Interaction between Applications and the Network

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