The difference between IPv4 and IPv6

IPv4 is the fourth revision in the long development of IP and it is actually the first to be widely deployed.  Combined with IPv6, it is the core of inter-networking methods of the Internet.  IPv4 is to this day the most widely deployed Internet Layer protocol.

IPv4 uses 32-bit (four-byte) addresses, which limits the address space to 4,294,967,296 (2³²) possible unique addresses. However, some are reserved for special purposes such as private networks (~18 million addresses) or multi-cast addresses (~16 million addresses). This reduces the number of addresses that can be allocated as public Internet addresses. As the number of addresses available are consumed, an IPv4 address shortage appears to be inevitable, however network address translation (NAT) has significantly delayed this inevitability.

This limitation has helped stimulate the push towards IPv6, which is currently in the early stages of deployment and is currently the only contender to replace IPv4.

IPv6 is the next generation Internet Layer protocol for inter-networks and the Internet.  In December 2008, despite celebrating its 10-year anniversary as a Standards Track protocol, IPv6 was only in its infancy in terms of general world-wide deployment. A recent study by Google indicates that penetration is still less than one percent of Internet traffic in any country. The leaders are Russia (0.76%), France (0.65%), Ukraine (0.64%), Norway (0.49%), and the United States (0.45%). Although Asia leads in terms of absolute deployment numbers, the relative penetration is smaller (e.g., China: 0.24%). IPv6 is implemented on all major operating systems in use in commercial, business, and home consumer environments. According to the study, Mac OS leads in IPv6 penetration of 2.44%, followed by Linux (0.93%) and Windows Vista (0.32%).

The length of network addresses emphasize a most important change when moving from IPv4 to IPv6. IPv6 addresses are 128 bits long (as defined by RFC 4291), whereas IPv4 addresses are 32 bits; where the IPv4 address space contains roughly 4 billion addresses, IPv6 has enough room for 3.4×10³⁸ unique addresses.

IPv6 addresses are typically composed of two logical parts: a 64-bit (sub-)network prefix, and a 64-bit host part, which is either automatically generated from the interface’s MAC address or assigned sequentially. Because the globally unique MAC addresses offer an opportunity to track user equipment, and so users, across time and IPv6 address changes, RFC 3041 was developed to reduce the prospect of user identity being permanently tied to an IPv6 address, thus restoring some of the possibilities of anonymity existing at IPv4. RFC 3041 specifies a mechanism by which time-varying random bit strings can be used as interface circuit identifiers, replacing unchanging and traceable MAC addresses.

So this brings us to the differences between IPv4 and IPv6:

1. Simplified header format. IPv6 has a fixed length header, which does not include most of the options an IPv4 header can include. Even though the IPv6 header contains two 128 bit addresses (source and destination IP address) the whole header has a fixed length of 40 bytes only. This allows for faster processing.
   Options are dealt with in extension headers, which are only inserted after the IPv6 header if needed. So for instance if a packet needs to be fragmented, the fragmentation header is inserted after the IPv6 header. The basic set of extension headers is defined in RFC 2460.
2. Address extended to 128 bits. This allows for hierarchical structure of the address space and provides enough addresses for almost every ‘grain of sand’ on the earth. Important for security and new services/devices that will need multiple IP addresses and/or permanent connectivity.
3. A lot of the new IPv6 functionality is built into ICMPv6 such as Neighbor Discovery, Autoconfiguration, Multi-cast Listener Discovery, Path MTU Discovery.
4. Enhanced Security and QoS Features.

posted by: Myke Reinhold
credit: Homerun-Networks, Google, Wikipedia

This entry was posted on 27. January 2009 at 15:04 and is filed under Internet, Networking, Security. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response or trackback from your own site.