IPv4

IPv4 Tutorial

Internet Protocol version 4 (IPv4) is the fourth version in the development of the Internet Protocol (IP) and the first version of the protocol to be widely deployed. IPv4 is described in IETF publication RFC 791 (September 1981), replacing an earlier definition (RFC 760, January 1980).

This tutorial will help you in understanding IPv4 and associated terminologies along with appropriate references and examples.

IPv4 - Overview

This era is said to be the era of computers. Computers have significantly changed lives and the way we used to live. A computing device when connected to other computing device(s) enables us to share data and information at lightning fast speed.

What is Network?

A Network in the world of computers is said to be a collection of interconnected hosts, via some shared media which can be wired or wireless. A computer network enables its hosts to share and exchange data and information over the media. Network can be a Local Area Network spanned across an office or Metro Area Network spanned across a city or Wide Area Network which can be spanned across cities and provinces.

Computer network can be as simple as two PCs connected together via a single copper cable or it can be grown up to the complexity where every computer in this world is connected to every other, the Internet. A network then includes more and more components to reach its ultimate goal of data exchange. Below is a brief description of the components involved in computer network:

• Hosts - Hosts are said to be situated at ultimate end of the network, i.e. a host is a source of information and another host will be the destination. Information flows end to end between hosts. A host can be a user’s PC, an internet Server, a database server etc.
• Media - If wired, then it can be copper cable, fiber optic cable, coaxial cable or if wireless, it can be free-to-air radio frequency or some special wireless band. Wireless frequencies can be used to interconnect remote sites too.
• Hub - A hub is a multiport repeater and it is used to connect hosts in a LAN segment. Because of low throughputs hubs are now rarely used. Hub works on Layer-1 (Physical Layer) of OSI Model.
• Switch - A Switch is a multiport bridge and is used to connect hosts in a LAN segment. Switches are much faster than Hubs and operate on wire speed. Switch works on Layer-2 (Data Link Layer) but Layer-3 (Network Layer) switches are also available.
• Router - A router is Layer-3 (Network Layer) device which makes routing decisions for the data/information sent for some remote destination. Routers make the core of any interconnected network and the Internet.
• Gateways - A software or combination of software and hardware putting together works for exchanging data among networks which are using different protocols for sharing data.
• Firewall - Software or combination of software and hardware, used to protect users’ data from unintended recipients on the network/internet.

All components in a network ultimately serve the hosts.

Host Addressing

Communication between hosts can happen only if they can identify each other on the network. In a single collision domain (where every packet sent on the segment by one host is heard by every other host) hosts can communicate directly via MAC address.

MAC address is a factory coded 48-bits hardware address which can also uniquely identify a host in the world. But if a host wants to communicate with a remote host, i.e. not in the same segment or logically not connected, then some means of addressing is required to identify the remote host uniquely. A logical address is given to all hosts connected to Internet and this logical address is calledInternet Protocol Address.

IPv4 - OSI Model

International Standard Organization has a well-defined Model for Communication Systems known as Open System Interconnection, or OSI Model. This layered model is a conceptualized view of how one system should communicate with the other, using various protocols defined in each layer. Further, each layer is designated to a well-defined part of communication system. For example, the Physical layer defines all the components of physical nature, i.e. wires, frequencies, pulse codes, voltage transmission etc. of a communication system.

OSI Model has following seven layers:

• Application Layer (Layer-7): This is where the user application sits who needs to transfer data between or among hosts. For example: HTTP, file transfer application (FTP) and electronic mail etc.
• Presentation Layer (Layer-6): This layer helps to understand data representation in one form on a host to other host in their native representation. Data from the sender is converted to on-the-wire data (general standard format) and at the receiver’s end it is converted to the native representation of the receiver.
• Session Layer (Layer-5): This layer provides session management capabilities between hosts. For example if some host needs a password verification for access and if credentials are provided then for that session password verification does not happen again. This layer can assist in synchronization, dialog control and critical operation management (e.g., an online bank transaction).
• Transport Layer (Layer-4): This layer provides end to end data delivery between/among hosts. This layer takes data from above layer and breaks it into smaller units called Segments and then gives it to Network layer for transmission.
• Network Layer (Layer-3): This layer helps to uniquely identify hosts beyond the subnets and defines the path which the packets will follow or be routed to reach the destination.
• Data Link Layer (Layer-2): This layer takes the raw transmission data (signal, pulses etc.) from Physical Layer and makes Data Frames and sends that to upper layer and vice versa. This layer also checks any transmission errors and sort it out accordingly.
• Physical Layer (Layer-1): This layer deals with hardware technology and actual communication mechanism like signaling, voltage, cable type and length etc.

Network Layer

The network layer is responsible for carrying data from one host to another. It provides means to allocate logical addresses to hosts and identify them uniquely using the same. Network layer takes data units from Transport Layer and cuts them in to smaller unit called Data Packet.

