IP version 6 (IPv6) is an update to version 4 of the Internet Protocol, the platform on top of which all Internet data is exchanged. The driving force behind the development of IPv6 is the rapidly dwindling supply of network addresses under the current IPv4. Some predict the exhaustion of these addresses will occur within the next 3 to 15 years.
Every device connected to the Internet must have an IP address. Under IPv4 these addresses are 32 bits long (which looks something like this: 194.62.132.105). The new specifications increases the address space to 128 bits, which theoretically means there could be a total of 340,282,366,920,938,463,463,374,607,431,768,211,456 devices hooked up to the Internet under IPv6.
It is not just inncreasing the number of Internet addresses, also IPv6 improves other features to the Internet Protocol, including encryption, authentication, quality of service, and other ways to support in the routing of packets. Most of these improvements are in development, and their actual usefulness will rely on the final specification and implementation.
There is an IPv6 backbone already in place in IPv6 experimentation, but it's not practical to connect an IPv6 network to the Internet yet. Since standards are still being ratified, and the IPv6 encryption technology is not universal, its difficult to predict the results. When the change does come, though, it will most likely start at the top with major backbone providers and work its way down.
Matt Stevens, 16 May 1997, The Low down on IPv6 [Online], Available hrefhttp://www.hotwired.com/webmonkey/geektalk/97/19/index4a.htmlThe IPV4 address capacity is the main cause for the change to IPV6. Secondly Ipv4 host implementation lack such essential features as auto configuration, network layer security, and others. Existing Ipv4 host stack implementation may no longer be adequate to address the requirements of the current network environment and ran out of numbers. IPv4 has 32 bit and IPv6 has 128bit.
Current support for the storage of Internet addresses in the Domain
Name System (DNS)[1,2] cannot easily be extended to support IPv6
addresses[3] since applications assume that address queries return
32-bit IPv4 addresses only.
To support the storage of IPv6 addresses we define the following
extensions:
A new resource record type is defined to map a domain name to an IPv6 address.
A new domain is defined to support lookups based on address.
Existing queries that perform additional section processing to
locate IPv4 addresses are redefined to perform additional section processing
on both IPv4 and IPv6 addresses.
The changes are designed to be compatible with existing software. The
existing support for IPv4 addresses is retained. Transition issues
related to the co-existence of both IPv4 and IPv6 addresses in DNS
are discussed in [4].
To allow IPv4 packet headers the flexibility to carry optional information relevant to the routing process or host applications, IPv4 headers included an options field. This little-used field is carried by all IPv4 packets and is meant to convey information about security, source routing, and other optional parameters. The IPv4 options field has been replaced in IPv6 by flexible extension headers that travel after the primary IPv6 header and before the transport header and application payload. IPv6 extension headers are optional and provide a powerful means to support security, fragmentation, source routing, network management, and many other functions. An IPv6 packet can carry virtually any number of extension headers between the initial header and the higher layer payload. Figure 7 shows encryption and fragmentation headers travelling after the primary IPv6 header and before the Transmission Control Protocol (TCP) header.
Figure 7 | IPv6 Extention Headers
The IPv6 extension header architecture replaces the IPv4 options field and also effectss the protocol type field, which is currently used to show the type of protocol within the datagram's payload, e.g., TCP or User Datagram Protocol (UDP). IPv6 replaces the protocol type field with a next header field that shows the protocol carried in the next extension or payload header (e.g., a TCP/UDP header or a IPv6 optional header).
The IPv6 standards groups have defined a number of extension headers and have also designed a given (but not mandatory) guideline for the order of header insertion.
The suggested order for extension headers is as follows:
References
- (Primary IPv6 header)
- Hop-by-Hop options header
- Destination options header-1
- Source Routing header
- Fragmentation header
- Authentication header
- IPv6 Encryption header
- Destination options header-2
- (Upper-layer headers)
- (Payload)
Bay Network, 1997, White Paper: IPv6 http://partnerweb.baynetworks.com/Products/Routers/Protocols/2789.html#2
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