Finding Your Shade of Grey on the Network Spectrum Towela P.R. Nyirenda-Jere Victor S. Frost

March 8, 2000 1

University of KansasDepartment of Electrical Engineering and Computer Science

Finding Your Shade of Grey on the Network

Spectrum

Towela P.R. Nyirenda-Jere

Victor S. Frost

(sponsored by Sprint)

March 8, 2000 2


The Network Spectrum

• Simple traffic handling + Huge Capacity

• Moderate traffic handling + Moderate Capacity

• Complex traffic handling + Minimal Capacity

March 8, 2000 3


The Problem

• Determining the equivalence of traffic handling mechanisms

• Understanding the trade-off between the complexity of traffic handling mechanisms and the network capacity required to support service guarantees

March 8, 2000 4


What we know

• Service guarantees depend on both traffic handling and network capacity

• Total aggregation schemes require more capacity than per flow schemes

• Partial aggregation schemes scale better than per-flow schemes when number of flows is large

March 8, 2000 5


What we don’t know

• How much more capacity do we need with total aggregation versus per-flow?

• How does the complexity of per-flow management measure up against the cost of additional capacity with aggregate traffic handling?

• What about partial aggregation schemes?

March 8, 2000 6


What we need

• Quantification of the gain obtained by using complex traffic handling with smaller network capacity versus using simple traffic handling with abundant network capacity

• Quantification of the sensitivity of traffic handling to changes in network load both in terms of the total load and in terms of the relative mix of different classes

March 8, 2000 7


What should be done

• Quantify trade-off between complexity of traffic handling and network capacity

• Determine scalability of the analytic methods with network size and capacity

• Provide analytic framework for capacity provisioning and traffic handling strategy

• Study the sensitivity of traffic handling schemes to changes in network load

March 8, 2000 8


Traffic Handling Mechanisms

March 8, 2000 9


Traffic Modeling

• Deterministic burstiness constraint model of Cruz et. al.

• Traffic described by two parameters: average rate and burstiness

• No assumptions on traffic type

• Aligns well with IETF and ATM Forum traffic description

March 8, 2000 10


Analytic Method

• Use Network Calculus approach of Cruz, Parekh & Gallagher

• WFQ is used as the reference mechanism

• Find number of voice, video, e-mail and WWW sources using WFQ taking into account delay requirements

• Find capacity required to support these sources using CBQ, PQ and FIFO

March 8, 2000 11


Applications and Service Requirements

March 8, 2000 12


Scenario

• Single-node Network

• OC-3 Link for WFQ

• Video load = 10% of OC-3

• Voice load varied from 10-90% of OC-3

• E-mail and WWW share remaining capacity using pre-defined ratios

March 8, 2000 13


CBQ Capacity Requirements• Capacity

requirements of CBQ same order of magnitude as WFQ

March 8, 2000 14


PQ Capacity Requirements

• Capacity requirements of PQ same order of magnitude as WFQ

• Non-monotonic

March 8, 2000 15


PQ and CBQ Capacity Requirements

• PQ capacity does not exceed CBQ capacity

March 8, 2000 16


FIFO Capacity Requirements• FIFO requires

two orders of magnitude more capacity than WFQ

March 8, 2000 17


Sensitivity to Design Point

• Goal is to explore the ability of the three schemes to provide acceptable delay guarantees when the traffic submitted exceeds the traffic for which the network was designed

• Two broad cases» voice as dominant class» WWW as dominant class

March 8, 2000 18


Sensitivity: Network designed for Voice

• WFQ1, CBQ sensitive to increase in voice

• PQ, FIFO not as sensitive

March 8, 2000 19


Sensitivity: Network designed for WWW

• FIFO most sensitive to increase in WWW traffic

• PQ least sensitive

March 8, 2000 20


Projections on Network Traffic and Capacity

• Assume 5% growth in Voice and 100% growth in WWW per year

• Initially OC-3 link with total utilization 45%» 5% voice, 15% e-mail and 25% WWW

March 8, 2000 21



• FIFO capacity at year 5 is 2000x capacity at year 1

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• CBQ and PQ capacity at year 5 is 8x capacity at year 1

• WFQ capacity at year 5 is 4x capacity at year 1

March 8, 2000 23


Shades of Grey

March 8, 2000 24


What Have We Learned

• It is possible to quantify the trade-off between network capacity and traffic management

• Sensitivity of the traffic handling schemes depend on the assumptions made in designing the network as well as the traffic class contributing to the growth in traffic

March 8, 2000 25


What’s Next

• Review methodology and define performance metrics/indices

• Extend analysis to carrier-size networks

• Incorporate stochastic bounds on performance

March 8, 2000 26


Significance

• Identifying the tradeoffs associated with the use of traffic handling mechanisms with respect to network capacity

• Sensitivity analysis will provide a tool for long-term planning

• Development of a methodology which can be used to compare traffic handling schemes in general

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Finding Your Shade of Grey on the Network Spectrum Towela P.R. Nyirenda-Jere Victor S. Frost

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