LSN Availability: Many midsized mobile operators use existing enterprise firewall devices to build high-availability LSN solutions. Cisco recently launched CGSE -- a blade for the CRS series of routers that performs NAT44 operations at speeds exceeding 10 gigabits.
IPv4 to IPv6 translation solutions: NAT444
Mobile users usually get one IP address (public or private) per device (mobile phone or tablet/laptop with 3G adapter). Landline users also get one public IP address, but frequently use CPE devices with NAT to connect their home networks to the internet (NAT in a CPE device allows them to hide their whole network behind a single public IP address). Combining the existing NAT in CPE devices with LSN results in dual NAT within the IPv4 address space (NAT444).
A single NAT operation is bad enough if you're trying to set up a peer-to-peer (P2P) session (which could be anything from a Skype call to file sharing) or configure a public server on your home network. NAT444 makes these operations even more complex, so it's fervently hated by everyone but the carriers planning to use it.
NAT444 availability: See LSN
IPv4 to IPv6 translation solutions: DS-Lite
The DS-Lite (see graph below) proposal removes the NAT in CPE, turning CPE into an IP-aware bridge (Basic Broadband Building Block, or B4) that forwards IP packets with private IPv4 addresses to the central LSN device (Address Family Translation Router, or AFTR). IPv6 is used as the transport mechanism between B4 and AFTR and for the native IPv6 connectivity. NAT is performed on the AFTR box, making it almost impossible to deploy a publicly reachable server behind B4.