lan design lan switching and wireless – chapter 1 vilina hutter, instructor

LAN Design

LAN Switching and Wireless – Chapter 1

Vilina Hutter, Instructor

Vilina Hutter, InstructorExploration 3, Ch 1 2

Hierarchical Network Design 3 layered model

• Access, Distribution, & Core Layers

• Each layer has specific functions

• Facilitates modularity

• Modularity facilitates scalability and enhanced performance

In small networks, the core and distribution layers can be combined—known as the collapsed core model


Access Layer

End user devices

•PCs, phones, printers

Access to network for users

Can include any networking device


Distribution Layer

Controls the flow of network traffic

•Policy implementation

•Broadcast containment

•VLAN connectivity

Switches and Routers


Core Layer

High-speed backbone

Routers or switches

Redundant links


Physical Layout of a Hierarchical Design

Less easy to see the hierarchical design layers in the physical layout!


Benefits of a Hierarchical Design


Four Design Principles

Network Diameter

Bandwidth Aggregation

Redundant Links

Start at the Access Layer!


Network Diameter

How many devices a packet must cross to reach its destination

•Lower is better!


Bandwidth Aggregation

Combining several parallel links between two switches to form one logical link


Redundant Links

Used between devices at the core and distribution layer to ensure network availability


Start at the Access Layer!

Business needs are met at the access layer

All network design is driven by the needs of the business and its users

U.S.A.F’s Network Centric Collaborative Targeting (NCCT) system


Converged Networks

Networks that carry video, data, and voice•Convergence has been slowed by installed analog phone infrastructure

Advantages of convergence:•One network to manage

•One set of cabling

•One ring to rule them all

•Lower management costs

•New technology options• Softphones, webcams• Videoconferencing


Selecting Network Devices Traffic Flow Analysis

•To select the right switches, network designers must accommodate present and projected network traffic requirements

•Traffic flow analysis tools are available to track, record, and analyze traffic patterns on a network


User Communities Analysis Consider the number of devices that need to join the

network now and in the projected future•Switch port number planning

Consider any special traffic flow needs for particular applications used by a particular user community

• If a community uses a traffic-intensive application, they should be located physically close to their server to reduce network diameter for the workers

Smaller diameter for HR Dept.


Data Stores and Data Servers Analysis

Examine traffic patterns between clients and their servers and between servers and data storage

•Potential bottlenecks between clients and servers can be reduced by aggregating bandwidth and by installing powerful switches

•High traffic volume between servers will have less impact on the entire network if the servers are physically close to each other

• Typically, all servers are located in a secure data center• Distribution layer switches are also located in the data center


Topology Diagram Analysis

Careful examination of a detailed topology map will all identification of potential bottlenecks

•Traffic flow analysis can then be focused on those likely problem spots


Switch Features Form Factor

•Fixed or modular hardware configuration

•Rack units (thickness)

•Stackable vs. non-stackable

Performance•Port density

•Forwarding rates

•Bandwidth aggregation

PoE (Power over Ethernet)

Layer 3 Functionality


Match the Appropriate Cisco Switch to each Layer in the Hierarchical Network Design Model

Identify the considerations used to select a switch for a hierarchical network


Form Factor—Fixed vs. Modular Fixed configuration switches cannot be modified or upgraded

Modular switches accept line cards

• Line cards contain the ports

• Line cards can be added or upgraded

• The larger the chassis, the more line cards can be supported


Form Factor--Stackable Stackable switches can be connected by a backplane

cable

Allows a group of switches to effectively act as one switch

•Backplane cables use a special fast port to connect switches

Cross-connections allow for fast recovery if a single switch fails


Match the Appropriate Cisco Switch to each Layer in the Hierarchical Network Design Model

Identify the switch features found in each level in a hierarchical network


Performance—Port Density Number of ports available on a

single switch

Higher port density is more efficient• Space considerations

• Power outlets/consumption

Fixed switches support a maximum density of 48 ports

Modular switches support up to 1000+ ports

If many fixed switches are installed, they must all be uplinked, consuming ports for link aggregation

Modular switches support the line port aggregation via the backplane


Performance—Forwarding Rates

How much total data the switch can forward per second

Especially at the distribution and core layers, the switch must support full speed on all port simultaneously

At the access layer, switches are limited by the uplink capability, so the forwarding rate is less crucial


Switch Performance—Link Aggregation

All switches should support link aggregation to avoid uplink bottlenecks


Switch Performance—PoE

PoE is the ability to provide electrical power to devices over the Ethernet ports

•Particularly useful for IP phones or access points which may need to be located away from electrical power lines

PoE is an expensive feature, which should not be ordered unless needed


Switch Performance—Layer 3 Functionality

Known as multilayer switching

Supports routing function and security policy implementation


Access Layer Switch Features


Distribution Layer Switch Features

Distribution layer switches are typically implemented in pairs to ensure availability. It is also recommended that distribution layer switches support multiple, hot swappable power supplies


Core Layer Switch Features

Because of the high workload carried by core layer switches, they tend to operate hotter than access or distribution layer switches, so they should have more sophisticated cooling options. Many true, core layer-capable switches have the ability to swap cooling fans without having to turn the switch off.


Switch Model Selection


Summary 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 the needs of each hierarchical layer as well as the needs of the business.

lan design lan switching and wireless – chapter 1 vilina hutter, instructor

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