Lectures Top-Down Network Design - Chapter 3: Characterizing the Existing Internetwork

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1. Top-Down Network Design, Ch. 3: Characterizing the Existing Internetwork Top-Down Network Design Chapter Three Characterizing the Existing Internetwork Copyright 2010 Cisco Press & Priscilla Oppenheimer What’s the Starting Point? • According to Abraham Lincoln: – “If we could first know where we are and whither we are tending, we could better judge what to do and how to do it.” Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 1
2. Top-Down Network Design, Ch. 3: Characterizing the Existing Internetwork Where Are We? • Characterize the existing internetwork in terms of: – Its infrastructure • Logical structure (modularity, hierarchy, topology) • Physical structure – Addressing and naming – Wiring and media – Architectural and environmental constraints – Health Get a Network Map Medford Roseburg Fast Ethernet Fast Ethernet 50 users 30 users Frame Relay Frame Relay CIR = 56 Kbps CIR = 56 Kbps DLCI = 5 DLCI = 4 Gigabit Grants Pass Ethernet HQ Gigabit Grants Pass Ethernet HQ Fast Ethernet 75 users FEP (Front End Processor) IBM Mainframe T1 Web/FTP server Eugene Ethernet T1 Internet 20 users Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 2
3. Top-Down Network Design, Ch. 3: Characterizing the Existing Internetwork Characterize Addressing and Naming • IP addressing for major devices, client netktworks, server net tkworks, and so on • Any addressing oddities, such as discontiguous subnets? • Any strategies for addressing and naming? – For example, sites may be named using airport codes • San Francisco = SFO, Oakland = OAK Discontiguous Subnets Area 0 Network 192.168.49.0 Router A Router B Area 1 Area 2 Subnets 10.108.16.0 - Subnets 10.108.32.0 - 10.108.31.0 10.108.47.0 Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 3
4. Top-Down Network Design, Ch. 3: Characterizing the Existing Internetwork Characterize the Wiring and Media • Single-mode fiber • Multi-mode fiber • Shielded twisted pair (STP) copper • Unshielded-twisted-pair (UTP) copper • Coaxial cable • Microwave • Laser • Radio • Infra-red Campus Network Wiring Horizontal Work-Area Wiring Wiring Wallplate TlTelecommuni cati ons Wiring Closet Vertical Wiring (Building Backbone) Main Cross-Connect Room Intermediate Cross-Connect Room (or Main Distribution Frame) (or Intermediate Distribution Frame) Campus Building A - HeadquartersBackbone Building B Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 4
5. Top-Down Network Design, Ch. 3: Characterizing the Existing Internetwork Architectural Constraints • Make sure the following are sufficient – Air conditioning – Heating – Ventilation – Power – Protection from electromagnetic interference – Doors that can lock Architectural Constraints • Make sure there’s space for: – Cabling conduits – Patch panels – Equipment racks – Work areas for technicians installing and troubleshootinggqp equipment Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 5
6. Top-Down Network Design, Ch. 3: Characterizing the Existing Internetwork Issues for Wireless Installations • Reflection • Absorption •Refraction • Diffraction Check the Health of the Existing Internetwork • Performance • Availability • Bandwidth utilization • Accuracy • Efficiency • Response time • Status of major routers, switches, and firewalls Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 6
7. Top-Down Network Design, Ch. 3: Characterizing the Existing Internetwork Characterize Availability DtDate an dDd Dura tion Cause of Last Fix for Last MTBF MTTR of Last Major Major Major Downtime Downtime Downtime Enterprise Segment 1 Segment 2 Segment n Network Utilization in Minute Intervals Network Utilization 16:40:00 16:43:00 16:46:00 16:49:00 16:52:00 16:55:00 Series1 Time 16:58:00 17:01:00 17:04:00 17:07:00 17:10:00 01234567 Utilization Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 7
8. Top-Down Network Design, Ch. 3: Characterizing the Existing Internetwork Network Utilization in Hour Intervals Network Utilization 13:00:00 14:00:00 15:00:00 Series1 Time 16:00:00 17:00:00 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Utilization Bandwidth Utilization by Protocol Relative Absolute Broadcast Multicast Network Network Rate Rate Utilization Utilization Protocol 1 Protocol 2 Protocol 3 Protocol n Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 8
9. Top-Down Network Design, Ch. 3: Characterizing the Existing Internetwork Characterize Packet Sizes Characterize Response Time Node A Node B Node C Node D X Node A X Node B Node C X Node D X Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 9
10. Top-Down Network Design, Ch. 3: Characterizing the Existing Internetwork Check the Status of Major Routers, Switches, and Firewalls • show buffers • show environment • show interfaces • show memory • show processes • show running-config • show version Tools • Protocol analyzers • Multi Router Traffic Grapher (MRTG) • Remote monitoring (RMON) probes • Cisco Discovery Protocol (CDP) • Cisco IOS NetFlow technology • CiscoWorks Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 10
11. Top-Down Network Design, Ch. 3: Characterizing the Existing Internetwork Summary • Characterize the existing internetwork before designing enhancements • Helps you verify that a customer’s design goals are realistic • Helps you locate where new equipment will go • Helps you cover yourself if the new network has problems due to unresolved problems in the old network Review Questions • What factors will help you decide if the existing internet wo rk is in good en ough sh ape to suppor t new enhancements? • When considering protocol behavior, what is the difference between relative network utilization and absolute network utilization? • Why should you characterize the logical structure of an internetwork and not just the physical structure? • What architectural and environmental factors should you consider for a new wireless installation? Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 11