Network layer defines the data path, the packets should follow to reach the destination. Routers work on this layer and provides mechanism to route data to its destination.

IPv4 - TCP/IP Model

Majority of the internet uses a protocol suite called the Internet Protocol Suite also known as TCP/IP protocol suite. This suite is a combination of protocols which encompasses a number of different protocols for different purpose and need. Because the two major protocols in this suites are TCP (Transmission Control Protocol) and IP (Internet Protocol), this is commonly termed as TCP/IP Protocol suite. This protocol suite has its own reference model which it follows over the internet. In contrast with OSI model, this model of protocols contains less layers.

[ Comparative depiction of OSI and TCP/IP Reference Models ]

This model is indifferent to the actual hardware implementation, i.e. Physical layer of OSI Model. This is why this model can be implemented on almost all underlying technologies. Transport and Internet layers correspond to the same peer layers. All three top layers of OSI Model are compressed together in single Application layer of TCP/IP Model.

Internet Protocol Version 4 (IPv4)

Internet Protocol is one of the major protocol in TCP/IP protocols suite. This protocol works at Network layer of OSI model and at Internet layer of TCP/IP model. Thus this protocol has the responsibility of identification of hosts based upon their logical addresses and to route data between/among them over the underlying network.

IP provides a mechanism to uniquely identify host by IP addressing scheme. IP uses best effort delivery, i.e. it does not guarantee that packets would be delivered to destined host but it will do its best to reach the destination. Internet Protocol version 4 uses 32-bit logical address.

IPv4 - Packet Structure 

Internet Protocol being a layer-3 protocol (OSI) takes data Segments from layer-4 (Transport) and divides it into what’s called packet. IP packet encapsulates data unit received from above layer and adds its own header information.

The encapsulated data is referred to as IP Payload. IP header contains all the necessary information to deliver the packet at the other end.

IP header includes many relevant information including Version Number, which, in this context, is 4. Other details are as follows:

• Version: Version no. of Internet Protocol used (e.g. IPv4)
• IHL: Internet Header Length, Length of entire IP header
• DSCP: Differentiated Services Code Point, This is Type of Service.
• ECN: Explicit Congestion Notification, carries information about the congestion seen in the route.
• Total Length: Length of entire IP Packet (including IP header and IP Payload)
• Identification: If IP packet is fragmented during the transmission, all the fragments contain same identification no. to identify original IP packet they belong to.
• Flags: As required by the network resources, if IP Packet is too large to handle these ‘flags’ tell that if they can be fragmented or not. In this 3-bit flag, the MSB is always set to ‘0’.
• Fragment Offset: This offset tells the exact position of the fragment in the original IP Packet.
• Time to Live: To avoid looping in the network, every packet is sent with some TTL value set, which tells the network how many routers (hops) this packet can cross. At each hop, its value is decremented by one and when the value reaches zero, the packet is discarded.
• Protocol: Tells the Network layer at the destination host, to which Protocol this packet belongs to, i.e. the next level Protocol. For example protocol number of ICMP is 1, TCP is 6 and UDP is 17.
• Header Checksum: This field is used to keep checksum value of entire header which is then used to check if the packet is received error-free.
• Source Address: 32-bit address of the Sender (or source) of the packet.
• Destination Address: 32-bit address of the Receiver (or destination) of the packet.
• Options: This is optional field, which is used if the value of IHL is greater than 5. These options may contain values for options such as Security, Record Route, Time Stamp etc.

IPv4 - Addressing

IPv4 supports three different type of addressing modes:

Unicast Addressing Mode:

In this mode, data is sent only to one destined host. The Destination Address field contains 32- bit IP address of the destination host. Here client sends data to the targeted server:

Broadcast Addressing Mode:

In this mode the packet is addressed to all hosts in a network segment. The Destination Address field contains special broadcast address i.e. 255.255.255.255. When a host sees this packet on the network, it is bound to process it. Here client sends packet, which is entertained by all the Servers:

Multicast Addressing Mode:

This mode is a mix of previous two modes, i.e. the packet sent is neither destined to a single host nor all the host on the segment. In this packet, the Destination Address contains special address which starts with 224.x.x.x and can be entertained by more than one host.

Here a server sends packets which are entertained by more than one Servers. Every network has one IP address reserved for network number which represents the network and one IP address reserved for Broadcast Address, which represents all the host in that network.

Hierarchical Addressing Scheme

IPv4 uses hierarchical addressing scheme. An IP address which is 32-bits in length, is divided into two or three parts as depicted:

A single IP address can contain information about the network and its sub-network and ultimately the host. This scheme enables IP Address to be hierarchical where a network can have many sub-networks which in turn can have many hosts.

