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Thread: Basic Networking Tutorial Pt.2

  1. #1
    Senior Member
    Join Date
    Jan 2002

    Post Basic Networking Tutorial Pt.2

    Well I start my vacation on Friday. So here is the second part to my series on netwotking before I go. It is continued from this thread:
    I hope this helps some of you.
    Subject of this tut is TCP/IP in networks.

    Basic TCP/IP, an understanding__
    The TCP/IP protocol suite is named for two of its most
    important protocols: Transmission Control Protocol (TCP)
    and Internet Protocol (IP). Another name for it is the
    Internet Protocol Suite, and this is the phrase used in
    official Internet standards documents. We shall use the
    more common term TCP/IP to refer to the entire protocol.
    The first design goal of TCP/IP was to build an
    interconnection of networks that provided universal
    communication services: an internet. Each physical network
    has its own technology-dependent communication interface,
    in the form of a programming interface that provides basic
    communication functions (primitives). Communication
    services are provided by software that runs between the
    physical network and the user applications and that
    provides a common interface for these applications,
    independent of the underlying physical network. The
    architecture of the physical networks is hidden from the
    The second aim is to interconnect different physical
    networks to form what appears to the the user to be one
    large network. Such a set of interconnected networks is
    called an internet.
    To be able to interconnect two networks, we need a
    computer that is attached to both networks and that can
    forward packets from one network to the other; such a
    machine is called a router. The term IP router is also
    used because the routing function is part of the IP layer
    of the TCP/IP protocol suite.

    The basic properties of a router are:
    From the network standpoint, a router is a normal host.
    From the user standpoint, routers are invisible. The user
    sees only one large internetwork.
    To be able to identify a host on the internetwork, each
    host is assigned an address, the IP address. When a host
    has multiple network adapters, each adapter has a separate
    IP address. The IP address consists of two parts:
    IP address = <network number><host number>
    The network number part of the IP address is assigned by a
    central authority and is unique throughout the Internet.
    The authority for assigning the host number part of the IP
    address resides with the organization which controls the
    network identified by the network number.
    TCP/IP, like most networking software, is modelled in
    layers. This layered representation leads to the term
    protocol stack which is synonymous with protocol suite. It
    can be used for situating (but not for comparing
    functionally) the TCP/IP protocol suite against others,
    such as SNA and Open System Interconnection (OSI).
    Functional comparisons cannot easily be extracted from
    this, as there are basic differences in the layered models
    used by the four different protocol suites.

    Application ***
    is a user process cooperating with another process on the
    same or a different host. Examples are TELNET (a protocol
    for remote terminal connections), FTP (File Transfer
    Protocol) and SMTP (Simple Mail Transfer Protocol). These
    are discussed in detail in Application Protocols.
    Transport ***
    provides the end-to-end data transfer. Example protocols
    are TCP (connection-oriented) and UDP (connectionless).
    Internet ***
    also called the internet layer or the network layer, the
    internet provides the ``virtual network'' image of
    internet (that is, this layer shields the higher levels
    from the typical network architecture below it). Internet
    Protocol (IP) is the most important protocol in this
    layer. It is a connectionless protocol which doesn't
    assume reliability from the lower layers. IP does not
    provide reliability, flow control or error recovery. These
    functions must be provided at a higher level, either at
    the Transport layer by using TCP as the transport
    protocol, or at the Application layer if UDP is used as
    the transport protocol. IP is discussed in detail in
    Internet Protocol (IP). A message unit in an IP network is
    called an IP datagram. This is the basic unit of
    information transmitted across TCP/IP networks.
    Network Interface ***
    also called the link layer or the data-link layer, the
    network interface layer is the interface to the actual
    network hardware. This interface may or may not provide
    reliable delivery, and may be packet or stream oriented.
    In fact, TCP/IP does not specify any protocol here, but
    can use almost any network interface available, which
    illustrates the flexibility of the IP layer. Examples are
    IEEE 802.2, X.25 and ATM.

    Bridges, Routers and Gateways In TCP/IP
    Forming an internet by interconnecting multiple networks
    is done by routers. It is important to distinguish between
    a router, a bridge and a gateway.

