1. LAN/WAN Optimization Techniques Harrell J. Van Norman Presented by Lin Shu-Ping

2. Outline Design Tools as Part of the Total Network Engineering Process Network Design Tool Utilization Network Design Tool

3. Design Tools as Part of the Total Network Engineering Process NDTs make up only one step in the total network engineering process.

4. Prior To Use Requires collecting current traffic measures and forecasting for network growth. The precision of any NDT is related to correctness of the design criteria upon which analysis is based. Typical questions asked by NDT Message profiles of each applications Message profiles of each applications Protocol characteristics Protocol characteristics Environment of transmission network Environment of transmission network Traffic Profiles Traffic Profiles

5. Prior To Use When using NDT accurately, defining design criteria is crucial. Integration of NDT into a network management system is a more credible approach. The optimization of the network will be proportional to precision of the design criteria.

6. During Use The network engineer postulates with “what if” scenario by changing node location. Using NDT involves iterative refinement generally produced during evaluating of various network alternatives.

7. Subsequent To Use Additional phases of network engineering include reconfiguration, equipment acquisition, verification, installation and administrator. Iterative improvements are made by evaluating network costs and performance against the operational criteria.

8. Outline Design Tools as Part of the Total Network Engineering Process Network Design Tool Utilization Network Design Tool

9. Network Design Tool Utilization NDT utilization step includes Selecting a design technique Selecting a design technique Acquiring a tool Acquiring a tool Developing a model Developing a model Analyzing the model Analyzing the model

10. Design Technique Selection Two basic design techniques Discrete event simulation Discrete event simulation Analytic heuristic modeling Analytic heuristic modeling If network engineer is interested only in network performance, using simulation. If the network engineer needs circuit cost and network performance combined, analytic heuristic is the preferred approach.

11. Tool Acquisition This step involves acquiring an NDT from among many suppliers of NDTs. “You get what you pay for” is generally true within the NDT market.

12. Model Development Generate a logical model of the network that requires analysis and design. The model is based on a set of locations for data input and termination.

13. Model Analysis Test model with various inputs and observe the resulting cost and performance outputs. Developing allowable ranges for acceptable input parameters assists in insuring the model accuracy.

14. Outline Design Tools as Part of the Total Network Engineering Process Network Design Tool Utilization Network Design Tool

15. Technical approach Analytic heuristic Analytic heuristic Discrete event simulation Discrete event simulation Design algorithms Multipoint line connection Multipoint line connection Backbone design Backbone design Topological structures Tree, Ring, Star, String Tree, Ring, Star, String

16. Technical approach There is nearly overwhelming number of possibilities in configuring a network. Insuperable amounts of computing times would be required for applying algorithms to find optimum constrained design. It is appropriate to use heuristic techniques or simulation-based approaches.

17. Heuristics Heuristics are chosen approximations of actual analytic calculations. Using heuristics is necessary whenever computational time and resources would be excessive to provide actual analytic solution.

18. Heuristics (cont.) No NDT can produce totally optimal design due to inaccurate input values. Evidence indicate that good heuristic algorithms can produce network designs that are within 5 percent of optimal solution.

19. Simulation Network simulation predicts performance characteristics. Whenever extremely precise performance evaluation is necessary, simulation is the preferred technique. The results of simulation predict how networks will perform under various loads.

20. Simulation (cont.) Simulations overcome deficiencies inherent in entirely analytic heuristic algorithm for predicting network reliability.

21. Design Algorithms When developing a network design, there are two basic classes of problems Developing acceptable line loading Developing acceptable line loading Optimal line configurations Optimal line configurations All NDTs address line loading constraints, with simulation models providing precise estimation of end-user response time.

22. Design Algorithms (cont.) Regardless of the method from determining acceptable lineloading constraints,designing a network configuration is necessary.

23. Multipoint Line Connection Multipoint lines reduce total circuit mileage costs by enabling multiple users to share circuits. To minimize the cost of that line involves computing the minimal spanning tree. Minimal spanning tree calculations are exact optimal algorithms with link-loading constraints or unconstrained limits.

24. Esau-Williams Algorithm Start with the simplest type of network One with a central controller hub connected to each remote terminal by a separate circuit. One with a central controller hub connected to each remote terminal by a separate circuit. Such network can be accepted when terminal are very heavily loaded or equipment precludes line sharing. Such network can be accepted when terminal are very heavily loaded or equipment precludes line sharing. Set aside each fully loaded line, because it obviously cannot be multipointed.

25. Esau-Williams Algorithm (cont.) In each iteration the node with the greatest differential distance from the hub to the nearest neighboring node is located. It reconnects that node to its nearest neighboring node, thereby providing the greatest cost benefits. In this manner, each iteration removes one expensive link and replaces it with the best alternative link.

26. Esau-Williams Algorithm (cont.)

27. Prim Algorithm Prim’s algorithm functions in the reverse of the Esau-Williams algorithm. It selects the nodes closest to the center then connects in those node that are closest to those already in the network. Minimizing the maximum costs by means of the Esau-Williams algorithm yields improved designs over Prim’s algorithm.

28. Prim Algorithm (cont.)

29. Concentrator Placement Given potential concentrator sites,determine the number and locations of concentrators and assign each terminal to concentrator. Add and Drop Algorithms

30. Step1:Clustering nearby nodes into COM nodes, thereby reducing the problem in size and converting to a point to point formulation. Step2:Using the add algorithm to partition the COM nodes with other COM nodes that give the greatest cost benefits by being connected to generic access facilities instead of resource connection point.