Subnet Mask

The 32-bit IP address contains information about the host and its network. It is very necessary to distinguish the both. For this, routers use Subnet Mask, which is as long as the size of the network address in the IP address. Subnet Mask is also 32 bits long. If the IP address in binary is ANDed with its Subnet Mask, the result yields the Network address. For example, say the IP Address 192.168.1.152 and the Subnet Mask is 255.255.255.0 then

This way Subnet Mast helps extract Network ID and Host from an IP Address. It can be identified now that 192.168.1.0 is the Network number and 192.168.1.152 is the host on that network.

Binary Representation

The positional value method is the simplest form of converting binary from decimal value. IP address is 32 bit value which is divided into 4 octets. A binary octet contains 8 bits and the value of each bit can be determined by the position of bit value '1' in the octet.

Positional value of bits is determined by 2 raised to power (position – 1), that is the value of a bit 1 at position 6 is 26-1 that is 25 that is 32. The total value of the octet is determined by adding up the positional value of bits. The value of 11000000 is 128+64 = 192. Some Examples are shown in the table below:

IPv4 - Address Classes

Internet Protocol hierarchy contains several classes of IP Addresses to be used efficiently in various situation as per the requirement of hosts per network. Broadly, IPv4 Addressing system is divided into 5 classes of IP Addresses. All the 5 classes are identified by the first octet of IP Address.

Internet Corporation for Assigned Names and Numbers - responsible for assigning IP addresses.

The first octet referred here is the left most of all. The octets numbered as follows depicting dotted decimal notation of IP Address:

Number of networks and number of hosts per class can be derived by this formula:

When calculating hosts IP addresses, 2 IP addresses are decreased because they cannot be assigned to hosts i.e. the first IP of a network is network number and the last IP is reserved for Broadcast IP.

Class A Address

The first bit of the first octet is always set to 0 (zero). Thus the first octet ranges from 1 – 127, i.e.

Class A addresses only include IP starting from 1.x.x.x to 126.x.x.x only. The IP range 127.x.x.x is reserved for loopback IP addresses.

The default subnet mask for Class A IP address is 255.0.0.0 which implies that Class A addressing can have 126 networks (2⁷-2) and 16777214 hosts (2²⁴-2).

Class A IP address format thus, is 0NNNNNNN.HHHHHHHH.HHHHHHHH.HHHHHHHH

Class B Address

An IP address which belongs to class B has the first two bits in the first octet set to 10, i.e.

Class B IP Addresses range from 128.0.x.x to 191.255.x.x. The default subnet mask for Class B is 255.255.x.x.

Class B has 16384 (2¹⁴) Network addresses and 65534 (2¹⁶-2) Host addresses.

Class B IP address format is, 10NNNNNN.NNNNNNNN.HHHHHHHH.HHHHHHHH

Class C Address

The first octet of Class C IP address has its first 3 bits set to 110, that is

Class C IP addresses range from 192.0.0.x to 192.255.255.x. The default subnet mask for Class B is 255.255.255.x.

Class C gives 2097152 (2²¹) Network addresses and 254 (2⁸-2) Host addresses.

Class C IP address format is 110NNNNN.NNNNNNNN.NNNNNNNN.HHHHHHHH

Class D Address

Very first four bits of the first octet in Class D IP addresses are set to 1110, giving a range of

Class D has IP address rage from 224.0.0.0 to 239.255.255.255. Class D is reserved for Multicasting. In multicasting data is not destined for a particular host, that's why there is no need to extract host address from the IP address, and Class D does not have any subnet mask.

Class E Address

This IP Class is reserved for experimental purposes only like for R&D or Study. IP addresses in this class ranges from 240.0.0.0 to 255.255.255.254. Like Class D, this class too is not equipped with any subnet mask.

IPv4 - Subnetting (CIDR)

Each IP class is equipped with its own default subnet mask which bounds that IP class to have prefixed number of Networks and prefixed number of Hosts per network. Classful IP addressing does not provide any flexibility of having less number of Hosts per Network or more Networks per IP Class.

CIDR or Classless Inter Domain Routing provides the flexibility of borrowing bits of Host part of the IP address and using them as Network in Network, called Subnet. By using subnetting, one single Class A IP addresses can be used to have smaller sub-networks which provides better network management capabilities.

Class A Subnets

In Class A, only the first octet is used as Network identifier and rest of three octets are used to be assigned to Hosts (i.e. 16777214 Hosts per Network). To make more subnet in Class A, bits from Host part are borrowed and the subnet mask is changed accordingly.

For example, if one MSB (Most Significant Bit) is borrowed from host bits of second octet and added to Network address, it creates two Subnets (2¹=2) with (2²³-2) 8388606 Hosts per Subnet.

