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Exploring Dynamic Circuit Services in Optical Networks: Applications and Future Directions

This presentation delves into Dynamic Circuit Services (DCS) within optical networks, comparing scheduled and unscheduled services. We discuss the types of applications best suited for these services, their operational realities, and the technological underpinnings necessary for their deployment. The role of optical transport technologies such as OTN, MPLS-TP, and Carrier Ethernet are explored, along with the differences between leased line services and dynamic circuits. We analyze insights from past research to suggest promising directions for future applications and improvements in DCS.

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Exploring Dynamic Circuit Services in Optical Networks: Applications and Future Directions

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  1. Interaction between Applications and the Network Malathi Veeraraghavan & Zhenzhen Yan University of Virginia mvee@virginia.edu Thanks to our sponsor, Department of Energy, ASCR program office Work done on grant DE-SC002350

  2. Outline • Questions • Dynamic circuit services (DCS) • Scheduled • Unscheduled • Applications for scheduled DCS • Two practical realities

  3. Optical networks and services • Many technologies for optical “transport” networks: • OTN • MPLS-TP • Carrier Ethernet (VLAN based) • SONET/SDH • Service offered: • Leased (private) lines • Run between routers

  4. Questions • Question 1: • Can we offer any other types of services with these optical networks? • Question 2: • What applications are suitable for these services?

  5. Networks: back to basics • What is the role of a network? • move data across a path consisting of one or more links • Single-link (switchless) networks • random-access (e.g., Wifi, hubbed Ethernet, WDM broadcast-and-select) • polling based (e.g., PON) • Multiple-link switched networks • switches interconnect links

  6. A classification of network switches • A circuit switch is necessarily connection-oriented as positions have to be allocated to a communication session before data transfer can start

  7. Connectivity services RHDP: Rate Hop Duration Product number of hops = n RHDP = 5.9n TB (T1*1 year) Gap to fill RHDP = 1500B RHDP = 1.4n MB (DS0*3 min) M. Veeraraghavan, M. Karol and G. Clapp, “Optical Dynamic Circuit Services,” IEEE Comm. Mag., Nov. 2010

  8. How does DCS differ from leased line service? Leased line Circuit/VC switch Customer device e.g., IP router DCS access link DCS access link Dynamic circuit Customer device e.g., cluster computer Customer device e.g., LCD display

  9. Differences • Differences between a “leased line” and a “dynamic circuit” ambiguous • BUT difference between leased-line service and dynamic-circuit service is clear

  10. Two types of DCS • Scheduled Dynamic Circuit Service (SDCS) • Unscheduled Dynamic Circuit Service • POTS generalized to any rate • The key differences are: • Call duration must be specified in SDCS • Cannot confirm book-ahead reservations without knowing when ongoing calls will terminate • SDCS requires a reservation scheduler

  11. Book-ahead or advance reservation • Terms “advance-reservation (AR)” and “immediate-request (IR)” have been used • Emphasis is on requested start time while this is less relevant than duration • Requested start time: optional • For elastic flows (file transfers), can accept “earliest start time” (EST type) • Inelastic flows (video conferencing) will need “specified start times” (SST type) • Hence we use the term scheduled and unscheduled (POTS like) dynamic circuit services

  12. When is SDCS necessary? • SDCS is more complex (needs scheduler) PLUS users are more constrained having to specify call durations while unscheduled (POTS like) service requires neither • Why deploy SDCS? Two reasons: • For inelastic flow apps, need to coschedule with other resources and hence need to book-ahead • If per-circuit rate is high, need SDCS if moderate utilization with low call blocking probability is desired to remain competitive

  13. Erlang-B formula for unscheduled dynamic circuit service • Call blocking probability (PB) against the link capacity expressed in channels (m) High blocking probability and low utilization when per-circuit rate allocation is high Example: Link capacity: 10Gb/s Per-channel bandwidth: 1Gb/s m = 10 We need Book-ahead! X. Zhu, M. Veeraraghavan, � Analysis and design of a book-ahead bandwidth-sharing mechanism, IEEE Trans. on Communications, Dec. 2008.

