Internet Protocol

## Internet agreement – Generalization ： From top to bottom , The closer you get to the user , The lower it goes, the closer it gets to the hardware – application layer : + Define the data format of the application + [HEAD( Ethernet header ) [HEAD(IP header ) [HEAD(TCP header ) DATA( Application layer packets )]]]

– Transport layer ( Port to port communication ): Define the port number + port ： * 0 To 65535(2^16) The integer of * The process uses the number of the network card * adopt IP+mac Determine host , Just determine the host + port ( Socket socket), Communication between programs can be carried out + UDP agreement ： * Add a new port dependent protocol to the packet * Data packets [HEAD( send out 、 receive mac) [HEAD( send out 、 receive ip) [HEAD( send out 、 Receive port ) DATA]]] * Simple , Poor reliability , I don't know whether the other party accepts the package + TCP agreement ： * With confirmation mechanism UDP agreement * complicated , Difficult to achieve , Consumption of resources “` tcp/ip connect: tcp/ip Three handshakes of Be marked with syn Data packets of ————-> Be marked with syn/ack Data packets of client <————- server Be marked with ack Data packets of ————–> “`

– The network layer ( Host to host communication ): Definition IP “` tcp/ip finish: tcp/ip Four handshakes fin <————- ack client ————-> server fin ————-> ack <————- “`

– The network layer ( Host to host communication ): + IP agreement * ipv4: – 32 Binary bits indicate , It is composed of network part and host part , – Subnet mask : The network part is 1, The host part is 0, Purpose judgment ip The network part of , Such as 255.255.255.0(11111111.11111111.11111111.00000000) – IP Data packets ： header Head+ data Data, Put into Ethernet packets Data part [HEAD [HEAD DATA]] – IP Packet delivery ： + Not the same network ： Can't get mac Address , Send data to gateway , Gateway processing – ARP(Address Resolation Protocol): Address Resolution Protocol , adopt ip analysis mac Address + The same network ：mac Address FF:FF:FF:FF:FF:FF:FF, Broadcast data , contrast ip, Does not conform to packet loss

– Link layer ： Definition mac + Define package ( frame Frame) * header (Head): Some description items of data package , Sender 、 The receiver 、 data type * data (Data): The specific content of the packet * Data packets :[HEAD DATA] + Define the network card and the unique network card mac Address * Ethernet stipulates that all terminals connected to the network should have network card interfaces , The packet must be from a network card mac Address to another network card interface mac Address * mac The only global ,16 position 16 Bitwise composition , front 6 Manufacturer number , after 6 Network card serial number + Broadcasting sends data * Send data packets to all devices in this network , Compare recipients mac Address , It's not packet loss , Is to accept

– Physical layer ： The physical layer + terminal (pc,phone,pad…) The physical connection of ( optical cable , cable , route …), Responsible for delivering 0 and 1 The signal

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