The Subnet mask is changed accordingly to reflect subnetting. Given below is a list of all possible combination of Class A subnets:

In case of subnetting too, the very first and last IP address of every subnet is used for Subnet Number and Subnet Broadcast IP address respectively. Because these two IP addresses cannot be assigned to hosts, Sub-netting cannot be implemented by using more than 30 bits as Network Bits which provides less than two hosts per subnet.

Class B Subnets

By Default, using Classful Networking, 14 bits are used as Network bits providing (2¹⁴) 16384 Networks and (2¹⁶-1) 65534 Hosts. Class B IP Addresses can be subnetted the same way as Class A addresses, by borrowing bits from Host bits. Below is given all possible combination of Class B subnetting:

Class C Subnets

Class C IP addresses normally assigned to a very small size network because it only can have 254 hosts in a network. Given below is a list of all possible combination of subnetted Class B IP address:

IPv4 - Variable Length Subnet Masking (VLSM)

Internet Service Providers may face a situation where they need to allocate IP subnets of different sizes as per the requirement of customer. One customer may ask Class C subnet of 3 IP addresses and another may ask for 10 IPs. For an ISP, it is not feasible to divide the IP addresses into fixed size subnets, rather he may want to subnet the subnets in such a way which results in minimum wastage of IP addresses.

For example, an administrator have 192.168.1.0/24 network. The suffix /24 (pronounced as "slash 24") tells the number of bits used for network address. He is having three different departments with different number of hosts. Sales department has 100 computers, Purchase department has 50 computers, Accounts has 25 computers and Management has 5 computers. In CIDR, the subnets are of fixed size. Using the same methodology the administrator cannot fulfill all the requirements of the network.

The following procedure shows how VLSM can be used in order to allocate department-wise IP addresses as mentioned in the example.

Step - 1

Make a list of Subnets possible.

Step - 2

Sort the requirements of IPs in descending order (Highest to Lowest).

• Sales 100
• Purchase 50
• Accounts 25
• Management 5

Step - 3

Allocate the highest range of IPs to the highest requirement, so let's assign 192.168.1.0 /25 (255.255.255.128) to Sales department. This IP subnet with Network number 192.168.1.0 has 126 valid Host IP addresses which satisfy the requirement of Sales Department. The subnet Mask used for this subnet has 10000000 as the last octet.

Step - 4

Allocate the next highest range, so let's assign 192.168.1.128 /26 (255.255.255.192) to Purchase department. This IP subnet with Network number 192.168.1.128 has 62 valid Host IP Addresses which can be easily assigned to all Purchase department's PCs. The subnet mask used has 11000000 in the last octet.

Step - 5

Allocate the next highest range, i.e. Accounts. The requirement of 25 IPs can be fulfilled with 192.168.1.192 /27 (255.255.255.224) IP subnet, which contains 30 valid host IPs. The network number of Accounts department will be 192.168.1.192. The last octet of subnet mask is 11100000.

Step - 6

Allocate next highest range to Management. The Management department contains only 5 computers. The subnet 192.168.1.224 /29 with Mask 255.255.255.248 has exactly 6 valid host IP addresses. So this can be assigned to Management. The last octet of subnet mask will contain 11111000.

By using VLSM, the administrator can subnet the IP subnet such a way that least number of IP addresses are wasted. Even after assigning IPs to every department, the administrator, in this example, still left with plenty of IP addresses which was not possible if he has used CIDR.

IPv4 - Reserved Addresses

There are few Reserved IPv4 address spaces which cannot be used on the internet. These addresses serve special purpose and cannot be routed outside Local Area Network.

Private IP Addresses

Every class of IP, (A, B & C) has some addresses reserved as Private IP addresses. These IPs can be used within a network, campus, company and are private to it. These addresses cannot be routed on Internet so packets containing these private addresses are dropped by the Routers.

In order to communicate with outside world, Internet, these IP addresses must have to be translated to some public IP addresses using NAT process or Web Proxy server can be used.

The sole purpose to create separate range of private addresses is to control assignment of already-limited IPv4 address pool. By using private address range within LAN, the requirement of IPv4 addresses has globally decreased significantly. It has also helped delaying the IPv4 address exhaustion.

IP class, while using private address range, can be chosen as per the size and requirement of the organization. Larger organization may choose class A private IP address range where smaller may opt for class C. These IP addresses can be further sub-netted be assigned to departments within an organization.

Loopback IP Addresses

The IP address range 127.0.0.0 – 127.255.255.255 is reserved for loopback i.e. a Host’s self-address. Also known as localhost address. This loopback IP address is managed entirely by and within the operating system. Using loopback addresses, enable the Server and Client processes on a single system to communicate with each other. When a process creates a packet with destination address as loopback address, the operating system loops it back to itself without having any interference of NIC.

Data sent on loopback is forward by the operating system to a virtual network interface within operating system. This address is mostly used for testing purposes like client-server architecture on a single machine. Other than that, if a host machine can successfully ping 127.0.0.1 or any IP from loopback range, implies that the TCP/IP software stack on the machine is successfully loaded and working.

