Protocols layer classification based on OSI Reference Model

A protocol is a standard set of rules that allow electronic devices to communicate with each other. Each rules are known to each machine in a network. It has all the information required to transmit a data from one machine to another machine. These rules includes what type of data to be transmitted, what commands are used to send and receive data, how to confirm data transfer etc.

Here in this post we will classify some protocol on the basis of OSI reference model, based on the layer they operates on.

The OSI Model (Open Systems Interconnection Model) is a conceptual framework used to describe the functions of a networking system. It defines universal set of rules, which make interoperability between different products and software possible. In the OSI reference model, the communications between a computing system are split into seven different abstraction layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

Some Protocols and OSI Layers

Protocol being classified:

  • SIP
  • SSI
  • DNS
  • FTP
  • Gopher
  • MIME
  • XDR
  • HTTP
  • NFS
  • NTP
  • SMPP
  • SMTP
  • SNMP
  • Telnet
  • DHCP
  • Netconf
  • IP
  • IPv4
  • ATM
  • SDLC
  • SCTP
  • DCCP
  • SPX
  • SAP
  • PPTP
  • RTP
  • IEEE 802.2
  • LLC
  • L2TP
  • IEEE 802.3
  • PDH
  • PON
  • OTN
  • DSL
  • IEEE 802.3
  • IPv6
  • ARP
  • ICMP
  • IGMP
  • IPX
  • Frame Relay
  • TCP
  • UDP
  • HDLC
  • SLIP
  • IEEE 802.11
  • IEEE 802.15
  • IEEE 802.16
  • Bluetooth
  • RS-232
  • RS-449
  • USB
Only short descriptions are provided here, you need to learn about each protocal your interested through other resources out there.


The Session Initiation Protocol (SIP) is an Application layer protocol. SIP was designed to initiate interactive sessions on an IP network. Programs that provide real-time communication between participants can use SIP to setup modify, and terminate a connection between two or more computers, allowing them to interact and exchange data.


The Simple Sensor Interface is an Application layer protocol. The SSI communications protocol is intented to be used to transfer data between sensor unit(s) and a terminal. It can also be used for point-to-point (UART) and networking (nanoIP) applications.


The Domain Name System is an Application layer protocol. DNS was designed for the Internet as a hierarchical and distributed database system to resolve the Internet's IP addresses from their corresponding domain names, and vice versa. DNS uses the User Datagram Protocol (UDP) on port 53 to serve DNS queries. UDP is preferred because it is fast and has low overhead.


The File Transfer Protocol is an Application layer Protocol. It is a protocol used to transfer files between an FTP host/server and an FTP client computer on the Internet. FTP uses port 20 for data transfer and port 21 for control transfer.


The Gopher protocol is a communications protocol designed for distributing, searching, and retrieving documents in Internet Protocol networks. Gopher uses port 70.


The Multipurpose Internet Mail Extension is an Presentation layer protocol. It allows the users to exchange different kinds of data files on the Internet: audio, video, images, application programs as well. MIME allows non-ASCII data to be sent through SMTP.


External Data Representation (XDR) is a standard data serialization format, for uses such as computer network protocols. It allows data to be transferred between different kinds of computer systems.


The Hypertext Transfer Protocol is an Application layer protocol. HTTP is a TCP/IP based communication protocol, that is used to deliver data (HTML files, image files, query results, etc.) on the World Wide Web. The default port is TCP 80. HTTP3 uses QUIC, transport layer protocol on top of UDP.


The Network File Transfer is an Application layer protocol. This distributed file system protocol allows a user on a client computer to access files over a network in the same way they would access a local storage file.


The Network Time Protocol is an Application layer protocol. NTP is a networking protocol for clock synchronization between computer systems over packet-switched, variable-latency data networks. NTP is one of the oldest Internet protocols in use.


The Short Message Peer to Peer is an Session layer protocol. It is a standard protocol designed to provide a flexible data communication interface for the transfer of short message. SMPP uses port 2775


The Simple Network Management Protocol is an application layer protocol. which uses UDP port number 161/162. SNMP is used to monitor the network, detect network faults and sometimes even used to configure remote devices.


Telnet is an application protocol. It is used on the Internet or local area network to provide a bidirectional interactive text-oriented communication facility using a terminal connection. User data is interspersed in-band with Telnet control information in an 8-bit byte oriented data connection over the Transmission Control Protocol (TCP). It uses port 23.


The Dynamic Host Configuration Protocol is an application layer protoc0l. DHCP is a way of dynamically and automatic assigning IP addresses to devices on a physical network. DHCP uses port 67.


The Network Configuration Protocol is an application layer protocol. Netconf is a network management protocol which, provides mechanisms to install, manipulate, and delete the configuration of network devices. The NETCONF protocol uses an Extensible Markup Language (XML) based data encoding for the configuration data as well as the protocol messages.


The Internet Protocol is an Internet layer protocol. It is used for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet. IP has the task of delivering packets from the source host to the destination host solely based on the IP addresses in the packet headers.


