OSI (Open Systems Interconnection) Model
The Open Systems Interconnection model (OSI) is a conceptual model that characterizes and standardizes the internal functions of a communication system by partitioning it into abstraction layers. The OSI Model is a conceptual, seven-layered model of how networks work. It tells us that how data is going through one computer to another computer, and also it simplifies to troubleshoot the network issues. A reference model to make sure products of different vendors would work together.
OSI (Open Source Interconnection) 7 Layer Model
HISTORY In the late 1970s, two projects began independently, with the same goal: to define a unifying standard for the architecture of networking systems. One was administered by the International Organization for Standardization (ISO), while the other was undertaken by the International Telegraph and Telephone Consultative Committee, or CCITT (the abbreviation is from the French version of the name). These two international standards bodies each developed a document that defined similar networking models.
OSI (Open Systems Interconnection) Model
In 1983, these two documents were merged together to form a standard called The Basic Reference Model for Open Systems Interconnection. That's a mouthful, so the standard is usually referred to as the Open Systems Interconnection Reference Model, the OSI Reference Model, or even just the OSI Model. It was published in 1984 by both the ISO, as standard ISO 7498, and the renamed CCITT (now called the Telecommunications Standardization Sector of the International Telecommunication Union or ITU-T) as standard X.200. The concept of a seven-layer model was provided by the work of Charles Bachman, Honeywell Information Services.
Network Layer Interaction
Network Layer Interconnection
OSI (Open Systems Interconnection) Model
Packet Structure Packet Description
OSI LAYER 1. Physical Layer
Physical Layer
OSI (Open Systems Interconnection) Model
Function of Layer 1
It defines the electrical and physical specifications of the data connection. It defines the relationship between a device and a physical transmission medium (e.g., a copper or fiber optical cable). This includes the layout of pins, voltages, line impedance, cable specifications, signal timing, hubs, repeaters, network adapters, host bus adapters (HBA used in storage area networks) and more. It defines the protocol to establish and terminate a connection between two directly connected nodes over a communications medium. It may define the protocol for flow control. It defines transmission mode i.e. simplex, half & full duplex. It defines topology. It defines a protocol for the provision of a (not necessarily reliable) connection between two directly connected nodes, and the modulation or conversion between the representation of digital data in user equipment and the corresponding signals transmitted over the physical communications channel. This channel can involve physical cabling (such as copper and optical fiber) or a wireless radio link.
Protocol
Telephone network modems- V.92 IRDA physical layer USB physical layer EIA RS-232, EIA-422, EIA-423, RS-449, RS-485 Ethernet physical layer Including 10BASE-T, 10BASE2, 10BASE5, 100BASE-TX, 100BASE-FX, 100BASE-T, 1000BASE-T, 1000BASE-SX and other varieties Varieties of 802.11 Wi-Fi physical layers DSL ISDN T1 and other T-carrier links, and E1 and other E-carrier links SONET/SDH Optical Transport Network (OTN) GSM Um air interface physical layer Bluetooth physical layer ITU Recommendations: see ITU-T IEEE 1394 interface TransferJet physical layer Etherloop ARINC 818 Avionics Digital Video Bus
OSI (Open Systems Interconnection) Model
G.hn/G.9960 physical layer CAN bus (controller area network) physical layer Mobile Industry Processor Interface physical layer
2. Data Link Layer The Data-Link layer contains two sub layers that are described in the IEEE-802 LAN standards:
Media Access Control (MAC) layer- responsible for controlling how computers in the network gain access to data and permission to transmit it.
Logical Link Control (LLC) layer- control error checking and packet synchronization.