Link-local Addresses

In case of the Host is not able to acquire an IP address from DHCP server and it has not been assigned any IP address manually, the host can assign itself an IP address from a range of reserved Link-local addresses. Link local address range is 169.254.0.0 - 169.254.255.255.

Assume a network segment where all systems are configured to acquire IP addresses from a DHCP server connected to the same network segment. If the DHCP server is not available, no host on the segment will be able to communicate to any other. Windows (98 or later), and Mac OS (8.0 or later) support this functionality of self-configuration of Link-local IP address. In absence of DHCP server, every host machine randomly chooses an IP address from the above mentioned range and then checks to ascertain by means of ARP, if some other host also has not configured himself with the same IP address. Once all hosts are using link local addresses of same range, they can communicate to each other.

These IP addresses cannot help system to communicate when they do not belong to the same physical or logical segment. These IPs are also not routable.

IPv4 - Example

This section tells how actual communication happens on the Network using Internet Protocol version 4.

Packet flow in network

All the hosts in IPv4 environment are assigned unique logical IP addresses. When a host wants to send some data to another host on the network, it needs the physical (MAC) address of the destination host. To get the MAC address, the host broadcasts ARP message and asks to give the MAC address whoever is the owner of destination IP address. All the host on that segment receives ARP packet but only the host which has its IP matching with the one in ARP message, replies with its MAC address. Once the sender receives the MAC address of receiving station, data is sent on the physical media.

In case, the IP does not belong to the local subnet. The data is sent to the destination by means of Gateway of the subnet. To understand the packet flow we must first understand following components:

• MAC Address: Media Access Control Address is 48-bit factory hard coded physical address of network device which can uniquely be identified. This address is assigned by device manufacturers.
• Address Resolution Protocol: Address Resolution Protocol is used to acquire the MAC address of a host whose IP address is known. ARP is a Broadcast packet which is received by all the host in the network segment. But only the host whose IP is mentioned in ARP responds to it providing its MAC address.
• Proxy Server: To access Internet, network uses Proxy Server which has a public IP assigned. All PCs request Proxy Server for a Server on Internet, Proxy Server on behalf of PC sends the request to server and when it receives response from the Server, the Proxy Server forwards it to the client PC. This is a way to control Internet access in computer networks and it helps to implement web based policies.
• Dynamic Host Control Protocol: DHCP is a service by which a host is assigned IP address from a pre-defined address pool. DHCP server also provides necessary information such as Gateway IP, DNS Server Address, lease assigned with the IP etc. By using DHCP services network administrator can manage assignment of IP addresses at ease.
• Domain Name System: This is very likely that a user does not know the IP address of a remote Server he wants to connect to. But he knows the name assigned to it for example, tutorialpoints.com. When the user types in the name of remote server he wants to connect to the localhost behind the screens sends a DNS query. Domain Name System is a method to acquire the IP address of the host whose Domain Name is known.
• Network Address Translation: Almost all PCs in a computer network are assigned private IP addresses which are not routable on Internet. As soon as a router receives an IP packet with private IP address it drops it. In order to access Servers on public private address, computer networks use an address translation service, which translates between public and private addresses, called Network Address Translation. When a PC sends an IP packet out of a private network, NAT changes the private IP address with public IP address and vice versa.

We can now describe the packet flow. Assume that a user wants to access www.only4programmers.blogspot.com from her personal computer. She is having internet connection from her ISP. The following steps will be taken by the system to help her reach destination website.

Step: 1 – Acquiring an IP Address (DHCP)

When user’s PC boots up, it searches for a DHCP server to acquire an IP address. For the same, PC sends a DHCPDISCOVER broadcast which is received by one or more DHCP servers on the subnet and they all respond with DHCPOFFER which includes all the necessary details like IP, subnet, Gateway, DNS etc. PC sends DHCPREQUEST packet in order to request the offered IP address. Finally, DHCP sends DHCPACK packet to tell PC that it can keep the IP for some given amount of time aka IP lease.

Alternatively a PC can be assigned an IP address manually without taking any help from DHCP Server. When a PC is well configured with IP address details, it can now speak to other computers all over the IP enabled network.

Step: 2 – DNS query

When a user opens a web browser and types www.tutorialpoints.com which is a domain name and a PC does not understand how to communicate with the server using domain names. PC sends a DNS query out on the network in order to obtain the IP address pertaining to the domain name. The pre-configured DNS server responds the query with IP address of the domain name specified.

Step: 3 – ARP request

The PC finds that the destination IP address does not belong to his own IP address range and it has to forward the request to the Gateway. Gateway in this scenario can be a router or a Proxy Server. Though Gateway’s IP address is known to the client machine but computers do not exchange data on IP addresses rather they need machine’s hardware address which is Layer-2 factory coded MAC address. To obtain the MAC address of the Gateway the client PC broadcasts an ARP request saying "Who owns this IP address?" The Gateway in response to the ARP query sends it MAC address. Upon receiving MAC address PC sends the packets to Gateway.

