IPv6 Operation
Neighbor discovery
The neighbor discovery protocol enables IPv6 nodes and routers to determine the link-layer address of a neighbor on the same network, and to find and track neighbors. The IPv6 neighbor discovery process uses IPv6 ICMP (ICMPv6) messages and solicited-node multicast addresses to determine the link-layer address of a neighbor on the same network, verify the reachability of a neighbor, and keep track of neighbor routers.
When a node wants to determine the linklayer address of another node on the same local link, a neighbor solicitation message is sent on the local link, carrying the sender own link-layer address. After receiving the neighbor solicitation message, the destination node replies by sending a neighbor advertisement message with its own link-layer address on the local link. After the neighbor advertisement is received, the source and destination nodes can communicate. Neighbor advertisement messages are also sent when there is a change in the link-layer address of a node on a local link.
Router discovery
To discover the routers on the local link, the IPv6 router discovery process uses router advertisement and solicitation messages. Router advertisements messages are sent out periodically on each configured interface of an IPv6 router, and also in response to router solicitation messages from IPv6 nodes on the link. When a host does not have a configured unicast address, it sends a router solicitation message, enabling the host to autoconfigure itself quickly without having to wait for the next scheduled router advertisement message.
A router advertisement contains or determines:
- The type of autoconfiguration a node should use ?stateless or stateful.
- The Hop limit value a node should place in the IPv6 header.
- The network prefix a node should use to form the unicast address.
- The lifetime information of the included network prefix.
- The maximum transmission unit (MTU) size a node should use in sending packets.
- Whether the originating router should be used as default router.
Stateless autoconfiguration and renumbering of IPv6 nodes
Stateless autoconfiguration enables serverless basic configuration of IPv6 nodes and easy renumbering. Stateless autoconfiguration uses the network prefix information in the router advertisement messages as the /64 of prefix of the node address. The remaining 64 bits address is obtained by the MAC address assigned to the Ethernet interface combined with additional bits in EUI-64 format. For instance, a node with Ethernet interface address 0003B61A2061, combined with network prefix 2001:0001:1EEF:0000/64 provided by router advertisement, will have an IPv6 address as 2001:0001:1EEF:0000:0003:B6FF:FE1A: 2061.
Renumbering of IPv6 nodes is possible through router advertisement messages, which contain both the old and new prefix. A decrease in the lifetime value of the old prefix alerts the nodes to use the new prefix, while still keeping their current connections intact with the old prefix. During this period, nodes have two unicast addresses in use. When the old prefix is no longer usable, the router advertisements will include only the new prefix.
文章整理：西部数码--专业提供域名注册、虚拟主机服务
Path Maximum Transfer Unit (MTU)
IPv6 routers do not handle fragmentation of packets, which is done, when necessary, by the originating or source node of the packet. IPv6 uses ICMP error reports to determine whether the packet size matches the MTU size along the delivery path. When a node reports 損acket too big?via an ICMP error report, the source node will reduce the size of the transmit packet. The process is repeated until there is no 損acket too big?error along the delivery path. This allows a node to dynamically discover and adjust to differences in the MTU size of every link along a given data path.
DHCPv6 and Domain Name Server (DNS)
In addition to stateless autoconfiguration, IPv6 also supports stateful configuration with DHCPv6. The IPv6 node has an option to solicit an address via DHCP server when a router is not found. The operation of DHCPv6 is mostly similar to that of DHCPv4; however, DHCPv6 uses multicast for many of its messages. IPv6 also introduces a new record type to accommodate IPv6 addresses in Domain Name Servers. The AAAA record, also known as 搎uad A? has been recommended by the IETF for mapping a host name to an IPv6 address.
IPv6 Deployment
IPv6 provides many benefits over legacy IPv4 technology; however, all agree that any successful strategy for IPv6 deployment requires it to coexist with IPv4 for some extended period of time. A number of strategies have been developed for managing this complex and prolonged transition from IPv4 to IPv6. The following subsections describe several of these strategies.
Dual-stack backbone
http://www.west263.com
以上信息与文章正文是不可分割的一部分,如果您要转载本文章,请保留以上信息，谢谢!
