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2006 Cisco Systems, Inc. All rights reserved. Cisco Public 1
LAN Switching and Wireless
LAN Switching and Wireless
Chapter 1
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Objectives
Describe how a hierarchical network supports the
voice, video and data needs of a small andmedium-sized business.
Match the appropriate Cisco switch to each layer inthe hierarchical network design model
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The Hierarchical Network Model
A hierarchical design model is used to successfully
build a LANEasier to manage and expand
Problems are solved more quickly
Involves dividing the network into discrete layers
Each layer provides specific functions that define its rolewithin the overall network
Network design becomes modular
Facilitates scalability and performance
Broken up in to three layers Access
Distribution
Core
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The Hierarchical Network Model
Access Layer
Provides a means of connecting devices to the networkand controlling which devices are allowed tocommunicate on the network
Interfaces with end devices - PCs, printers, IP phones
Includes routers, switches, bridges, hubs, and wireless access
points (AP)
Distribution Layer
Aggregates data received from access layer switchesbefore transmitting to core layer
Controls flow of network traffic using policies
Separates broadcast domains by routing between virtualLANs (VLANs)
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The Hierarchical Network Model
Core Layer
High-speed backbone of the internetwork
Critical for interconnectivity between distribution layerdevices
Needs to be highly available and redundant
Aggregates traffic from all distribution layer devices
Must be capable of forwarding large amounts of data quickly
Note:
In smaller networks, distribution layer and core layer may becombined into one layer
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The Hierarchical Network Model
Access Layer
Distribution Layer
Core Layer
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The Hierarchical Network Model
Benefits of a Hierarchical Network
Scalability Modular design allows networks to expand very well
Redundancy
Redundant switches are placed at each layer to ensure path
redundancy
If a switch fails, there is an alternate path through the redundantswitch
Performance
Aggregated data is sent between layers at near wire speed inmost cases (backbone links)
High performance switching at the local level provides near wirespeed and maximum bandwidth for network traffic
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The Hierarchical Network Model
Security
Port security on access layer switches controls which devices areallowed to connect to the network
Advanced security policies at the distribution layer define whichcommunication protocols are permitted and where they arepermitted to go
Manageability
Switch functions are defined for each layer, providing consistency
Changes and additions are easily duplicated across each of thelayers
Maintainability
Switch functions are defined for each layer Switching infrastructure is selected to suit the requirements of
each layer
Modular design minimises the impact of changes at each of thelayers
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Principles of Hierarchical Network Design
Hierarchical Network Design Principles
Network Diameter
Number of devices that a packet has to cross before it reaches itsdestination (source to destination)
Low diameter ensures low and predictable latency betweendevices
Bandwidth Aggregation Combining multiple physical switch ports into a single logical link
to provide higher throughput (bandwidth) between switches
Redundancy
Creating a highly available network by implementing extraconnections such as installing extra switches and extraconnections between devices
Redundant devices and paths
Increases cost
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Principles of Hierarchical Network Design
Network Diameter Bandwidth Aggregation
Redundancy
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Principles of Hierarchical Network Design
Start at the Access Layer
Understand the business goals of the organization
Select equipment and infrastructure to implement thedesign
1. Devices needing access to the network
2. Access layer switches
Estimated traffic generated
3. Distribution layer switches
To meet performance and redundancy required
4. Core layer switches
Maintain the performance of the network
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What is a Converged Network?
Convergence is the process of combining voice
and video communications on a data network Legacy Equipment
Initially, converged networks were only feasible in largeenterprise organizations
Expensive network infrastructure requirements and complexmanagement
Minimal expertise by support staff
Legacy equipment holding back progress
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What is a Converged Network?
Separate Voice, Video and Data Networks
Voice network contains isolated phone lines running to aPBX switch to allow phone connectivity to the PublicSwitched Telephone Network (PSTN).
Videoconferencing equipment is wired separately from
the voice and data networksData network interconnects the workstations and servers
on a network to facilitate resource sharing
Separate support staff to support each network
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What is a Converged Network?
Advanced Technology
Infrastructure costs have reduced, technology hasadvanced and expertise has increased:
Convergence now occurring right across small to largeenterprises
One network to manage
One wired infrastructure to manage Lower implementation and management costs
One group managing both the voice and data networks
New Options
Voice and video communications directly into a desktop
Software phones rather than physical phones provide alot of flexibility for businesses
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What is a Converged Network?