An IP packet has both source and destination addresses and this connects host with a remote host logically. Whereas MAC addresses helps systems on a single network segment to transfer actual data. This is important that source and destination MAC addresses change as they travel across the Internet (segment by segment) but source and destination IP address never changes.

IPv4 - Summary

The Internet Protocol version 4 was designed to be allocated to approx. 4.3 billion addresses. At the beginning of Internet this was considered a much wider address space for which there was nothing to worry about.

The sudden growth in Internet users and its wide spread use has exponentially increase the number of devices which needs real and unique IP to be able to communicate. Gradually, an IP is required by almost every digital equipment which were made to ease human life, such as Mobile Phones, Cars and other electronic devices. The number of devices (other than computers/routers) expanded the demand for extra IP addresses, which were not considered earlier.

Allocation of IPv4 is globally managed by Internet Assigned Numbers Authority (IANA) under coordination with Internet Corporation for Assigned Names and Numbers (ICANN). IANA works closely with Regional Internet Registries, which in turns are responsible for efficiently distribute IP address in their territories. There are five such RIR exist. According to IANA reports, all the IPv4 address blocks have been allocated. To cope up with the situation, as an early steps the following practices were being done:

• Private IPs: Few blocks of IPs were declared for private use within a LAN so that the requirement for public IP addresses can be reduced.
• NAT: Network address translation is a mechanism by which multiple PCs/hosts with private IP addresses are enabled to access using one or few public IP addresses.
• Unused Public IPs were reclaimed by RIRs.

Internet Protocol v6 (IPv6)

IETF (Internet Engineering Task Force) has redesigned IP addresses and to mitigate the drawbacks of IPv4. The new IP address has version 6 and is 128-bit address, by which every single inch of the earth can be given millions of IP addresses.

Today majority of devices running on Internet are using IPv4 and it is not possible to shift them to IPv6 in coming days. There are mechanisms provided by IPv6, by which IPv4 and IPv6 can coexist unless the Internet entirely shifts to IPv6:

• Dual IP Stack
• Tunneling (6to4 and 4to6)
• NAT Protocol Translation.

Mobile Computing

Mobile Computing Tutorial

Mobile Computing is a technology that allows transmission of data, voice and video via a computer or any other wireless enabled device without having to be connected to a fixed physical link.

This tutorial will give your brief overview of Mobile Computing and then it will take you through what are current trends and where they will go in future along with their classifications and security issues involved.

Mobile Computing Brief Overview

Mobile Computing is a technology that allows transmission of data, voice and video via a computer or any other wireless enabled device without having to be connected to a fixed physical link. The main concept involves:

• Mobile communication
• Mobile hardware
• Mobile software

Mobile communication

The mobile communication in this case, refers to the infrastructure put in place to ensure that seamless and reliable communication goes on. These would include devices such as Protocols, Services, Bandwidth, and Portals necessary to facilitate and support of the stated services. The data format is also defined at this stage. This ensures that there is no collision with other existing systems which offer the same service.

Since the media is unguided/unbounded, the overlaying infrastructure is more of radio wave oriented. That is, the signals are carried over the air to intended devices that are capable of receiving and sending similar kinds of signals.

Mobile hardware

Mobile hardware includes mobile devices or device components that receive or access the service of mobility. They would range from Portable laptops, Smartphones, Tablet Pc's, Personal Digital Assistants.

These devices will have receptor medium that are capable of sensing and receiving signals. These devices are configured to operate in full- duplex, whereby they are capable of sending and receiving signals at the same time. They don't have to wait until one device has finished communicating for the other device to initiate communications.

Above mentioned devices use an existing and established network to operate on. In most cases, it would be a wireless network.

Mobile software

Mobile software is the actual program that run on the mobile hardware. It deals with the characteristics and requirements of mobile applications. This is the engine of that mobile device. In other terms, it is the operating system of that appliance. It's the essential component that makes the mobile device operate.

Since portability is the main factor, this type of computing ensures that users are not tied or pinned to a single physical location, but are able to operate from anywhere. It will incorporate all aspects of wireless communications.

This tutorial will look into the concept of mobile computing, current and future trends, advantages, applications, and major security concerns.

Mobile Computing Current Trends

In today's computing world, different technologies have come up. These have grown to support existing computer networks all over the world. With mobile computing, we find that the need to be confined within one physical location has been eradicated. We hear of terms such as tele commuting. This is being able to work from home or the field but at the same time accessing resources as if one is in the office.

