Application layer presentation layer session layer transport layer network layer data link layer physical layer

All people seem to need data processing. Please do not throw sausage pizza away.

  • Abtract model

  • Set of specifically created protocols

  • Protocols not used in any network system

Layer 1: Physical layer

  • Bottome layer

  • Concerned with physical transmission of raw data

  • Transmits data in the form of 1s and 0s

  • Defines encoding methods to transmit data

  • Defines how bits are placed on media

  • Defines how to know when bits start and stop

  • Defines specifications for media usage

  • Define kinds of media permitted

  • Defines how physical connections are made

  • Defines pin usage in physical connections

  • Specifies standards that apply to specific types of media

  • Provides error-free transmission from one node to the next over physical media

  • Establishes and terminates links between nodes

  • Responsible for traffic control

  • Transmits and receives frames sequentially

  • Responsible for frame acknowledgement

  • Provides and expects frame acknowledgement

  • Detects and recovers from errors on physical layer

  • Retransmits nonacknowledged frames

  • Handles duplicate frame receipt

  • Responsible for frame delimiting

  • Creates and recognizes frame boundaries

  • Responsible for error checking

  • Checks received frames for data integrity

  • Provides media access management - determine when node is allowed to use physical media

Layer 3: Network Layer

  • Controls the operations of the subnetwork it is on

  • Determines best physical path for data

  • Uses network conditions to choose best path

  • Uses priority of service to determine best path

  • Uses other factors to determine best path

Functions it provides

  • Routing
    • Routes frames among connected networks
  • Subnet traffic control
    • Allows routers to send instructions to sending nodes to “throttle back” frame transimissions when buffles are filled
  • Frame fragmentation

    • Determines frame size of routers located down stream

    • Frame size called maximum transimission unit size

  • Logical-physical address mapping

    • Translates logical addresses into physical addresses

  • Subnet usage accounting

    • Has function that allows device to keep track of frames forwarded by subnet intermediate systems

    • Uses this to produce billing information

Communications Subnets

  • Build headers used by network layer on other devices to route packets to destination

  • Relieve higher layers of the need-to-know data transmission and switching technologies

  • Use protocols on lower layers to send data to destinations separated by intermediate nodes

  • Send information between adjacent nodes

Transport Layer

  • Ensures messages delivered error-free

  • Ensures messages delivered in sequence

  • Ensures messages delivered with no loss or duplication

  • Relieves higher protocols of concern for transfer of data

  • Size and complexity of transport protocols dependent on service provided by network

Segmentation

  • Accepts messages from session layer

  • Splits message into smaller units

  • Imposes message size limits on network layer protocols

  • Prepares header for each smaller units created

  • Passes smaller uints to network layer

  • Reassemble message at destination

  • Header for smaller units contain certain elements

    • Header contains start and end flags

    • contains sequence information

  • Message acknowledgement

    • Provides reliable end-to-end delivery of messages

    • End-to-end delivery accompanied by acknowledgements

  • Message traffic control

    • Controls rate of traffic sent when no buffers available

  • Session multiplexing

    • Breaks all the data coming in on one link into separate data streams

    • Those data streams are called sessions

    • Tracks which message belongs to which session

End-to-End layers

  • Transport layer and above layers not responsible for transmission between nodes

  • Transport and above layers responsible for source to destination transmission

  • Source-to-destination transmissions also called end-to-end communications

  • Upper layers not concerned with underlying communications facility

Session Layer

  • Responsible for establishing sessions between processes running on different computers

  • Provides several functions to accomplish this

  • Session establishment, maintenance, and termination

  • Session support

Maintenance Termination

  • Allows application processes on different machines to do several things between the machines

  • Allows processes to establish a connection

  • Allows processes to use a connection

  • Allows processes to terminate a connection

Session support

  • Performs the function of allowing processes to communicate over network

  • Performs security

  • Performs name recognition

  • Performs logging on

  • Performs other functions that are less common

Presentation Layer

  • Formats data to be presented to the application layer

  • Translator for the network

  • At sending station translates data from application layer format to common format recognized by across networks

  • At receiving station translates data from common format to format used by application layer

    TCP/IP

TCP - Transport Control Protocol

IP - Internet Protocol

  • It is the protocol used by the Internet!

Application

Transport

Internet