Characterizing the Existing Network


Background.  The following short list gives a broad overview of the things you need to do to characterize an existing network
  • Identify any bottlenecks
  • Determine whether and how anticipated growth will impact the network
  • Recognize legacy systems that must be incorporated
  • Recognize business constraints and inputs on the new design

Business constraints are business related issues (not technical issues) that may impact and/or place limitations on your design.  For example, at a very general level, the firm may have a highly centralized control view of how their organization should be run or they may have a business that requires unusual backup and reliability considerations.

Data Gathering.  Now we will broadly discuss the sorts of data that needs to be collected.  The first collection of data can be characterized as administrative data.  The following table summarizes and describes the sorts of data this encompasses.


Administrative Data

Corporate Business Goals
  • What are the firm's major business goals for the year and the next five years?
  • Investigate their industry and competitors and what needs to be done with the infrastructure to improve competitiveness.
  • Determine overall financial constraints.
Corporate Structure
  • Have the client help you determine corporate structure.
  • What is the departmental structure?
  • How does this structure impact the network structure?
Geographical Structure
  • Determine locations of major user communities.
  • Recognize layouts of actual facilities.
Current and Future Staffing
  • What is the status of the internetworking expertise already at the firm?
  • Does the company plan to expand/contract staff in order to adjust to new design?
  • Who will be your IT or business representative(s) to assist you in your design.
  • Will the design cause changes in job functions and how will this impact implementation and acceptance.
Policies and Politics
  • What designs have been tried before?
  • What was the success/failure of these designs?
  • Who created and/or owned previous designs?
  • Are their people on the project that don't want to implement changes?


You also need to gather a seemingly never ending amount of technical data.  The following table gives a succinct summary of typical requirements.


Technical Data

Identify Applications
  • Identify current applications
  • Identify plans for future applications
    • What protocols are required
    • Influence on traffic levels
    • Influence on networking devices
Analyzing Information Flows
  • Where does information flow within the firm?
  • How will information flow for future applications?
    • Type of data
    • Amount of traffic
    • Traffic concentrations
  • How does manual data flow that might be carried by the new network design?
  • Document any anticipated significant changes
Shared Data
  • Where does shared data reside?
    • file servers
    • database servers
  • Do they need to develop particular shared data sources?
  • What users and applications use the shared data?
Network Traffic and Access
  • What traffic flows from which LAN segment to which others
  • What data or traffic important to the business comes from/goes to outside the company
Network Performance Characteristics
  • What are the performance characteristics?
    • Document all difficulties
  • If possible, do a baseline analysis of the existing network
    • If too large then focus on backbones and critical network segments


The next web page will go into more detail about the specifics of the data and the process for collecting it.