IP protocol from 0 to 1

Network layer protocol: IP protocol Internet Protocol

Responsibilities of the network layer: realize the communication between the host and the host across the local area network, and complete the routing function

Routing problem: solve the problem of long-term goals and short-term goals, and solve the problem of short-term goals through long-term goals

IP address:

IPV4: 32-bit unsigned positive number (4 bytes), usually expressed in dotted decimal: 127.0.0.1

IPV6: 128-bit unsigned integer

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IP address consists of routing number + host number.

Disassembly of the network number:

1, static mode: divided into 5 types of networks

Class A network IP: The network number occupies 8 bits, the first digit is 0, and the host number occupies 3 bytes (8 bits * 3)

For example: 10.192.93.2 into binary: 0b 0000 1010 . 192.93.2

The network number is 8 bytes of money: 0000 1010 -> 10.0.0.0 is the network number

Host ID: 0.192.93.2

2, dynamic, adds a netmask

Netmask: Unsigned 32-bit integer, characteristic, all 1s in front, all 0s in the back

For example: mask 224.0.0.0, written in binary: 1110 0000.0.0.0, the first three digits are all 1s, followed by all 0s, 1110 0000.0.0.0 and / 3 This way of writing expresses the same thing, both meannetmask: 224.0.0.0;

ip address = network number + host number

Calculation of network number and host number:

Special IP address

If the host number is all 0 (network number), it will not be allocated. If the host number is all 1 (broadcast number), it will not be allocated.

127.0.0.0/8 is reserved as the loopback address,

IP addresses are divided into intranet and public addresses.

Intranet IP range:

The IPs of the same intranet cannot be duplicated, and the host IPs of different intranets can be duplicated, but the external IPs cannot be duplicated.

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IP routing and forwarding function

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IP protocol header parsing

DNS Protocol: Domain Name Resolution Protocol

In order to solve the problem that IP addresses are difficult to remember, a protocol for resolving IP addresses using domain names is specified.