IPV6 vs IPV4
Internet protocol version 6 (IPV6) or IP V6 is a successor of internet protocol version 4 (IPV4). An internet protocol is used to deliver data and resource packets from host device to destination device. IPV4 was the first used internet protocol which was developed in 1981. This version had the addressing capacity of about 4 billion addresses. This number seemed adequate then when there wasn’t wide networking. Internet was at its early stage at that time. But gradually by the late 1980’s the greater use of internet dictated the need to conserve address space.
Even a classless internet model developed in early 1990’s to slow the growth of routing tables on routers across the Internet, and to help prevent the exhaustion of IPV4 could not conserve the address space. Then by 1996 a memorandum called RFC (request for comments) was published by Internet Engineering Task Force to specify the methods and the research that can be applied to the working of internet. These Series of RFC’s defined Internet Protocol Version 6. It was said to be the advanced version of IPV4 but for the communication amongst the nodes or devices of both these versions an intermediary gateway is required. They are treated as two distinct and separate networks and are mainly incompatible.
IPV4 is a type of protocol which is used to deliver packets or datagram’s from host device to the destination device across the network. The destination address is specified by the internet protocol. It is also called as internet layer protocol. IPV4 uses packet switching system for the delivery of data packets over a network. Packet switching uses a digital networking communication system that groups the data into smaller subgroups called packets with no consideration to the type, content and structure of the data. The main purpose behind the development of this version was the anticipated address exhaustion of the IPV4.
Every host on an internet protocol network has to be assigned a unique IP address so as to communicate with other hosts on the same network. The version 4 of the internet protocol initially carried sufficient address 232 to assign to each hosts but with the proliferation in the use of internet the routable addresses are becoming insufficient. Thus IPV6 came into being to give a distinct address to every host on IP network for the purpose of identification.
IPV6 has a large address capacity. It supports 128-bit i.e. 2128 addresses against the address space of IPV4 which is 32-bit. With IPV4 an existing network had to be renumbered for every new connectivity provider having different routing prefixes. This enhancement provides significant flexibility and choice to allocate addresses amongst the internet devices or services. This allows a better, more orderly and arranged allocation of addresses and well organized route aggregation.
Another benefit of IPV6 is the elimination of network address translation (NAT). At first, the network address information was altered in the packet headers while they were in the process of being sent so that the address space can be reused. IPV6 has helped to efficiently overcome this method of conserving address spaces.
IPV6 has many other features. It has simplified the way addresses are assigned to the host devices and the renumbering of network when changing internet connectivity providers. The subnet is the subdivision of an IP network so that all computers in an IP network belonging to a subnet can be addressed with a common and similar address. The subnet size of IPV6 has been standardized by fixing the size of the host identifier portion of an address to 64 bits i.e. the size of the subnet is 264 addresses.
Thus space utilization is lower in IPV6 but efficiency and routing management is twice as that of IPV4.
The characteristics of IPV6 also incorporate network security which consists of the policies used to avoid and examine any misuse or unauthorized access of computer network and the resources accessible from the network. It has also specified a new packet format which minimizes the processing of packet headers by the routers.
As mentioned earlier IPV6 is an advanced but incompatible form of IPV4. They are two different networks and it the devices need to access both networks it is done via tunneling of IPV6 on IPV4 and vice versa. However their incompatibility is only at the packet level. Most transport and application protocols require no tunneling to run over IPV6. Some of the application protocols that need change to operate over IPV6 are FTP and NTPV3.
The use of stateless address auto configuration (SLAAC) is another major feature of IPV6. With SLAAC all hosts on an IPV6 can configure themselves automatically to the routed network using Internet Control Message Protocol version 6 (ICMPv6). ICMPv6 is an integral component of IPV6 and performs several other functions such as error reporting, router discovery etc. all operating systems of IPV6 protocols provide link-local addresses to network devices even when routable addresses are also assigned. Thus they have more than one address. When a device or interface is first connected to a network the device or the host sends the link-local configuration request to the router.
If configuration is done properly the router sends an advertisement packet that contains configuration parameters. If configuration is not done properly, the network does it statically or by using Dynamic Host Configuration Protocol version 6 (DHCPv6).
