IPv4 addressing has the following characteristics:
- IPv4 addresses are 32 bits in length.
- IPv4 addresses are divided into various classes (e.g., Class A networks accommodate more than 16 million unique IP addresses, Class B networks support more than 65,000 IP addresses, and Class C networks permit 254 usable IP addresses). Originally, organizations applied for an entire network in one of these classes. Today, however, subnetting allows a service provider to give a customer just a portion of a network address space, in an attempt to conserve the depleting pool of IP addresses. Conversely, service providers can use supernetting (also known as classless interdomain routing [CIDR]) to aggregate the multiple network address spaces that they have. Aggregating multiple network address spaces into one reduces the amount of route entries a router must maintain.
- Devices such as PCs can be assigned a static IP address by hard coding the IP address in the device’s configuration. Alternatively, devices can dynamically obtain an address from, for example, a DHCP server.
- Because names are easier to remember than IP addresses, most publicly accessible Web resources are reachable by name. However, routers must determine the IP address with which the name is associated to route traffic to that destination. Therefore, a Domain Name System (DNS) server can perform the translation between domain names and their corresponding IP addresses.
- Some IP addresses are routable through the public Internet, whereas other IP addresses are considered private and are intended for use within an organization. Because these private IP addresses might need to communicate outside the local network, Network Address Translation (NAT) can translate a private IP address into a public IP address.
A major challenge with IPv4 is the limited number of addresses available. A newer version of IP, specifically IPv6, fixes this concern. An IPv6 address is 128 bits long, compared to the 32-bit length of an IPv4 address.
To make such a large address more readable, an IPv6 address uses hexadecimal numbers and the 128-bit address is divided into eight fields. Each field is separated by a colon, as opposed to the four fields in an IPv4 address, which are separated by a period. Consider some of the benefits offered by IPv6:
- IPv6 dramatically increases the number of addresses available.
- Hosts can have multiple IPv6 addresses, allowing those hosts to multihome to multiple Internet Service Providers (ISPs).
- Other benefits include enhancements relating to Quality of Service (QoS), security, mobility, and Multicast technologies.