Bufferbloat are we there yet?
Stephen Hemminger
Linuxcon Japan May 2014
@networkplumber
Bufferbloat
Bufferbloat
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What is the problem
What causes the problem
Solutions
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Demonstration
Current status
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The Good
The Bad
The Ugly
Bufferbloat: definition
How bad is it?
User
Refresh
Ssh
timeout
Desktop
Lag
10
100
1000
10000
Latency
ms
VOIP
ARP, ND
100000
1000000
Queuing Theory Basics
utilization
averagetimeinqueue=
servicerate
1 − utilization
From Fred Baker: Bufferbloat!
Graphic courtesy Sprint, Apricot 2004
Netalyzr: Downstream
Netalyzr: Upstream
Classical TCP
TCP throughput dynamics
Increasing Measurable Throughput
meanthroughput =
effectivewindow
meanround triptime
Bottleneck Capacity
“knee”
Queue
Depth
“cliff”
Increasing TCP Window
From Fred Baker: Bufferbloat!
Blame Linux
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Windows XP
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Windows 7
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Maximum window 64k
Bandwidth limit to 80 mbits
Android
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Receive window limited
Blame the customer
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Customers call
support
Applications are
using more
bandwidth
Block and charge
Back to Reality
Benchmark issues
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Bad
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Bytes/sec
Packes/sec
Latency
FIFO – the default
Ping 1sec!
Upload
Download
Høiland-Jørgensen T., Battling Bufferbloat
Stochastic Fair Queue
Høiland-Jørgensen T., Battling Bufferbloat
Controlled Delay - codel
Høiland-Jørgensen T., Battling Bufferbloat
Fair Queue Controlled Delay
Høiland-Jørgensen T., Battling Bufferbloat
Bufferbloat Success
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Queuing disciplines
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Linux internal
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Codel, PIE, ...
BQL, FQ, Pacing
Industry awareness
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DOCIS 3.0, IETF
Bufferbloat Issues
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Legacy equipment
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OEM focus on cost not AQM
Congestion on backbone
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Problem is political not technical
Wireless failures
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Aggregation
Multicast
Proprietary firmware
Questions?
Dave T<dave.taht@bufferbloa
Thank you
Stephen Hemminger
@networkplumber
[email protected]
Bufferbloat resources
Bufferbloat.net: http://bufferbloat.net
Email Lists: http://lists.bufferbloat.net
IRC Channel: #bufferbloat on chat.freenode.net
CeroWrt: http://www.bufferbloat.net/projects/cerowrt
Other talks: http://mirrors.bufferbloat.net/Talks
Jim Gettys Blog – http://gettys.wordpress.com
RRUL Testhttps://github.com/tohojo/netperf-wrapper
A big thanks to the bloat mailing list, Jim, Kathie, Van, and Eric, ISC, the
CeroWrt contributors, OpenWrt, the Internet Civil Engineering
Institute, and the Google Fiber for their interest and support in
the work!

Results - Eurorallye