Lecture 1-5 Find out Networks Per Class & Hosts Per Network
IPv4 today
In 1993 the introduction of Classless Inter-Domain Routing (CIDR) gave greater flexibility for allocating blocks of addresses. CIDR adds a suffix to the IP address to identify how many of the leading bits represent the network address. For IPv4, that means a number between 0 and 32. The higher the suffix, the fewer available host addresses available on the network.
CIDR slowed the growth of routing tables and extended the life of IPv4 by reducing the number of wasted addresses that plagued the class system. CIDR is still the most widely used network routing method used today for both IPv4 and IPv6 routing.
IPv4 address exhaustion
2011 saw the last distribution of IPv4 address blocks to the five regional Internet registries, one of which ran out of addresses completely within the next few months. The individual Internet service providers keep IPv4 alive by recycling addresses as they become available.
As noted earlier, IPv4 has a cap just short of 4.3 billion available addresses. With the Internet’s explosion in growth and the Internet of Things, the number of available addresses quickly depleted. To remedy the situation, the IETF released IPv6 with its 128-bit address space for a nearly inexhaustible 340 undecillions (340 followed by 37 zeros) available addresses. Learn more about IPv4 address exhaustion.
IPv4 and IPv6 compatibility
Although IPv4 and IPv6 use CIDR to handle their network and host addressing, the two protocols are not interchangeable. IPv6 also fixes many other networking issues inherent in IPv4, such as smaller routing tables, simplified packet headers, and uses multicast instead of broadcast.
A single device can support both IPv4 and IPv6. Dual-stack IP allows for a single router, switch, or server to process either address space. You cannot connect to an IPv6-only device using an IPv4 connection and vice-versa.
IPv4 speed
Some of the baggage IPv4 carries to extend the number of addresses does affect network speed. In the perfect IPv6 environment, IPv6 outperforms IPv4. However, the IPv6 network still requires work, and so depending on local architecture, IPv4 is often faster. An algorithm called Happy Eyeballs used by some browsers will test the speed of both network protocols and use the faster version.
ipv4
