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Difference 1.OSI and tcp / ip's?
(1) osi There are three definite core, services, interfaces, protocols. The tcp / IP and there is no clear distinction.
(2) osi before the protocol is invented, tcp / ip is invented in the protocol.
(3) osi seven layers, tcp / ip has four
(4) osi supports connectionless communication only connected to the network layer, the transport layer but supports connection-oriented communication.
tcp / ip at the network layer supports connection-oriented communication, support two types of communication connection at the transport layer at the same time.
Layer 2 and Layer 2.osi difference of
(1) based on the MAC address forwarding Layer, Layer IP based forwarding.
(2) Network Layer limited, three support large networks.
(3) is a basic Layer 2 network security domain, which means that the same story can network security from inside the terminal on the network is basically the same, unless there are other special security measures, the network can be divided into three a plurality of independent zones.
(4) based on the second floor DHCP VLAN technology. . Layer the OSPF EIGRP the ISIS technique the BGP the RIP
3.VRRP characteristics
characteristics: fast conversion, can use the IP and MAC address of the gateway, router conversion is transparent to the host, tracking uplink may be implemented.
Protocol: a local area network within the host are configured default route, when the host within the network
when the default router is closed, the virtual router over by Vice router, to the backup gateway.
Three 3.tcp handshake off four times.
(1) refers to the three-way handshake to establish a TCP when the need for client and server sends another SYN ACK packet and a total of three.
(2) means that the specified three-way handshake port of the server, to establish tcp connection, and connecting the client and synchronization server sequence number and acknowledgment number, and the size of the window tcp.
(3) in the three-way handshake is complete, the only thing is not sent to the other party, does not indicate that everything has been sent, it can not close the connection immediately, this time need to send a FIN message, it agreed to close the connection, so ack packet and fin packets are usually separate.
4.rip
(. 1) RIP is a distance-vector routing protocol, the shared routing table, using the hop count as the metric distance is management 120.
(2) work based on UDP, the port number is 520, and the presence of asynchronous update triggered updates.
Asynchronous update function: 1. no ack2 keep alive.
(3) broken ring mechanism: split level, not only from the intake port from the port.
Poison reverse split horizon, which is triggered update.
The maximum number of hops 15 hops.
Suppression timer, when the loops of the router, the router does not inhibit the addition table, inhibition for 180 seconds.