31. Add and Drop Algorithms (cont.) Step3:Local optimization by selecting one specific node site for the generic access facility. Step4:Line layout by replacing all the COM nodes with the actual nodes.

32. Backbone Design In hierarchical network involves two design problems. Design of the regional subnetworks Design of the regional subnetworks Backbone portion of the network Backbone portion of the network The cut saturation algorithm is a common example of backbone design algorithm. It iteratively finds the least-cost backbone network for a specified throughput, subject to time delay and reliability constraints.

33. Cut Saturation Algorithm Cut saturation algorithm consists of five basic steps in any one iteration Routing Routing Saturated cutset determination Saturated cutset determination Add-only step Add-only step Delete-only operation Delete-only operation Perturbation setp Perturbation setp

34. Cut Saturation Algorithm (cont.) Routing setting up at each node along the path a routing table directing messages with a particular destination address to appropriate outgoing link. setting up at each node along the path a routing table directing messages with a particular destination address to appropriate outgoing link. Saturated cutset determination Links are ordered according to their utilization Links are ordered according to their utilization Links are then removed, one at a time, in order of utilization Links are then removed, one at a time, in order of utilization The minimal set that disconnects the network is called a saturated cutset The minimal set that disconnects the network is called a saturated cutset

35. Cut Saturation Algorithm (cont.) Add-only step Adding the least-cost links to the network that will direct traffic from the saturated cutset. Adding the least-cost links to the network that will direct traffic from the saturated cutset. Nodes that are at least two links removed from the cutset are chosen as candidates for possible linkages. Nodes that are at least two links removed from the cutset are chosen as candidates for possible linkages. Delete-only step Links from a highly connected topology are eliminated. Links from a highly connected topology are eliminated. One link at a time is removed at each iteration by finding maximum cost link. One link at a time is removed at each iteration by finding maximum cost link.

36. Cut Saturation Algorithm (cont.) Perturbation step Once a desired throughput range has been attained, network links are rearranged by add- only and delete-only operations to reduce cost. Once a desired throughput range has been attained, network links are rearranged by add- only and delete-only operations to reduce cost. Add-only and delete-only operations are used sequentially as long as throughput remains within the bounds. Add-only and delete-only operations are used sequentially as long as throughput remains within the bounds.

37. Routing and Service Options Effective design dynamics include Fractional Fractional Hubless Hubless LEC Bridging LEC Bridging Routing Strategies Routing Strategies

38. Routing and Service Options (cont.) Three service options Total service Total service Coordinated service Coordinated service Baseline service Baseline service

39. Routing and Service Options (cont.) Total service AT&T will design, order, and bill the entire circuit. AT&T will design, order, and bill the entire circuit. Require the highest degree of dependence upon AT&T Require the highest degree of dependence upon AT&T Coordinated service Carrier responsibility for ordering and maintaining the circuit as well as a measure of customer control over the network Carrier responsibility for ordering and maintaining the circuit as well as a measure of customer control over the network

40. Routing and Service Options (cont.) Baseline service Taking all responsibilities for their network Taking all responsibilities for their network Sophisticated diagnostic equipment and experienced technicians should be on hand Sophisticated diagnostic equipment and experienced technicians should be on hand

41. Topologies Supported Topology of a network may be organized according to two level Terminal access network (TAN) Terminal access network (TAN) Backbone-mesh network (BMN) Backbone-mesh network (BMN) For BMN, satisfactory design are typically star, ring, and hyper-ring. NDT should support these network topologies.

42. Structures Evaluated Average number of links per node A higher link-per-node ration indicates a more expensive network topology A higher link-per-node ration indicates a more expensive network topology Maximum number of intermediate nodes The accessibility of any node to any other node The accessibility of any node to any other node A large number of intermediate node results in higher delay A large number of intermediate node results in higher delay

43. Structures Evaluated (cont.) Maximum node capacity A measure of node vulnerability, defined as the maximum number of links that connect to a given node. A measure of node vulnerability, defined as the maximum number of links that connect to a given node. Amount of traffic a specific node is required to support. Amount of traffic a specific node is required to support. Number of nonredundant routes A measure of network reliability A measure of network reliability A high number of nonredundant routes points to a network topology with good reliability. A high number of nonredundant routes points to a network topology with good reliability.

44. Structures Evaluated (cont.) Total interconnect have a high cost and degree of reliability Tree, star, and string have a low cost and degree of reliability Ring and hyper-ring have relatively low cost combined with high degree of reliability.

45. Tariff Tariff are descriptions of telecom services and prices of those services. Accurate and completer tariff data is essential for bill verification. Telecom companies provide three basic types of transmission services: private line, switched, and packet services.

46. Tariff (cont.) Three methods of obtaining tariff data Getting data directly from tariff database supplier requires the least cost by the NDT provider Getting data directly from tariff database supplier requires the least cost by the NDT provider Obtaining from tariff data supplier and then incorporated into internal database structures requires significantly greater effort. Obtaining from tariff data supplier and then incorporated into internal database structures requires significantly greater effort. Obtaining tariff data directly from the FCC or by subscribing to the filing bodies themselves demands the greatest degree of effort and skill by NDT provider. Obtaining tariff data directly from the FCC or by subscribing to the filing bodies themselves demands the greatest degree of effort and skill by NDT provider.