The emergence of portable computers and laptops, personal digital Assistants (PDA), PC Tablets and Smartphones, has in turn made mobile computing very convenient. The portability of the devices ensures and enables user to access all services as if they were in the internal network of their company. For example, the use of Tablet Pc and Ipads. This new technology enables users to update documents, surf the internet, send and receive e-mail, stream live video files, take photographs and also support video and voice conferencing.

The constant and ever increasing demand for superior and robust smart devices has been as a catalyst for market share. Each manufacturer is trying to curve a niche of themselves in the market. These devices are invented and innovated to provide top of the class applications and services. With cellular phones, different manufacturers have come up with unique Smartphones that are capable of performing the same tasks as computers and at the same processing speed. The market share for different competitors is constantly being fought for. For example the manufacturers of Apple's Iphone OS, Google's Android' Microsoft Windows Mobile, Research In Motion's Blackberry OS, are constantly competing to offer better products with each release.

The need for better, portable, affordable, and robust has also made these vendors to constantly be innovative. Market figure and statistics show an ever rapidly growing need to purchase and use such devices for either professional or home use. Since technology is driven by market needs, it's in this light that services suited for a long term implementation are developed or innovated. This has also pushed other industry vendors to adopt services that will provide better service delivery. For example, cellular service providers are forced to improve and be innovative to capture more subscribers. This can be in terms of superior services such as high speed internet and data access, voice and video service etc. hence the adoption of different generations of networks like of 2G, 2.5G, 3G, 4G networks services.

The essence of mobile computing is to work from any location. The use of Ipads, Tablets, Smartphones, and notes books, have in turn pushed the demand for these devices. Modern day workers have such devices that enable them carry out their work from the confines or comfort of their present location. These devices are configured to access and store large amounts of vital data. Executive and top management can act of decisions based of ready information without going to the office. For example, sales reports and market forecasts can be accessed through this devices or meeting carried out via video or audio conferencing through the device. With such features being high in demand, manufacturers are always and constantly coming up with applications geared to supporting different service delivery in terms of mobile computing.

Mobile Computing Classification

Mobile computing is not limited to Mobile Phones only, but also there are various gadgets available in the market helping mobile computing. They are usually classified in the following categories:

Personal Digital Assistant (PDA)

The main purpose of this device was to act as an electronic organizer or day planner that is portable, easy to use and. capable of sharing information with your with a computer systems.

PDA was an extension of the PC, not a replacement. These systems were capable of sharing information with a computer system through a process or service known as synchronization. Where both devices will access each other to check for changes or updates in the individual devices. The use of infrared and Bluetooth connections enabled these devices to always be synchronized.

With PDA devices, a user could; browsers the internet, listen to audio clips, watch video clips, edit and modify office documents, and many more services. They had a stylus and a touch sensitive screen for input and output purposes.

Smartphones

This kind of phone combines the features of a PDA with that of a mobile phone or camera phone. It has a superior edge over other kinds of mobile phones.

Smartphone have the capability to run multiple programs concurrently. These phones include high-resolution touch enabled screens, web browsers that can access and properly display standard web pages rather than just mobile-optimized sites, and high-speed data access via Wi-Fi and high speed cellular broadband.

The most common mobile operating systems (OS) used by modern Smartphones include Google's Android, Apple's iOS, Nokia's Symbian, RIM's BlackBerry OS, Samsung's Bada, Microsoft's Windows Phone, and embedded Linux distributions such as Maemo and MeeGo. Such operating systems can be installed on many different phone models, and typically each device can receive multiple OS software updates over its lifetime.

Tablet PC and I-Pads

This mobile device is larger than a mobile phone or a personal Digital Assistant and integrates into a touch screen and operated using touch sensitive motions on the screen. They are often controlled by a pen or touch of a finger. They are usually in slate form and are light in weight. Examples would include; Ipads, Galaxy Tabs, Blackberry Playbooks etc.

They offer the same functionality as portable computers. They support mobile computing to a far superior way and have enormous processing horse power. User can edit and modify document files, access high speed internet, stream video and audio data, receive and send e-mails, perform lectures and presentations among very many other functions. They have excellent screen resolution and clarity.

Mobile Computing Major Advantages

Mobile computing has changed the complete landscape of human being life. Following are the clear advantages of Mobile Computing:

Location flexibility

This has enabled user to work from anywhere as long as there is a connection established. A user can work without being in a fixed position. Their mobility ensures that they are able to carry out numerous tasks at the same time perform their stated jobs.

Saves Time

The time consumed or wasted by travelling from different locations or to the office and back, have been slashed. One can now access all the important documents and files over a secure channel or portal and work as if they were on their computer. It has enhanced telecommuting in many companies. This also reduces unnecessary expenses that might be incurred.

Enhanced Productivity

Productive nature has been boosted by the fact that a worker can simply work efficiently and effectively from which ever location they see comfortable and suitable. Users are able to work with comfortable environments.

