Network Planning & Design: An Art or a Science?


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With the rapid growth of IP networks in South-Asia in the past
few years, and the advent of new services and applications -- be they
wireless/wireline broadband Internet access, cable telephony, VoIP, remote
teleconferencing, e-governance, or mobile entertainment -- a key
issue before carriers is how to design and operate their networks as
methodically and as efficiently as possible to maximize both customer
retention and profits.

While several best practices typically emerge from each provider\'s
unique situation and cumulative experience (the "art" of network design), there
are certain operational precepts that systematize and streamline the
complex, multi-dimensional task of designing and managing modern, operational
IP networks (the "science" of network design).

In this talk, we first discuss the overall network design process and the
manner in which control over the network must be exercised at varying
timescales to achieve efficient operation. Next we discuss the
functions that the operational, engineering, and planning teams at a
carrier must typically execute, their inter-relationships, and
the importance/rationale for performing them to optimize network

We then outline some network design best practices that have evolved
over the past decade, drawing upon examples of carriers such as
Sprint, Global Crossing, AT&T, NTT, and Reliance. We conclude with
a look at some automated traffic engineering and planning tools,
and how they enable carriers to rapidly identify potential
performance problems, rigorously experiment with/evaluate design
options, perform thorough scenario and network analysis, and
develop robust designs.

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Network Planning & Design: An Art or a Science?

