Shulou(Shulou.com)06/01 Report--

I. Overview of IPv6

The IP addresses currently used are all IPv4 versions, and the IPv6 version is mainly developed for the following reasons:

1. Insufficient IPv4 address space and unreasonable allocation

2. The IPv4 head is too complicated.

3. Use IPv4 to make router and host configuration complex.

4. It is difficult for IPv4 to re-address

5. Using IPv4 will result in huge routing table information.

6. IPv4 does not have enough support for security, multicast and mobile networks.

In view of the above problems, the current solutions are as follows:

1 、 NAT

Use NAT technology to convert private addresses of the intranet into IP addresses that can communicate in the public network, saving address space; but doing NAT will consume system resources and destroy end-to-end IP applications.

2. Subnetting

Subnetting divides a large IP segment into multiple small IP segments to meet more network needs, but subnetting will further lead to a waste of IP, each network has a network address and a broadcast address, these two addresses can not communicate, so the more networks are divided, the more IP is wasted.

3 、 DHCP

DHCP can automatically assign IP addresses as needed, and IP that has not been used for a long time will be recycled for re-allocation.

4. Classless inter-domain routing (CIDR)

CIDR is used to solve the problem of large routing table. CIDR aggregates multiple routing entries belonging to a subnet into a single route to reduce the complexity of the routing table.

5. Strengthen address management

2. IPv6 basic header

The basic header of IPv6 is much less than that of IPv4, and the meanings of its items are as follows:

Version: version with a value of 6

Traffic class: equivalent to Service Type in IPv4, it is used to identify the type of service.

PPP: indicates the priority of IP packets and is rarely used

D: 0 indicates general delay, 1 indicates low delay

T: 0 indicates general transmission, and 1 indicates high transmission

R: if 0 means general reliability, if 1 means high reliability.

Flow Label: stream label, 20 bits long, used to identify the same data stream.

PayloadLength: the total length of the packet, equivalent to the Package Length in IPv4.

Next header: the upper layer protocol behind the packet, which is equivalent to Protocol in IPv4.

1:ICMP

4:IP

6:TCP

17:UDP

In addition to the above protocol identification, Next header can also be an identity extension header, which will be described later.

Hop Limit: TTL equivalent to IPv4, with a value range of 1-255.

III. IPv6 extension header

The extension header is located in the position between the basic headers of the IPv6 and the four segment headers.

Six option extension headers are defined in IPv6: hop-by-hop option header, routing header, segment header, destination option header, authentication header (AH) header, encapsulating security payload (ESP) header.

Extension headers are used to implement the extension functions in IPv6. Since IPv6 has not popularized the functions of each extension header, it will not be described here. Let's take a look at the corresponding values of each extension header in the Next header field.

0: jump head by head

43: choose the head of the road

44: segment header

51: authentication header

52: encapsulated security payload head

59: no next hop

60: destination option header

RFC1883 stipulates that extension header links should be in the following order:

1. IPv6 basic header

2. Hop-by-hop option head

3. Destination option header

4. select the head of the road

5. Sectional head

6. Authentication header

7. Encapsulate the security payload head

IV. IPv6 addressing

IPv6 uses 128bit binary values to identify address information, which is converted to hexadecimal values in order to simplify the difficulty of writing and memorizing.

There are three representations of IPv6 addresses, which are:

1. Preferred format

Converts a binary number directly to a hexadecimal number.

2. Compressed representation

Method 1: leading 0 is omitted.

Method 2: the 0 between two consecutive colons can be omitted and can be directly used with two colons, such as "::", but an IPv6 address can only be used once, otherwise confusion will occur.

IPv6 address is divided into unicast address, multicast address and anycast address.

1. Unicast address

A unicast address is an address that can communicate on the Internet. The range of unicast is: 2000 3fff::/4.

2. Link-local address

It is used to communicate between neighboring nodes on the same link, which is equivalent to the 169.254.0.0 IPv4 16 address. IPv6 routers do not forward packets with link-local addresses. Its prefix is FE80::/64, and its prefix is fixed.

3. Site local address

For local networks that cannot access the internet, you can use the site local address, which is equivalent to the private address in the IPv4. The prefix is FEC0::/48. The local address of the site has been reclaimed because there is enough IPv6 data that a private address is not needed to save space.

4. Loopback address

The loopback address:: 1 is used to identify a loopback interface that allows a node to send packets to itself. Equivalent to the loopback address of IPv4 127.0.0.1.

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