Service providers are struggling to prepare their networks for the influx of IPv6 addresses.
With exponential growth in global broadband deployments, next-gen wireless rollouts on the horizon and fast-growing smartphone numbers, the industry is predicting an increase of five billion unique endpoints between 2010 and 2015.
While the internet is rich with IPv6 content and services – Google is already supporting IPv6 on its search, news, docs, maps and YouTube – IPv4 won’t just “go away.” That duality creates a challenging situation for service providers that must upgrade their network infrastructure to handle IPv4 and IPv6 co-existence.
While network cores are well-equipped for handling both IPv4 and IPv6, broadband access networks are not. Co-existence puts tremendous stress on the underlying network systems, which can potentially introduce latency, degrade network responsiveness, and compromise service level agreements.
The biggest transition concern is the impact on customers: will introducing IPv6 endpoints, forwarding tables, and services affect connectivity speed, service quality, and network reliability?
An abrupt transition of the legacy IPv4 infrastructure to IPv6 is not practical because most Internet services are still based on IPv4 and many customers are still running operating systems not fully compatible with IPv6. Service providers must support both IPv4 and IPv6 endpoints and services in order to guarantee the quality of service defined in their service level agreements.
There are different methods that can be used to achieve the goal across broadband access networks.
The easiest way to conserve the depleting IPv4 address space is to use translation so that the outward facing interface uses a public interface, while the private network uses IP addresses that are not routed on the Internet. However, the known performance and scalability issues compel most service providers to deploy either tunneling or dual-stack transition mechanisms in broadband access networks.
Tunneling techniques are used to send IPv6 traffic over IPv4 networks and vice versa. The two tunneling schemes currently receiving significant industry attention are Dual-Stack Lite (DS-Lite), and IPv6 Rapid Deployment.
A DS-Lite device is provisioned with IPv4 and IPv6 address on its interface(s). DS-Lite uses IPv6-only links between the provider and the customer. When a device in the customer network sends an IPv4 packet to an external destination, it is encapsulated in an IPv6 packet for transport into the provider network. There is no network address translation (NAT) service on the customer premise equipment device, such as home gateway.
If a home device needs to access an IPv6 service, it is transported “as is”, and routed to an internet server. The IPv6 tunnel source address is added to the NAT table along with IPv4 source address and port to disambiguate the customer’s private address and provide the reference for the tunnel endpoint.
With DS-Lite technology, the communications between end-nodes stay within their address family without requiring protocol family translation.
IPv6 Rapid Deployment(6rd) relies on IPv4 and is designed to deliver production-quality IPv6 alongside IPv4 with as little change to IPv4 networking and operation as possible.
The 6rd mechanism relies on an algorithmic mapping between the IPv6 addresses and IPv4 addresses that are assigned for use within the service provider network. An IPv6 prefix, called a “6rd prefix,” is selected by the service provider for use by a compatible domain. The IPv6 packet is encapsulated inside IPv4 by a 6rd customer edge (CE) router and follows the IPv4 routing topology within the service provider network among CEs and border relays.
Many service providers are planning to deploy dual-stack networks as a long-term strategy, supporting a mixture of IPv4 and IPv6 applications for customers that require both protocols. Dual-Stack-capable devices are compatible with IPv4 and IPv6, from the network layer to the applications. Applications choose IPv4 or IPv6 based on the type of IP traffic and particular requirements of the communication. Dual-Stack deployments are more cost and time-intensive than tunneling technologies, since all devices in the network require a software upgrade (at minimum) to run both protocol stacks.
Dual-Stack PPP resolves IPv4/IPv6 compatibility issues and facilitates transition to IPv6 by enabling IPv6/IPv4 nodes to send and receive IPv4 and IPv6 packets. Each individual PPP session results in getting an IPv4 address and IPv6 prefix that can be used to assign addresses to IP devices at the customer site.
With IPv4 address depletion, IPv6 applications and endpoints will soon become ubiquitous across end-to-end networks. 2011 will be a year of significant access network upgrades to support IPv6 and the dual-stack technologies required for IPv6 services.
To ensure this evolution is transparent to subscribers, network equipment vendors and service providers must demonstrate that network equipment is ready for IPv4/IPv6 co-existence.
Tara Van Unen is a senior manager for market development at converged network and application performance testing provider Ixia. For more information, visit http://www.ixiacom.com/