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Traffic Shaping

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Traffic Shaping

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    1. Traffic Shaping Why traffic shaping? Isochronous shaping Isochronous shaping with Priority schemes Shaping Bursty Traffic Patterns Conclusions

    2. 1.Why traffic shaping? Network knows what traffic to expect Network can determine if the flow should be allowed to send Network monitor the flows traffic - confirm the flows behavior as promised

    3. 1.Why traffic shaping? 1. Regulating traffic - 100 MB / 1 s vs 1 KB / 10 s 2. Deciding weather to accept the flows data - can buffer 100 MB ? 3. Policing a flow - detect misbehaving flows

    4. 1.Properties of good traffic shaping scheme Shaping scheme should describe wide range of schemes Shaping rules should make it easy to describe traffic patterns Shaping scheme should be easy to police

    5. 2. Isochronous Shaping regular amounts of data emitted at regular intervals

    6. 2.1. Simple Leaky Bucket Each flow has its own bucket send rate ? bucket size Cell & datagram traffic Easy to implement & to describe. ex: FIFO + Timer

    7. 2.2. (r,T) Smooth Traffic Based on stop and go algorithm Send no more than r bits in any T time period Limitation 2r sized datagram cant be sent Implementation -simple Bit counter, refreshed every T bit times

    8. 2.3. Limitations of Isochronous Shaping Easy to implement Easy description & traffic policing The range of behavior limited to fixed rate data flow. Var. rate flows request the peak rate -> wasting network capacity - peak values occurs rarely

    9. 3. Isochronous Shaping with Priority Schemes Uses bit patterns for priority How prioritizing is done: application: knows less important data network: marks the incoming cells at exceeding rates

    10. 3. Isochronous Shaping with Priority Schemes Limitations of priority schemes: low priority packets dont get through bandwidth reservation for low priority traffic selectively discard packets many com. devices uses FIFOs - continuous memory ~ sufficiently flexible ~ used in first generation cell switches

    11. 4. Shaping Bursty Traffic Patterns Token Bucket Token Bucket with Leaky Bucket Rate Control

    12. 4.1. Token Bucket Tokens inserted at rate ? into bucket if bucket is full -> token is dropped send allowed if there are b tokens in bucket, b*size = packet-size +t/? tokens worth data at any t time interval long term transmission rate is = ?

    13. 4.1. Token bucket - limitations No need for discard & priority policy discards tokens and leaves to the flow the managing transmission queue if the flow overdrives the regulator easy to implement (counter + timer) policing -> bit more difficult - possibility for cheating in data rate

    14. 4.2. Token Bucket with Leaky Bucket Rate Control