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IPv4 addresses used up at an alarming rate. Around the year 1990 approximately 536 million or one eighth of the available IPv4 IP addresses had been used. This number continued to double every five years. At this rate it was predicted that the address space for IPv4 would run out sometime between 2005 and 2011 this was declared the "exhaustion point".

Initially the IETF started on a protocol called the Next Generation Internet Protocol (IPng). This slowly led to the concept of IPv6. Therefore a new Internet Protocol was born called IPv6. IPv6 was first published in 1995 and became a standard in 1998.

The details of the fragmentation mechanism, as well as the overall architectural approach to fragmentation, are different between IPv4, the first official version of the Internet Protocol, and IPv6, the newer version. In IPv4, routers perform fragmentation, whereas in IPv6, routers do not fragment, but drop the packets that are larger than the MTU.

Though the header formats are different for IPv4 and IPv6, analogous fields are used for fragmentation, so the algorithm can be reused for fragmentation and reassembly.

IPv4 is an abbreviation of “Internet Protocol Version Four”. It is also known as RFC 719. IPv4 was the fourth generation of Internet Protocol and was also the first version to be widely deployed. 

IPv6 was designed to solve the problems of IPv4. The a new version of the protocol serves the same functions as IPv4. 

This set of Web pages provides information of Internet Protocol Version 6 (IPv6). IPv6 is sometimes also called the Next Generation Internet Protocol or IPng. IPv6 was recommended by the IPng Area Directors of the Internet Engineering Task Force at the Toronto IETF meeting on July 25, 1994 in RFC 1752,  

The Recommendation for the IP Next Generation Protocol .The recommendation was approved by the Internet Engineering Steering Group and made a Proposed Standard on November 17, 1994.The core set of IPv6 protocols were made an IETF DraftStandard on August 10, 1998.Internet Protocol Version 6 is abbreviated to IPv6 (where the "6" refers to it beingassigned version number 6). The previous version of the Internet Protocol is version 4 (referred to as IPv4).

IPv6 is a new version of IP which is designed to be an evolutionary step from IPv4. It is a natural increment to IPv4. It can be installed as a normal software upgrade in internet devices and is interoperable with the current IPv4. Its deployment strategy is designed to not have any flag days or other dependencies. IPv6 is designed to run well on high performance networks.

IPv6 includes a transition mechanism which is designed to allow users to adopt and deploy IPv6 in a highly diffuse fashion and to provide direct interoperability between IPv4 and IPv6 hosts. The transition to a new version of the Internet Protocol must be incremental, with few or no critical interdependencies, if it is to succeed. The IPv6 transition allows the users to upgrade their hosts to IPv6, and the network operators to deploy IPv6 in routers, with very little coordination between the two.

We are slowly approaching the implementation of IPv6 in a mass scale and thus we must be ready to learn some significant differences over IPv4. IPv6 uses 128 bits as apposed to IPv4's 32. This means that by comparison, IPv6 has a lot more addresses. This is also a main reason for using IPv6 in the future.

There are two types of IP addresses: IPv4 and IPv6. An IPv4 address, for example,, has 4 octets separated by decimals. They are called octets because each of them represents 8 bits (in binary) of the address. The first octet represents the network address and the last three octets are to identify the host. Each of the octets can take any number from 0 to 255 as that is the largest number possible in an 8-bit binary. This limits the number of unique possible combinations of IPv4 addresses to 232.

IPv6 on the other hand uses hexadecimal system and each address is assigned a space of 16 bytes (compared to 4 bytes in IPv4). This increases the number of possibilities to 2128 or 3.408 X 1038, the number which looks vast enough to accommodate the need of all networks in the foreseeable future. A typical IPv6 address looks like this: 2001:0db8:85a3:08d3:1319:8a2e:0370:7334.

The reason we may need to switch from Ipv4 to Ipv6 is because of the population of the world. The rate at which the world’s population is growing is nothing to look down at. 

