Network Communications (CPT Demos) 38th Edition
Network communications provide the required connectivity for distributed GIS operations. Network capacity, in many cases, can limit the software technology solutions that perform well within your organization. System architecture design must identify and address network communication constraints and provide the right technical solution for a successful GIS implementation.
This section will use the CPT to demonstrate network latency, Network configuration, and provide an overview of the network performance parameters identified on the CPT Workflow tab.
- Network latency
- Network latency performance delays on the Calculator tab.
- Network latency performance delays on the Design tab.
- Network suitability analysis
- Configuring network architecture on the Calculator tab.
- Configuring network architecture on the Design tab.
- Network performance factors
- Network performance factors on the Workflow tab.
- 1 CPT network latency performance delays
- 2 CPT Calculator network suitability analysis
- 3 CPT Design user requirements workflow loads analysis
- 4 CPT Design network suitability analysis
- 5 Network performance parameter look-up list
- 6 Network contribution to Web performance
- 7 CPT Capacity Planning videos
CPT network latency performance delays
Network chatter is included in each workflow on the CPT Workflow tab. Network latency is defined on the remote site network segments for each user workflow. The CPT will multiply network latency by workflow chatter to account for latency delays in calculating display response time.
CPT Calculator tab
Figure A-6.2 shows how network latency is addressed in the CPT Calculator tab.
CPT Calculator rows 12, 13, and 14 address network communication traffic.
- Row 12 is the LAN traffic, while rows 13 and 14 represent remote site communications.
- Network bandwidth connections are identified in column G (cells G12:G14).
- Network display response time (cells K12:K14), shown in yellow if network contention.
- Remote site productivity adjustments due to network contention (cells T13:T14)
- >LAN display performance is limited by client connection (client NIC bandwidth 100 Mbps).
- >Remote bandwidth analysis assumes the data center is not the bottleneck (set remote site bandwidth).
Best practice: The CPT Design tab must be used to complete a proper Data Center bandwidth suitability analysis.
- Total number of remote users sharing the remote site connections is identified in column D.
- Latency is identified for remote connections in column E.
- Communication chatter is identified in column I (default of 10 for web and WTS workflows; 200 for medium workstation workflows, adjusted by display complexity).
- Latency delay is shown as pink in the Workflow Performance Summary.
CPT Design tab
Figure A-6.3 shows how network latency is addressed in the CPT Design tab.
Network analysis is completed in the CPT Design Requirements Analysis section.
- Gray rows represent the data center LAN, WAN, and Internet connections.
- Green rows represent the remote site network connections.
- Network bandwidth for each network row is set in column H.
- The Network latency setting (milliseconds) for the remote sites is set in column S (workflow network chatter is also identified in column S).
- Latency delay is shown as pink in the Workflow Performance Summary.
- RED productivity cells in column E identify performance contention.
- > RESET ADJUST function (Cell T2) adjusts workflow productivity to resolve performance contention.
CPT Calculator network suitability analysis
Figure A-6.4 shows how the CPT Calculator tab can be used to complete a workflow network suitability analysis.
- Data center and remote site service connections identify bandwidth constraints that must be evaluated during the system design.
- Standard workflow display traffic loads are used to evaluate network suitability across all WAN and Internet site connections.
- The Capacity Planning Calculator can be used to estimate workflow client display traffic (megabits per display).
- Client traffic (Mbpd) is included with the workflow service times on the CPT Workflow tab and used by the Design tab to complete the workflow network suitability analysis.
Best practice: CPT Calculator is a useful tool for evaluating single workflow network traffic contributions and the impact of available network capacity on remote site user productivity.
Warning:The CPT Calculator is limited to addressing a single workflow environment. Additional network traffic from other business operations will need to be included to complete the analysis.
CPT Design user requirements workflow loads analysis
Figure A-6.5 shows an overview of how the CPT Design tab can be configured to complete an enterprise network performance analysis.
The CPT Design shows the user workflow location relative to the data center and remote site network infrastructure.
- Data center networks are represented by gray rows and remote sites by green rows.
- Client workflows are located within the network segments where they work.
- The available bandwidth for each network segment is identified in column H.
- Network traffic must flow through both the remote site and data center connections to reach the server environment.
Best practice: GIS user workflow loads analysis should be completed before establishing the final system architecture design.
The CPT Design requirements analysis module layout makes it possible to represent workflow display traffic flow across the appropriate service provider network connections.
- Configuration of the data center and remote site network segments.
- Entering the existing network bandwidth.
- Configuring the user workflows based on user location.
- Entering the peak concurrent users and service throughput values from the user workflow loads analysis.
- Completing the network traffic range updates.
Best practice: System design configuration begins with results from a user workflow loads analysis.
Figure A-6.6 shows a sample of the results of a workflow loads analysis (Business Requirements Summary):
- User requirements include three workflows (DeskEdit, DeskView, and WebMap)
- Users are located at different network locations (local users, remote site 1, remote site 2, and public internet)
- Peak workflow usage is identified for each network location
- Local Area Network (peak users for each workflow)
- Remote site 1 (peak users for each workflow)
- Remote site 2 (peak users for each workflow)
- Public Internet connection (peak transactions per hour for WebMap services)
Figure A-6.7 shows how to configure these same user requirements in the CPT Design
- Select and copy the green row at the bottom of the Requirements Analysis module for use as a remote site template.