  1. 1. Network Planning and Design: An Art or a Science? Vishal Sharma, Ph.D. Metanoia, Inc. [email_address] Metanoia, Inc. Critical Systems Thinking™ © Copyright 2007 All Rights Reserved
  2. 2. Agenda <ul><li>Overall network planning process </li></ul><ul><li>Network design -- control at different timescales </li></ul><ul><li>“ Science” of network planning/design </li></ul><ul><ul><li>Architecture and design philosophy </li></ul></ul><ul><ul><li>Network planning functions by organization – ops, eng., & planning </li></ul></ul><ul><li>“ Art” and “science” of network planning/design </li></ul><ul><ul><li>Best practice examples – GBLX, Sprint, Reliance </li></ul></ul><ul><li>Role of automated TE and planning tools </li></ul><ul><li>Conclusions </li></ul>
  3. 3. Overall Network Design Process Metanoia, Inc. Critical Systems Thinking™
  4. 4. A View of the Overall Network Planning/Layout Process We are here Note: In a combined multi-layer network design , this strict division may not hold
  5. 5. Network Design: Exercising Control over Different Timescales
  6. 6. The “Science” of Network Planning Metanoia, Inc. Critical Systems Thinking™
  7. 7. Network Design System: Architecture <ul><li>Centralized or distributed? </li></ul><ul><li>Obtaining network topology & utilization info? </li></ul><ul><li>Inputs </li></ul><ul><ul><li>Their formats? </li></ul></ul><ul><ul><li>Interface with n/w elements? </li></ul></ul><ul><li>Outputs </li></ul><ul><ul><li>Their formats? </li></ul></ul><ul><ul><li>Installing routes/LSPs in n/w? </li></ul></ul><ul><li>Path route computation </li></ul><ul><ul><li>On-line, dynamic? </li></ul></ul><ul><ul><li>Off-line, global? </li></ul></ul><ul><ul><li>Combination of above? </li></ul></ul><ul><li>Route computation trigger </li></ul><ul><ul><li>User? Administrator? </li></ul></ul><ul><ul><li>New request(s)? </li></ul></ul><ul><li>Scalability </li></ul><ul><ul><li># of links & nodes handled? </li></ul></ul><ul><ul><li># of flows, LSPs, circuits? </li></ul></ul><ul><ul><li># of constraints handled? </li></ul></ul>
  8. 8. Network Design System: Philosophy <ul><li>Control-centric </li></ul><ul><ul><li>Long time scales </li></ul></ul><ul><ul><li>Large granularity flows </li></ul></ul><ul><li>Verisimilitude-centric </li></ul><ul><ul><li>Pkt. by pkt. sims. of elements & network </li></ul></ul><ul><ul><li>Traffic trace-based perf. simulations </li></ul></ul><ul><li>Hybrids </li></ul><ul><ul><li>Long time scale analysis for network perf. </li></ul></ul><ul><ul><li>Pkt. level sims. for element & flow performance </li></ul></ul>
  9. 9. Key Carrier Network Design Functions by Organization 1 2 3 4 5 6 7 8 9 10
  10. 10. The “Art” of Network Planning (and some “science”) Metanoia, Inc. Critical Systems Thinking™
  11. 11. Global Crossing IP Backbone Network 100,000 route miles 27 countries 250 major cities 5 continents 200+ POPs Courtesy: Thomas Telkamp, GBLX
  12. 12. Global Crossing: Network Design Philosophy <ul><li>Ensure there are no bottlenecks in normal state </li></ul><ul><li>On handling congestion </li></ul><ul><ul><li>Prevent via MPLS-TE </li></ul></ul><ul><ul><li>Manage via Diffserv </li></ul></ul><ul><li>Over-provisioning </li></ul><ul><ul><li>Well traffic engineered network can handle all traffic </li></ul></ul><ul><ul><li>Can withstand failure of even the most critical link(s) </li></ul></ul><ul><li>Avoid excessive complexity & features </li></ul><ul><ul><li>Makes the network unreliable/unstable </li></ul></ul>
  13. 13. Global Crossing’s Approach: Big Picture
  14. 14. Global Crossing’s LSP Layout and Traffic Routing Methodology
  15. 15. SprintLink TM IP Backbone Network 19+ countries 30+ major intl. cities 5 continents (reach S. America as well) 400+ POPs Courtesy: Jeff Chaltas Sprint Public Relations Represents connectivity only (not to scale) 110,000+ route miles (common with Sprint LD network)
  16. 16. SprintLink TM IP Design Philosophy <ul><li>Large networks exhibit arch., design & eng. (ADE) non-linearities not seen at smaller scales </li></ul><ul><ul><li>Even small things can & do cause huge effects ( amplification ) </li></ul></ul><ul><ul><li>More simultaneous events mean greater likelihood of interaction ( coupling ) </li></ul></ul><ul><li>Simplicity Principle: simple n/wks are easier to operate & scale </li></ul><ul><ul><li>Complexity prohibits efficient scaling, driving up CAPEX and OPEX! </li></ul></ul><ul><li>Confine intelligence at edges </li></ul><ul><li>No state in the network core/backbone </li></ul><ul><li>Fastest forwarding of packets in core </li></ul><ul><ul><li>Ensure packets encounter minimal queueing </li></ul></ul>
  17. 17. SprintLink TM Deployment Strategy
  18. 18. Reliance Communications: India Network 80,000-100,000 route kms 4000 towns, 350, 000 villages 3+ p2p paths on metro rings Ring + mesh design, 130+ rings Source: FLAG Telecom Extranet
