Staying focused on the
big unsolved problems
e.g. resource accountability
Bob Briscoe
Chief Researcher, BT Group
Sep 2008
main problems with the current Internet
• interconnecting the information world with the physical world
•
publish-subscribe
• commercial viability & flexible comms industry structure
•
resource accountability
•
policy controls on overlay / inter-provider routing
• scaling for extreme dynamics
•
mobility, re-routes & failures, time-variable resources
•
high speed transfers, very short transfers
• availability & robustness to attack (not infoSec problem, nec.)
•
malware transmission & DDoS
•
reachability for the good guys through middlewalls
• management
2
•
failure tracking
•
policy-driven auto-config
"Hey, if you try this instead of that, simulations show it rocks and it's
much better."
research style
– keeping focused
"We've invented this cool way to share resources in an ad hoc,
cognitive, autonomic, meshed network of tetherless hospital beds,
which is probably novel based on a survey of papers found on the
first page of a Google search."
• all need a 'big science' approach
•
monumental but tedious research process
•
sustainable research teams
•
consensus on what each problem is separately
–
•
a range of solutions proven much better than today for each problem
–
•
based on rigorous analysis (engineering & economic)
rigorously analysed and strong economic cases for deployment
process for rough consensus on solution(s) to deploy
• computing / networking research not set up like that
3
•
the next sexy start-up idea from the lone PhD
•
research as marketing – crafted to hide weaknesses
•
little critical analysis of other work
•
emphasising novelty
•
de-emphasising commonality of analytical model
•
specialisation, not abstraction
Flow-Rate Fairness: Dismantling a Religion
experience of trying to bring science into Internet research
rate
time
flow
activity
2Mbps access each
80 users of
attended apps
10Mbps
20 users of
unattended apps
usage type
no. of
users
activity
factor
ave.simul
flows /user
TCP bit rate
/user
vol/day
(16hr) /user
traffic
intensity /user
attended
80
5%
=
417kbps
150MB
21kbps
unattended
20
100%
=
417kbps
3000MB
417kbps
x1
x20
x20
4
two arbitrary approaches fighting
bit-rate
time
throttling heavy volume usage
'flow-rate equality'
the Internet way (TCP)
operators (& users)
‘flow rate equality’
‘volume accounting’
multiple flows


activity factor


application control


congestion variation


degree of freedom
• each arbitrarily cancels out the worst failings of the other
• Internet looks like 'it works OK'
• but arbitrary fighting leaves collateral damage
5
fairer is faster – incentivise end host behaviour
bit-rate
light
light
heavy
heavy
time
'unfair' TCP sharing
heavier usage takes
higher sharing weight
throttling heavy usage
light
heavy
•
•
lighter usage takes
higher sharing weight
enabler: limit congestion, not volume
then end system congestion control will quickly evolve
•
•
•
•
heavy usage will back away whenever light usage appears
so light usage can go much faster
hardly affecting completion times of heavy usage
differentiated
QoS as if in the network
6
limiting congestion
with flat fee pricing
Acceptable Use Policy
Your 'congestion volume' allowance:
1GB/month (= 3kb/s continuous)
This only limits the traffic you can try to
transfer above the maximum the
Internet can take when it is congested.
Under typical conditions this will allow
you to transfer about 70GB per day.
If you use software that seeks out
uncongested times and routes, you will
be able to transfer a lot more.
•
•
only throttles traffic when
contribution to congestion
elsewhere exceeds allowance
otherwise free to go at any bit-rate
Your bit-rate is otherwise unlimited
congestion · bit-rate
0% · 2 Mb/s = 0.0kb/s
0.3% · 0.3Mb/s = 0.9kb/s
0.1% · 6 Mb/s = 6.0kb/s
6.9kb/s
2 Mb/s
0.3Mb/s
6 Mb/s
bulk
congestion
policer
7
Internet
0%
0.3%
congestion
0.1%
mismatch of aspirations
experience of trying to bring science into Internet research
• [y] Kelly's "Charging & Rate Control for Elastic Traffic": 1997
• [z] "Dismantling a Religion" repeated the message: 2006
• a rich and rigorous vein to tap for fixing the Internet
• resource accountability, simpler e2e QoS mechanism, e2e QoS for
mobility, differentiated flow start-up, interconnection contracts, targeted
liability for DDoS, traffic engineering and congestion routing, removing the
need for deep packet inspection, removing need for rate limits into shared
access networks (PON, cable, wireless)...
• context of all citations so far (paraphrasing)
• "There are a number of approaches to fairness [w,x]; recently these have
been deeply challenged [y|z]; but we build on [x] which is generally used in
the research community."
• Typical mailing list discussions "What's the problem? TCP works"
• ug
8
Staying focused on the big
unsolved problems
e.g. resource accountability
Q&A