List of OSI protocal

Layer 2 protocols (Data Link Layer)

    ARCnet　Attached Resource Computer NETwork
    CDP Cisco Discovery Protocol
    DCAP Data Link Switching Client Access Protocol
    Distributed Multi-Link Trunking
    Distributed Split Multi-Link Trunking
    Dynamic Trunking Protocol
    Econet
    Ethernet
    FDDI Fiber Distributed Data Interface
    Frame Relay
    ITU-T G.hn Data Link Layer
    HDLC High-Level Data Link Control
    IEEE 802.11 WiFi
    IEEE 802.16 WiMAX
    LACP Link Aggregation Control Protocol
    LattisNet
    LocalTalk
    L2F Layer 2 Forwarding Protocol
    L2TP Layer 2 Tunneling Protocol
    LAPD Link Access Procedures on the D channel
    LLDP Link Layer Discovery Protocol
    LLDP-MED Link Layer Discovery Protocol - Media Endpoint Discovery
    PAgP - Cisco Systems proprietary link aggregation protocol
    PPP Point-to-Point Protocol
    PPTP Point-to-Point Tunneling Protocol
    Q.710 Simplified Message Transfer Part
    Multi-link trunking Protocol
    RPR IEEE 802.17 Resilient Packet Ring
    SLIP Serial Line Internet Protocol (obsolete)
    StarLAN
    STP Spanning Tree Protocol
    Split multi-link trunking Protocol
    Token ring a protocol developed by IBM; the name can also be used to describe the token passing ring logical topology that it popularized.
    VTP VLAN Trunking Protocol

Layer 2+3 protocols

    ARP Address Resolution Protocol
    RARP Reverse Address Resolution Protocol
    ATM Asynchronous Transfer Mode
    Frame relay, a simplified version of X.25 welcome
    MPLS Multi-protocol label switching
    SPB Shortest Path Bridging
    X.25


    MTP Message Transfer Part
    NSP Network Service Part

Layer 3 protocols (Network Layer)

    CLNP Connectionless Networking Protocol
    EGP Exterior Gateway Protocol
    EIGRP Enhanced Interior Gateway Routing 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
    Routed-SMLT
    SCCP Signalling Connection Control Part
    AppleTalk DbP

Layer 3 protocols (Network Layer management)

    IS-IS Intermediate System-to-Intermediate System
    OSPF Open Shortest Path First
    NDP Neighbor Discovery Protocol
    Gateway Discovery Protocol (GDP) is a Cisco protocol similar to IRDP
    IGRP
    EIGRP
    ICMP

L2 or L3 protocol like OSPF, BGP,ISIS, RIP,MPLS, DSL,ADSL, SDH,Sonet, DSLAM,VLAN,ATM,QoS,framerelay,

Layer 3.5 protocols

HIP Host Identity Protocol

Layer 3+4 protocol suites

    AppleTalk
    DECnet
    IPX/SPX
    Internet Protocol Suite
    Xerox Network Systems

Layer 4 protocols (Transport Layer)

    AH Authentication Header over IP or IPSec
    ESP Encapsulating Security Payload over IP or IPSec
    GRE Generic Routing Encapsulation for tunneling
    IL Originally developed as transport layer for 9P
    SCTP Stream Control Transmission Protocol
    Sinec H1 for telecontrol
    SPX Sequenced Packet Exchange
    TCP Transmission Control Protocol
    UDP User Datagram Protocol
    DCCP Datagram Congestion Control 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 Block
    SOCKS "SOCKetS"

Other protocols

    Controller Area Network (CAN)

Layer 7 protocols (Application Layer)

