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  1. #1
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    من يشرح لي الطبقات الـ 7 و بروتوكولاتها ؟



    السسسسسسسسسسسسلام عليكم




    طلب صغنوووووووووووون !!!


    ابغاك تفصل النت و تشرب كأسة شااااااي ........ وتحضر كاسة ثانية ......

    وتبدأ تشرح اليرات السبع والبروتوكولات بتعتها وشوية تفاصيل



    تبتغي الاجر من الله و في خوانك المسلمين في هذا الشهر الفضيل ......



    شكراً وفي الانتظار ......


    لا تستح من القليل فأن الحرمان اقل منه .......


    بنتيوم 5
    اللهم صلى على نبيك محمد صلى الله عليه و سلم
    ** قالت العرب من كثر حديثه كثر سقطه وقالت اهل نجد من فل شريطه بان خريطه **

  2. #2
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    لا اعرف من انت !! لكن شكراً لك على اية حال !! ( ناقل الموضوع )
    اللهم صلى على نبيك محمد صلى الله عليه و سلم
    ** قالت العرب من كثر حديثه كثر سقطه وقالت اهل نجد من فل شريطه بان خريطه **

  3. #3
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    السلام عليكم

    يوجد كتاب يشرح طبفات OSI بالعربي اذا احبتت ارسلته لك واذا كان هناك ايه سؤال فإذن الله نساعد في الإجابة.

    بالنسبة ل بريدي الإلكتروني هوا نفسه Cisco_designer على الهوت ميل .

    ودمتم

  4. #4
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    How OSI Works

    by Jeff Tyson




    Virtually all networks in use today are based in some
    fashion on the Open Systems Interconnection (OSI)
    standard. OSI was developed in 1984 by the
    International Organization for Standardization (ISO),
    a global federation of national standards
    organizations representing approximately 130
    countries.

    The core of this standard is the OSI Reference Model,
    a set of seven layers that define the different stages
    that data must go through to travel from one device to
    another over a network. In this article, you'll find
    out all about the OSI standard.



    The Layers
    Think of the seven layers as the assembly line in the
    computer. At each layer, certain things happen to the
    data that prepare it for the next layer. The seven
    layers, which separate into two sets, are:

    Application Set

    Layer 7: Application - This is the 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.

    Layer 6: Presentation - Layer 6 takes the data
    provided by the Application layer and converts it into
    a standard format that the other layers can
    understand.

    Layer 5: Session - Layer 5 establishes, maintains and
    ends communication with the receiving device.

    Transport Set

    Layer 4: Transport - This layer maintains flow control
    of data and provides for error checking and recovery
    of data between the devices. 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.

    Layer 3: Network - The way that the data will be sent
    to the recipient device is determined in this layer.
    Logical protocols, routing and addressing are handled
    here.

    Layer 2: Data - In this layer, the appropriate
    physical protocol is assigned to the data. Also, the
    type of network and the packet sequencing is defined.

    Layer 1: Physical - This is the level of the actual
    hardware. It defines the physical characteristics of
    the network such as connections, voltage levels and
    timing.

    The seven layers of the OSI Reference Model

    The OSI Reference Model is really just a guideline.
    Actual protocol stacks often combine one or more of
    the OSI layers into a single layer.



    Protocol Stacks
    A protocol stack is a group of protocols that all work
    together to allow software or hardware to perform a
    function. The TCP/IP protocol stack is a good example.
    It uses four layers that map to the OSI model as
    follows:


    Layer 1: Network Interface - This layer combines the
    Physical and Data layers and routes the data between
    devices on the same network. It also manages the
    exchange of data between the network and other
    devices.

    Layer 2: Internet - This layer corresponds to the
    Network layer. The Internet Protocol (IP) uses the IP
    address, consisting of a Network Identifier and a Host
    Identifier, to determine the address of the device it
    is communicating with.

    Layer 3: Transport - Corresponding to the OSI
    Transport layer, this is the part of the protocol
    stack where the Transport Control Protocol (TCP) can
    be found. TCP works by asking another device on the
    network if it is willing to accept information from
    the local device.