  19. 19. Reliance Network Design Philosophy <ul><li>Be integrated telecom provider: e2e ownership of entire architecture </li></ul><ul><ul><li>Access systems, national fiber-optic backbone, international cable systems, Internet gateways, wireless base stations, and aggregation devices </li></ul></ul><ul><li>80,000 km of high-capacity, pan-India fiber-optic digital network </li></ul><ul><li>Common infrastructure for wireline & wireless traffic </li></ul><ul><ul><li>Integrate packetized voice, video, data and circuit-switched voice on same network </li></ul></ul><ul><li>Ring architecture for physical redundancy (2+ disjoint paths) </li></ul><ul><li>SONET/SDH for framing and OAM capability (easier management) </li></ul><ul><li>MPLS LSPs for resilience ( avoid SONET/SDH protection at PHY layer) </li></ul>
  20. 20. A Look at Planning Tools (advancing the “science”) Metanoia, Inc. Critical Systems Thinking™
  21. 21. Canonical Structure of Automated Planning Tools
  22. 22. Modern Planning Tools: Recent Enhancements <ul><li>IGP tuning – Layer 3 traffic engineering </li></ul><ul><li>Incorporation of FRR – bypass, detour </li></ul><ul><li>Routing of VoIP calls – with queueing delay and MOS </li></ul><ul><li>Diff-Serv aware TE – set pool boundaries </li></ul><ul><li>Coupling with physical layer topology </li></ul><ul><li>Multicast support – for multimedia apps. </li></ul><ul><li>Modeling new services – VPLS, PWs, L3 VPNs </li></ul>
  23. 23. OPNET SP Guru: Components & Features <ul><li>Network simulation and analysis </li></ul>
  24. 24. OPNET SP Guru: Internal Operation <ul><li>Operates in 3 flavors </li></ul><ul><ul><li>Fully-detailed, event-driven simulations </li></ul></ul><ul><ul><li>Partially event-driven simulations </li></ul></ul><ul><ul><li>Analytic simulations </li></ul></ul>
  25. 25. OPNET Solutions: Key Characteristics <ul><li>NetDoctor for configuration & network operations analysis </li></ul><ul><li>VNE Server </li></ul><ul><ul><li>Automated I/F to various network data components </li></ul></ul><ul><ul><li>Ability to build a complete network view </li></ul></ul><ul><li>Hybrid simulation techniques </li></ul><ul><ul><li>Provide balance between speed and resolution </li></ul></ul><ul><li>Ability to add SP’s own rules, algorithms, modules </li></ul><ul><li>Facility to map actual IP addressing to internal network model </li></ul>
  26. 26. Cariden MATE: TE Process
  27. 27. Cariden MATE: IGP Traffic Engineering <ul><li>Problems </li></ul><ul><li>Uneven link utilization </li></ul><ul><li>Heuristic/ad-hoc planning </li></ul><ul><li>Coarse capacity upgrade rules (e.g. at 50 or 75%) </li></ul>Above 60% utilization expected in 6 mo! Sample network with projected traffic growth in 6 months Original network state
  28. 28. Cariden MATE: Routing Optimization [Reproduced with permission: Cariden Technologies] <ul><li>Objectives </li></ul><ul><li>Max. headroom on failure </li></ul><ul><li>Max. normal headroom </li></ul><ul><li>Minimize latency </li></ul><ul><li>Constraints </li></ul><ul><li>Fixed intra-site metrics </li></ul><ul><li>Symmetric weights </li></ul><ul><li>Latency bounds </li></ul><ul><li>Results </li></ul><ul><li>Max. link util. 89%  59% </li></ul><ul><li>Max. link util. on failure 110%  92% </li></ul>All links brought to below 60% utilization under normal conditions
  29. 29. Cariden MATE: Resilience Capabilities Before (worst case) After (worst case) >> 95% utilization Max. utilization under 92%
  30. 30. Cariden MATE: Key Characteristics <ul><li>Demand estimation & characterization </li></ul><ul><ul><li>Estimate p2p demands from aggregate node/intf. demands & routing </li></ul></ul><ul><ul><li>Estimate effective b/w per queueing class to meet QoS for demands </li></ul></ul><ul><li>Robust routing changeovers </li></ul><ul><ul><li>Sequence of moves to transition network from one routing/LSP pattern to another via a series of “make-before-break” operations </li></ul></ul><ul><li>IGP metric-tuning based optimization in IP networks </li></ul><ul><li>Practical BGP simulations – peering, load balancing </li></ul><ul><li>Fully cross-platform – supports client/server or client-only model </li></ul>
  31. 31. A Perspective on Some Current Carrier Requirements <ul><li>Accurate planning models </li></ul><ul><li>IP n/w planning with peering </li></ul><ul><li>Usability and consistency </li></ul><ul><li>Obtain precise traffic matrices </li></ul><ul><li>Good interface with monitoring tools </li></ul><ul><li>Intelligent heuristics </li></ul><ul><li>Extensible architecture </li></ul><ul><li>Application-level performance monitoring </li></ul><ul><li>Multicasting for multi-media services support </li></ul>
  32. 32. Concluding Remarks <ul><li>Designing and operating networks methodically will be crucial for South-Asian carriers with growing networks </li></ul><ul><li>Services, not size, will dictate the sophistication needed </li></ul><ul><ul><li>“ Small” carriers offering same advanced services as “big” ones </li></ul></ul><ul><ul><li>So, a systematic approach is must for sustained competitiveness </li></ul></ul><ul><li>A “science” of network design can be used to … </li></ul><ul><ul><li>Identify potential problems, experiment with solns, verify designs </li></ul></ul><ul><li>An “art” will always be there … </li></ul><ul><ul><li>Dictated by unique local or evolutionary needs </li></ul></ul><ul><li>Tools and expertise exist to help operate world-class networks! </li></ul>