IPv4 vs IPv6
IPv4 is used by most network devices. However, IPv4 is running out soon as more and more computers access the Internet. IPv4 has limits of 4,294,967,296 unique IP addresses only. IPv6 was published as working standard in 1998 by IETF to replace IPv4. The estimated numbers of IPv6 is 340,282,366,920,938,463,463,374,607,431,768,211,456 or 2128 unique IP addresses.
Below table shows some highlights of the difference between IPv4 and IPv6.
| IPv4 | IPv6 |
| IP addresses are 32 bits (4 bits) in length. | IP addresses are 128 bits (16 bytes) in length. |
| Pointer resource records in the IN-ADDR.ARPA DNS domain to map IPv4 addresses to host names. | Pointer resource records in the IP6.ARPA DNS domain to map IPv6 addresses to host names. |
| IPSec is optional and can be supported externally. | Support IPSec. |
| Header does not identify packet flow for QoS handling by router. | Header contains Flow Label field, which Identifies packet flow for QoS handling by router. |
| Header includes a checksum. | Header does not include a checksum. |
| Header includes options. | Optional data is supported as extension header. |
| Routers and sending host support packet fragmentation. | Routers do not support packet fragmentation. Sending host fragments packets. |
| Uses ARP to resolve IP to MAC address. | Uses MNS (Multicast Neighbor Solicitation) to resolve IP address to MAC address. |
| IGMP (Internet Group Management Protocol) manages membership in local subnet groups. | MLD (Multicast Listener Discovery) messages manage membership in local subnet groups. |
| Uses broadcast addresses to send traffic to all nodes on a subnet. | Uses link-local scope all-node multicast for sending traffic. |
| It is needed to configure manually or through DHCP. | It does not require any manual configuration or DHCP. |
| It supports a 576-byte packet size (possibly fragmented). | It supports a 1280-byte packet size (without fragmentation). |