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SCALE 11x 23 Feb 2013
Bufferbloat
What is Bufferbloat?
Stephen Hemmingerstephen@networkplumber.org
SCALE 11x 23 Feb 2013
SCALE 11x 23 Feb 2013
Solving Plumbing problems
● Discovery
● Blame
● Enlightenment
● Nirvana
SCALE 11x 23 Feb 2013
Bufferbloat: definition
SCALE 11x 23 Feb 2013
Queuing Theory Basics
averagetimeinqueue=utilization
servicerate1 − utilization
Graphic courtesy Sprint, Apricot 2004
From Fred Baker: Bufferbloat!
SCALE 11x 23 Feb 2013
How bad is it?
150ms – VOIP
20ms – Desktop lag
100ms – DNS lookup fail
ARP, ND – Can't find machine
1000ms – User's give up
scp copy fails
DHCP – Machine falls off network
SCALE 11x 23 Feb 2013
Triggers
● Uploads– Youtube
– Dropbox
– Torrent
– Large Email attachments
– Backup services
● Downloads– Movie downloads
– Image heavy websites
– Video teleconferencing
SCALE 11x 23 Feb 2013
Netalyzr: Downstream
SCALE 11x 23 Feb 2013
Netalyzr: Upstream
SCALE 11x 23 Feb 2013
Gettys J., Bufferbloat: “Dark” Buffers in the Internet
SCALE 11x 23 Feb 2013
SCALE 11x 23 Feb 2013
Classical TCP
SCALE 11x 23 Feb 2013
Antonin BasStanford Cs244 assignment
SCALE 11x 23 Feb 2013
SCALE 11x 23 Feb 2013
TCP throughput dynamicsIn
crea
sing
Mea
sura
ble
Thr
ough
put
Increasing TCP Window
“knee” “cliff”
Bottleneck Capacity
QueueDepth
meanthroughput= effectivewindowmeanroundtriptime
From Fred Baker: Bufferbloat!
SCALE 11x 23 Feb 2013
Blame Linux
● Windows XP
– Maximum window 64k
● Windows 7
– Bandwidth limit to 80 mbits
● Android– Receive window limited
SCALE 11x 23 Feb 2013
Blame the customer
● Customers call support
● Applications are using more bandwidth
● Block and charge
SCALE 11x 23 Feb 2013
SCALE 11x 23 Feb 2013
Back to Reality
SCALE 11x 23 Feb 2013
Benchmark issues
● Bad
– Bytes/sec
– Packes/sec
– Latency
SCALE 11x 23 Feb 2013
Making a good test
● Combinations
– RRUL
SCALE 11x 23 Feb 2013
FIFO – the default
Høiland-Jørgensen T., Battling Bufferbloat
Ping 1sec!
Upload
Download
SCALE 11x 23 Feb 2013
Stochastic Fair Queue
Høiland-Jørgensen T., Battling Bufferbloat
SCALE 11x 23 Feb 2013
Controlled Delay - codel
Høiland-Jørgensen T., Battling Bufferbloat
SCALE 11x 23 Feb 2013
Fair Queue Controlled Delay
Høiland-Jørgensen T., Battling Bufferbloat
SCALE 11x 23 Feb 2013
Fight Bufferbloat
SCALE 11x 23 Feb 2013
Linux Everywhere
In the Datacenter
In the Home
If we fix Bufferbloat, the world will change... eventually
SCALE 11x 23 Feb 2013
The ICSI Netalyzr
SCALE 11x 23 Feb 2013
Bufferbloat project
● Information
– Research
– Presentations
– Mailing lists
SCALE 11x 23 Feb 2013
Cerowrt
● Development platform
– Openwrt based
SCALE 11x 23 Feb 2013
Future Research
● Systemic view
● Change Linux default?
● Wireless
● High speed 10/40/100G?
SCALE 11x 23 Feb 2013
Thank youStephen Hemminger
stephen@networkplumber.org
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