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Evolution Of The Public Network


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This is a presentation on the evolution of the public network, including POTS, ATM, SONET, DWDM, RPR, Ethernet, and other technologies. Explains how needs and design principles have changed over time and compares the different technologies. A full research paper is available at

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Evolution Of The Public Network

  1. 1. Presented by Eric Goldman
  2. 2. Introduction I. II. Current Technologies III. Emerging Technologies IV. Comparison of Technologies V. Prediction of Future Needs VI. Summary VII. Questions VIII. References Copyright © 2009 - Eric Goldman - 2
  3. 3. We don’t usually worry about  the “stuff” in the “cloud”  The public network consists of all the ISP, network provider, and cable, and telephone networks and their interconnections  Used to transport TV, phone, Internet – One Network to rule them all! Copyright © 2009 - Eric Goldman - 3
  4. 4. Originally designed for voice communications   Voice traffic is very uniform and predictable Internet introduced new challenges   Data communications are bursty & unpredictable  Many short conversations between multiple senders and receivers  Complicated QoS demands that may be application based Most traffic on the public network was local, but  Internet traffic is usually long haul Copyright © 2009 - Eric Goldman - 4
  5. 5. Invented to facilitate intro of cable TV in FRA  Connection oriented and offers good QoS  Uses a small fixed-length packet (53 Bytes)   this design reduces delay and jitter Great for voice and video, bad for the Internet   Fixed-length doesn’t map well to TCP/IP packets  IP over ATM requires extra, expensive software Still around because so much money was  initially invested in the technology Copyright © 2009 - Eric Goldman - 5
  6. 6. Optical Multiplexing technique based on TDM   Synchronous nature avoid need for bit stuffing and reduces unwanted overhead Excellent management and administration  Can operate in many topologies, usually ring  Designed to easily combine T1, T3, etc   Preexisting bandwidth classes for telecom However, provides limited flexibility  Copyright © 2009 - Eric Goldman - 6
  7. 7. Provides increased capacity w/o new wires  Allows for all optical switching   Each carrier can be individually routed as well Can achieve VERY high data rates  Significantly less expensive than SONET/ATM  However, ineffective QoS  Signal cleaning and repeating is more  complicated, and must be done individually Copyright © 2009 - Eric Goldman - 7
  8. 8. A well designed carrier of all traffic types   Combines aspects of Ethernet and SONET  Designed with capabilities for voice, data, & QoS  Easily interfaces with both Ethernet & SONET Operates with at least two rings where data  travels in opposite directions Low amount of intermediary data processing  Bandwidth can easily be reclaimed at any  point on the ring Copyright © 2009 - Eric Goldman - 8
  9. 9. We dream of end-to-end Ethernet   Would make it very homogenize the network; simplifying interconnects and management Not well suited for the Public Network   No included QoS in vanilla Ethernet  Public network is made of rings, not meshed Enhanced or modified versions of Ethernet  could be possible if standardized Copyright © 2009 - Eric Goldman - 9
  10. 10. ATM SONET DWDM RPR Ethernet Initial Voice/Video Voice/Video Any Any Data Purpose: Costs: Highest High Low Low Lowest Low Delay, Effective High Common on Interoperability, Advantages: QoS subscriber nets Low Jitter Management Capacity Dis- Overhead, Time Slot vs Rigid carrier Early Lack of QoS, advantages: very old bursty data constraints development connectionless Current High, Minimal High Increasing Minimal Usage: dropping (on pub net) Copyright © 2009 - Eric Goldman - 10
  11. 11. Success of a technology will depend on future  traffic flows and needs Dependent upon physical infrastructure   Ring topology, unused dark fiber Use combinations of technologies   For example combine DWDM with SONET or RPR Vendors will continue to use legacy  technology until it becomes cost effective to upgrade or change Copyright © 2009 - Eric Goldman - 11
  12. 12. The needs of the network will likely continue  to evolve as our data demands change Decisions will be constrained by current  infrastructure and knowledgebase It is very difficult to ensure that all types of  traffic are delivered the way we would like There are many stake holders with different  objectives. Copyright © 2009 - Eric Goldman - 12
  13. 13. The floor is now opened for questions. Copyright © 2009 - Eric Goldman - 13
  14. 14. Eogogics Inc. (2005). Tutorial on Optical Networking. Retrieved September 5, 2008, from Eogogics  Knowledge Center: Green, M., & Schlicht, L. (2002, September 3). Maximize the Metro With Resilient Packet Ring.  Retrieved September 16, 2008, from CommsDesign:;jsessionid=OBV1GC3HCJ2AAQSNDLPSKH0CJ UNN2JVN?articleID=16505799 Greenfield, D. (2002). The Essential Guide to Optical Networks. Upper Saddle River, NJ: Prentice  Hall PTR. Horak, R. (2001, April 3). SONET vs. DWDM. Retrieved September 16, 2008, from Call Center  Magazine: html?articleId=8704557&pgno=1 Kerner, S. M. (2008, January 11). Ethernet Traffic Doubles, While ATM and SONET/SDH Dip.  Retrieved September 16, 2008, from Optically Networked: Optical Networks: DWDM and SONET. (2008). Retrieved September 16, 2008, from The Insight  Research Corporation: Tektronix. (n.d.). Synchronous Optical Network. Retrieved September 5, 2008, from  Copyright © 2009 - Eric Goldman - 14