    ADC, A peer-to-peer file sharing protocol
    AFP, Apple Filing Protocol
    BACnet, Building Automation and Control Network protocol
    BitTorrent, A peer-to-peer file sharing protocol
    BGP Border Gateway Protocol
    BOOTP, Bootstrap Protoc;
    CAMEL, an SS7 protocol tool for the home operator
    Diameter, an authentication, authorization and accounting protocol
    DICOM includes a network protocol definition
    DICT, Dictionary protocol
    DNS, Domain Name System
    DSM-CC Digital Storage Media Command and Control
    DSNP, Distributed Social Networking Protocol
    DHCP, Dynamic Host Configuration Protocol
    ED2K, A peer-to-peer file sharing protocol
    FTP, File Transfer Protocol
    Finger, which gives user profile information
    Gnutella, a peer-to-peer file-swapping protocol
    Gopher, a hierarchical hyperlinkable protocol
    HTTP, Hypertext Transfer Protocol
    HTTPS, Hypertext Transfer Protocol Secure
    IMAP, Internet Message Access Protocol
    IRC, Internet Relay Chat
    ISUP, ISDN User Part
    LDAP Lightweight Directory Access Protocol
    MIME, Multipurpose Internet Mail Extensions
    MSNP, Microsoft Notification Protocol (used by Windows Live Messenger)
    MAP, Mobile Application Part
    NetBIOS, File Sharing and Name Resolution protocol - the basis of file sharing with Windows.
    NNTP, Network News Transfer Protocol
    NTP, Network Time Protocol
    NTCIP, National Transportation Communications for Intelligent Transportation System Protocol
    POP3 Post Office Protocol Version 3
    RADIUS, an authentication, authorization and accounting protocol
    RDP, Remote Desktop Protocol
    Rlogin, a UNIX remote login protocol
    rsync, a file transfer protocol for backups, copying and mirroring
    RTP, Real-time Transport Protocol
    RTSP, Real-time Transport Streaming Protocol
    SSH, Secure Shell
    SISNAPI, Siebel Internet Session Network API
    SIP, Session Initiation Protocol, a signaling protocol
    SMTP, Simple Mail Transfer Protocol
    SNMP, Simple Network Management Protocol
    SOAP, Simple Object Access Protocol
    SMB, Microsoft Server Message Block Protocol
    STUN, Session Traversal Utilities for NAT
    TUP, Telephone User Part
    Telnet, a remote terminal access protocol
    TCAP, Transaction Capabilities Application Part
    TFTP, Trivial File Transfer Protocol, a simple file transfer protocol
    WebDAV, Web Distributed Authoring and Versioning
    XMPP, an instant-messaging protocol

FUNCTION OF OSI LAYERS

We will now discuss the purpose of each layer in the OSI model.

Application Layer

The Application layer is the top layer of the OSI model. It is used to allow applications to access network services. It handles general network access, flow control, and error recovery. Some of the functions it supports are:

	Accessing remote files
	Accessing remote printers
	Accessing remote databases
	Electronic mail

Presentation Layer

The next layer down is the Presentation layer which is located at layer 6. It is the translator for the network as it determines the format used to exchange data among the computers on the network. Some of its functions are:

	Protocol conversion
	Data translation
	Data encryption
	Data compression
	Conversion of the character set

Session Layer

Layer 5 is the Session layer, which establishes a communications connection between processes running on different computers. It performs name recognition and related functions; for example, user authentication and resource-access security that are needed to allow processes to communicate over the network. To ensure that all data gets sent, it uses checkpoints placed in the data stream to provide for synchronization. In the case of network failure the only data that needs to be sent again is the data after the last checkpoint. The Session layer is also responsible for controlling when and for how long each side transmits.

Transport Layer

Layer 4 is the Transport layer, which is responsible for ensuring that all the data is delivered in the correct sequence, error free, with no losses. It is the Transport layer that breaks up large messages into smaller packets for delivery. Some of the other functions provided by the Transport layer are:

	Error handling
	Flow control by notifying the transmitting computer to not transmit when the receiving computer has no available receive buffers

Network Layer

Layer 3, the Network layer, is responsible for determining the route that is taken from the transmitting computer to the receiving computer. It is also responsible for addressing messages and the translation of logical addresses into physical addresses. The Network layer determines what path the data should take based upon several factors, including the condition of the network and the priority of service.

Data Link Layer

Layer 2 is the Data Link layer, which is responsible for providing error-free transfer of frames from one computer to another using the Physical layer. A frame is a bundle of information sent as a single entity. Some of the other functions provided by the Data Link layer are:

	Transmitting and receiving frames sequentially
	Providing frame acknowledgment for frames it receives
	Retransmitting frames that are not acknowledged by the receiving computer

Physical Layer

The Physical layer is located at layer 1, the bottom of the OSI model. The Physical layer handles the unstructured, raw, bit-stream data that is transferred over a physical medium. It also defines how the physical medium, or cable, is attached to the Network Interface Card (NIC). It does that by determining how many pins are in the connector that is being used and also the function of each of the pins. The Physical layer sends out bits equaling 1s and 0s and determines how long each bit lasts and how it is translated into the suitable optical or electrical impulse for the network cable.