Internet Protocol version 4 (IPv4) is the fourth version of the Internet Protocol (IP). It is one of the core protocols of standards-based internetworking methods in the Internet and other packet-switched networks. IPv6, a successor protocol is ongoing deployment


The Asynchronous Transfer Mode operates on Data Link - Network layer. ATM is a communication protocol which can be used to transfer data, videos and speech.


SDLC is a transmission protocol developed by IBM in the 1970s as a replacement for its binary synchronous (BSC) protocol. SDLC is equivalent to Data Link layer of the Open Systems Interconnection (OSI) model of network communication.


The Stream Control Transmission Protocol is a transport-layer protocol. The SCTP ensures reliable, in-sequence transport of data. SCTP provides multihoming support where one or both endpoints of a connection can consist of more than one IP address.


The Datagram Congestion Control Protocol is a transport-layer protocol. DCCP is a message-oriented transport layer protocol. DCCP implements reliable connection setup, teardown, Explicit Congestion Notification (ECN), congestion control, and feature negotiation.


Then Internetwork Packet Exchange/Sequenced Packet Exchange is a transport-layer protocol. IPX and SPX are networking protocols used initially on networks using the Novell NetWare operating systems, but became widely used on networks deploying Microsoft Windows LANS, as they replaced NetWare LANS.


The Session Announcement Protocol is a Session layer protocols. It is a protocol used for advertising multicast session information. SAP typically uses Session Description Protocol (SDP) as the format for Real-time Transport Protocol (RTP) session descriptions.


Then Point to Point Tunneling Protocol is a Session layer Protocol. PPTP is an obsolete method for implementing virtual private networks. PPTP uses a TCP control channel and a Generic Routing Encapsulation tunnel to encapsulate PPP packets.


The Real Time Transport Protocol is a Session layer Protocol: The Real-time Transport Protocol is a network protocol used to deliver streaming audio and video media over the internet, thereby enabling the Voice Over Internet Protocol (VoIP). RTP uses port 5004 for data transfer and 5005 for control transfer.

IEEE 802.2

IEEE 802 is a Data Link layer protocol. IEEE 802.2 is the original name of the ISO/IEC 8802-2 standard which defines logical link control (LLC) as the upper portion of the data link layer of the OSI Model.


The Logical Link Control is a Data Link layer protocol. LLC data communication protocol layer is the upper sublayer of the data link layer (layer 2) of the seven-layer OSI model. The LLC provides a single data link control protocol for all IEEE, where as MAC layer where we have different protocol versions for different LANs.


The Layer 2 Tunnelling Protocol is a Data Link layer protocol. L2TP is a tunneling protocol used to support virtual private networks (VPNs) or as part of the delivery of services by ISPs. L2TP creates a tunnel across the Internet between an L2TP Access Concentrator (LAC) and an L2TP Network Server (LNS), enabling Point-to-Point Protocol (PPP) link layer frames to be encapsulated and carried across the Internet.

IEEE 802.3

IEEE 802.3 is a set of standards and protocols that define Ethernet-based networks. IEEE 802.3 specifies the physical layer and the channel-access portion of the Data Link layer, but does not define a logical link control protocol. It is implemented in the hardware.


The Plesiochronous Digital Hierarchy is a Physical layer protocol. PDH was the standard originally for telephone networks. PDH uses time division multiplexing. It was also designed to support digital voice channels running at 64kbps.


The Synchronous Optical Networking/ Synchronous Digital Hierarchy is a Physical layer protocol. SONET/SDH are standardized protocols that transfer multiple digital bit streams synchronously over optical fiber using lasers or highly coherent light from light-emitting diodes (LEDs). Standard developed by ANSI and Exchange Carrier Standards Association (ECSA) SONET links can be used in place of dark fiber.


The passive optical network is a Physical layer protocol. PON is a fiber-optic telecommunications technology for delivering broadband network access to end-customers. Its architecture implements a point-to-multipoint topology, in which a single optical fiber serves multiple endpoints by using unpowered (passive) fiber optic splitters.


The Optical Transport Network is a Physical layer protocol: OTN is a set of Optical Network Elements (ONE) connected by optical fiber links, able to provide functionality of transport, multiplexing, switching, management, supervision and survivability of optical channels carrying client signals.


The Digital Subscriber Line is a Physical layer protocol. DSL is a way to transmit digital data over a telephone line. Telephone lines only transmit a limited spectrum of signals (roughly 20 Hertz to 20,000 Hertz, for voice). This means that the other frequencies can be used to transmit data. The data is combined or multiplexed onto the telephone line. At both ends, a device called a Splitter (or DSL filter) separates the data part and the telephony part.


The Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communications protocol that provides an identification and location system for computers on networks and routes traffic across the Internet. Internet Protocol version 6 uses 128-bit logical address.