    Layer 4: Application - Layer 4 combines the Session,
    Presentation and Application layers of the OSI model.
    Protocols for specific functions such as e-mail
    (Simple Mail Transfer Protocol, SMTP) and file
    transfer (File Transfer Protocol, FTP) reside at this
    level.
    As you can see, it is not necessary to develop a
    separate layer for each and every function outlined in
    the OSI Reference Model. But developers are able to
    ensure that a certain level of compatibility is
    maintained by following the general guidelines
    provided by the model


    ================================================== ==============================\
    ============================


    The 7 Layers of the OSI Model

    The OSI, or Open System Interconnection, model defines
    a networking framework for implementing protocols in
    seven layers. Control is passed from one layer to the
    next, starting at the application layer in one
    station, proceeding to the bottom layer, over the
    channel to the next station and back up the hierarchy.

    Application
    (Layer 7) This layer supports application and end-user
    processes. Communication partners are identified,
    quality of service is identified, user authentication
    and privacy are considered, and any constraints on
    data syntax are identified. Everything at this layer
    is application-specific. This layer provides
    application services for file transfers, e-mail, and
    other network software services. Telnet and FTP are
    applications that exist entirely in the application
    level. Tiered application architectures are part of
    this layer.
    Presentation
    (Layer 6) This layer provides independence from
    differences in data representation (e.g., encryption)
    by translating from application to network format, and
    vice versa. The presentation layer works to transform
    data into the form that the application layer can
    accept. This layer formats and encrypts data to be
    sent across a network, providing freedom from
    compatibility problems. It is sometimes called the
    syntax layer.
    Session
    (Layer 5) This layer establishes, manages and
    terminates connections between applications. The
    session layer sets up, coordinates, and terminates
    conversations, exchanges, and dialogues between the
    applications at each end. It deals with session and
    connection coordination.
    Transport
    (Layer 4) This layer provides transparent transfer of
    data between end systems, or hosts, and is responsible
    for end-to-end error recovery and flow control. It
    ensures complete data transfer.
    Network
    (Layer 3) This layer provides switching and routing
    technologies, creating logical paths, known as virtual
    circuits, for transmitting data from node to node.
    Routing and forwarding are functions of this layer, as
    well as addressing, internetworking, error handling,
    congestion control and packet sequencing.
    Data Link
    (Layer 2) At this layer, data packets are encoded and
    decoded into bits. It furnishes transmission protocol
    knowledge and management and handles errors in the
    physical layer, flow control and frame
    synchronization. The data link layer is divided into
    two sublayers: The Media Access Control (MAC) layer
    and the Logical Link Control (LLC) layer. The MAC
    sublayer controls how a computer on the network gains
    access to the data and permission to transmit it. The
    LLC layer controls frame synchronization, flow control
    and error checking.
    Physical
    (Layer 1) This layer conveys the bit stream -
    electrical impulse, light or radio signal -- through
    the network at the electrical and mechanical level. It
    provides the hardware means of sending and receiving
    data on a carrier, including defining cables, cards
    and physical aspects. Fast Ethernet, RS232, and ATM
    are protocols with physical layer components.




    ================================================== ==============================\
    ============================


    some useful links:


    http://www.geocities.com/SiliconVall...l.html#Session


    http://www.geocities.com/SiliconVall.../ne/netoc.html

    فى الخدمة.... دعواتكم

  5. #5
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    OSI Seven-Layer Model
    In the 1980s, the European-dominated International Standards Organization (ISO), began to develop its Open Systems Interconnection (OSI) networking suite. OSI has two major components: an abstract model of networking (the Basic Reference Model, or seven-layer model), and a set of concrete protocols. The standard documents that describe OSI are for sale and not currently available online.

    Parts of OSI have influenced Internet protocol development, but none more than the abstract model itself, documented in OSI 7498 and its various addenda. In this model, a networking system is divided into layers. Within each layer, one or more entities implement its functionality. Each entity interacts directly only with the layer immediately beneath it, and provides facilities for use by the layer above it. Protocols enable an entity in one host to interact with a corresponding entity at the same layer in a remote host.



    The seven layers of the OSI Basic Reference Model are (from bottom to top):


    The Physical Layer describes the physical properties of the various communications media, as well as the electrical properties and interpretation of the exchanged signals. Ex: this layer defines the size of Ethernet coaxial cable, the type of BNC connector used, and the termination method.

