16-02-2011, 12:48 PM
Around year 1992, theInternet EngineeringTask Force (IETF) becameaware of shortage of IPv4 addresses inthe world, and technical obstacles indeploying new protocols due to limitationimposed by IPv4. IPng (IP nextgeneration) effort was started to solvethese issues. After large amount of discussions,around year 1995, IPv6 (IPversion 6) was picked as the final IPngproposal.
Larger IP Address SpaceIPv4 uses only 32 bits for IP addressspace, which allows only 4 billion nodesto be identified on the Internet. 4 billionmay look like a large number, however,it is less than the human populationon the earth. IPv6 allows 128 bitsfor IP address space, allowing threehundred forty undecillion nodes to beuniquely identified on the Internet.Larger address space allows true end toend communication, without NAT orother short term workaround againstIPv4 address shortage.
Deploy New TechnologiesAfter IPv4 was specified 20 years ago,we have seen a plethora of technicalimprovements in networking. IPv6covers a number of those improvementsin its base specification, allowing usersto assume these features available everywhere,anytime.
AutoconfigurationWith IPv4, DHCP has been available,but only as an option. The novice usercan go into trouble when visiting anoffsite without DHCP server. WithIPv6, the stateless host autoconfigurationmechanism is mandatory.
SecurityWith IPv4, IPSec is optional and youneed to ask the peer if it supports IPSecor not. With IPv6, IPSec support ismandatory. By mandating IPSec, youcan secure your IP communicationwhenever talking to IPv6 devices.
MulticastMulticast is mandatory in IPv6, whichwas optional in IPv4. IPv6 base specificationsalso extensively use multicast.
Ad-Hoc NetworkingScoped addresses allow better supportfor ad-hoc or “zeroconf ” networkingconfiguration. IPv6 supports anycastaddresses, which can also contribute toservice discoveries.
Flexible Protocol ExtensionsIPv6 allows a more flexible protocol extensionthan IPv4 does. This is withoutimposing any overhead to intermediaterouters. It is achieved by splittingheaders into two flavours: the headersintermediate routers need to examine,and the headers the end nodes will examine.This also eases hardware accelerationfor IPv6 routers
.No Routing Table GrowthIPv4 backbone routing table size has been a big headache to ISPs and backboneoperators. The IPv6 addressingspecification restricts the number ofbackbone routing entries by advocatingroute aggregation.
Simplified Header StructuresIPv6 has simpler packet header structuresthan IPv4. It will allow future vendorsto implement hardware accelerationfor IPv6 routers easier.
Smooth Transition From IPv4Many IPv4 considerations were madeduring the IPv6 development. Also,there is a large number of transitionmechanisms available. This will allowsmooth migration from IPv4 to IPv6
.Same Design Principles as IPv4IPv4 was very successful design, asproven by the ultra large-scale deploymentin the world. IPv6 is the new versionof IP, and it follows many of designsthat made IPv4 very successful.