 KNOW HOW THEY WORK WITH FIGURE

Data flow in osi model

The OSI model presents a standard data flow architecture, with protocols specified in such a way that the receiving layer at the destination computer receives exactly the same object as sent by the matching layer at the source computer. Figure A.2 shows the OSI model data flow.

Figure A.2 OSI Model Data Flow

As data passes from one layer to the next layer, additional formatting or addressing is added from the sending computer so that it can be transmitted successfully.  

We sent the data through the inter face of the application.the data may be voice,text,images.The sending process passes data to the application layer. The application layer attaches an application header and then prepares the frame and passes the frame to the presentation layer.
The presentation layer can transform data in various ways, if necessary, such as by translating it and adding a header. It gives the result to the session layer. The presentation layer is not aware of which portion (if any) of the data received from the application layer is the application header and which portion is actually user data, because that information is irrelevant to the presentation layer's role.
The process of adding headers is repeated from layer to layer until the frame reaches the data link layer. There, in addition to a data-link header, a data-link trailer is added. The data-link trailer contains a checksum and padding if needed. This aids in frame synchronization. The frame is passed down to the physical layer, where it is transmitted to the receiving computer.
On the receiving computer, the various headers and the data trailer are stripped off one by one as the frame ascends the layers and finally reaches the receiving process.
Although the actual data transmission is vertical, each layer is programmed as if the transmission were horizontal. For example, when a sending transport layer gets a message from the session layer, it attaches a transport header and sends it to the receiving transport layer. The fact that the message actually passes through the network layer on its own computer is unimportant.

The data recieving process is just the reverse work done to sent. Formatting and addressing information is stripped away at each layer as it is passed up the layers until it arrives at the seventh layer, the Application layer, where it is returned back to its original state that can be interpreted by the receiving computer.

HERE ARE FUNCTION AND WORKING OF THE LAYERS:

We will now discuss the purpose of each layer in the OSI model.

Application Layer

The Application layer is the top layer of the OSI model. It is used to allow applications to access network services. It handles general network access, flow control, and error recovery. Some of the functions it supports are:

	Accessing remote files
	Accessing remote printers
	Accessing remote databases
	Electronic mail

Presentation Layer

The next layer down is the Presentation layer which is located at layer 6. It is the translator for the network as it determines the format used to exchange data among the computers on the network. Some of its functions are:

	Protocol conversion
	Data translation
	Data encryption
	Data compression
	Conversion of the character set

Session Layer

Layer 5 is the Session layer, which establishes a communications connection between processes running on different computers. It performs name recognition and related functions; for example, user authentication and resource-access security that are needed to allow processes to communicate over the network. To ensure that all data gets sent, it uses checkpoints placed in the data stream to provide for synchronization. In the case of network failure the only data that needs to be sent again is the data after the last checkpoint. The Session layer is also responsible for controlling when and for how long each side transmits.

Transport Layer

Layer 4 is the Transport layer, which is responsible for ensuring that all the data is delivered in the correct sequence, error free, with no losses. It is the Transport layer that breaks up large messages into smaller packets for delivery. Some of the other functions provided by the Transport layer are:

	Error handling
	Flow control by notifying the transmitting computer to not transmit when the receiving computer has no available receive buffers

Network Layer

Layer 3, the Network layer, is responsible for determining the route that is taken from the transmitting computer to the receiving computer. It is also responsible for addressing messages and the translation of logical addresses into physical addresses. The Network layer determines what path the data should take based upon several factors, including the condition of the network and the priority of service.

Data Link Layer

Layer 2 is the Data Link layer, which is responsible for providing error-free transfer of frames from one computer to another using the Physical layer. A frame is a bundle of information sent as a single entity. Some of the other functions provided by the Data Link layer are:

	Transmitting and receiving frames sequentially
	Providing frame acknowledgment for frames it receives
	Retransmitting frames that are not acknowledged by the receiving computer

Physical Layer

The Physical layer is located at layer 1, the bottom of the OSI model. The Physical layer handles the unstructured, raw, bit-stream data that is transferred over a physical medium. It also defines how the physical medium, or cable, is attached to the Network Interface Card (NIC). It does that by determining how many pins are in the connector that is being used and also the function of each of the pins. The Physical layer sends out bits equaling 1s and 0s and determines how long each bit lasts and how it is translated into the suitable optical or electrical impulse for the network cable.