Ease of research

Research has been made easier, since users will go to the field and search for facts and feed them back to the system. It has also made it easier for field officer and researchers to collect and feed data from wherever they without making unnecessary trip to and from the office to the field.

Entertainment

Video and audio recordings can now be streamed on the go using mobile computing. It's easy to access a wide variety of movies, educational and informative material. With the improvement and availability of high speed data connections at considerable costs, one is able to get all the entertainment they want as they browser the internet for streamed data. One can be able to watch news, movies, and documentaries among other entertainment offers over the internet. This was not such before mobile computing dawned on the computing world.

Streamlining of Business Processes

Business processes are now easily available through secured connections. Basing on the factor of security, adequate measures have been put in place to ensure authentication and authorization of the user accessing those services.

Some business functions can be run over secure links and also the sharing of information between business partners. Also it's worth noting that lengthy travelling has been reduced, since there is the use of voice and video conferencing.

Meetings, seminars and other informative services can be conducted using the video and voice conferencing. This cuts down on travel time and expenditure.

Mobile Computing Security Issues

Mobile computing has its fair share of security concerns as any other technology. Due to their nomadic nature, it's not easy to monitor the proper usage. User might have different intentions on how to utilize this privilege. Improper and unethical practices such as hacking, industrial espionage, pirating, online fraud and malicious destruction are some but few of the problems experienced by mobile computing.

Another big problem plaguing mobile computing is credential verification. It's not possible to that the person using that person is the true barrier. Other users share username and passwords. This is also a major threat to security. This being a very sensitive issue, most companies are very reluctant to implement mobile computing to the dangers of misrepresentation.

The problem of identity theft is very difficult to contain or eradicate. Issues with unauthorized access to data and information by hackers, is also a plaguing problem. They gain access to steal vital data from companies. This problem has been a major headache and hindrance in rolling out mobile computing services.

No company wants to lay open their secrets to hacker and other intruders, who will in terms sell them to their competitors. It's also important to take the necessary precautions to minimize these threats from taking place. Some of those measures include:

• Hiring qualified personnel.
• Installing Security Hardware and Software.
• Educating the Users on proper Mobile computing ethics.
• Auditing and developing sound, effective policies to govern mobile computing.
• Enforcing proper access rights and permissions.

These are just but a few ways to help deter possible threats to any company planning to offer mobile computing. Since information is vital, all possible measures should be evaluated and implemented for safeguard purposes.

In the absence of such measures, it's possible for exploits and other unknown threats to infiltrate and cause irrefutable harm that would cost a huge of damage. These maybe in terms of reputation or financial penalties. In such cases, it's very easy to be misused in different unethical practices.

The other issue would be online security. If this factor isn't properly worked on, it might be an avenue for constant threat. Theft and Espionage can be also another fact limiting its full utilization. Various threats to security still exist in implementing this kind of technology.

Mobile Computing Future Trends

This chapter will list down current and future mobile technologies starting from 3G technologies which is the hotest mobile technology available in the market.

3G

3G or 3rd generation mobile telecommunications is a generation of standards for mobile phones and mobile telecommunication services fulfilling the International Mobile Telecommunications-2000 (IMT-2000) specifications by the International Telecommunication Union. Application services include wide-area wireless voice telephone, mobile Internet access, video calls and mobile TV, all in a mobile environment.

GPS (Global Positioning System)

The Global Positioning System (GPS) is a space-based satellite navigation system that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites. The GPS program provides critical capabilities to military, civil and commercial users around the world. In addition, GPS is the backbone for modernizing the global air traffic system, weather, location services.

Long Term Evolution (LTE)

LTE is a standard for wireless communication of high-speed data for mobile phones and data terminals. It is based on the GSM/EDGE and UMTS/HSPA network technologies, increasing the capacity and speed using new modulation techniques. Its related with the implementation of forth Generation (4G) technology.

WiMax

WiMAX (Worldwide Interoperability for Microwave Access) is a wireless communications standard designed to provide 30 to 40 megabit-per-second data rates, with the latest update providing up to 1 Gbit/s for fixed stations. It is a part of a fourth generation, or 4G, of wireless-communication technology. WiMax far surpasses the 30-metre wireless range of a conventional Wi-Fi local area network (LAN), offering a metropolitan area network with a signal radius of about 50 km.WiMax offers data-transfer rates that can be superior to conventional cable-modem and DSL connections, however, the bandwidth must be shared among multiple users and thus yields lower speeds in practice.

Near Field Communication

Near field communication (NFC) is a set of standards for Smartphones and similar devices to establish radio communication with each other by touching them together or bringing them into close proximity, usually no more than a few centimeters. Present and anticipated applications include contactless transactions, data exchange, and simplified setup of more complex communications such as Wi-Fi. Communication is also possible between an NFC device and an unpowered NFC chip, called a "tag".