IPv6 has been around for quite sometime now. A detailed look at the underlining technology and the potential it holds. by Mahesh Rathod

IPv6 is the "next generation" Internet protocol developed by the IETF, and is a natural increment to IPv4

IPv6 offers security features at the router level of the TCP/IP architecture, where they can benefit all TCP/IP applications

The Internet has experienced a phenomenal growth in a short span with more than 450 million users connected to it worldwide. With the Internet penetrating each and every home and office, the number of users hooked on to the Net is expected to reach 950 million by 2005. This growth has exposed limitations of the currently used protocol for the Internet, IPv4 (Internet Protocol Version 4). The main drawback is the dearth of IPv4 addresses. To overcome this limitation, IETF (Internet Engineering Task Force) began working on the next-generation protocol called IPv6 (Internet Protocol Version 6).

Problems with IPv4
The main bottleneck with IPv4 is the shortage of IPv4 addresses. IPv4 being 32-bit, it allows more than 4 billion addresses. But with the massive growth in Internet usage, this pool of addresses has started drying up. The other drawback of IPv4 is the destruction of end-to-end communication by Network Address Translator (NAT) which was introduced to ease the shortage of addresses. This makes application development less practical. The final problem with IPv4 is that with more users connecting to the Internet, the routing information that the routers need to remember is also on the rise. This could be a fatal problem for a router with little capacity.

What is IPv6?
IPv6 is the "next-generation" Internet protocol developed by the IETF, and is a natural increment to IPv4. IPv6 makes use of 128-bit addresses instead of 32-bit. This provides an estimated 340 undecillion (cardinal number equal to 1036) IP addresses, one for every living thing on this planet. IPv6 is scalable and offers security in term of encryption of packets and authentication of the sender. It also has built in plug-n-play in terms of automatically configuring devices and networks. IPv6 can be installed as a normal software upgrade in Internet devices and is interoperable with the current IPv4. IPv6 runs well on high performance networks (e.g. ATM, Gigabit Ethernet, etc.) and on low bandwidth networks (e.g. wireless).

Features of IPv6

Auto configuration:
One of the best improvements of IPv6 over IPv4 is auto configuration. One approach of IPv6 will be to offer a "stateful" auto configuration, which is similar to that of the DHCP (Dynamic Host Configuration Protocol). This will allow servers to dynamically assign unique addresses to computers as they request them, drawing from a database of pre-allocated values. The other approach is "stateless" auto configuration. Here an IPv6 node creates a unique IP address by combining its LAN MAC (Medium Access Control) address with a prefix provided by the network router.

Security:
Security was optional in IPv4, whereas in IPv6 it has been made mandatory. IPv6 offers security features at the router level of the TCP/IP architecture, where they can benefit all TCP/IP applications. IPv6 provides security encryption, authentication and data integrity safeguards essential for any organization. The IPv6 authentication header extension guarantees that the recipient receives a packet that is truly from its source address and also provides end-to-end encryption at the network layer. With IPv6, IPsec support is mandatory. By mandating IPsec, a secure IP communication is available whenever you talk to IPv6 devices.

Multicast/anycast:
Multicast has been made mandatory in IPv6, which was optional in IPv4. Multicast is beneficial for streaming technologies. IPv6's new multicast address format allows for trillions of possible multicast group codes, each identifying two or more packet recipients. IPv6 also initiates a new kind of addressing called anycast address. An anycast address enables a source to specify that it wants to contact any one node from a group of nodes via a single address. A packet with such an address will be routed to the nearest interface in the group, according to the router's measure of distance.

Quality of Service:
IPv6 has two "Quality of Service" features: flow labels and priority. A flow is a sequence of packets sent from a unicast source to a unicast or multicast destination. The IPv6 flow label enables the flow's source to identify a logical sequence of packets; intervening routers that support this feature can then maintain a context for the flows currently in transit, thus opening the door for possible optimized performance and congestion management. Hosts can also specify a packet priority, a feature that will allow IPv6 routers to discriminate and favorably accommodate TCP/IP applications that require faster response time.

Mobile IP:
These days we all would love to be connected to the Internet while we are on the move. To make this possible, we would require a mobile IP. IP mobility under IPv4 required additional infrastructure as it requires informing any agent in the routing process about a new location. Mobile IP via IPv6 requires no such infrastructure as it eliminates triangular routing and instead implements a transitory second address. It defines a multilevel global routing infrastructure.

Backward compatibility
In order to protect huge investments in TCP/IP, backward compatibility is ensured with transition mechanisms for communicating with IPv4-based networks. IPv6 can indefinitely exist with IPv4 in both routers and host computers. IPv6 is designed to work concurrently with IPv4, which will continue to support existing TCP/IP applications. IPv6 can run on the same machine concurrently with IPv4. As IPv6 implementations become available, systems managers and network administrators need upgrade only as many devices at a time as they can handle.

While the IPv4-to-IPv6 details for any particular device will depend on the vendor's implementation, the migration will depend on key characteristics of IPv6 architecture.

Mahesh Rathod can be reached at rathodmp@hotmail.com