There are a number of ways to deal with IPv4 exhaust and  IPv6 transition, including Carrier Grade NAT and stateful Dual Stack Lite. Cisco has added another method called Mapping of Address and Port (MAP) based on two IETF drafts currently in the process of standardization indraft-ietf-softwire-map(MAP-E) anddraft-ietf-softwire-map-t(MAP-T). The real advantage with MAP is that it's stateless and doesn't require additional hardware as traffic grows. In fact, the MAP implementation on the Cisco ASR 1000 or ASR 9000 is just a software feature that can be enabled as needed.

There are two versions of MAP -translated (MAP-T) and encapsulated (MAP-E). In MAP-E IPv4 traffic is encapsulated into IPv6 using a v6 header before it is sent over the v6 network. At the network operator's boundary router, the IPv6 header is then stripped, and the IPv4 traffic is forwarded to the v4 Internet. In MAP-T, the IPv4 packet header is mapped to the IPv6 header and back. The difference between the two options is evident in their names. MAP-E uses IPv6 to encapsulate and de-encapsulate IPv4 traffic, whereas MAP-T uses NAT64 to translate IPv4 to IPv6 and back.

In either case however, no additional hardware is required at the boundary router, making MAP-based solutions easier to deploy and scale for future services. Traffic is also delivered more efficiently and with lower latency, and because IP address sources are easily traceable, the cost of complying with government Lawful Intercept and Address Logging requirements is much lower compared to DS Lite.

To learn more about the benefits of MAP, check out the following video: