Technical Features of IPv6
3.1 What are the significant advantages of IPv6 over IPv4?
Compared with IPv4, IPv6 has the following significant advantages:
1) The address capacity is greatly expanded from the original 32-bit to 128-bit, which completely solves the problem of IPv4 address insufficiency. the hierarchical address structure is supported to facilitate addressing; extended support for multicast and any multicast address, which allows data packets to be sent to any node or group of nodes;
2) large-capacity address space can be automatically configured with stateless addresses, enabling IPv6 terminals to quickly connect to the network without manual configuration, achieving real plug-and-play;
3) The Header Format is greatly simplified, which effectively reduces the overhead of the router or switch for header processing, which is very beneficial to the vro or switch designed for hardware header processing;
4) Enhanced support for Extended Headers and options. This not only makes forwarding more effective, but also provides full support for loading new applications on the network in the future;
5) The use of stream tags allows us to provide personalized network services for the data packet type, and effectively ensure the service quality of related services;
6) authentication and Privacy: IPv6 uses IPSec as a required protocol to ensure the integrity and confidentiality of end-to-end communication at the network layer;
7) IPv6 has made many improvements in mobile networks and real-time communication. In particular, unlike IPv4, IPv6 has powerful automatic configuration capabilities, which simplifies system management for mobile hosts and local networks.
3.2 header Structure
3.2.1 what is the IPv6 Header structure?
The structure of the new IPv6 Header is much simpler than that of IPv4. The IPv6 Header deletes many uncommon fields in the IPv4 header and adds them to the option and header extension; the options in IPv6 are more strictly defined. IPv4 has 10 fixed-length domains, 2 address spaces, and several options. IPv6 only has 6 domains and 2 address spaces.
Although the IPv6 Header occupies 40 bytes, It is 1.6 times that of the 24-byte IPv4 header, but because of its fixed length, the IPv4 header is longer), it does not need to consume too much memory capacity.
Header length in IPv4), service type of service, TOS), identifier identification), flag), segment offset fragment offset) and header checksum) these six domains are deleted. Total Packet length), protocol type), and time to live, TTL) the names or functions of the three domains are changed, and the options function is changed completely, two new domains are added, namely priority and flow tag.
Compare IPv4 with IPv6 headers.
| Table 1 IPv4 Header Format |
| 4bit version |
4-bit Header Length |
8bit service type |
16-bit Packet Length |
| Identifier 16bit) |
Flag (4bit) |
Segment offset 12bit) |
| 8 bit survival time) |
8 bit transmission protocol) |
Header checksum and 16bit) |
| Source IP address 32bit) |
| Destination IP address 32bit) |
| Option 24bit) |
Fill (8bit) |
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| Table 2 ipv6 Header Format |
| 4bit version |
4bit priority |
24bit stream tag |
| Net charge length (16 bits) |
Next header (8bit) |
HOP limit (8bit) |
| Source IP address 128bit) |
| Destination IP address 128bit) |
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3.3 address question 3.3.1 why is the IPv6 Protocol address length 128 bits?
Some may ask, if the IPv4 address is not enough, just add a few more addresses to IPv4. Why not use the IPv6 128-bit address? This type of question is caused by a lack of understanding of the chip design and CPU processing methods, and insufficient foresight for future network expansion. In the chip design, we know that all values are represented by "0" and "1, the CPU processing wordlength has now gone through 4-bit, 8-bit, 16-bit, 32-bit, 64-bit, etc. We know that in the computer, when the data can be expressed by the binary number of 2 exponential power characters, the CPU has the highest processing efficiency. The IPv4 address corresponds to a 32-bit font because the CPU size of the host on the Internet was 32 bits. Currently, 64-bit machines are widely used, and 128-bit machines are growing. Setting the address as 64-bit is insufficient in terms of network scalability. Setting the address as another length will reduce the efficiency of hardware chip design and programming, therefore, considering the processing efficiency and future network scalability, it is very appropriate to set the IPv6 address length to 128 bits.
3.3.2 what is the concept of IPv6 128-bit address?
IPv6 provides a 128-bit address space. The huge address capacity that IPv6 can provide can be described in the following aspects: There are 2128 different IPv6 addresses, that is, the number of globally allocable addresses is 340,282,366,920,938,463,463,374,607,431,768,211,456. if the address is allocated by land area, 2.2*1020 addresses can be obtained per square centimeter. The chances of IPv6 address depletion are very small. For a long foreseeable period, IPv6's 128-bit address length forms a huge address space that can provide a globally unique address for all conceivable network devices, IPv6's ample address space will greatly meet the address growth needs with the emergence of smart network devices, such as personal data Assistant PDA), Mobile Phone) and the home network access device HAN. 3.3.3 what is the IPv6 address representation?
IPv4 addresses are represented in dotted-decimal format. 32-bit addresses are divided into four eight-bit groups. Each eight-bit address is written in decimal format and separated by dots. The IPv6 128-bit address is a 16-bit grouping. Each 16-bit grouping is written into four hexadecimal numbers separated by colons, which are called the colon hexadecimal format. For example, 21DA: 00D3: 0000: 2F3B: 02AA: 00FF: FE28: 9C5A is a complete IPv6 address. IPv6 address representation has the following special situations: the leading and leading zeros in each 16-bit group in an IPv6 address can be removed for simplified representation, but each group must retain at least one digit. In the preceding example, the address is written as 21DA: D3: 0: 2F3B: 2AA: FF: FE28: 9C5A after the leading zero bit is removed. Some addresses may contain long zero-sequence columns. To further simplify the notation, you can also combine adjacent consecutive zero-bit pairs in the colon hexadecimal format, expressed by double colons. The ":" symbol can only appear once in an address. It can also be used to compress the adjacent zero bits in the front and end of the address. For example, the address 1080: 0: 0: 0: 8: 800: 200C: Jun A, 0: 0: 0: 0: 0: 0: 0: 0: 0: 0: 0: 0: 0: 0 can be expressed as the compression format 1080: 8: 800: 200C: 0000a,: 1 ,::. In IPv4 and IPv6 hybrid environments, it is sometimes more suitable to use another form: x: d. d. d. d, where x is the hexadecimal value of the six high-order 16-bit groups in the address, and d is the standard IPv4 representation of the four low-order 8-bit groups in the address ). For example, the address 0: 0: 0: 0: 0: 13.1.68.3, 0: 0: 0: 0: 0: FFFF: 129.144.52.38 is compressed in the format of: 13.1.68.3 ,:: FFFF.129.144.52.38. To use a text IPv6 address in a URL, the text address should be closed with the symbols "[" and. For example, the text IPv6 address FEDC: BA98: 7654: 3210: 7654: FEDC: BA98: 3210: 7654: http: // [FEDC: BA98: 3210: FEDC: BA98: 7654: 3210]: 80/index.html.
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3.3.4 if the IPv6 address is 128 bits, does it take a lot of time to configure the address? IPv6 supports automatic address configuration, which is a plug-and-play mechanism. The IPv6 node automatically obtains the IPv6 address and gateway address through address configuration. IPv6 supports automatic configuration of stateless addresses and automatic configuration of stateful addresses. In the automatic configuration mode of stateless addresses, the network interface that needs to configure the addresses first uses the neighbor discovery mechanism to obtain a local link address. After obtaining the local address of the link, the network interface receives the address prefix advertised by the router and obtains a global address based on the Interface ID. The automatic configuration of status addresses, such as Dynamic Host Configuration Protocol DHCP, requires a DHCP server to Obtain Address Configuration Information from the DHCP server in Client/Server mode. 3.3.5 what types of IPv6 addresses are available? All types of IPv6 addresses are allocated to interfaces instead of nodes. An IPv6 address is a 128-bit identifier of a single interface or a group of interfaces. There are three types: (1) Unicast) The identifier of a single interface. The packet sent to the unicast address is sent to the interface identified by the address. Any Unicast address of a node with multiple interfaces can be used as the identifier of the node. An IPv6 unicast address is an address that is aggregated with a continuous bit mask, similar to an IPv4 address of CIDR. Unicast addresses in IPv6 can be allocated in multiple forms, including all globally aggregated unicast addresses, NSAP addresses, IPX hierarchical addresses, site local addresses, link local addresses, and host addresses running IPv4. The Unicast address has the following two special addresses: uncertain address: 0: 0: 0: 0: 0: 0: 0: 0: 0: 0: 0: 0: 0. It cannot be assigned to any node. One of its application examples is that when initializing a host, you can put an uncertain address in the source address field of any IPv6 packet sent by the host before the host has obtained its own address. The uncertain address cannot be used as the destination address in the IPv6 package or in the IPv6 route header. The loopback address Unicast address 0: 0: 0: 0: 0: 0: 0: 0: 1 is called the loopback address. The node uses it to send IPv6 packets to itself. It cannot be assigned to any physical interface. (2) IDs of An AnyCast address group of interfaces generally belong to different nodes. The packet sent to any multicast address is sent to one of the interfaces identified by this address. The Routing Protocol measures the distance closest ). Any IPv6 multicast address has the following restrictions: · any multicast address cannot be used as the source address, but only as the destination address. · any multicast address cannot be specified for an IPv6 host but only for an IPv6 router;
The identifier of an IPv6 MultiCast address (3) MultiCast address group interface generally belongs to different nodes. The packet sent to the multicast address is sent to all interfaces identified by the address. The address starting from 11111111 indicates that the address is a multicast address. IPv6 multicast address IPv6 does not have a broadcast address, and its function is being replaced by a multicast address. In addition, in IPv6, all "0" and "1" fields are valid unless otherwise excluded. In particular, the prefix can contain the "0" value field or end with "0. A single interface can specify multiple types of IPv6 addresses for unicast, multicast, Or multicast) or range.
3.3.6 what is an IPv6 clustered global unicast address? IPv6 designs an Address with a hierarchical structure for point-to-point communication. This Address is called Aggregatable Global Unicast Address, which is defined in RFC2374. Clustering addresses have three levels of hierarchical structure: Public topology: suppliers and exchange groups that provide public Internet transfer services; site topology: specific local sites or organizations, public transfer service is not provided to nodes outside the site. Interface identifier: identifies the interface on the link. the hierarchical structure of global unicast addresses can be clustered, as shown in. The first three addresses are the prefix of the address type, which is used to distinguish other address types. The subsequent 13-bit tla id, 32-bit nla id, 16-bit sla id, and 64-bit host interface ID are used to identify the Top-down TLA Level Aggregator in the hierarchical structure, top aggregation), NLANext Level Aggregator, lower aggregation), SLASite Level Aggregator, site-Level aggregation) and host interface. RES reserved for future TLA or NLA extension. TLA is a public network access point that is connected to long-distance service providers and telephone companies. It obtains the address from an international Internet Registrar such as IANA. NLA is usually a large ISP. It requests an address from TLA and assigns an address to the SLA. An SLA can also be called a subscriber). It can be an organization or a small ISP. The SLA is responsible for allocating addresses to its subscribers. The SLA usually assigns its subscribers an address block consisting of consecutive addresses so that these organizations can establish their own address hierarchical structure to identify different subnets. The bottom layer of the hierarchical structure is the network host.
This address format is designed to support clustering based on the current supplier and a new clustering type called the Exchange Board. Its Combination enables efficient route aggregation to be used to directly connect to the vendors and sites connected to the Exchange Board. The site can be connected to any of the two types of clustering points. 3.3.7 what is the difference between IPv6 Address Allocation and IPv4 address allocation? In IPv4, the address is owned by the user. That is to say, once a user applies for an address space from an organization, he will always use the address space, regardless of the Internet service provider's ISP. The disadvantage of this method is that the ISP must maintain a table item for each user's network number in the route table. As the number of users increases, there will be a large number of special routes that cannot converge. Even if there is no classless Inter-Domain Routing CIDR, such route table explosion cannot be handled. IPv6 changes the address allocation mode from user-owned to ISP-owned. The global network number is assigned to the ISP by the Internet address allocation organization IANA. the user's global network address is a subset of the ISP address space. Whenever a user changes the ISP, the global network address must be updated to the address provided by the new ISP. In this way, the ISP can effectively control route information and avoid route explosion. 3.3.8 how many addresses does an IPv6 host have? Generally, an IPv6 host has multiple IPv6 addresses, even if the host has only one single interface. An IPv6 host can have the following single point transfer addresses at the same time: · The local link address of each interface; · The Unicast address of each interface can be a local site address and one or more global addresses that can be aggregated); · loopback) the loopback address of the interface: 1 ). In addition, each host must always listen to the following multi-point transfer address information: · all nodes in the local node multicast address FF01: 1 ); · All node multicast addresses within the local range of The Link FF02: 1); · Request node solicited-node) multicast address if an interface of the host is added to the request node group ); · multicast address if an interface of the host is added to any multicast group ). 3.3.9 what are the addresses of an IPv6 router? An IPv6 router can be assigned the following spof addresses: · Local Link addresses of each interface; · The Unicast address of each interface can be a local site address and one or more global addresses that can be aggregated); · subnet-vro any multicast address; · other any multicast addresses are optional ); · The loopback address of the loopback interface: 1 ). Similarly, in addition to the preceding addresses, the vro must always listen to the information flow from the following multicast addresses: · all node multicast addresses within the local range of the node FF01: 1 ); · All vro multicast addresses within the local range of the node FF01: 2); · all node multicast addresses within the local range of The Link FF02: 1 ); · All vro multicast addresses within the local range of The Link FF02: 2); · all vro multicast addresses within the local range of the site FF05: 2 ); · Request node solicited-node) multicast address if an interface of the router is added to the requesting node group); · multicast address if an interface of the router is added to any multicast group ).
