TCP/IP protocol & amp; packet notes

1. The protocol name corresponds to the device data packet name. The application layer http ftp transport layer TCP/UDP segment network layer IP router data packet datasync
Transmission reliability is not guaranteed. The upper layer protocol provides support for Link Layer Ethernet protocol switch frame Nic device drive, frame synchronization, conflict detection, data error verification, physical layer HUB twisted pair connection, and signal relay.
Ip packet format:

IP Address: loop back: 127. * is used for loop back testing on the local machine, usually 127.0.0.1. Loopback is a special network device in the system. If the destination address of the sent data packet is a loopback address or the IP address is the same as that of other network devices on the local machine, the data packet will not be sent to the network media, instead, the device is sent back to the upper-layer protocols and applications,

Route table explanation:
The Destination of the route table is the Destination network address, Genmask is the subnet mask, Gateway is the next hop address, Iface is the sending interface, and the U mark in Flags indicates that the entry is valid (some entries can be disabled ), the G flag indicates that the next hop address of this route entry is the address of a vro, And the entry without the G flag indicates that the destination network address is a network directly connected to the local interface and does not need to be forwarded by the vro, therefore, the next hop address is marked "*".

Tcp packet format: