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1.Why traffic shaping?. Network knows what traffic to expectNetwork can determine if the flow should be allowed to sendNetwork monitor the flow's traffic - confirm the flow's behavior as promised. 1.Why traffic shaping?. 1. Regulating traffic- 100 MB / 1 s vs 1 KB / 10 s2. Deciding weather
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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 flow’s traffic - confirm the flow’s behavior as promised
3. 1.Why traffic shaping? 1. Regulating traffic
- 100 MB / 1 s vs 1 KB / 10 µs
2. Deciding weather to accept the flow’s 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 ß
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 can’t 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 don’t 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
ß+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