Download Design Review of Using Prices to Allocate Resources at a H

Using Prices to Allocate
Resources at Access Points
Jimmy Shih, Randy Katz, Anthony Joseph
Network
Resources
Access
Point A
Access
Point B
One
Administrative
Domain
User A
User B
Problem & Proposed Solutions
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Access points are congested. E.g modem
pools, access routers.
Can add capacity, perform admission control,
balance loads between the access points,
allow advance reservation, or constrain usage.
For admission control, use prices to allocate
the access points to those who value them the
most.
For load balancing, use prices to encourage
users to use the less capable access points.
State-of-the-Art on Congestion
Pricing
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Lots of theoretical & simulation work on
congestion pricing. Explored issues like
benefits, stability, fairness, & robustness.
Lots of work on auctions. But prices are very
unpredictable.
Lots of systems deployed using usage-based
pricing.
No discussion of exactly how to implement
systems that use congestion pricing.
No system deployed using congestion pricing.
Today’s Goal & Outline
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Goal:
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Discuss our hypotheses about congestion pricing, and
how we can verify them through simulations and
deployments.
Outline:
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Use the following two examples:
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Using a H.323 gateway to make & receive telephone calls on
the Internet.
Using an access router to send & receive IP packets.
How to design systems that use congestion pricing?
How effective can congestion pricing affect users’
behaviors?
What is a H.323 Gateway?
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Connect the Internet to the Public Switched Telephone
Network (PSTN).
Allow users to make & receive computers-to-PSTN, computerto-computer, and PSTN-to-PSTN calls.
The bottleneck resource is the number of PSTN phone lines
connected to the gateway.
The bottleneck resource is connection oriented.
Each call uses the same amount of the bottleneck resource.
Internet
H.323
Gateway
PSTN
What Do We Want To Do?
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Provide students in the UC Berkeley dorms
with a H.323 computer telephony service
that allows them to use a web interface to
make & receive telephone calls.
System Architecture:
Web Clients
Web
Java Applet
Interface NetMeeting
Web
Java Applet
Interface NetMeeting
H.323 Computer Telephony Service
Web Server
Control Database
Data Path
Lucent Elemedia’s
H.323 Protocol Stack
Motorola
Vanguard H.323
Gateway
Phones
PSTN
Primary Rate ISDN Line
(23 Simultaneous Calls)
Problem & Proposed Solutions
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Congestion is a serious problem because users
don’t have dedicated lines or an overprovisioned network.
Use congestion pricing for admission control to:
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Encourage users not to call when the system is
congested.
Encourage users to make their calls shorter when the
system is congested.
Proposed Solutions (cont.)
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Use congestion pricing for load balancing to:
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Encourage users to use their computers instead of
telephones to minimize using the bottleneck resource.
Internet
H.323
Gateway
PSTN
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Give each user a certain number of tokens per week for
making & receiving phone calls.
Only need to perform accounting at the gateway.
Only need to provide users with a web interface
containing the current prices.
Hypotheses
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Congestion pricing can:
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Given enough incentives:
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Reduce bursts on demand at the gateway.
Minimize the number of long duration calls.
Users would choose congestion pricing over flat
rate pricing.
Users would use their computers instead of
telephones.
Through proper policies, we can ensure that
the system is stable when using congestion
pricing.
Policies for Admission Control
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Let the gateway decides the price it wants to
charge.
Set the price equals to a function on the load.
Inform users the current price and the next
minute price. The current price will not change
while the next minute price will change
depending on the congestion.
Have the gateway gradually inform users of new
prices.
Policies for Load Balancing
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Charge users a flat minute rate for using their
telephones, and congestion prices for using
their computers.
Inform users the current connection qualities
if they use their computers.
When users use their telephone to make &
receive calls, inform them how much cheaper
it would be if they switch to their computers.
Possible User Web Interface
Current Price for Using
Your Computer:
10
Tokens/min
Next Minute Price for
Using Your Computer:
20 Tokens/min
Current Price for Using
Your Telephone:
35
Tokens/min
Next Minute Price for
Using Your Telephone:
35 Tokens/min
Packet Loss Rate When Using Your Computer: 3%
Handoff the Current Call to Your Telephone:
(510) 642-8919 Yes?
Handoff the Current Call to Your Computer:
annie.cs.berkeley.edu Yes?
Simulations
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What if users’ demands are not
sensitive to changing prices?
What if users take a long time to react
to changing prices?
Use calling patterns from our previous
deployments of a H.323 computer
telephony service to perform these
simulations.
Deployment Experiments
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In August, provide the service to 200 students in
the UC Berkeley dorms.
Alternate between congestion pricing, time of day
pricing, and flat rate pricing on a weekly basis.
Offer users the option at the beginning of each
week of paying congestion prices, a flat minute
rate per call, or a flat minute rate for the whole
week.
Charge users congestion prices for using their
computers and a flat minute rate for using their
telephones.
Congestion Pricing at
an Access Router
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Lots of people in a local area network trying to send
and receive IP packets through a bottleneck link
router. E.g. 500 students in a dorm sharing an access
router.
The bottleneck resource is connectionless.
Users can adjust their bandwidth and duration usage.
Only need to modify the access router and provide
users with a web interface containing the current
prices.
Users in a
Local Area
Network
Access
Router
Internet
Hypotheses
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Congestion pricing can
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Be used to decide whose incoming and outgoing
packets to drop during congestion.
Quickly free up large amount of bandwidth.
Reduce bursts on demand at the router.
Encourage users to reduce their bandwidth and
duration usage during congestion.
Policies for Admission Control
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Inform users the amount of bandwidth they are using.
Allow users to reserve the amount of incoming and
outgoing bandwidth they need, and the most they are
willing to pay for them.
Have each Mbyte of bandwidth cost the same.
Don’t provide rebate if users don’t use all their reserved
resources.
Allow users to change their reservations at any time.
Don’t charge users fees for changing their reservations.
Possible User Web Interface
Current Price Per
Mbyte Per Sec:
10 Tokens
Tokens Left
for Today:
200 Tokens
Current Usage: 4 Mbyte Per Sec
How Much Bandwidth to Purchase:
3 Mbyte Per Sec
Most Willing to Pay Per Mbyte Per
Sec: 30 Tokens
Simulations
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What if users can only adjust their
bandwidth usage? What if they can
only adjust their duration usage? Etc.
What if users take a long time to
react to changing prices?
Use IP traces from the Internet Traffic
Archive to perform these simulaitons.
Deployment Experiments
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In the Fall, replace our research group’s
subnet router with a Nortel Java
Programmable router that uses congestion
pricing to decide whose packets to drop.
Measure how quickly a user can obtain large
amount of bandwidth if he is willing to pay
for them.
Measure users’ willingness to pay at any
given time.
Measure a user’ willingness to pay throughout
a day.
Summary
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Lots of hypotheses about congestion pricing.
Determine the right policies for using congestion
pricing.
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E.g. How to ensure price & system stability, minimize
starvation, prevent denial of service attacks, etc.
Determine how well congestion pricing can affect
users behaviors.
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E.g. Amount of incentives required for users to choose
congestion pricing over flat rate pricing, to adjust their
behaviors during congestion, to use the less capable
access points, etc.
Discussion
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Is it a good idea to use congestion
pricing to allocate resources at access
points?
What are our hypotheses about
congestion pricing?
How can we verify them through
simulations and deployments?