Multicasting is also one of the advantages of IPV6. IPV6 does not need to define broadcast address because it does not transmit the packets traditionally with IP broadcast i.e. sending the packet to all hosts using the unique broadcast address. With IPV4 a packet containing resources and data can be sent to more than one destination in a single operation. This is base specification in IPV6. IPV4 also had this feature but it was optional though mostly used. Moreover IPV6 has also eliminated the need for certain protocols making its multicast different and improved from that of IPV4. With IPV6 it is possible to insert the 64 bit address prefix into the multicast address format thus providing each user with routable multicast groups for multicast applications, a feature not possible in IPV4.
The other significant improvement in IPV6 is the enhanced security of the protocol. An integral part of the IPV6 suite is the use of IPsec (internet protocol security). It is one of the most famous standard for securing IP communications by encrypting and checking the validity of all packets at the network layer. IPsec support is mandatory in IPv6; whereas in IPv4 it is discretionary. IPsec is better and more flexible than the other encryption standards because it functions at the network layer and secures both TCP and UDP-based protocols. However the use of IPsec has made IPV6 more complex.
Simplification of the process by the routers is also another attribute of IPV6. The process of packet forwarding has been made relatively easier and more efficient thereby broadening the end-to-end principle. Although the addressing capacity of IV6 is four times as that of IPV4, the packet header used in IPV6 is simpler than that in IPV4 with seldom used fields to separate options.
Secondly the process of fragmentation which means forming the packets smaller than the original size so that they pass through link with smaller (MTU) maximum transmission unit is not implemented. Rather the routers in IPV6 perform PMTU discovery or send the packets that are not larger than the size of default MTU.
The third element which simplifies the router functioning is the elimination of the computation of checksum. A checksum is a data computed from any random block of digital data to detect the errors that may have occurred during the storage or transmission of data. Rather using the checksum algorithm, IPV6 routers assures protection by link layer and higher layer error detection. Each time the header field’s change there is no need to compute checksum. Lastly the routers do not have to calculate the time a packet has spent in being transmitted through the network.
IPV6 is a mobile protocol; one that does not encounters the problem of triangular routing. In triangular routing a packet is first sent to a proxy system before being transmitted to the original destination. IPV6 does not face this problem. It supports the network mobility in a away which allows entire subnets to move to move to a new router connection point without renumbering.
IPV4 had limited options in the protocol header which had a standard size of 4O octets. In IPV6 additional options are created by adding extension headers after the IPV6 header. This mechanism provides support for further services. Without redesigning of the protocol it extends the services to provide quality of service (QOS) which means prioritizing different applications or users to assure a certain level of performance to the flow of data. Besides QOS the options are extended to provide better security and mobility.
Coexistence is another characteristic op IPV6. Using the technique of tunneling the IPV6 packets can coexist and route over the networks that are using IPV4. The IPV6 packets are inserted in IPV4 headers to pass through the network without any inconvenience. To make this happen, first the address are changed to IPV6 format form IPV4 by adding extra zeroes and the IPV6 packet is put within the header area of IPV4 packet ready to be transmitted in the network which uses IPV4 protocol.
At the end of transmission IPV6 router takes the packet out of the IPV4 header and routes it to its intended destination. Thus the IPV6 packets are encapsulated within IPV4 using IPv4 as a link layer for IPv6 and this is indicated by IP protocol number 41.
The packet of IPV6 has two parts, the packet header and the payload. The header part consists of a fixed size having the least functionality required for all packets and also contains extension features to provide additional services. The size of the header is 40 octets which is 320 bits. It contains information like the address of the source device and the destination device, the route classification options, hop counter and an option for extension headers if there are any.
Each extension points to the next feature in the chain of extensions. Extension headers carry options that are used for special handling of a packet in the network, e.g. for routing, fragmentation, and for security purposes using the IPsec framework. The last field points to the upper layer protocol which is in the packet’s payload part. The payload of a packet is the size of 64 KIB when it does not contain extension headers or it can be larger than this.
Thus IPV6 is a successful advancement in the field of protocols. Many products that are used in networks globally e.g. Cisco routers, windows XP, Solaris; juniper routers etc are ready to support IPV6. Such broad support will make the shift from IPv4 to IPv6 much easier.
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