    The Data Link Layer describes the logical organization of data bits transmitted on a particular medium. Ex: this layer defines the framing, addressing and checksumming of Ethernet packets.

    The Network Layer describes how a series of exchanges over various data links can deliver data between any two nodes in a network. Ex: this layer defines the addressing and routing structure of the Internet.

    The Transport Layer describes the quality and nature of the data delivery. Ex: this layer defines if and how retransmissions will be used to ensure data delivery.

    The Session Layer describes the organization of data sequences larger than the packets handled by lower layers. Ex: this layer describes how request and reply packets are paired in a remote procedure call.

    The Presentation Layer describes the syntax of data being transferred. Ex: this layer describes how floating point numbers can be exchanged between hosts with different math formats.

    The Application Layer describes how real work actually gets done. Ex: this layer would implement file system operations.
    The original Internet protocol specifications defined a four-level model, and protocols designed around it (like TCP) have difficulty fitting neatly into the seven-layer model. Most newer designs use the seven-layer model.



    --------------------------------------------------------------------------------
    دعواتكمممممم

  6. #6
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    What do the layers do?
    As data passes from an application and moves down the stack, each layer adds a header according to the protocol that exists at that layer. This is known as encapsulation. The only exception is the data link layer, a header and a trailer is added. After the data has been transmitted across whatever media is in use, the process of deencapsulation begins. Each layer of the stack, at the destination, removes the header (or header and trailer in the case of the data link layer) that was placed by its corresponding source layer. The physical and data link layers exist in hardware, all other layers are software driven.


    Layer 7 - Application
    This layer has protocols that support user applications, but it does not include the applications themselves. There is an opinion that the network operating system should be included in this layer, but this is open to disagreement. Strictly speaking, this layer deals with file access and management and includes the OSI X.400 and X.500 email protocols. X.400 allows interoperability between different email software and X.500 synchronises email across different systems.


    Layer 6 - Presentation
    The presentation layer protocols deal with data syntax during transfer between two application processes. If the client and server are using different file formats, this layer has conversion protocols. Therefore, computers using different file formats can still communicate with each other. Data encryption and decryption protocols also exist at the presentation layer.


    Layer 5 - Session
    Protocols at this layer are necessary for establishing, maintaining and ending sessions between user applications. Such protocols are designed to make the differences, across various platforms, transparent to the user.


    Layer 4 - Transport
    Transport layer protocols are responsible for the reliability of end to end connections. These protocols assemble multiple network layer packets into a coherent message. This layer also provides flow-control and error recovery.


    Layer 3 - Network
    The network layer protocols establish, maintain and terminate end to end (network) links. These protocols route messages across the network(s) between two computers. Different network operating systems often have their own network layer protocols, but can also use other protocols. This flexibiltity is essential when communicating accross multiple client/server platforms.


    Layer 2 - Data Link
    Data link protocols provide logical link control and medium access control. These protocols provide reliability to the physical layer transmission by ordering the data into frames and adding error checking and addressing information. The network interface card assembles the data link layer frames.


    Layer 1 - Physical
    Protocols at the physical layer are responsible for establishing, maintaining and ending physical connections (point to point) between computers. These protocols are manifested in the media across which transmission occurs. These protocols do not specify the various cables and connectors, these specifications are sometimes said to belong to layer 0.




    لو فى اى اسئلة اتفضل اسأل

  7. #7
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    Layer
    Function Protocols Network Components
    Application
    User Interface
    used for applications specifically written to run over the network
    allows access to network services that support applications;
    directly represents the services that directly support user applications
    handles network access, flow control and error recovery
    Example apps are file transfer,e-mail, NetBIOS-based applications
    DNS; FTP; TFTP; BOOTP; SNMP;RLOGIN; SMTP; MIME; NFS; FINGER; TELNET; NCP; APPC; AFP; SMB Gateway
    Presentation
    Translation
    Translates from application to network format and vice-versa
    all different formats from all sources are made into a common uniform format that the rest of the OSI model can understand
    responsible for protocol conversion, character conversion,data encryption / decryption, expanding graphics commands, data compression
    sets standards for different systems to provide seamless communication from multiple protocol stacks
    not always implemented in a network protocol
    Gateway
    Redirector

