LAN Design

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LAN Design

• Semester III

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LAN Design Goals

• The first step in designing a LAN is to establish
  and document the goals of the design.
• Functionality-the network must work.
• Scalability-the network must be able to grow.

3
LAN Design Goals

• Adaptability-the network must be designed with an
  eye toward future technologies.
• Manageability-the network should be designed to
  facilitate network monitoring and management.

4
Server Placement

• Servers provide file sharing, printing,
  communication, and application services, such as
  word processing. Servers typically do not
  function as workstations Rather, they run
  specialized operating systems, such as NetWare,
  Windows NT, UNIX, and Linux.
• Today, each server usually is dedicated to one
  function, such as e-mail or file sharing.

5
Workgroup and Enterprise Servers

• An enterprise server supports all the users on
  the network by offering services, such as e-mail
  or domain name system (DNS).
• A workgroup server supports a specific set of
  users, offering services such as word processing
  and file sharing, which are services only a few
  groups of people would need.

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Workgroup and Enterprise Servers

• Enterprise servers should be placed in the main
  distribution facility (MDF).
• Ideally, workgroup servers should be placed in
  the intermediate distribution facilities (IDFs)
  closest to the users accessing the applications.

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Intranet

• Intranets are designed to be accessed by users
  who have access privileges to an organization's
  internal LAN.
• Web servers and browser technology are used as
  the common front-end to access information, such
  as financial data or graphical and text-based
  data stored on those servers.

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Segmentation

• Segmentation is the process of splitting a single
  collision domain into two or more collision
  domains. Routers, bridges, and switches can
  segment.
• Non-VLAN capable switches and bridges (as well as
  repeaters and hubs) do not create smaller
  broadcast domains Only VLANs and routers can do
  that.

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Segmentation

• All broadcasts from any host in the same
  broadcast domain are visible to all other hosts
  in the same broadcast domain. Broadcasts must be
  visible to all hosts in the broadcast domain in
  order to establish connectivity.
• It is important to remember that bridges and
  switches forward broadcast (FF-FF-FF-FF-FF)
  traffic, and that routers normally do not.

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Bandwidth and BroadcastDomains

• A bandwidth domain is everything associated with
  one port on a bridge or switch.
• Also known as a collision domain.

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Network Design Methodology

• Gathering the users' requirements and
  expectations. Gather data about the
  organizational structure, history and current
  status, projected growth, operating policies and
  management procedures, office systems and
  procedures, and the viewpoints of the people who
  will be using the LAN. .
• Analyze requirements of users and of the network.

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Network Design Methodology

• Design the layer 1, 2, and 3 LAN structure (that
  is, topology). Determine who in the organization
  has authority over addressing, naming, topology
  design, and configuration. Look to see if there
  is a MIS department.
• Documenting the logical and physical network
  implementation. An organization's existing
  computer hardware and software must be
  documented, and projected hardware and software
  needs identified.

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Designing Layer 1

• The physical cabling is one of the most important
  components to consider when designing a network.
• Layer 1 cabling media include types such as
  category 5 unshielded twisted-pair (UTP) and
  fiber-optic cable, along with the TIA/EIA-568-A
  standard for layout and connection of wiring
  schemes.
• Fiber-optic cable should be used in the backbone
  and risers, with category 5 UTP cable in the
  horizontal runs.

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Designing Layer 1

• The TIA/EIA-568-A standard specifies that every
  device connected to the network should be linked
  to a central location with horizontal cabling.
  This is true if all the hosts that need to access
  the network are within the 100-meter distance
  limitation for category 5 UTP Ethernet.

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Elements of the Logical Diagram (Cross-connect)

• The exact locations of the MDF and IDF wiring
  closets.
• The type and quantity of cabling used to
  interconnect the IDFs with the MDF.
• Detailed documentation of all cable runs, the
  identification numbers, and which port on the HCC
  or VCC the run is terminated on.

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Layer 3 Network Design

• Routers can be used to create unique LAN segments
  and allow communication between segments based on
  layer 3 addressing, such as IP addressing. They
  also allow for connectivity to (WANs), such as
  the internet. They forward data packets based on
  destination addresses.
• Routers do not forward LAN-based broadcasts such
  as ARP requests.

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Routers Logical Structure

• Routers can be used to provide IP subnets to add
  structure to addresses. Hosts using protocols
  with network-layer addressing can solve the
  problem of finding other hosts without flooding.

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Routers Logical Structure

• If the destination address is local, the sending
  host can encapsulate the packet in a data-link
  header and send a unicast frame directly to the
  station. The sending host might have to use ARP.
• If the destination is not local, then the sending
  station transmits the packet to the router. The
  router sends the frame to the destination or to
  the next hop, based on its routing table.