IP Network Routing Technology

In recent years, the TCP/IP-based Internet has gradually developed into a super-large computer network with the largest number of users and the most resources in the world, therefore, TCP/IP has become a de facto industrial standard. IP networks are gradually becoming the mainstream of modern and future computer networks.

An IP network is composed of IP subnets connected by routing devices. These routing devices are responsible for finding routes between IP subnets and forwarding IP groups to the next IP subnet.

　　IP address

An IP address is the basis for data transmission in an IP network. It identifies a connection in an IP network. A host can have multiple IP addresses. The IP addresses in the IP Group remain unchanged during network transmission.

1. Basic address format

The current IP address uses a 32-bit address, represented in dotted decimal format, for example, 172.16.0.0. The address format is: IP address = network address + host address or IP address = Host address + subnet address + host address.

The network address is allocated by the Internet authority (InterNIC) to ensure the global uniqueness of the network address. The host address is assigned by the system administrator of each network. Therefore, the uniqueness of the network address and the host address in the network ensure the global uniqueness of the IP address.

2. Reserved Address Allocation

IP addresses can be divided into public addresses and private addresses based on their purposes and security levels. Public addresses are used in the Internet and can be accessed freely on the Internet. Private addresses can only be used in internal networks and can communicate with the Internet only through proxy servers.

To connect an organization or network to the Internet, you must apply for a public IP address. However, in consideration of special situations such as network security and internal experiments, three private addresses are reserved in the IP address. The address range is as follows:
10.0.0.0/8:10. 0.0.0 ~ 10.20.255.255
172.16.0.0/12: 172.16.0.0 ~ 172.31.255.255
192.168.0.0/16: 192.168.0.0 ~ 192.168.255.255

Networks with reserved addresses can only communicate internally, but cannot communicate with other networks. Because the reserved addresses in the Network may also be used by other networks, if the network is connected, the problem may occur because the address is not unique when looking for a route. However, these networks that use reserved addresses can interconnect with external networks by translating the reserved addresses in the network into public addresses. This is also an important way to ensure network security.

　　Classless Inter-Domain Routing (CIDR)

As the number of hosts connected to the Internet doubles every year, the Internet is faced with crises such as a shortage of Class B addresses, route table explosion, and exhaustion of the entire address. Classless Inter-Domain Routing (CIDR) is a direct solution developed to solve these problems. It gives the Internet enough time to wait for the generation of the next-generation IP protocol.

According to the CIDR policy, you can apply for several Class C addresses instead of applying for a separate class B address to solve the problem of lack of Class B addresses. The assigned Class C addresses are not random, but continuous. They have the same highest bit, that is, they have the same prefix. Therefore, the route table only needs one table item to represent a group of network addresses, this method is called "route table clustering ".

In addition to the "route table clustering", each ISP can obtain an address space from InterNIC and then allocate these addresses to users.

　　Route Selection technology

The route selection in the IP network is completed by the routing device. A vro executes a certain routing protocol to find the best route to the destination host or network for the IP datagram, and forwards the datagram to achieve route selection.

1. Routing Protocol

There are two types of routing protocols:

Routing Protocol)
These protocols use certain routing algorithms to find the optimal path to the target host or network, such as RIP.

Routed Protocol)
This type of protocol transmits data packets along the selected path. For example, you can use the IP protocol to convert a physical connection to a network connection to achieve the main function of the network layer-route selection.

2. Direct Connection and non-direct connection

The IP protocol forwards data based on the route. There are two types of routes in a vro: directly connected routes and non-directly connected routes.

The network directly connected to each network interface of the router uses a direct connection route for communication. A direct connection route is automatically generated after the IP address of the router network interface is configured. Therefore, if no special restrictions are imposed on these interfaces, the directly connected networks of these interfaces can communicate directly.

Communication between two or more vrouters uses a non-direct connection route. A non-direct connection route is a static route manually configured or a dynamic route obtained by running the dynamic routing protocol. Static Routing is more operable and secure than dynamic routing.

IP networks have gradually become the standard of modern networks. When using the IP protocol to build a network, you must use a routing device to interconnect IP subnets and use routing mechanisms between IP subnets, establish a hierarchical Internet through IP Gateway interconnection.

[1]

Article entry: csh responsible editor: csh