    Session
    "syncs and sessions"
    establishes, maintains and ends sessions across the network
    responsible for name recognition (identification) so only the designated parties can participate in the session
    provides synchronization services by planning check points in the data stream => if session fails, only data after the most recent checkpoint need be transmitted
    manages who can transmit data at a certain time and for how long
    Examples are interactive login and file transfer connections, the session would connect and re-connect if there was an interruption; recognize names in sessions and register names in history
    NetBIOS
    Names Pipes

    Mail Slots

    RPC
    Gateway
    Transport

    packets; flow control & error-handling
    additional connection below the session layer
    manages the flow control of data between parties across the network
    divides streams of data into chunks or packets; the transport layer of the receiving computer reassembles the message from packets
    "train" is a good analogy => the data is divided into identical units
    provides error-checking to guarantee error-free data delivery, with on losses or duplications
    provides acknowledgment of successful transmissions; requests retransmission if some packets don’t arrive error-free
    provides flow control and error-handling
    TCP, ARP, RARP;
    SPX

    NWLink

    NetBIOS / NetBEUI

    ATP
    Gateway
    Advanced Cable Tester

    Brouter

    Network

    addressing; routing
    translates logical network address and names to their physical address (e.g. computername ==> MAC address)
    responsible for
    addressing
    determining routes for sending
    managing network problems such as packet switching, data congestion and routing
    if router can’t send data frame as large as the source computer sends, the network layer compensates by breaking the data into smaller units. At the receiving end, the network layer reassembles the data
    think of this layer stamping the addresses on each train car
    IP; ARP; RARP, ICMP; RIP; OSFP;
    IGMP;

    IPX

    NWLink

    NetBEUI

    OSI

    DDP

    DECnet
    Brouter
    Router

    Frame Relay Device

    ATM Switch

    Advanced Cable Tester

    Data Link

    data frames to bits
    turns packets into raw bits 100101 and at the receiving end turns bits into packets.
    handles data frames between the Network and Physical layers
    the receiving end packages raw data from the Physical layer into data frames for delivery to the Network layer
    responsible for error-free transfer of frames to other computer via the Physical Layer
    this layer defines the methods used to transmit and receive data on the network. It consists of the wiring, the devices use to connect the NIC to the wiring, the signaling involved to transmit / receive data and the ability to detect signaling errors on the network media
    Logical Link Control
    error correction and flow control
    manages link control and defines SAPs
    802.1 OSI Model

    802.2 Logical Link Control
    Bridge
    Switch

    ISDN Router

    Intelligent Hub

    NIC

    Advanced Cable Tester

    Media Access Control
    communicates with the adapter card
    controls the type of media being used:
    802.3 CSMA/CD (Ethernet)

    802.4 Token Bus (ARCnet)

    802.5 Token Ring

    802.12 Demand Priority

    Physical

    hardware; raw bit stream
    transmits raw bit stream over physical cable
    defines cables, cards, and physical aspects
    defines NIC attachments to hardware, how cable is attached to NIC
    defines techniques to transfer bit stream to cable
    IEEE 802
    IEEE 802.2

    ISO 2110

    ISDN
    Repeater
    Multiplexer

    Hubs

    Passive
    Active
    TDR

    Oscilloscope

    Amplifier

  8. #8
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    السلام عليكم


    بدر ... .. ما تقصر اخوي ووصلتك رسالة ع بريدك .وجزاك الله خير ... والي يريد الكتاب يرد في نفس الموضوع ....


    nana17 شاكر لك ... والله يجزاك خير ..... المصدر هو اليوزفل لينك ؟؟




    تبدأ الجلسة الان ...... واي اسئلة ان شاء الله راح تكون هنا


    تحياتي للجميع ....

    عمر ... بنتيوم 5
    اللهم صلى على نبيك محمد صلى الله عليه و سلم
    ** قالت العرب من كثر حديثه كثر سقطه وقالت اهل نجد من فل شريطه بان خريطه **

  9. #9
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    السلام عليكم

    بارك الله فيك أخي عمر والكتاب فعلاً قد تم إرساله وأرجو أن ينال استحسانك ،،،، وإذا وُجد أي استفسار فبإذن الله نحن في الخدمة.....

    ودمتم

المواضيع المتشابهه

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