M07 Basic Network Design

• Network Architecture Components Review 1

  •The local area network (LAN) enables users to access the network• Some vendors call this component the access layer• The second network architecture component is the building backbone network• It distributes network traffic to and from the LANsSome vendors call the distribution layer

  
• Network Architecture Components Review 2

  •The third network architecture component is the campus backbone• Sometimes called the core layer• Connects all the buildings on one campus• The fourth network architecture component is the data center• Contains the organization’s servers• Is essentially a LAN but is designed and managed very differently

  
• Network Architecture Components Review 3

  •The last three components of the network architecture make up the enterprise edge•The parts that connect the campus to the rest of the world•The wide area network (WAN) is a private network that connects its different campus locations•Usually leased from a common carrier such as AT&T

  
• Network Architecture Components Review 4

  •The Internet access component enables the organization to connect to the Internet• Large organizations use the same technologies to connect to the Internet as they use in the WAN• The e-commerce edge is a special LAN that enables electronic data exchange between the organization and the external entities with which it does business

  
• Traditional Network Design

  •A structured systems analysis and design process• Network analysis phase includes:◦ Meeting with users to determine the needs and applications◦ Estimating data traffic on each part of the network• During the network design phase, the logical and physical networks are designed and circuits and hardware selected.• The implementation phase involves the building and implementing of the network.

  
• Traditional Network Design (cont’d.) (Legacy/Old school)

  •Pros • Useful for static and slowly evolving networks• Less risk of overdesign• Cons• Costly• Time consuming. • Approach probably not adequate today due to:• Rapid changes in technology• Escalating network traffic demands• Decrease in hardware costs and increase in staff costs
• The Building Block Network Design Process

  •Goal – simplicity of design• Starts with a few standard components and uses them over and over again, even if they provide more capacity than is needed• The process:◦ Can easily be changed as needs and technologies change◦ Cyclical
• Building Block Network Design (cont’d.)

  •Iterative design phases◦ Needs analysis◦ Understand current and future network needs (users and applications)◦ Technology design◦ Examine available technologies to determine which meet or exceed needs◦ If needs are difficult to estimate, build higher capacity◦ Cost assessment◦ Evaluate financial costs of technology

  
• The Three Steps in the Building Block Network Design

  The Three Steps in the Building Block Network Design
. 1. Needs analysis: during which the designer attempts to understand the fundamental current and future network needs of the users 2. Technology design: examines the available technologies and assesses which options meet users’ needs 3. Cost assessment: the relative costs of the technologies are considered

  
• The Cyclical Nature of Network Design

  •The process then cycles back to the needs analysis, which is refined using the technology and cost information to produce a new assessment of users’ needs• This, in turn, triggers changes in the technology design and cost assessment• By cycling through these three processes, the final network design is established

  
• Needs Analysis

  •Why is the network design needed?◦ Performance issues may exist.◦The organization may be standardizing.◦ Hardware may need replacement.• What users and applications must be supported?• Goals differ depending on the network component.◦ LANs and BNs typically are built with organizational ownership and are often built with excess capacity.◦ WANs rely more on leased equipment and circuits are typically designed at or near capacity with organizations leasing additional circuits as required.
• Needs Analysis -- Baselines


  •Create metrics of current operations to compare against design requirements• Baselines may include:◦ Sequence of operations◦ Processing times ◦ Work volumes◦ Existing costs of current network◦ Existing user/management needs
• Needs Analysis – The Logical Design


  •Break down the network into architectural components◦ The logical design◦ All seven components◦ Often easiest to start with WANs◦ Geographic scope of network• Review the existing and expected applications that will use the network◦ Identify hardware and software requirements for these applications◦ Identify protocols used by applications
• Needs Analysis – Requirements


  •Identify and assess network users◦ Some users may have very different needs◦ How many of each type of user?• Categorize network requirements◦ Mandatory◦ Desirable◦ Wish-list
• Needs Analysis Deliverable – The Logical Network Design


