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LAN Design

LAN Design. LAN Switching and Wireless – Chapter 1 Vilina Hutter, Instructor. Hierarchical Network Design. 3 layered model Access, Distribution, & Core Layers Each layer has specific functions Facilitates modularity Modularity facilitates scalability and enhanced performance.

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LAN Design

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  1. LAN Design LAN Switching and Wireless– Chapter 1 Vilina Hutter, Instructor

  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

  3. Access Layer • End user devices • PCs, phones, printers • Access to network for users • Can include any networking device

  4. Distribution Layer • Controls the flow of network traffic • Policy implementation • Broadcast containment • VLAN connectivity • Switches and Routers

  5. Core Layer • High-speed backbone • Routers or switches • Redundant links

  6. Physical Layout of a Hierarchical Design • Less easy to see the hierarchical design layers in the physical layout!

  7. Benefits of a Hierarchical Design

  8. Four Design Principles • Network Diameter • Bandwidth Aggregation • Redundant Links • Start at the Access Layer!

  9. Network Diameter • How many devices a packet must cross to reach its destination • Lower is better!

  10. Bandwidth Aggregation • Combining several parallel links between two switches to form one logical link

  11. Redundant Links • Used between devices at the core and distribution layer to ensure network availability

  12. 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

  13. 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

  14. 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

  15. Smaller diameter for HR Dept. 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

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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

  21. 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

  22. 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

  23. 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

  24. 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

  25. Switch Performance—Link Aggregation • All switches should support link aggregation to avoid uplink bottlenecks

  26. 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

  27. Switch Performance—Layer 3 Functionality • Known as multilayer switching • Supports routing function and security policy implementation

  28. Access Layer Switch Features

  29. 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

  30. 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.

  31. Switch Model Selection

  32. 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.

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