The Address Resolution Protocol is a Data Link layer protocol: The purpose of Address Resolution Protocol (ARP) is to map an IPv4 address (32 bit Logical Address) to the physical address (48 bit MAC Address). Network Applications at the Application Layer use IPv4 Address to communicate with another device. But at the Data link layer, the addressing is MAC address (48 bit Physical Address), and this address is burned into the network card permanently.


The Internet Control Message Protocol is a Network layer protocol. ICMP is a supporting protocol in the Internet protocol suite. It is used by network devices, including routers, to send error messages and operational information indicating success or failure when communicating with another IP address.


The Internet Group Management Protocol is a Network layer protocol. IGMP is a communications protocol used by hosts and adjacent routers on IPv4 networks to establish multicast group memberships. IGMP is an integral part of IP multicast and allows the network to directmulticast transmissions only to hosts that have requested them.


The Internet Packet Exchange is a Network layer protocol: IPX is a networking protocol that conducts the activities and affairs of the end-to-end process of timely, managed and secured data.

Frame Relay

The Frame Relay operates at two layers: Physical layer and Data Link layer. Frame Relay is a packet-switching technology offered as a telecommunications service by long-distance carriers, used primarily for WAN links. Frame relay can be used to encapsulate local area network (LAN) traffic such as Ethernet frames for transmission over digital data transmission lines for wide area networks (WANs) and can connect multiple LANs to form a multipoint WAN.


The Transmission Control Protocol is a Transport layer protocol. TCP is a standard that defines how to establish and maintain a network conversation through which application programs can exchange data. TCP works with the Internet Protocol (IP), which defines how computers send packets of data to each other.


The User Datagram Protocol is a Transport layer protocol. UDP is a communication protocol used across the Internet for especially time-sensitive transmissions such as video playback or DNS lookups. It speeds up communications by not formally establishing a connection before data is transferred. This allows data to be transferred very quickly, but it can also cause packets to become lost in transit.


The High-Level Data Link Control is a Data Link layer protocol: High-level Data Link Control (HDLC) is a group of communication protocols of the data link layer for transmitting data between network points or nodes. Since it is a data link protocol, data is organized into frames. A frame is transmitted via the network to the destination that verifies its successful arrival. It is a bit - oriented protocol that is applicable for both point - to - point and multipoint communications.


The Compressed Serial Line Internet Protocol is a Data Link layer protocol. CSLIP reduces the size of the headers in IP packets by eliminating a certain amount of redundancy. This improves interactive performance.


The Serial Line Internet Protocol is a Data Link layer protocol. SLIP is a simple protocol that works with TCP/IP for communication over serial ports and routers. They provide communications between machines that were previously configured for direct communication with each other.

IEEE 802.11

IEEE 802.11 is part of the IEEE 802 set of local area network (LAN) protocols, and specifies the set of media access control (MAC) and physical layer (PHY) protocols for implementing wireless local area network (WLAN) Wi-Fi computer communication in various frequencies.

IEEE 802.15

IEEE 802.15 is a working group of the Institute of Electrical and Electronics Engineers (IEEE) IEEE 802 standards committee which specifies wireless personal area network (WPAN) standards.

IEEE 802.16

IEEE 802.16 is a series of wireless broadband standards written by the Institute of Electrical and Electronics Engineers (IEEE). The IEEE Standards Board established a working group in 1999 to develop standards for broadband for wireless metropolitan area networks. The Workgroup is a unit of the IEEE 802 local area network and metropolitan area network standards committee.


Bluetooth is a Physical layer protocol. Bluetooth is a wireless technology standard used for exchanging data between fixed and mobile devices over short distances using UHF radio waves in the industrial, scientific and medical radio bands, from 2.402 GHz to 2.480 GHz, and building personal area networks (PANs). It was originally conceived as a wireless alternative to RS-232 data cables.


RS232 is a standard protocol used for serial communication, it is used for connecting computer and its peripheral devices to allow serial data exchange between them. As it obtains the voltage for the path used for the data exchange between the devices.


The RS-449 serial data standard was intended as an enhancement to RS232. It was aimed at providing serial data transmission at speeds up to 2 Mbps whilst still being able to maintain compatibility with RS232. One of the ways in which the RS449 data communications standard is able to send at high speeds without straynoise causing interference is to use a differential form of signalling.


The Transport Layer Security and Secure Sockets Layer are Presentation layer protocol. For TCP/IP model, they operates between the Transport layer and the Application Layer. It just wraps Application Layer traffic in encryption during transport. SSL and TLS are cryptographic protocols that authenticate data transfer between servers, systems, applications and users. For example, a cryptographic protocol encrypts the data that is exchanged between a web server and a user. SSL was a first of its kind of cryptographic protocol. TLS on the other hand, was a recent upgraded version of SSL.


The Universal Serial Bus is a Physical layer protocol. USB is a plug and play interface that allows a computer to communicate with peripheral and other devices. USB-connected devices cover a broad range; anything from keyboards and mice, to music players and flash drives. USB may also be used to send power to certain devices, such as powering smartphones and tablets and charging their batteries.

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