Data Link Layer
OSI (Open Systems Interconnection) Model
Function of Layer 2
Link establishment and termination: establishes and terminates the logical link between two nodes. Frame traffic control: tells the transmitting node to "back-off" when no frame buffers are available. Frame sequencing: transmits/receives frames sequentially. Frame acknowledgment: provides/expects frame acknowledgments. Detects and recovers from errors that occur in the physical layer by retransmitting non-acknowledged frames and handling duplicate frame receipt. Frame delimiting: creates and recognizes frame boundaries. Frame error checking: checks received frames for integrity. Media access management: determines when the node "has the right" to use the physical medium.
Protocol
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
OSI (Open Systems Interconnection) Model
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 VLAN Virtual Local Area Network
3. Network Layer
Network Layer
OSI (Open Systems Interconnection) Model Function of Layer 3
Routing: routes frames among networks. Subnet traffic control: routers (network layer intermediate systems) can instruct a sending station to "throttle back" its frame transmission when the router's buffer fills up. Frame fragmentation: if it determines that a downstream router's maximum transmission unit (MTU) size is less than the frame size, a router can fragment a frame for transmission and re-assembly at the destination station. Logical-physical address mapping: translates logical addresses, or names, into physical addresses. Subnet usage accounting: has accounting functions to keep track of frames forwarded by subnet intermediate systems, to produce billing information.
Protocol
ARP Address Resolution Protocol RARP Reverse Address Resolution Protocol ATM Asynchronous Transfer Mode Frame relay, a simplified version of X.25 IS-IS, Intermediate System - Intermediate System (OSI) MPLS Multi-protocol label switching SPB Shortest Path Bridging X.25 MTP Message Transfer Part NSP Network Service Part HIP Host Identity Protocol
Protocol Layer 3+4
AppleTalk DECnet IPX/SPX Internet Protocol Suite Xerox Network Systems TCP/IP
OSI (Open Systems Interconnection) Model
4. Transport Layer
Transport Layer Function of Layer 4
Message segmentation: accepts a message from the (session) layer above it, splits the message into smaller units (if not already small enough), and passes the smaller units down to the network layer. The transport layer at the destination station reassembles the message. Message acknowledgment: provides reliable end-to-end message delivery with acknowledgments. Message traffic control: tells the transmitting station to "back-off" when no message buffers are available. Session multiplexing: multiplexes several message streams, or sessions onto one logical link and keeps track of which messages belong to which sessions (see session layer).
OSI (Open Systems Interconnection) Model Protocol
AH Authentication Header over IP or IPSec 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
5. Session Layer
Session Layer
OSI (Open Systems Interconnection) Model
Function of Layer 5
Session establishment, maintenance and termination: allows two application processes on different machines to establish, use and terminate a connection, called a session. Session support: performs the functions that allow these processes to communicate over the network, performing security, name recognition, logging, and so on.
Protocol
9P Distributed file system protocol developed originally as part of Plan 9 NetBIOS, File Sharing and Name Resolution protocol - the basis of file sharing with Windows. NetBEUI, NetBIOS Enhanced User Interface NCP NetWare Core Protocol NFS Network File System SMB Server Message Block SOCKS "SOCKetS"
6. Presentation Layer
Presentation Layer
OSI (Open Systems Interconnection) Model Function of Layer 6
Character code translation: for example, ASCII to EBCDIC. Data conversion: bit order, CR-CR/LF, integer-floating point, and so on. Data compression: reduces the number of bits that need to be transmitted on the network. Data encryption: encrypt data for security purposes. For example, password encryption.
Protocol
TLS Transport Layer Security
7. Application Layer
Application Layer
OSI (Open Systems Interconnection) Model
Function of Layer 7
Resource sharing and device redirection Remote file access Remote printer access Inter-process communication Network management Directory services Electronic messaging (such as mail) Network virtual terminals
Protocol
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
OSI (Open Systems Interconnection) Model
LDAP Lightweight Directory Access Protocol MIME, Multipurpose Internet Mail Extensions MSNP, Microsoft Notification Protocol (used by Windows Live Messenger) MAP, Mobile Application Part Mosh, Mobile Shell 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