| The ISO OSI model are explained below.
| |
| | of upper layer protocols to ensure that
|
| The seven layers of the OSI model are:
| |
| | the information had reached the intended
|
|
| |
| | partner(s). Hence, UDP is often called
|
| Application
| |
| | connectionless protocol.
|
| Presentation
| |
| |
|
| Session
| |
| | Application programs that do not need
|
| Transport
| |
| | connection-oriented protocol generally
|
| Network
| |
| | use UDP.
|
| Antiqua">Data Link
| |
| | 5. Network layer: Network layer is
|
| Physical
| |
| | responsible for the routing of packets
|
| 1 Application layer: This layer
| |
| | through the entire network. The layer
|
| provides a means for the user to access
| |
| | uses logical addressing for this purpose.
|
| information on the network through an
| |
| | Note that the physical address (like MAC
|
| application. Many user applications that
| |
| | address) keeps changing from hop to hop
|
| need to communicate over the network
| |
| | when a packet travels from source to
|
| interact with the Application layer
| |
| | destination. As a result, an address that
|
| protocol directly. The user applications
| |
| | doesn't change is required to ensure
|
| are not part of OSI Application layer,
| |
| | continuity between hops. This is nothing
|
| use the networking services offered by
| |
| | but logical address. For IP networks, IP
|
| the networking protocol suite.
| |
| | address is the logical address; and for
|
| Application layer functions typically
| |
| | Novell network, IPX address is the
|
| include identifying communication
| |
| | logical address, and so on. This layer
|
| partners, and determining availability of
| |
| | also provides for congestion control, and
|
| required resources. Some examples of
| |
| | accounting information for the network.
|
| application layer implementations include
| |
| | IP (Internet Protocol) is an example of a
|
| Telnet, File Transfer Protocol (FTP), and
| |
| | network layer protocol. 6. Data link
|
| Simple Mail Transfer Protocol (SMTP). 2
| |
| | layer: Data link layer provides delivery
|
| Presentation layer: Presentation layer
| |
| | of information frames between
|
| converts local host computer data
| |
| | communicating partners. This layer is
|
| representations into a standard network
| |
| | responsible for flow regulation, error
|
| format for transmission on the network.
| |
| | detection and correction, and framing of
|
| On the receiving side, it changes the
| |
| | bits for transmission. The network data
|
| network format into the appropriate host
| |
| | frame is made up of checksum, source
|
| computer's format so that data can be
| |
| | address, destination address, and the
|
| utilized independent of the host
| |
| | data itself. The largest frame size that
|
| computer. ASCII and EBCDIC conversions,
| |
| | can be sent is known as the maximum
|
| cryptography, and the like are handled
| |
| | transmission Unit (MTU).Important
|
| here.
| |
| | features of Data link layer:
|
| Examples of Presentation layer coding
| |
| | Assembles bits into frames, making them
|
| and conversion schemes include common
| |
| | ready for transmission over the network.
|
| data representation formats, conversion
| |
| | Provides error detection, and correction
|
| of character representation formats,
| |
| | to transmitted frames. If the checksum is
|
| common data compression schemes, and
| |
| | not correct, it asks for retransmission.
|
| common data encryption schemes.
| |
| | (Send a control message).
|
| Presentation layer implementations are
| |
| | Consists of two sub layers:
|
| not typically associated with a
| |
| | Logical Link Control (LLC): Defines how
|
| particular protocol stack. Some
| |
| | data is transferred over the cable and
|
| well-known standards for video include
| |
| | provides data link service to the higher
|
| QuickTime and Motion Picture Experts
| |
| | layers.
|
| Group (MPEG). QuickTime is an Apple
| |
| | Medium Access Control (MAC): Controls
|
| Computer specification for video and
| |
| | media access by regulating the
|
| audio, and MPEG is a standard for video
| |
| | communicating nodes using pre-defined set
|
| compression and coding.3. Session layer:
| |
| | of rules. (i.e. Token passing, Ethernet
|
| The session layer establishes, manages,
| |
| | [CSMA/CD] all have MAC sub-layer
|
| and terminates communication sessions.
| |
| | protocol).
|
| Communication sessions consist of service
| |
| |
|
| requests and service responses that occur
| |
| |
|
| between applications located in different
| |
| |
|
| network devices. These requests and
| |
| |
|
| responses are coordinated by protocols
| |
| | Different Data link layer protocols
|
| implemented at the session layer. Some
| |
| | define different network and protocol
|
| examples of session-layer implementations
| |
| | characteristics, including physical
|
| include AppleTalk's Zone Information
| |
| | addressing, network topology, error
|
| Protocol (ZIP), and Decent Phase Session
| |
| | notification, sequencing of frames, and
|
| Control Protocol (SCP).4.Transport layer:
| |
| | flow control. Physical addressing (as
|
| Transport layer is responsible for
| |
| | opposed to logical addressing) defines
|
| providing reliable service between the
| |
| | how devices are addressed at the data
|
| hosts. Upper layer datagrams are broken
| |
| | link layer. The protocols used in Data
|
| down into manageable datagrams and then
| |
| | link layer are SLIP, PPP, and CSLP.7.
|
| appropriate header information (such as
| |
| | Physical layer: This is the bottom-most
|
| sequence number, port number, etc.) is
| |
| | layer of the OSI model. The Physical
|
| added to the datagram before passing it
| |
| | layer handles the bit-level
|
| on to the Network layer. Two frequently
| |
| | communications across the physical
|
| used transport protocols are the TCP
| |
| | medium. The physical medium could be made
|
| (Transmission Control Protocol) and the
| |
| | up of wired electrical signals, or light,
|
| UDP (User Datagram Protocol). Important
| |
| | or radio (wireless) signals. Physical
|
| features of Transport layer:
| |
| | layer specifications define
|
| Transport layer ensures reliable
| |
| | characteristics such as media, data
|
| service.
| |
| | rates, maximum transmission distances,
|
|
| |
| | and physical connectors.
|
| Breaks the message (from sessions layer)
| |
| | Some of the important standards that
|
| into smaller datagrams, and appends
| |
| | deal with physical layer specifications
|
| appropriate unit header information.
| |
| | are:
|
|
| |
| | RS-232(for serial communication lines),
|
| Responsible for communicating with the
| |
| | X.21, EIA 232, and G730.
|
| Session layer
| |
| | Physical layer and Data link layer
|
| Important features of TCP/UDP:
| |
| | implementations can be categorized as
|
| TCP/IP widely used protocol for
| |
| | either LAN or WAN specifications.
|
| Transport/Network layers
| |
| | Vijayanand has done his post graduation
|
| TCP: (Transport Control Protocol) TCP
| |
| | (M.E.) in Communication Systems. He has
|
| ensures that a packet has reached its
| |
| | several years of experience in electronic
|
| intended destination by using an
| |
| | assembly and design, rf testing, and
|
| acknowledgement. If not, it retransmits
| |
| | networking. He is a Cisco Certified
|
| the lost messages. Hence, TCP is called a
| |
| | Networking Professional, and an MCSE
|
| connection oriented protocol.
| |
| | (Microsoft Certified Systems Engineer).
|
|
| |
| | He is a director of Anand Software and
|
| UDP (Universal Data gram Protocol): UDP
| |
| | Training Pvt. Ltd. Complete tutorial on
|
| simply transmits packets over the
| |
| | Networking is available at
|
| internet. It does not wait for an
| |
| | SimulationExams.
|
| acknowledgement. It is the responsibility
| |
| |
|