  •The key deliverable for the needs assessments stage is a set of logical network diagrams, showing the applications, circuits, clients, and servers

  
• Technology Design


  •Development of a physical network design (or set of possible designs)• The design includes clients, servers, circuits, and networking devices (routers, gateways, access points, switches, etc.).• What new hardware needs to be purchased?• Can the existing equipment be upgraded?
• Technology Design – Clients and Servers


  •Specify the devices needed in standard units• “Typical” users are allocated base-level clients• “Advanced” users are allocated advanced clients• Servers are similarly allocated based on application needs• Definitions of “typical” and “advanced” change as hardware costs fall and capabilities increase
• Technology Design – Designing Circuits


  •Capacity planning is the estimation of circuit size and type required for each network architecture component.•Circuit loading is an assessment of the amount of data transferred across a circuit (currently or in the future).
• Technology Design – Estimating 


  •Estimating circuit traffic◦ Average traffic vs. peak traffic◦ Designing for peak traffic is ideal• Estimating message volume◦ Count messages sent in the current network and multiply by the expected growth rate• Precision may not be the major concern.◦ Obtaining precise estimates is difficult and expensive.◦ Standard circuit speeds “stair step”. Traffic typically increases more than anticipated.
• Technology Design – Capacity 


  •Should network designers plan for excess capacity?◦ Upgrading costs 50-80% more than designing higher capacity time◦ Very few complaints about overcapacity• Most organizations intentionally overbuild• The turnpike effect occurs when traffic increases faster than forecasts◦ When networks are efficient and fast, users will use them more frequently◦ Most networks designed with excess capacity end up using overcapacity within three years
• Network Design Tools

  •Modeling◦ Users create diagrams of existing or proposed networks• Discovery◦ Some tools can automatically create network diagrams by examining existing network • Simulation◦ A mathematical technique used to model the behavior of a network under real conditions◦ Simulates applications and users generating traffic and responding to messages May highlight potential problems
• Technology Design Deliverable – The Physical Network Design 


  •The key deliverable is a set of one or more physical network designs• Most designers like to prepare several physical designs so they can trade-off technical benefits and costs

  
• Cost Assessment


  •Financial analysis of the various technology design alternatives• Complex process that requires analysis of many factors◦ Circuit costs (cabling and installation)◦ Internet working devices (switches and routers)◦ Hardware costs (clients, servers, power supplies)◦ Software costs (operating systems, application software and middleware)◦ Network management and maintenance costs ◦ Operations costs to run the network◦ WAN and Internet circuits
• Cost Assessment – RFPs 


  •Request for proposal (RFP)◦ Detailed specification of equipment, software, and services desired from vendors◦ Typically used in large network purchases◦ May include timeline and evaluation criteria for proposals• Allows the organization to evaluate offerings from different vendors• Multi-vendor proposals◦ May provide better performance◦May be less expensive◦ May be more difficult to manage
• Sample RFP Components

  
• Cost Assessment – How to Sell It to Management


  •Acknowledge that networks, data centers, and most information technology areviewed as cost centers.•Make a business case by focusing on organizational needs and strategy.•The importance of network speed, reliability, and security are easy for non-technical users to understand.•Avoid focusing on technical details and jargon.
• Deliverables – Cost Assessment


  •Finalized RFP that is sent to vendors• Revised technology design with detailed specifications, including exact products and costs• Business case for the network design◦ How might cost constraints affect physical design choices? ◦ When should these constraints be discussed during the design process?
• Implications for Cyber Security

  •Each component in a network design can be managed separately in terms of security ◦ Tightest security are usually the core layer and the data center ◦ Servers in the data center are usually heavily protected ◦ The Internet Access component has to be managed carefully—and constantly◦ The e-commerce edge often has the lightest security but needs to be carefully monitored because it is a prime target◦ Each building can be managed separately