In association with heise online

Address Switching

On a practical level, the biggest changeover problem is switching addresses during normal operation, and IPv6 resolves this problem through renumbering. This should cause considerably smaller routing tables since IPv4 routing tables contain fragmented address spaces: the entire XY address space may belong to one provider, but the subspace Z it contains could belong to a former customer who has switched to a different ISP.

If spaces like these became fragmented, they could no longer be routed as an aggregate, and the global routing table would explode. IPv6 renumbering avoids this, and customers wishing to switch entire corporate networks to a different provider can dare to do so since there is far less effort involved.

If clients change from IPv4 to IPv6 at the same time, various LAN and internet technologies ensure smooth transitions. Switching to IPv6 starts in the LAN. Here, we basically have devices which work at layer 1 (e. g. hubs), at layer 2 (switches) or at layer 3 (routers). Layer 1 devices are transparent for IPv6 and don't require any adjustment. Layer 2 devices like switches must be capable of multicasting. All modern switches are.

While traffic is limited to the LAN, layer 3 devices (routers) in home networks usually delimit the network edge and, therefore, initially don't concern themselves with routing IPv6 traffic. This means that IPv6 already works fine within the LAN environment - but if the LAN is to be connected to the internet via IPv6, the lights go dim for home network routers. However, it only takes two LAN cards to turn PCs into routers: One for the PPPoE connection to the IPv6 provider, and the other for hooking up the LAN. Linux based router distributions can then make the kernel's IPv6 abilities available.

Bilingual

The popular PC operating systems are well prepared for a seamless transition to IPv6. Linux, Mac OS X and also Windows offer dual stacks which enable them to use both IPv6 and IPv4 (RFC 4213). In Windows Vista, IPv6 is the default rather than just being part of the shipment, like in its predecessor XP. PCs running Vista automatically access network services via IPv6 wherever possible.

Several techniques can be used to boost the currently patchy deployment of IPv6 and enable IPv6 traffic across an IPv4 infrastructure. IPv6 islands can easily be connected via the internet using static tunnels. This was demonstrated by the 6BONE project which was shut down after successfully completing its test phase in mid-2006.

Tunnel principle
Islands to continents: First IPv6 networks use, for example, Multicast tunnels to bridge IPv4 structures until they eventually replace them.

In 6over4, two IPv6 hosts exchange data through a Multicast tunnel via the IPv4 network. To make this viable for dynamic IPv4 addresses, the Centro Studi e Laboratori Telecomunicazioni (CSELT) developed tunnel brokers which serve for automatically activating the tunnel after dial-up. 6to4 enables two IPv6 hosts to encapsulate data in IPv4 packets and exchange them through the IPv4 network. Teredo, a technology which has been incorporated in Vista, tunnels IPv6 traffic via UDP through NAT routers. Find more information about these and other transition methods for example on the web page of IPv6 service Six Access.

Outlook

For most users who have IPv6 on their PCs the new protocol will initially probably only work behind the scenes. Mac OS X and also Vista don't offer any additional graphic user interfaces - there, IPv6 generally does its job on auto-pilot and allows at least basic surfing without user interference.

Coupled with various transition mechanisms, especially Vista should provide a considerable boost. A first wave already happened when IPv6 was introduced in Japan and South Korea. From 2008 it will also be compulsory for backbones in the US, which should trigger the decisive domino in favour of IPv6. After that, it should not be long before the first ready-made IPv6 router boxes for home users become available. (je)

Print Version | Permalink: http://h-online.com/-747386
  • Twitter
  • Facebook
  • submit to slashdot
  • StumbleUpon
  • submit to reddit
 


  • July's Community Calendar





The H Open

The H Security

The H Developer

The H Internet Toolkit