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IPV4 vs IPV6 | difference between IPV4 and IPV6

Both IPV4 and IPV6 are IP address schemes available to assign IP addresses to the computers connected to the network. We will see here difference between IPV4 and IPV6.

IP is a layer-3 protocol in OSI stack. Packets are routed with the help of destination address. The functions of IP are as follows:
• Connectionless best effort data delivery based on destination ip address.
• Fragmentation and re-assembly of datagrams to support links with different MTUs(Maximum Transmission Units).


IPV4 header

IPV4 has 32 bit IP address space. There are different classes Class A, Class B, Class C, Class D and Class E. For more refer our page on IP address. The figure depicts IPV4 header fields used in the IP protocol. IPV4 is defined in RFC 791. Table-1 below mentions all the fields of IPV4 header with functional description.

IPV4 header field Description
Version It signifies version of IPV4 or IPV6 in use
IHL(Header length) datagram length in 32 bit words
Type of Service specify how upper layers would like datagram to be handled.
Total Length (data + header) size in bytes before fragmentation
Identification helps in reassembly of fragments of datagram. Same ID has been assigned to all the fragments of a datagram
Flags(3bits) 2 lower bits are used, lowest one signify whether the packet can be fragmented or not, middle one specify whether the packet is the last one in the series of fragments of the packet
Fragment offset indicates offset position of data fragment from starting position of datagram
Time to Live counter which decrements to zero at the point of discarded datagram. This helps to prevent any misrouted packet.
Protocol Indicates whether higher layer is TCP (value 6) or UDP(value 17)
Header hecksum Requires for error detection at the destination host
Source address Address of sending node
Destination address Address of receiving node
Options Support various other options such as security etc.
Data Contains upper layer data information
Related link TCPIP packet format


IPV6 header

IPV6 has 128 bit IP address,which helps support one billion networks, hence extends the drawbacks of IPV4 system. The figure depicts IPV6 header fields used in the IP protocol. IPv6 is defined in RFC 2460. Table-2 below mentions all the fields of IPV6 header with functional description.

IPV6 header field Description
Version(4bit) contains 0110
Traffic Class(8 bit) equivalent to Type of Service field of IPV4,
used to classify IPv6 priorities
Flow label(20 bit) Used by source node to label sequence of packets for which it requests a special type of handling by IPv6 routers.
Payload length(16 bit) Length of payload in bytes
Next Header(8 bit) indicates type of header IPv6 follows such as TCP, UDP, ICMPv4 or ICMPv6
Hop Limit(8 bit) Decrements 1 by 1 after forwarding the packets by each nodes. When zero packets are discarded and error message is being returned This is equivalent to Time to Live field of IPv4 protocol header.
Source address(128 bit) Origin of IPv6 packet
Destination address(128 bit) destination of IPv6 packet

Both IPV4 and IPV6 coexist in a multiprotocol configuration. To do this task network access layer should support multiplexing of IPV4 and IPV6 packets. There are three methods of transition strategies from IPV4 to IPV6 protocol format. They are dual stack, tunneling and header translation. It is recommended to have both IPV4 and IPV6 protocol stacks in the device before migrating to the IPV6.


Basics of OSI and TCP-IP Layers
Networking tutorial
What is an IP address
What is MAC address

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