Addresses are 32 bits (4 bytes) in length.
Addresses are 128 bits (16 bytes) in length
Address (A) resource records in DNS to map host names to IPv4 addresses.
Address (AAAA) resource records in DNS to map host names to IPv6 addresses.
Pointer (PTR) resource records in the IN-ADDR.ARPA DNS domain to map IPv4 addresses to host names.
Pointer (PTR) resource records in the IP6.ARPA DNS domain to map IPv6 addresses to host names.
IPSec is optional and should be supported externally
IPSec support is not optional
Header does not identify packet flow for QoS handling by routers
Header contains Flow Label field, which Identifies packet flow for QoS handling by router.
Both routers and the sending host fragment packets.
Routers do not support packet fragmentation. Sending host fragments packets
Header includes a checksum.
Header does not include a checksum.
Header includes options.
Optional data is supported as extension headers.
ARP uses broadcast ARP request to resolve IP to MAC/Hardware address.
Multicast Neighbor Solicitation messages resolve IP addresses to MAC addresses.
Internet Group Management Protocol (IGMP) manages membership in local subnet groups.
Multicast Listener Discovery (MLD) messages manage membership in local subnet groups.
Broadcast addresses are used to send traffic to all nodes on a subnet.
IPv6 uses a link-local scope all-nodes multicast address.
Configured either manually or through DHCP.
Does not require manual configuration or DHCP.
Must support a 576-byte packet size (possibly 
Must support a 1280-byte packet size (without fragmentation).

These are special addresses assigned to IPv6-capable devices, such as so-called “dual stack” devices that speak both IPv4 and IPv6. They have all zeroes for the middle 16 bits; thus, they start off with a string of 96 zeroes, followed by the IPv4 address.

Both IPv4 and IPv6 are level 3 routing protocols.  However IPv6 is just that bit quicker, smarter and lot more scaleable.  Nevertheless, it is the realization that the 32bit IPv4 just cannot deliver sufficient unique address, which has been the driving force to upgrade to a 128bit IPng (new generation), or IPv6 as it's better known.

Here are five keywords that will aid your understanding should you read IPv6 RFC 
(Request for comments) articles: Stateful and Stateless; Link-Local and Site-Local addresses, also ND (Neighbor Discovery)
  1. A stateful IP address is one given by a DHCP server.  Usually DHCP gives more information than just the IP address, for example the IP address of the DNS server and also the default gateway.
  2. A stateless IP address is one that is automatically configured by router discovery.  The host assigns itself an IPv6 address automatically rather like the IPv4 APIPA.
  3. Link-Local IPv6 addresses only allow connections with neighbors on that subnet (link), these address beginning with FEC0 are not forwarded by routers.  End of story.
  4. Site-Local address are routable, but not to the internet, thus hosts with Site-Local IPv6 addresses can use private (not ICANN) IP addresses, AND can connect to any other Site-Local address within the organization.  All Site-local address begin with FE80.
  5. Neighbor Discovery - ND Replaces IPv4's ARP and ICMP Router Discovery.  The idea is for machines to discover information about their nearest router.  In addition, if an IPv6 stack can obtain information about other hosts, then it won't duplicate their IP addresses should it need to use Auto configuration.

Address Format
32 Bits Dotted Decimal Notation.
128 Bits Hexadecimal Notation.
Number of Addresses
Subnet identified by subnet mask.
Subnet identified within the address.
Routing Protocols
Classfull / Classless
Classful and Classless.
Classless Addressing Scheme.
Address Configuration
Static, DHCP
Stateless Autoconfiguration, DHCP v6.
Loopback Address
Broadcast Address Types
Multicast / Broadcast
Header Length
20 bytes
40 bytes

Leading zeros in an IPv6 address are optional. For example an IP address of 2001:db8:31:0:0:0:0:1 can also be written as 2001:db80:31::1 the missing zeros are calculated to make the address 128 bits. In this case it is clear that four zeros were removed. This process is called zero compression. Successive fields of zeros are allowed, but only one time in an address.

Similar to IPv4’s, Ipv6 has its own loop back address.  The loopback in Ipv6 is 0:0:0:0:0:0:0:1 or can also be zero compressed to ::1. This address is also used for troubleshooting a network.

Within the Ipv6 protocol there is a similar notation to a forward slash net mask prefix in IPv4.  The prefix notation in IPv6 determines how many left most bits are assigned by authority and how many bits are assigned locally, or how many bits of the address specify the prefix


The above differences show how advanced IPv6 is and how efficient it can be in data transfer. So let us wait for the time when IPv6 completely takes over IPv4.
This Article Written Author By: Premakumar Thevathasan. CCNA, CCNP, CCIP, MCSA, MCSE, MCSA - MSG, CIW Security Analyst, CompTIA Certified A+.

1 comment:

Anonymous said...

Excellent sir.