    Interconnects LAN segments at the Network Interface layer
    level and forwards frames between them. A bridge performs
    the function of a MAC relay, and is independent of any
    higher layer protocol. It provides MAC layer protocol
    conversion, if required. A bridge can be said to be
    transparent to IP. That is, when a host sends an IP
    datagram to another host on a network connected by a
    bridge, it sends the datagram directly to the host and the
    datagram ``crosses'' the bridge without the sending host
    being aware of it.
    Interconnects networks at the internetwork layer level and
    routes packets between them. The router must understand
    the addressing structure associated with the networking
    protocols it supports and take decisions on whether, or
    how, to forward packets. Routers are able to select the
    best transmission paths and optimal packet sizes. The
    basic routing function is implemented in the IP layer of
    the TCP/IP protocol stack. Therefore any host or
    workstation running TCP/IP may be used as a router.Because
    IP provides this basic routing function, the term ``IP
    router'', is often used. Other, older, terms for router
    are ``IP gateway'', ``Internet gateway'' and ``gateway''.
    The term gateway is now normally used for connections at a
    higher level than the router level. A router can be said
    to be visible to IP. That is, when a host sends an IP
    datagram to another host on a network connected by a
    router, it sends the datagram to the router and not
    directly to the target host.

    Interconnects networks at higher levels than bridges or
    routers. A gateway usually supports address mapping from
    one network to another, and may also provide
    transformation of the data between the environments to
    support end-to-end application connectivity. Gateways
    typically limit the interconnectivity of two networks to a
    subset of the application protocols supported on either
    one. For example, a VM host running TCP/IP may be used as
    an SMTP/RSCS mail gateway. Note: The term ``gateway'',
    when used in this sense, is not synonymous with ``IP
    gateway''. A gateway can be said to be opaque to IP. That
    is, a host cannot send an IP datagram through a gateway:
    it can only send it to a gateway. The higher-level
    protocol information carried by the datagrams is then
    passed on by the gateway using whatever networking
    architecture is used on the other side of the gateway.

    Closely related to routers and gateways is the concept of
    a firewall or firewall gateway which is used to restrict
    access from the Internet to a network or a group of
    networks controlled by an organization for security

    IP Routing
    Incoming datagrams will be checked to see if the local
    host is the IP destination host:
    The datagram is passed to the higher-level protocols.
    The datagram is for a different host. The action depends

    on the value of the ipforwarding flag.
    The datagram is treated as an outgoing datagram and is
    routed to the next hop according to the algorithm
    described below.
    The datagram is discarded.
    In the internet protocol, outgoing IP datagrams pass
    through the IP routing algorithm which determines where to
    send the datagram according to the destination IP address.
    If the host has an entry in its IP routing table which
    matches the destination IP address, the datagram is sent
    to the address in the entry. If the network number of the
    destination IP address is the same as the network number
    for one of the host's network adapters (that is, the
    destination and the host are on the same network) the
    datagram is sent to the physical address of the host
    matching the destination IP address. Otherwise, the
    datagram is sent to a default router. This base algorithm,
    needed on all IP implementations, is sufficient to perform
    the base routing function.
    As noted above, a TCP/IP host has basicrouter
    functionality included in the IP protocol. Such a router
    is adequate for simple routing, but notforcomplex
    networks. The IP routing mechanism is combined with the
    "layered'' view of the TCP/IP protocol stack. This shows
    an IP datagram, going from one IP address (network number
    X, host number A) to another (network number Y, host
    number B), through two physical networks. Note that at the
    intermediate router, only the lower part of the TCP/IP
    protocol stack (the internetwork and the network interface
    layers) are involved.
    The COOKIE TUX lives!!!!
    Windows NT crashed,I am the Blue Screen of Death.
    No one hears your screams.

  2. #2
    Senior Member
    Join Date
    Jan 2002
    Forgot to add. The next part (3) will deal with specific hardware devices and interfaces. I should have it out in the next couple of weeks.
    The COOKIE TUX lives!!!!
    Windows NT crashed,I am the Blue Screen of Death.
    No one hears your screams.

  3. #3
    Fastest Thing Alive s0nIc's Avatar
    Join Date
    Sep 2001
    lol nice tut!! ermm just need a little work on your white space coordination to make it pleasant to read

    but u get greenies for that

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