Five agreements: the number of physical network should pass
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2019-09-05 22:31:29
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Physical Layer: electrical 010101
data link layer:
The physical layer stratified electrical signal, each set of data called packets or data frames, each data frame is divided into: a header and a data head data of two parts, the head: a fixed 18 bytes, 6: sender address / 6: receiver address / 6: data type
Network layer:
Each card has a unique address mac: 12 hexadecimal number (the first six are the vendor ID, the line number is six), ip: ipv4: 32-bit binary represented: dotted decimal from 0.0 .0.0 to 255.255.255.255, the range is limited, not shown all the network devices, so there ipv6- subnet Mask: subnet mask and ip is determined by two ip is in the same network segment, the ip address and subnet mask do a bitwise ip address: 172.16.10.1: 10101100.00010000.00001010.000000001 Subnet Mask: 255.255.255.0: 11111111.11111111.11111111.000000000 bitwise aND operation: 172.16.10.0 10101100.00010000.00001010.000000000-172.16.10.10 / 24 comprising the ip address and subnet mask -ip have relations with mac converter - host 172.16.10.10/24 access 172.16.10.11/24 - ARP protocol: broadcast way to send packets, the destination hosts mac address -mac address learning: mac ip address and address mapping table - the first one will be added to the received data { '172.16.10.11 ": ddsadfgegsdgsdg} in ip / mac mapping table - and any kind of protocol has its head content
Transport Layer:
tcp agreement: - three-way handshake, four wave (focus, Figure), how the connection is established, how to send data to ensure reliable, disconnect how to disconnect, there is a state in the process of establishing a connection - If you see a large number of services syn_rcvd state -dos and ddos attacks: denial of service attacks, distributed denial of service attacks - port number: port range 0-65535,0-1023 to occupy the port system -udp protocol: - send no need to respond, so the data can not rely on , (see video) - port - + IP subnet mask uniquely determined by a device - via IP subnet mask + CD + port number uniquely identify a software - semijoin pool
Application layer:
Origin www.cnblogs.com/oxtime/p/11466551.html