IMPORTANT PROTOCOLS AT DIFFERENT LAYERS.....

Layer 1 protocols (Physical Layer):-
 ADSL Asymmetric digital subscriber line
 ISDN Integrated Services Digital Network RS-232, a serial line interface originally developed to connect modems and computer terminals
 SONET Synchronous Optical NETworking


Layer 2 protocols (Data Link Layer):- ARCnet
 DCAP Data Link Switching Client Access Protocol
 Econet
 Ethernet
 FDDI Fiber Distributed Data Interface
 Frame Relay
 HDLC High Level Data Link Control
 IEEE 802.11
 IEEE 802.16
 LocalTalk
 L2F Layer 2 Forwarding Protocol
 L2TP Layer 2 Tunneling Protocol
 LAPD Link Access Procedures on the D channel
 LLDP Link Layer Discovery Protocol
 PPP Point-to-Point Protocol
 PPTP Point-to-Point Tunneling Protocol
 Token ring

Layer 3 protocols (Network Layer) :-
 ICMP Internet Control Message Protocol
 IGMP Internet Group Management Protocol
 IGRP Interior Gateway Routing Protocol
 IPv4 Internet Protocol version 4
 IPv6 Internet Protocol version 6
 IPSec Internet Protocol Security
 IPX Internetwork Packet Exchange OSPF Open Shortest Path First
 BGP Border Gateway Protocol
 RIP Routing Information Protocol

Layer 4 protocols (Transport Layer) :-
 TCP Transmission Control Protocol
 UDP User Datagram Protocol

Layer 5 protocols (Session Layer) :- 9P Distributed file system protocol developed originally as part of Plan 9
 NCP NetWare Core Protocol
 NFS Network File System
 SMB Server Message

Layer 7 protocols (Application Layer):-

 DNS, Domain Name System
 DHCP, Dynamic Host Configuration Protocol
 FTP, File Transfer Protocol
 Gopher, a hierarchical hyperlinkable protocol
 HTTP, HyperText Transfer Protocol
 IMAP, Internet Message Access Protocol
 IRC, Internet Relay Chat protocol
 ISUP, ISDN User Part
 MIME, Multipurpose Internet Mail Extensions
 NetBIOS, File Sharing and Name Resolution protocol - the basis of file sharing with Windows.
 rsync, a file transfer protocol for backups, copying and mirroring
 SMTP, Simple Mail Transfer Protocol
 SNMP, Simple Network Management Protocol
 SOAP, Simple Object Access Protocol
 Telnet, a remote terminal access protocol TFTP, Trivial File Transfer Protocol, a simple file transfer protocol