Converged voice, videoand data on a hierarchicalnetwork design
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Considerations For Hierarchical NetworkSwitches
Traffic Flow Analysis
Selecting appropriate switches for a layer in ahierarchical network requires:
Specifications detailing traffic flows
Understanding user communities
Data servers and data storage servers needs Understanding of switches needed in the core, distribution, and
access layers to accommodate bandwidth requirements
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Considerations For Hierarchical NetworkSwitches
Traffic Flow Analysis
Process of measuring bandwidth usage on a networkand analyzing data for the purpose of performancetuning, capacity planning, and making hardwareimprovement decisions
All network data contributes to traffic, regardless of itspurpose or source
Use traffic flow analysis software to measure amount of data sentthrough a network for a given period of time
Provides data to allow accurate tuning and information for
possible upgrades
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Considerations For Hierarchical NetworkSwitches
User Communities Analysis
Process of identifying various groupings of users andtheir impact on network performance
Affects issues related to port density and traffic flow
Influences selection of network switches
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Considerations For Hierarchical NetworkSwitches
Future Growth
Network plan includes rate of personnel growth overprevious years to anticipate future growth
Purchase switches that can accommodate growth, such asstackable or modular switches
Investigate network traffic generated by end-userapplications
Servers and users located where needed on the network
Reducing impact of traffic across rest of the network
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Considerations For Hierarchical NetworkSwitches
Data Stores and Data Servers Analysis
When analyzing traffic on a network: Consider where data stores and servers are located to determine
impact of traffic on the network
Data stores can be servers, storage area networks (SANs),network-attached storage (NAS), tape backup units, any otherdevice or component where large quantities of data are stored
When considering traffic for data stores and servers, considerboth client-server traffic and server-server traffic
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Considerations For Hierarchical NetworkSwitches
By examining data paths for various applications used by different usercommunities:
Identify potential bottlenecks where performance of theapplication can be affected by inadequate bandwidth
To improve the performance:
Aggregate links to accommodate the bandwidth
Replace slower switches with faster switches capable ofhandlin traffic load
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Considerations For Hierarchical NetworkSwitches
Topology Diagrams
Graphical representation of a network infrastructureShows how all switches are interconnected, detailed
down to which switch port interconnects the device
Graphically displays any redundant paths or aggregated
ports between switches that provide for flexibility andperformance
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Switch Features
Switch Form Factors
Need to decide between fixed configuration or modularconfiguration, and stackable or non-stackable
Thickness of the switch expressed in number of rackunits
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Switch Features
Fixed Configuration Switches
Cannot add features or options to the switch beyondthose that originally came with the switch
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Switch Features
Modular Switches
Offer more flexible configurationDifferent sized chassis to allow for installation of different
numbers of modular line cards
Line cards contain the ports
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Switch Features
Stackable Switches
Interconnected using special backplane cable to providehigh-bandwidth throughput between the switches
Switches stacked one atop the other
Cables connect switches in daisy chain fashion
Effectively operate as single larger switch
Fault tolerance and bandwidth availability in critical environments
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Switch Features
Performance
Consider ability of switch to support port density,forwarding rates, and bandwidth aggregationrequirements of network
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Switch Features
Port Density
Number of ports available on a single switch
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Switch Features
Forwarding Rates
Processing capabilities of a switch by rating how muchdata switch can process per second
Entry-layer switches have lower forwarding rates thanenterprise-layer switches
Forwarding rate too low, cannot accommodate full wire-speed communication across all of its switch ports
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Switch Features
Link Aggregation
Helps reduce bottlenecks of traffic by allowing up to eightswitch ports to be bound together for datacommunications
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Switch Features
PoE and Layer 3 Functionality
When selecting a switch consider Power over Ethernet(PoE) and Layer 3 functionality
Power over Ethernet (PoE)
Allows switch to deliver power to a device over theexisting Ethernet cabling
IP phones and some wireless access points
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Switch Features
Layer 3 Functions
Provided by switches in a hierarchical networkLayer 3 switches offer advanced functionality
Known as multilayer switches
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Switch Features in a Hierarchical Network
Access Layer Switch Features
Facilitate connection of end node devices to the network Need to support features such as port security, VLANs,
Fast Ethernet/Gigabit Ethernet, PoE, and linkaggregation
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Switch Features in a Hierarchical Network
Distribution Layer Switch Features
Provide inter-VLAN routing functions so that one VLANcan communicate with another on the network
Support Layer 3 functions
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Switch Features in a Hierarchical Network
Security Policies
Access Control Lists (ACLs) used to control how trafficflows through the network
Prevent certain types of traffic and permit others
Control which network devices can communicate on the network
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Switch Features in a Hierarchical Network
Quality of Service
Maintain the prioritization of traffic coming from theaccess layer switches that have implemented QoS
Priority policies ensure audio and video communicationsare guaranteed adequate bandwidth to maintain an
acceptable quality of service Support redundancy for adequate availability
Typically implemented in pairs to ensure availability
Support multiple, hot swappable power supplies
Need to support link aggregation
To ensure adequate bandwidth to accommodate trafficgenerated on the access layer
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Switch Features in a Hierarchical Network
Core Layer Switch Features
High-speed backbone of network and switches need tohandle very high forwarding rates
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Switch Features in a Hierarchical Network
Link Aggregation
Need to support link aggregation to ensure adequatebandwidth coming into the core from the distributionlayer switches
Redundancy
Availability of core layer is critical, build in as muchredundancy as possibility
Redundant power supplies and fans that can be swapped whileswitch is operational
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Switch Features in a Hierarchical Network
QoS is an important part of the services provided
by core layer switches Mission-critical and time-sensitive traffic such as voice
should receive higher QoS guarantees than less time-sensitive traffic such as file transfers or e-mail
Because QoS provides a software based solution toprioritize traffic, cost effective way of supporting optimalbandwidth
Switches for Small and Medium Sized Business
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Switches for Small and Medium Sized Business(SMB)
Features of Cisco Catalyst Switches
Switches need to be selected to meet the requirementsof the enterprise
Switches cannot be selected just on the size of the business
Small businesses might be integrated into larger networks andrequire all of the advanced LAN services available at thecorporate head office
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Hierarchical Design model addresses performance,
scalability, maintainability & manageability issues. Traffic Analysis is used to monitor network
performance.
Hierarchical Design Model is composed of 3 layers:Access
Distribution
Core
Switches selected for each layer must meet theneeds of each hierarchical layer as well as theneeds of the business.
Summary
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A converged understanding