Layers in the Internet Protocol suite

he IP suite uses encapsulation to provide abstraction of protocols and services. Generally a protocol at a higher level uses a protocol at a lower level to help accomplish its aims. The Internet protocol stack has never been altered, by the IETF, from the four layers defined in RFC 1122. The IETF makes no effort to follow the seven-layer OSI model and does not refer to it in standards-track protocol specifications and other architectural documents.

4. Application	DNS, TFTP, TLS/SSL, FTP, Gopher, HTTP, IMAP, IRC, NNTP, POP3, SIP, SMTP, SNMP, SSH, TELNET, ECHO, RTP, PNRP, rlogin, ENRP
	Routing protocols like BGP, which for a variety of reasons run over TCP, may also be considered part of the application or network layer.
3. Transport	TCP, UDP, DCCP, SCTP, IL, RUDP
2. Internet	Routing protocols like OSPF, which run over IP, are also to be considered part of the network layer, as they provide path selection. ICMP and IGMP run over IP and are considered part of the network layer, as they provide control information.
	IP (IPv4, IPv6)
	ARP and RARP operate underneath IP but above the link layer so they belong somewhere in between.
1. Network access	Ethernet, Wi-Fi, token ring, PPP, SLIP, FDDI, ATM, Frame Relay, SMDS

Some textbooks have attempted to map the Internet Protocol suite model onto the seven layer OSI Model. The mapping often splits the Internet Protocol suite's Network access layer into a Data link layer on top of a Physical layer, and the Internet layer is mapped to the OSI's Network layer. These textbooks are secondary sources that contravene the intent of RFC1122 and other IETF primary sources. The IETF has repeatedly stated that Internet protocol and architecture development is not intended to be OSI-compliant.

RFC3439, on Internet architecture, contains a section entitled: "Layering Considered Harmful": Emphasizing layering as the key driver of architecture is not a feature of the TCP/IP model, but rather of OSI. Much confusion comes from attempts to force OSI-like layering onto an architecture that minimizes their use.