressing scheme. The class is determined by the number of usable addresses in that range. Class A has well over 16 million usable addresses and is only needed by extremely large organizations that have hundreds of interconnected networks.

The reason why most routers come setup with a Class C IP address is because it can still handle over 65,000 IP addresses, enough for just about any home or small business.

The first usable address in the Class C network is 192.168.0.1, usually what the router is set to. Note that if you like, you could change the default IP address to either a Class B or Class A network IP and it would still work fine.

There is actually no other difference between the different private IP ranges besides the available addresses.

Note that there are other private IP address ranges, such as 1.0.0.0/8 and 2.0.0.0/8, but they are not being used. The other private IP address you may have seen is 169.254/16. These are called link-local addresses and are only used when there is no DHCP server to assign IP addresses.

The devices will automatically assign an IP address to themselves in the range 169.254.0.0 to 169.254.255.255. This ensures that the devices can still communicate with other another even without a DHCP server or without having to manually assign IP addresses.

Anyway, so hopefully that explains a little bit about why routers have addresses like 192.168.0.1 or 10.0.1.1, etc. I’m sure my explanation was not perfect, so if I made any incorrect statement, please feel free to post a comment! Enjoy!