05 January 2014

IP Address

IP is the network layer protocol that has properties and its role as a connectionless, ie, each data packet transmitted at some time going through these independently. IP packet or datagram going through a route determined by each router that is passed by the datagram. This allows the entire datagram to the destination location in a different order for different route anyway.

Unreliable or unreliability is the IP protocol does not guarantee datagram sent surely get to the destination. He will only do a best effort delivery that is doing their best so that the packets sent to the destination.

IP is also designed to be able to pass through various communication media characteristics and different speeds. On an Ethernet network, the length of the datagram will be greater than the length of the datagram on the network using the public telephone network media, or the wireless network. This difference is solely to achieving a good throughput on each medium.

In general, the faster the data transfer capabilities in the media, the greater the maximum datagram length used. As a result of these differences, the IP datagram may be fragmented when switching from high speed to medium low speed eg 10 Mbps Ethernet LAN to a leased line using Point - to- Point Protocol at a speed of 64 kbps.

On the router / receiver hosts, datagram this fragment which happened to be put back together before it is forwarded to the next router, or to the transport layer at the destination host. This adds to the processing time on the routers and cause delay. Whole properties described in the above is due to the protocol efficiency is sacrificed as a consequence of the advantages of IP protocol.


IP Address

These advantages such as the ability to combine a variety of communications media of different characteristics, with the development of a flexible network, routing can be changed automatically if a route has failed, and so on. For example, to be able to dynamically change routing, routing mechanism selected is determined by the condition of the network and router network elements. In addition, the routing process should also be carried out for each datagram, not only at the beginning of the relationship. Let us consider the structure of the header of the IP protocol and its functions, respectively. Each protocol has extra bits beyond the information / data it carries.

In addition to information, Bit Bit also serves as a means of control. In terms of efficiency, the greater the number of extra bits, the smaller the efficiency of ongoing communication. Conversely the smaller the number of extra bits, the higher the efficiency of communication is running.

Here do trade- off between reliability and efficiency datagram. For example, in order to find the IP datagram purpose, additional information is required to be included in the header.


IP Address

IP addresses are categorized into two categories :

Private Adress : This is the address used on the private network, and are not visible on the Internet. They are often used by network address translators to connect to the global public Internet.
Public Addresses : This is the IANA (IANA) registered address is visible on the Internet.

IP version 6 addresses
The next generation of Internet Protocol, to replace IPv4, and to develop the ability of Internet addresses on the Internet, is the Internet Protocol Version 6 (IPv6). Large address size from 32-128 bits to 16 octets, with performance that easily, is considered good enough to use for the foreseeable future.

Static IP and Dynamic IP
When a computer is configured to use the same IP address every time in the setting, this is known as a static IP address. Conversely, in situations when the computer 's IP address is assigned automatically, known as a dynamic IP address.

IP Address can be made with Many diagnostic methods such as the following :


  • Dynamically assign an IP address via Dynamic Host Configuration Protocol (DHCP) : IP address assigned by the DHCP server is regarded as the IP address dynamically assigned. The DHCP server assigns an IP address from the IP address that has been assigned by DHCP or within the DHCP IP Address ranges.
  • Making the IP address manually : provide IP Address to the computer can be time consuming, and may result in duplicate IP addresses. IP addresses manually is usually given when not configured by the DHCP server on the network or to several computers that have a static IP address or to a specific computer for other purposes such as computer control (administrator) or other server (DNS), so they must have IP Address specific and are not included in the list of DHCP IP Address.
  • Assign an IP address automatically through Automatic Private IP Addressing (APIPA) : APIPA can be used as an alternative if there is no other way for the DHCP server assigns IP addresses dynamically. APIPA works well on smaller networks.

Special IP Address :

Some IP addresses are reserved for special purposes. IP addresses are reserved :


  1. Network segment address specified for zeros/0s : Setting this network as a subnet (local network).
  2. Network segment address specified for ones/1s : Setting this network and all associated subnets.
  3. 127 Network Address : Address reserved for Testing Feedback (loopback test).
  4. Origin of all zeros/0s address : This address is usually used in the routing table, and reference network, but no specific host on the network.
  5. Host address of all ones/1s (Host Address) : This is used as a broadcast address to all computers on a particular network.


Each IP packet carries the data is divided into several sections are:
Version is the version of the IP protocol used.
Length header contains the length of the IP packet header in 32 bit word count.
Type of Service provides quality service that may affect the handling of IP packets.
Of the total length is the length of the IP datagram Datagram total bytes in size.
Identification, Flags, Fragment Offset and contains data related packet fragmentation.
Time to Live contains the number of routers/hops through which the maximum IP packet (datagram). The maximum value of this field is 255. Each time an IP packet through a router, the contents of this field minus one. If the TTL has expired and the package still has not reached its destination, the packet is discarded and the last router will send ICMP time exceeded. This is done to prevent IP packets are in the network continuously.
Protocol contains a number that identifies the upper layer protocol user data content of the IP packet.
Header Checksum contains a checksum value is calculated from the total field of the IP packet header. Before sending the IP protocol first calculating the checksum of the IP packet header for later recalculated at the receiving end. If there is a difference, then this package is considered broken and discarded.
Source Address and Destination Address contents of each field is quite clear, the address of the sender and recipient addresses of the datagram. Each field consists of 32 bits, the corresponding length of the IP addresses that are used in the Internet. Destination address is the field that will be read by each router to determine where the IP packet will be forwarded to reach the destination address.

