This chapter focuses on Internet protocol (IP) and its extensions, which have withstood the test of time over the past three decades. The Internet Engineering Task Force (IETF) has designed the next version of IP to meet the growing needs of the Internet. IPv6 is much more than simply an extension of IPv4 with a larger address space—its architecture is designed to provide easier administration and greater performance, security, and mobility. IPv6 uses Plug and Play computing and greatly eases the burden on network administrators. IPv6's Plug and Play support extends to mobile computing: mobile hosts acquire care-of addresses as they travel, and home agents bind the care-of addresses to home addresses to ensure that mobile users retain connectivity away from home, and provides integrated security support with two extension headers. The Authentication Header's Integrity Encrypted payloads can be transmitted with the Encrypted Security Payload (ESP) Header. IPv6's design enhances network performance. Its larger address space eliminates the need for network and port address translation, thus reducing overhead. Core routing overhead is significantly reduced by the ability to aggregate addresses and in turn reduces the size of routing tables. The layered network model generally protects upper-layer protocols from an expensive transition to IPv6. Standardization enables each manufacturer and software vendor to follow the same blueprint rather than developing proprietary versions of the protocol.