Large-scale NAT

Intro

IPv4 - with its 32-bit addressing scheme which supports 4.3 billion devices - has served the world well for decades. But internet growth, personal computers, smartphones and now Internet of Things (IoT) has nearly exhausted that address space. IPv6 - with its 128-bit addressing scheme, supports 340 trillion trillion (2¹²⁸) addresses - is the answer.

LSN, also referred to as Carrier-Grade NAT (CGN), mitigates the problem of IPv4 address exhaustion by enabling end sites to be configured with private IPv6 network addresses and then translated to public IPv4 addresses by NAT devices in the network operator's network. This allows exhausted public address space to be shared by many end sites and devices. It also shifts network address translation from the end customer to the service provider network.

But scalable, cost-effective LSN/CGN is challenging.

Hardware-based solutions require sizable ternary content-addressable memory (TCAM) to mange address translation at speed. TCAM-intensive products are expensive and difficult to scale to the levels needed.