Transcript Computer Networks - Department of Computing

Introduction to Layered Network Model
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Network Planning for Enterprise networks
 Network Planning and Design
◦ Need
◦ Benefits
 Reference Model
◦ Cisco Model
 Hierarchical model
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Cisco specifies: A good network design
should
 Build networks using a hierarchical
model.
 Eliminate points of failure.
 Characterize application and protocol
traffic.
 Analyze bandwidth availability.
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Flat Design
◦ Using hubs
Hierarchical design
◦ Design network in layers
 Analogy to OSI model for communication system
 Simplify understanding communication process
◦ Using layered design of networks allows selection
of right systems and features
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Issues
In a large flat (switched)
network, broadcast packets
are burdensome.
◦ A broadcast packet interrupts
the CPU on each device within
the broadcast domain, and
demands processing time on
every device for which a
protocol understanding for that
broadcast is installed. This
includes routers, workstations,
and servers
A
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C
D
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Advantages
 Hierarchical design can facilitate
changes.
 Modularity in network design
◦ Design elements can be replicated
as the network grows.
 Improved fault isolation
◦ Easy to isolate and troubleshoot
problems
 Easy to upgrade
◦ Cost and complexity of making the
upgrade is constrained to a small
subset of the overall network
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A hierarchical network design
includes the following three
layers:
 •The backbone (core) layer
that provides optimal
transport between sites
 •The distribution layer that
provides policy-based
connectivity
 •The local-access layer that
provides workgroup/user
access to the network
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Connection point for local end users.
Shared/ Switched bandwidth
MAC layer filtering
Access layer can give remote sites access to the
corporate network using WAN technology, such as
Frame Relay
◦ E.g., Campus Network
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 Address
or area aggregation
 Departmental or workgroup access
 Broadcast/multicast domain definition
 Virtual LAN (VLAN) routing
 Any media transitions that need to occur
 Security
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High-speed switching backbone
Should be designed to switch packets as fast as
possible.
This layer of the network should not perform any
packet manipulation to prevent slow switching of
packets.
◦ Access lists
◦ Packet filtering,
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Determine the total number of hosts in a network,
accounting for present and future requirements
Hosts include
◦ PCs, printers, servers, speciality devices
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Given a network requirement, determine the optimum
number of sub networks in the larger inter-network.
◦ Count on the basis of
 Departments
 Locations..
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Devices are grouped
into sub-networks
◦ Based on
geographical location
◦ Based on
Functionality
 Departments
◦ Communication
requirements
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HCC- Horizontal
cable cabinet
VCC- Vertical cable
cabinet
IDF – Intermediate
Distribution Frame
MDF – Main
Distribution Frame
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 Add
them to your blog
 Apply network model for the given task
 Document in your blog
 Task: Analyse and design a home
network
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