Tuesday, February 1, 2011

IPv6 Basics II - 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 “IPv6 Addressing.”
IPsec support is optional.
IPsec support is required. For more information, see “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 included in the IPv6 header using the Flow Label field. For more information, see “IPv6 Header.”
Fragmentation is done by both routers and the sending host.
Fragmentation is not done by routers, only by the sending host. For more information, see “IPv6 Header.”
Header includes a checksum.
Header does not include a checksum. For more information, see “IPv6 Header.”
Header includes options.
All optional data is moved to IPv6 extension headers. For more information, see “IPv6 Header.”
Address Resolution Protocol (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 “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 “Multicast Listener Discovery.”
ICMP Router Discovery is used to determine the IPv4 address of the best default gateway and is optional.
ICMP Router Discovery is replaced with ICMPv6 Router Solicitation and Router Advertisement messages and is required. For more information, see “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.”
Must be configured either manually or through DHCP.
Does not require manual configuration or DHCP. For more information, see “Address Autoconfiguration.”
Uses host address (A) resource records in the Domain Name System (DNS) to map host names to IPv4 addresses.
Uses host address (AAAA) resource records in the Domain Name System (DNS) to map host names to IPv6 addresses. For more information, see “IPv6 and DNS.”
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.ARPA DNS domain to map IPv6 addresses to host names. For more information, see “IPv6 and DNS.”
Must support a 576-byte packet size (possibly fragmented).
Must support a 1280-byte packet size (without fragmentation). For more information, see “IPv6 MTU.”

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