some TCP/IP basics 5 layer model There are several TCP/IP layer models with 4 or 5 layers. The OSI model consists of 7 layers. The TCP/IP layers do not fit nicely into the OSI model. num layer function PDU protocols associated devices 5 Application Interface to user applications Data, Message BGP, DNS, DHCP, SMTP, SSH, HTTPS End user devise: PC, smartphone 4 Transport Ensures reliability and correct sequence Segment, Datagram TCP, UDP Firewall, gateway 3 Network Logical addressing, routing Packet, Datagram IP, ICMP, IGMP Layer 3 switch, router 2 Data Link Node-to-node data transfer Frame ARP, MAC, PPP Layer 2 switch, bridge, NIC, modem 1 Physical Raw transmission of binary data Bits IEEE 802.3 (Ethernet), IEEE 802.11 (WiFi) Network cable, hub, repeater, NIC PDU: Protocol Data Unit
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