Table 1-1 highlights some of the key differences between IPv4 and IPv6.
Table 1-1. Differences Between IPv4 and IPv6
IPv4 | IPv6 |
---|---|
Source and destination addresses are 32 bits (4 bytes) in length. | Source and destination addresses are 128 bits (16 bytes) in length. For more information, see Chapter 3, "IPv6 Addressing." |
IPSec support is optional. | IPSec support is required. For more information, see Chapter 4, "The IPv6 Header." |
No identification of packet flow for QoS handling by routers is present within the IPv4 header. | Packet flow identification for QoS handling by routers is present within the IPv6 header using the Flow Label field. For more information, see Chapter 4, "The IPv6 Header." |
Fragmentation is performed by the sending host and at routers, slowing router performance. | Fragmentation is performed only by the sending host. For more information, see Chapter 4, "The IPv6 Header." |
Has no link-layer packet size requirements and must be able to reassemble a 576-byte packet. | Link layer must support a 1,280-byte packet and must be able to reassemble a 1,500-byte packet. For more information, see Chapter 4, "The IPv6 Header." |
Header includes a checksum. | Header does not include a checksum. For more information, see Chapter 4, "The IPv6 Header." |
Header includes options. | All optional data is moved to IPv6 extension headers. For more information, see Chapter 4, "The IPv6 Header." |
ARP uses broadcast ARP Request frames to resolve an IPv4 address to a link-layer address | ARP Request frames are replaced with multicast Neighbor Solicitation messages. For more information, see Chapter 6, "Neighbor Discovery." |
Internet Group Management Protocol (IGMP) is used to manage local subnet group membership. | IGMP is replaced with Multicast Listener Discovery (MLD) messages. For more information, see Chapter 7, "Multicast Listener Discovery." |
ICMP Router Discovery is used to determine the IPv4 address of the best default gateway and is optional. | ICMPv4 Router Discovery is replaced with ICMPv6 Router Solicitation and Router Advertisement messages and is required. For more information, see Chapter 6, "Neighbor Discovery." |
Broadcast addresses are used to send traffic to all nodes on a subnet. | There are no IPv6 broadcast addresses. Instead, a link-local scope all-nodes multicast address is used. For more information, see "Multicast IPv6 Addresses" in Chapter 3, "IPv6 Addressing." |
Must be configured either manually or through DHCP for IPv4. | Does not require manual configuration or DHCP for IPv6. For more information, see Chapter 8, "Address Autoconfiguration." |
Uses host address (A) resource records in the Domain Name System (DNS) to map host names to IPv4 addresses. | Uses AAAA records in the DNS to map host names to IPv6 addresses. For more information, see Chapter 9, "IPv6 and Name Resolution." |
Uses pointer (PTR) resource records in the IN-ADDR.ARPA DNS domain to map IPv4 addresses to host names. | Uses pointer (PTR) resource records in the IP6.INT DNS domains to map IPv6 addresses to host names. For more information, see Chapter 9, "IPv6 and Name Resolution." |