- Select below where you want to insert a new remote site and insert copied cells to add a remote site row within the WAN workflows.
- Select and copy any existing workflow row and then insert copied cells to add a new workflow within a site network.
- Select and delete any existing workflow you want to remote from a site.
- Select the existing network bandwidth for each of the new site locations in column H.
- Network client and traffic summation ranges in columns E and F are automatically updated to complete the remote site configurations and match the user workflow requirements.
Best practice: Configuring the user requirements analysis module establishes a foundation for completing the CPT Design tab network suitability analysis.
CPT Design network suitability analysis
Initial user requirements loads analysis
Figure A-6.8 shows an initial CPT Design tab requirements analysis configuration. The CPT Design tab will identify network contention (bottlenecks) as you complete configuration and inputs to the user requirements analysis.
- Negative think time is a clear sign of an invalid workflow.
- Sufficient bandwidth is not available to handle peak traffic flow.
- Existing bandwidth capacity will restrict user productivity.
Best practice: Increase network bandwidth to roughly twice expected peak traffic flows.
RESET ADJUST function
Figure A-6.9 shows the CPT Design once productivity was adjusted using the RESET ADJUST function. You can use the RESET ADJUST function to identify expected user productivity with existing bandwidth.
Best practice: Start with a Blink setting of 10 in cell U2.
- Select ADJUST in cell T2.
- Excel will complete up to 500 circular iterations to reach a valid workflow solution and then stop.
- A valid solution exists if the following are true if:
- Workflow minimum think time (Column T) is equal to or less than calculated think time (Column U).
- Peak users in column C show green once a valid workflow is found (applies to all reduced productivity workflows).
- Hardware tier platform utilization do not exceed 100 percent.
- If there is no valid solution, try selecting the ADJUST function again.
- If calculated think time blinks between positive and negative values, reduce the BLINK setting by a factor of 10 and repeat steps.
Note: ADJUST function uses excel iterations to identify productivity for batch processing workflows. As computed think time approaches zero, queue time increases to infinity (discontinuity) and processing loads exceed 100 percent capacity (not a valid solution). The BLINK setting determines the size of the productivity adjustments between each excel iteration. If the BLINK is too small, it can take thousands of iterations to converge on the correct productivity solution. If the BLINK setting is too large, the calculation will step across the discontinuity and the calculation must cycle below 100 percent capacity and try again. During high capacity loads, the BLINK setting should be reduced until the calculations can converge on the correct solution. Once the valid solution is reached, the throughput input cells will turn green.
The RESET ADJUST function resolves network bottlenecks.
- Valid reduced productivity workflows are identified with green blocks in column C.
- Minimum and calculated think time are equal for reduced productivity workflows.
- Reduced productivity is shown in column E.
- Reduced network traffic is shown in columns F:G.
Excel circular reference warning
Under the Excel Options > Formulas section, make sure that the 'Enable iterative calculation' option is selected.
- Maximum iterations should be set at a minimum of 500.
- Minimum change should be set at 0.001.
Warning: CPT will show a Circular Reference Warning if the enable iterative calculation option is not selected. You will need to reset the enable iterative calculation settings shown above for the CPT to work properly.
Workflow performance summary
Figure A-6.11 shows the Workflow Performance Summary following the productivity adjustment. Once you have resolved all workflows to a valid workflow solution, you can review the workflow performance summary to evaluate workflow response times for each user site location.
The Workflow Performance Summary will identify queue times for the reduced productivity workflows.
Validated design solution
Figure A-6.12 shows the upgraded CPT Design solution. Once you complete your network suitability analysis, you should work with the network administrator to identify appropriate network bandwidth upgrades.
Best practice: Network bandwidth should be roughly twice the expected peak traffic loads to avoid performance bottlenecks.
Warning: Network traffic utilization over 60 percent could contribute to network contention with low bandwidth connections.
Note: Higher network utilization levels are acceptable with higher capacity connections. Network contention (queue time) is less sensitivity with high bandwidth capacity (bandwidth connections over 45 Mbps). Final bandwidth recommendations should consider cost and performance tradeoffs and traffic variability during peak loads.
Once you agree on bandwidth upgrades, you can enter them in the CPT Design to complete your analysis.
Network performance parameter look-up list
Figure A-6.13 shows the key network traffic parameters identified on the CPT Workflow tab. Workflow display chatter, client display traffic, and database traffic columns are established when creating a user workflow and are available in the CPT Workflow tab.
Key workflow network performance inputs provided on the CPT Workflow tab.
- Client traffic (megabits per display) is provided in column C.
- Workflow chatter used for latency delay calculations is provided in column B.
- Database traffic (megabits per display) is provided in column J.
- Minimum think time (default three seconds) is provided in column L.
- Workflow productivity is provided in column M.
Network contribution to Web performance
Network performance counts. Network transport time is a major contribution to web client display response times.
Best practice: Network performance impacts should be considered carefully during design and deployment of web services.
CPT Capacity Planning videos
Chapter 6 Capacity Planning Video will demonstrate impact of network latency on performance, show how to configure the CPT Calculator and Design tab to complete a network suitability analysis. This is an important demo showing how to configure networks and workflows in the Design requirements analysis to represent an enterprise system environment.
Specific license terms for this content
System Design Strategies 26th edition - An Esri ® Technical Reference Document • 2009 (final PDF release)