Transcript LAN DESIGN – first step

LAN DESIGN – first step
5 ISB – school year 2006/07
LAN design
1. LAN Design Goals and Components
2. Network Design Methodology
3. Layer 1 Design
4. Layer 2 Design
5. Layer 3 Design
LAN Design Goals and Components
• Main requirements of the networks are:
scalable, manageable , reliable
• There is not a unique
solution, each
network has distinct design requirement
• The first step is to establish and
document the goals of the design
Typical LAN Design Goals
• Functionality - the network must work, must
provide user-to-user and user-to-application
connectivity with reasonable speed and reliability
• Scalability- the network must be able to grow
• Adaptability - the network must be designed
with an eye toward future technologies
• Manageability- the network should be designed
to facilitate network monitoring and management
Critical components of LAN design
The critical components of the overall LAN
design for high-speed technologies and
multimedia-based applications are:
• the function and placement of servers
• Collision detection
and Segmentation
• Bandwidth versus Broadcast domains
Placement of servers
Servers provide file sharing, printing,
communication, and application services.
Servers can be categorized
into two distinct
classes: enterprise servers and workgroup 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.
Placement of servers
Enterprise servers should be placed in the main
distribution facility (MDF).
Workgroup servers should be placed in the
intermediate distribution facilities (IDFs) closest to
the users accessing the applications on these
servers.
Within the MDF and IDFs, the Layer 2 LAN
switches should have 100 Mbps or more allocated
for these servers.
Collision detection
The designer has to decrease collision detection
and media contention on networks. The possible
causes of excessive collisions and broadcasts are:
• too many client packets looking for services,
• too many server packets announcing services,
• too many routing table updates,
• too many other broadcasts dependent on the
protocols, such as Address Resolution Protocol.
Collision detection
As traffic increases on the shared media, the
rate of collisions also increases. An excessive
number of collisions will reduce available
bandwidth. In most cases, the actual available
bandwidth is reduced to a fraction (about 35%
to 40%) of the full 10/100 Mbps.
This reduction in bandwidth can be remedied by
segmenting the network by using bridges,
switches, or routers.
Segmentation
Segmentation
is the process
of splitting
a
single collision
domain into
two or more
collision
domains.
Bandwidth Domain vs Broadcast Domain
A bandwidth domain (collision domain in Ethernet )
is everything associated with one port on a bridge
or switch.
A broadcast
domain is
everything
associated
with one port
on a router.
Gathering and analyzing requirements
Beginning steps for a LAN design are:
• gathering the users' requirements
expectations
and
• analyzing requirements
• designing the Layer 1, 2, and 3 LAN structure
• documenting the logical and physical network
implementation
Gathering and analyzing requirements
Information to be gathered:
• organization's history and current status,
• projected growth,
• operating policies and management procedures,
• office systems and procedures,
• viewpoints of the people who will be using the
LAN
Gathering and analyzing requirements
You need to answer the following questions:
• Who are the people who will be using the
network?
• What is their level of skill?
• What are their attitudes
computer applications?
toward computers and
• Have some data and operations been declared
mission critical ?
Focus on identifying the resources and constraints
of the organization, existing computer
hardware/software and human resources.
Physical topologies used in networking
The next step is to decide on an overall LAN
topology (typically star or extended-star).
Design the layer 1 topology
The physical cabling design issues include the type
of cabling
to be used
(typically
copper or
fiber) and
the overall
structure
of the
cabling.
Design the layer 1 topology
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 and maximum distance.
Diagramming a standards-based Ethernet
cable run from the workstation to the HCC
HCC, VCC, MDF and IDF
It is usual to have more than one wiring closet
So multiple areas are created.
Main wiring closet is
called MDFs (Main
Distribution Facility),
and secondary are
referred to as IDFs
(Intermediate
Distribution Facility).
.
HCC, VCC, MDF and IDF
TIA/EIA 568-A
Standards
specify that
IDFs should be
connected to the
MDF by using
vertical cabling,
also called
backbone
cabling.
HCC, VCC, MDF and IDF
A vertical crossconnect (VCC)
is used to
interconnect the
various IDFs to
the central MDF.
For cable length
issues, fiberoptic cabling
normally is used
in VCCs.