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WAN design

WAN design. ผศ. ดร. อนันต์ ผลเพิ่ม Asst.Prof.Anan Phonphoem, Ph.D. anan@cpe.ku.ac.th http://www.cpe.ku.ac.th/~anan Computer Engineering Department Kasetsart University, Bangkok, Thailand. Types of WAN Service. WAN Technology. WAN requirements. Optimise WAN bandwidth Minimise cost

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WAN design

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  1. WAN design ผศ.ดร. อนันต์ ผลเพิ่ม Asst.Prof.Anan Phonphoem, Ph.D. anan@cpe.ku.ac.th http://www.cpe.ku.ac.th/~anan Computer Engineering Department Kasetsart University, Bangkok, Thailand

  2. Types of WAN Service

  3. WAN Technology

  4. WAN requirements • Optimise WAN bandwidth • Minimise cost • Maximise the effective service to end users

  5. LAN/WAN integration • LAN/WAN, previously logically separated, must now be fully integrated for seamless performance • Both now must be able to handle... • Voice traffic (VoIP) • Bandwidth intensive multimedia applications • Video conferencing • On-line training • Increased business critical data access

  6. Goals • Availability • Total cost of ownership

  7. Concerns • Environmental variables • Performance constraints • Networking variables

  8. WAN Design strategies • Mesh • Network is flat • All routers perform same function • Expansion proceeds haphazardly • Hierarchical • Organized in layers • Easier to implement/Troubleshooting • Scalability • Predictability

  9. Important of Layers • Designing networks using the OSI model • designed in layers • simplify the tasks required for internetworking • Design elements can be replicated as grows • Therefore, networks should be designed using a hierarchical model. • Unfortunately, most networks are thrown together into a mesh (“a mess!”) with little or no vision of future needs.

  10. Benefit of Hierarchical Design • Scalability • allows for future growth without sacrificing control or functionality • Ease of Implementation • logically constructed layers specify the functions of each layer • Ease of troubleshooting • well-defined functions at each layer aid in the isolation of problems

  11. Benefit of Hierarchical Design • Predictability • behavior of functional layers can be estimated and planned for • Protocol support • allows easier implementation of future technologies because the network has been logically constructed • Manageability • All the above aids net. admin. in overall management of the network

  12. The Hierarchical Design ModelThe Three-Layer

  13. The Hierarchical Design ModelThe Three-Layer • Core layer--provides transport between remote sites • Distribution layer--provides policy-based connectivity • Access layer--provides workgroup/user access to network

  14. Core Layer • Fast WAN connections between remote sites • Core links are normally point-to-point with no host devices • Core services include: • T1/T3 • Frame Relay • ATM • SMDS

  15. Distribution Layer • Provides WAN services to multiple LANs • Usually the campus backbone • Uses Fast Ethernet (or Gigabit Ethernet) • Used on large sites to interconnect blgs.

  16. Access Layer • Usually a LAN or group of LANs • Gives access to specific users and workgroups • This layer is where all hosts (including servers) are attached to the network

  17. WAN Layer Functions • Core Layer Functions • Distribution Layer Functions • Access Layer Functions

  18. Core Layer Functions • Optimize Transport Between Remote Sites • Redundant paths to guard against circuit outages • Provide load sharing and rapid convergence when link states change • Efficient use of bandwidth by... • Implementing scalable routing protocols and • Blocking local traffic access to the core

  19. Distribution Layer Functions • Policy-Based Connectivity • Boundary definition & packet manipulation • Control access to services of the core layer and other distribution layer routers • VLAN routing • Address aggregation (i.e., subnets) & route optimization • ACLs and other security measures

  20. Access LayerFunctions • Workgroup & User Access to the Network • Isolation of Broadcast Traffic • Shared and Switched Bandwidth • MAC-layer filtering • Microsegmentation

  21. Other Hierarchical Options • One-Layer Design • Two-Layer Design

  22. One-Layer Design • Only a few remote sites need to be connected • Servers are placed in farms or in each workgroup to reduce traffic on the backbone

  23. Two-Layer Design • WAN link is used to interconnect separate sites • Link does not have to be dedicated. An alternative would be ISDN.

  24. Hierarchical Design Advantages • Controlling data traffic patterns through source/destination network layer addressing • A packet only needs to travel up the hierarchy as far as it needs to find the destination. • With good design, most traffic would be contained in the access layer with users accessing their workgroup servers

  25. Hierarchical Design Advantages • Server Placement • Enterprise Servers needed by all workgroups should be placed in the Distribution Layer (e.g. email, DNS, etc.) • Workgroup Servers needed by a unique set of users should be placed in the Access Layer, preferably in the same broadcast domain as the users

  26. References • Cisco course material • Allan Johnson’s material (from cisco) • user:dam0c00k’s material (from cisco)

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