ex3ch1 lan design

8/2/2019 Ex3Ch1 LAN Design

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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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2006 Cisco Systems, Inc. All rights reserved. Cisco Public

2LAN Switching and Wireless Ch1 Exploration 3

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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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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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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Access Layer

Distribution Layer

Core Layer


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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





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




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





Network Diameter Bandwidth Aggregation

Redundancy





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




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





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





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





Converged voice, videoand data on a hierarchicalnetwork design




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





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





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





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





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





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





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




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




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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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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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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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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Core Layer Switch Features

High-speed backbone of network and switches need tohandle very high forwarding rates


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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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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

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