7 Rate Limiting and Traffic Shaping Flashcards
What is motivation for traffic classification and shaping
- resource control
- ensure flows do not exceed rate
4 Traffic Shaping approaches
- Leaky bucket
- (r,T) traffic shaper
- Token bucket
- Composite
Classification of Sources
Data: bursty, periodic, regular
Audio: continuous, periodic
Video: continuous, bursty (compression), periodic
What is CBR
constant-bit-rate
shaped according to peak (audio)
What is VBR
variable-bit-rate
shaped according to average and peak (video, data)
Leaky bucket
Isochronous - 1986
one bucket per flow
size of bucket (beta)
drain rate / regulator (ro)
(r,T) Traffic shaping
Traffic divided into T-bit frames
Flow can inject <= r bits in any T-bit frame
conforming flows are called (r,T) smooth
Token bucket
beta is token bucket size
ro is the rate at which tokens are placed in bucket
bucket is full, b tokens removed, b packets sent
empty, wait until b tokens arrive
What is power boost
June 2006 (Comcast) allows subscribers to send at a higher rate for a brief time
What is buffer bloat
delay because data in buffer
modem has buffer, ISP has buffers
Two types of network measurement
passive and active
What is passive measurement
collection of packets, flow stats that are already on the network
What is active measurement
inject additional traffic to measure various characteristics (ping, traceroute)
Why do network measurement
- Billing
- Security
What is CIR
committed info rate (95th percentile) - throughput measured every 5 mins