IP address is the address identification of the computer / host on the network. With the IP address of the data sent by the host / sending computer can be sent via the TCP / IP to get to the host / target computer.

Each computer / host has a unique IP address so that two computers / different hosts should not have the same IP address in one network.

IP address format
IP address expressed in binary structure consisting of 32 bits of the form.

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

example

11000000000010100001111000000010

So it is easy to read the IP address, then the 32 -bit number that is divided into 4 segments each containing 8 bits. The eight bits that can be called octet.

Furthermore, each octet translated into decimal numbers. For example :

11000000 = 192

00001010 = 10

00011110 = 30

00000010 = 2

The largest value of 8 bits is 11111111 or equal to 225. Thus, the total number of IP addresses is 225 x 225 x 225 x 225.

Structure of an IP address consists of two parts, namely the NetworkID and hostid. NetworkID show ID network address where the hosts are located, while the hostid is the part that shows the host is located. Simply put, NetworkID such as street names while the hostid is the house number on the street.

Grouping classes in IP ADDRESS
In order to facilitate the distribution of IP addresses are divided into different classes, as follows.

a) Class A
Class A IP address consists of 8 bits for the network ID and the remaining 24 bits are used for the host ID, so the IP address is used for class A network with a very large number of hosts. In the first bit is given a number from 0 to 127.

Characteristics of IP Class A

Format : 0NNNNNNN.HHHHHHHH.HHHHHHHH.HHHHHHHH
The first bit : 0
NetworkID : 8 bits
HostID : 24 bits
The first octet : 0-127
Total network : 126 ( for 0 and 127 are reserved )
IP Range : 1.x.x.x - 126.x.x.x
The number of IP addresses : 16,777,214

example :
The IP address 120.31.45.18 :

· NetworkID = 120
· HostID = 31.45.18

So, having a host with IP on 31.45.18 at network numbers 120

 b ) Class B
Class B IP address consists of 16 bits for the network ID and the remaining 16 bits are used for the host ID, so the class B IP address used to network the number of hosts is not too large. In the first 2 bits, given the number 10.

Characteristics of Class B IP

Format : 10NNNNNN. NNNNNNNN.HHHHHHHH.HHHHHHHH
The first bit : 10
NetworkID : 16 bits
HostID : 16 bits
The first octet : 128-191
Total network : 16,384
IP Range : 128.1.x.x - 191.255.x.x
The number of IP addresses : 65,534

example :
The IP address 150.70.60.56 :

· NetworkID = 150.70
· HostID = 60.56

Thus, the above IP has hosted the number 60.56 in 150.70 networks

c ) Class C
Class C IP address consists of 24 bits for the network ID and the remaining 8 bits are used for the host ID, so the class C IP address is used for small sized networks. Class C is usually used for Local Area Network or LAN. In the first 3 bits, given the number 110.

Characteristics of Class C IP

Format : 110NNNNN.NNNNNNNN. NNNNNNNN.HHHHHHHH
First Bit : 110
NetworkID : 24 bits
HostID : 8 bits
The first octet : 192-223
Total network : 2,097,152
IP Range : 192.0.0.x - 223.255.225.x
The number of IP addresses : 254

example :
The IP address 192.168.1.1 :

· NetworkID = 192.168.1
· HostID = 1

Thus, the above IP has hosted with the number 1 on the 192.168.1 network

Other IP addresses are Class D and E, but the IP class D and E are not used for normal IP allocation, but it is used for IP multicasting and experimental.

Table: Number of NetworkID and hostid

Class

Range

Number of network

Number of Network Hosts

A

1 s.d. 126

126

2.097.152

B

128 s.d. 191

126

65.534

C

192 s.d. 223

2.097.152

   254


Table: Range of IP addresses for each class

Class

Initial Address

End Address

A

XXX.0.0.1

XXX.255.255.255

B

XXX.XXX.0.1

XXX.XXX.255.255

C

XXX.XXX.XXX.1

XXX.XXX.XXX.255

subnet Mask
The value of the subnet mask is used to separate the network ID with the host ID. The subnet mask required by TCP / IP to determine whether the network in question is local or nonlocal network. For the nonlocal network means that the TCP / IP must transmit data packets through a router. Thus, it is necessary to filter the address mask and IP address of data packets in and out of the network.

Network ID and a host ID in an IP address are distinguished by the use of a subnet mask. Each subnet mask using the pattern number is a 32-bit groups of all one bits (1) that indicates the network ID and all zeros (0) indicate the host ID portion of the IP address.

For example, class B address: 170.203.93.5 binary numbers are:

10101010 11001011 01011101 00000101
The default subnet mask for a class B address is:
11111111 11111111 00000000 00000000
Can also be written in decimal notation:
255.255.0.0

Table: The subnet mask for the Internet address classes


Class

Bit Subnet

Subnet Mask

A

11111111 00000000 00000000 00000000

225.0.0.0

B

11111111 11111111 00000000 00000000

225.225.0.0

C

11111111 11111111 11111111 00000000

225.225.225.0

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