Understanding the advantages of IPv6 network protocol (1)

The IP address of IPv4 has come to an end, so it is extremely important to use the IPv6 network protocol. So is IPv6 only used to relieve the Internet address pressure? Of course, the answer is NO. So what advantages is it worth using? Now let's take a look at how it is said in the article.

(1) huge address space

The source and target addresses of IPv6 are both 128-bit (16 bytes) and can provide IP addresses almost unrestricted. 128-bit can express combinations of over 3.4x1038 possible combinations, that is to say, the whole Earth can be allocated 6.65X1023 IP addresses per square meter. The purpose of this huge address space is to better divide the router domain name into layers, it also better reflects the topology of the modern Internet, makes the design of addressing and routing layers more flexible, and allows multi-level subnet division and address allocation, covers all subnets that range from the Internet backbone to the organization. These are what IPv4-based Internet lacks. Even if all IP addresses have been assigned to the host, IPv6 still has enough addresses for future use. Because there are more available addresses, some address-saving technologies are no longer needed, such as NAT translation, in this way, end-to-end connections can be fully established.

(2) New Protocol Header Format

The IPv6 Header adopts a new format to minimize the protocol header overhead. The IPv6 Header consists of a basic packet header and multiple extended packet headers. The basic packet header has a fixed length of 40 bytes and must be processed by all routers. Because most packets on the Internet are simply forwarded by routers, a fixed header length will help speed up routing. To achieve this goal, the number of fields in the IPv6 packet header has been reduced from 12 (including options) in IPv4 to 8; the number of fields that must be processed by the Intermediate router has been reduced from 6 to 4, in this way, the intermediate router in the network is more efficient when processing this simplified IPv6 protocol header. Few fields are used, such as fields that support splitting and the options in IPv4 headers, it is moved to the extended packet header of the IPv6 packet header. IPv6 defines multiple extension headers, which can provide strong support for multiple applications and support new applications in the future. IPv4 and IPv6 headers are not interoperable. IPv6 is not a superset of IPv4, that is, it is not backward compatible with IPv4. Therefore, each host or router must implement both IPv4 and IPv6 protocols to identify and process two different protocol headers. Although the number of addresses in the new IPv6 protocol is four times the number of IPv4 addresses, the length of the new IPv6 protocol header is only two times that of the IPv4 protocol header.

(3) Effective and hierarchical addressing and Routing Structure

Similar to the IPv4 address space division rules, the IPv6 Network Protocol address space is also divided based on the value of the high bit of the address. High positions and their fixed values are called format prefixes (FP ). Divide IPv6 address space based on the number of format prefix bits. Currently, allocated network service access points (NSAP) globally available unicast addresses, local link unicast addresses, local site unicast addresses, and multicast addresses, the Unicast address set that can be used by IPv6 nodes is composed of global unicast addresses, local link unicast addresses, and local site addresses. The field in the global address in IPv6 creates a three-layer topology.

IPv6 uses global addresses to create an effective, hierarchical, and generalized Routing Structure Based on the existing multi-level ISP system. A public topology is a collection of large and small ISPs that provide access services. The site topology is a collection of internal subnets of an organization site. The interface identifier uniquely identifies an interface on the internal subnet of an organization site. In the Internet with IPv6, the backbone router has a smaller route table, which corresponds to the Routing Structure of the global ISP.

(4) stateful and Stateless Address Configuration

To simplify host configuration, IPv6 supports both stateful Address Configuration (for example, Address Configuration when a DHCPv6 server is available) and Stateless Address Configuration (for example, in the absence of a DHCPv6 server ). In Stateless Address configuration, the host on the Link automatically configures the IPv6 address (called the local link address) suitable for this link, or the IP address suitable for IPv4 and IPv6 coexistence, or the IP address prefixed by the local router. Even if no vro is available, all hosts on the same link can automatically configure their local link addresses so that communication can be performed without manual configuration. The local link address can be automatically configured within one second, so the communication between nodes on the same link is almost done immediately. In contrast, an IPv4 host using DHCP takes an entire 1 minute: First discard the DHCP configuration, and then configure an IPv4 address.