  14. Who offersScheduled Dynamic Circuit Services? • Research-and-education networks (RENs) • Department of Energy’s ESnet • Separate IP-routed network and MPLS virtual circuit network • On-Demand Secure Circuits and Advance Reservation System (OSCARS) scheduler • Inter-Domain Controller Protocol (IDCP) • Internet2: also deployed OSCARS • Research work supported by NSF OCI through projects such as CHEETAH, DRAGON • New NSF OCI project called DYNES

  15. Who offersScheduled Dynamic Circuit Services? • Commercial service providers • Verizon Bandwidth on Demand (BoD) service • AT&T Optical Mesh Service (OMS) • Contracts: • Facility: Access link: long-term contract • As needed, for short durations, circuit between any two BoD or OMS customers or sites

  16. Answer to Question 1 • Can we offer any other types of services with these optical networks? • Answer: • Scheduled dynamic circuit services • Unscheduled dynamic circuit services • Based on the needs of applications, current interest is greater in SDCS

  17. Outline • Questions • Dynamic circuit services (DCS) • Scheduled • Unscheduled • Applications for scheduled DCS • Two practical realities

  18. Question 2 • What applications are best suited for these types of services? • Practical realities • Scalability issue with circuit/virtual-circuit networks • With TDM, 192 OC1 slots in an OC192 – out of favor! • But with VLANs, rate policing only for a few VLANs per interface • Need for end-to-end deployment

  19. In the days of ATM • Applications that require QoS guarantees such as interactive audio/video streams • Best handled with virtual circuits • Both practical realities thwarted deployment of ATM dynamic “circuit” services (called SVC service)

  20. New thinking now • File transfers are best suited for dynamic circuit service • Counter-intuitive • No QoS requirement • But no intrinsic burstiness in a file transfer • Why? • Elephant flows hurt mice flows • TCP congestion control algorithm

  21. Flow classification taxonomy K-C. Lan, J. Heidemann, ” A measurement study of correlations of Internet flow characteristics,” The International Journal of Computer and Telecommunications Networking,Volume 50, Issue 1, January 2006

  22. eScience applications • Scientific discovery through advanced computing (SCIDAC) • 2-20 Petaflop  Exaflop computing • Storage grows with computing speeds • Petabytes to exabytes storage • Need to move very large datasets • Other applications: remote instrument control, remote visualization – latency sensitive

  23. Approach in DOE science community • Move heavy-hitter flows to dynamic circuits • Two reasons • Avoid adverse effects on other flows • Some apps need rate-guaranteed service • Nice side effect • One of the “practical realities” problems, scalability issue, goes away! • Why? Only few flows qualify

  24. Second practical realities problem: end-to-end • Problem: • Core networks: IP and Dynamic Circuit Service • Regional and enterprise networks: IP (mainly) • Solution: • Lambda Station: applications are modified to communicate with servers that signal core networks allowing “elephant” flows to be directed to the circuits • HNTES: flow history analysis; route packets of heavy-hitter flows to pre-established or dynamically established circuits Featured topic: Hybrid Networking IEEE Comm. Mag., May 2011

  25. Commercial applications • Dynamic CDN • Sudden surge: Recruit CDN servers and push web pages • Client at a remote site w/o close-by CDN server • Transfers between different CDN providers • Automatic business private line and Internet access private line rate increases (bottleneck) • Per-file transfer based rate increases of PL rate: server replication/disaster recovery • Surge based increase of web server clusters access link rate

  26. Practical realities • In both the applications: • Dynamic CDN: surges, remote clients • Automatic private line rate changes • neither of the practical problems exist • Only few flows: no scalability issue • Ends are in PoPs (Points of Presence) – so no upgrades of access/enterprises are required

  27. Summary • Key points • Bring value of optical networks more directly to applications • Add dynamic circuit services to leased-line services • Applications with heavy-hitter needs are better suited for dynamic circuits than light-usage flows with QoS requirements • Applications that need high rates on unpredictable basis, e.g., dynamic CDN • Any questions, comments, feedback? • Email: mvee@virginia.edu

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