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osi notes
Question | Answer |
---|---|
physical | Responsible for transmission of bits across a physical circuit b. Focused on hardware: connectors, cables, repeaters, etc. |
data link | Establishes connections among host machines. Can reach any machine on the network, but cannot reach machines on other networks |
data link | Breaks data into frames, transmits frames, and processes acknowledgment frames sent back by receiver--error checking function |
data link | Provides Medium Address Code (MAC) A bridge is a layer 2 device Provides Medium Address Code (MAC) |
network | Responsible for routing and relaying data (packets) from one device to another through the network |
network | Routing decisions made by layer 3 address (i.e. IP address) A router is a layer 3 device |
transport | Responsible for handling the processes that use the network for communication. These functions include flow control, error detection and correction & congestion control. |
transport | Get’s data from one computer’s port to another’s Example: TCP |
session | Maintains and manages sessions between applications Half duplex and full duplex communication; synchronization Example: web conferencing applications |
presentation | Responsible for representation of data, translation of data Formatting data for display Example services: encryption, compression |
application | Provides network services to user applications Layer closest to user Example: email |
application | layer that actually interacts with the operating system or application whenever the user chooses to transfer files, read messages or perform other network-related activities. |
presentation | takes the data provided by the Application layer and converts it into a standard format that the other layers can understand. |
sessions | establishes, maintains and ends communication with the receiving device. |
transport | maintains flow control of data and provides for error checking and recovery of data between the devices. |
transport | Flow control means that the Transport layer looks to see if data is coming from more than one application and integrates each application's data into a single stream for the physical network. |
network | the data will be sent to the recipient device is determined in this layer |
data | appropriate physical protocol is assigned to the data. Also, the type of network and the packet sequencing is defined. |
physical | level of the actual hardware. It defines the physical characteristics of the network such as connections, voltage levels and timing. |
physical | Encoding and Signaling; Physical Data Transmission; Hardware Specifications; Topology and Design Bits Electrical or light signals sent between local devices (Physical layers of most of the technologies listed for the data link layer) |
Data | Logical Link Control; Media Access Control; Data Framing; Addressing; Error Detection and Handling; Defining Requirements of Physical Layer |
Data | Frames Low-level data messages between local devices IEEE 802.2 LLC, Ethernet Family; Token Ring; FDDI and CDDI; IEEE 802.11 (WLAN, Wi-Fi); HomePNA; HomeRF; ATM; SLIP and PPP |
Network | Logical Addressing; Routing; Datagram Encapsulation; Fragmentation and Reassembly; Error Handling and Diagnostics Datagrams / Packets Messages between local or remote devices |
Network | IP; IPv6; IP NAT; IPsec; Mobile IP; ICMP; IPX; DLC; PLP; Routing protocols such as RIP and BGP |
transport | Process-Level Addressing; Multiplexing/Demultiplexing; Connections; Segmentation and Reassembly; Acknowledgments and Retransmissions; Flow Control Datagrams / Segments |
transport | Datagrams / Segments Communication between software processes TCP and UDP; SPX; NetBEUI/NBF |
session | Session Establishment, Management and Termination Sessions Sessions between local or remote devices NetBIOS, Sockets, Named Pipes, RPC |
presentation | Data Translation; Compression and Encryption Encoded User Data Application data representations SSL; Shells and Redirectors; MIME |
application | User Application Services User Data Application data |
application | DNS; NFS; BOOTP; DHCP; SNMP; RMON; FTP; TFTP; SMTP; POP3; IMAP; NNTP; HTTP; Telnet |
application | layer at which communication partners are identified, quality of service is identified, user authentication and privacy are considered, and any constraints on data syntax are identified. |
presentation | usually part of an operating system, that converts incoming and outgoing data from one presentation format to another (for example, from a text stream into a popup window with the newly arrived text). Sometimes called the syntax layer. |
session | sets up, coordinates, and terminates conversations, exchanges, and dialogs between the applications at each end. It deals with session and connection coordination. |
transport | manages the end-to-end control (for example, determining whether all packets have arrived) and error-checking. It ensures complete data transfer. |
network | handles the routing of the data (sending it in the right direction to the right destination on outgoing transmissions and receiving incoming transmissions at the packet level). The network layer does routing and forwarding. |
data link | provides synchronization for the physical level and does bit-stuffing for strings of 1's in excess of 5. It furnishes transmission protocol knowledge and management. |
physical | conveys the bit stream through the network at the electrical and mechanical level. It provides the hardware means of sending and receiving data on a carrier. |
data link | error-free transfer of data frames from one node to another over the physical layer, allowing layers above it to assume virtually error-free transmission over the link. |
data link | •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. |