With the expectation of significant growth among mobile networks, of increased market share in IP-enabled phones, and of severe limitations in the IPv4 address space, it would be difficult to overstate the growing need for IP addressability. Hence, service providers, which have been talking about IPv6 for years, are starting to move in the direction of both IPv4+IPv6 and IPv6-only mobile networks. Toward that goal, 3GPP (3rd-Generation Partnership Project, the standards development organization tasked with developing standards for third-generation networks) and the IETF held a joint workshop on IPv6 in cellular networks in San Francisco in March 2010. The workshop was sponsored by China Mobile.
The two-day workshop featured more than 40 presentations covering everything from problems to solutions, to successes with regard to deployment of IPv6 on cellular networks. Many of the operators in attendance revealed they are conserving public IPv4 address space by using RFC 1918 space internally and operating large-scale network-address-translation (NAT)44 devices. However, due to the size of those operators’ internal networks, it’s likely that RFC 1918 space will not be large enough to accommodate the traffic without splitting the network into overlapping segments-a solution that complicates the delivery of services provided by the carrier itself and that raises concern about operating NAT44 devices in perpetuity.
Most operators plan to provide both IPv4 (using RFC 1918 space) and IPv6 for handsets, and to NAT the IPv4 traffic. Some concern was expressed that with most Internet content being IPv4, merely enabling IPv6 on handsets is not enough to move traffic to IPv6. However, Google was cited as an example of an IPv6 content provider. By placing IPv6 on handsets, IPv6 content is accessed directly (due to RFC 3484 preference rules), thus avoiding the operator’s NAT44. One operator at the workshop announced plans to deploy IPv6-only handsets that will use NAT64 (and DNS64) to access IPv4 content. Doing so will mean that all traffic from those handsets will be IPv6 over that operator’s network. Some of the newer cellular services, such as automated machine-to-machine communication, are expected to function more smoothly over IPv6.
The meeting concluded with participants reiterating that tools already exist to facilitate IPv6 deployment and that, for the most part, new work is unnecessary. Additional work is required in the BEHAVE WG on stateful NAT64 (which provides a mechanism for an IPv6-only handset to share an IPv4 address), on per-interface NAT44, and in the SOFTWIRE WG, where consideration will be given to gateway-initiated dual stack lite.
Further discussion on IPv6 in cellular networks can be found on the 3gv6 mailing list.
This article was posted on 26 June 2010 .