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Interaction between Applications and the

Network

Malathi Veeraraghavan & Zhenzhen YanUniversity of Virginiamvee@virginia.edu

Thanks to our sponsor, Department of Energy, ASCR program officeWork done on grant DE-SC002350

OutlineQuestionsDynamic circuit services (DCS)

– Scheduled– Unscheduled

• Applications for scheduled DCS• Two practical realities

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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

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Questions• Question 1:

– Can we offer any other types of services with these optical networks?

• Question 2:– What applications are suitable

for these services?

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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

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A classification of network switches

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Line cards (multiplexing)

Controller(admission control or not)

Circuit mode(position-based mux:time, frequency, port)

Packet mode(header-based mux)

Connectionless (CL)(no admission control)

e.g., IP routers, Ethernet switches

Connection-oriented (CO)(admission control)

e.g., SONET, WDM switches

Virtual-circuit switches (VLAN, MPLS)

• A circuit switch is necessarily connection-oriented as positions have to be allocated to a communication session before data transfer can start

Connectivity services

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RHDP: Rate Hop Duration Product number of hops = n RHDP = 1500B

RHDP = 1.4n MB (DS0*3 min)

RHDP = 5.9n TB (T1*1 year)

Gap to fill

M. Veeraraghavan, M. Karol and G. Clapp, “Optical Dynamic Circuit Services,” IEEE Comm. Mag., Nov. 2010

How does DCS differ from leased line service?

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Leased line Circuit/VC switchCustomer

devicee.g., IP router

Customer devicee.g., cluster computer

DCS access link DCS access link Dynamic

circuit

Customer devicee.g., LCD display

Differences

Service Leased line service

Dynamic circuit service

Components of contract

One contract:• duration• rate•specified endpoints

Two contracts:•DCS access link of certain rate (like IP access link, and POTS access link)•as needed, requests for circuits of certain duration, rate, between any two DCS endpoints

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

clear

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

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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 11

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

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Erlang-B formula for unscheduled dynamic circuit service

High blocking probability and low utilization when per-circuit rate allocation is high

We need Book-ahead!

Call blocking probability (PB) against the link capacity expressed in channels (m)

Example:Link capacity: 10Gb/sPer-channel bandwidth: 1Gb/sm = 10

X. Zhu, M. Veeraraghavan, � Analysis and design of a book-ahead bandwidth-sharing mechanism, IEEE Trans. on Communications, Dec. 2008.

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

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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

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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

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Outline• Questions• Dynamic circuit services (DCS)

−Scheduled−Unscheduled

Applications for scheduled DCSTwo practical realities

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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

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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)

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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

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Flow classification taxonomy

Dimension Heavy hitter Non-heavy hitter

Size (bytes) Elephant MiceRate Cheetah SnailDuration Tortoise DragonflyBurstiness Porcupine Stingray

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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

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

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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

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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

24Featured topic: Hybrid NetworkingIEEE Comm. Mag., May 2011

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

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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

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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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