From TCP to Net Neutrality and Back

1
From TCP to Net Neutrality and Back

• Aleksandar Kuzmanovic
• EECS Department
• Northwestern University

http//networks.cs.northwestern.edu
2
Todays Talk

• TCP congestion control
• Reusing CDNs measurements
• Net neutrality

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TCP Congestion Control

• Question
• Why do we care about TCP congestion control in
  the year 2007?
• Overwhelming opinion
• TCP research is incremental
• Not relevant any more
• It is boring
• No high-impact breakthroughs are possible any
  more

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Non-Incremental Advances are Possible
throughput increases by more than 40 while
the average web response time simultaneously
decreases by nearly an order of magnitude.
Server

• A. Kuzmanovic, The Power of Explicit Congestion
  Notification, in ACM SIGCOMM 2005.

• A. Kuzmanovic, S. Floyd, and K. K. Ramakrishnan
  Adding Explicit Congestion Notification (ECN) to
  TCPs SYN/ACK Packets, IETF Draft, work in
  progress.

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TCP Congestion Control

• Slow-start phase
• Double the sending ... ... rate each round-trip
  ... time
• Reach high throughput ...quickly

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TCP Congestion Control

• Additive Increase ...Multiplicative
  Decrease
• Fairness among flows

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TCP Congestion Control

• Exponential
• .backoff
• System stability

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Breakthroughs are Possible

• Exponential backoff
• fundamentally wrong!

• A. Mondal and A. Kuzmanovic, Removing
  Exponential Backoff from TCP, work in progress.

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Todays Talk

• TCP congestion control
• Reusing CDNs measurements
• Net neutrality

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Drafting Behind Akamai

• Fact
• CDNs (e.g., Akamai) perform extensive network and
  server measurements
• Publish the results through DNS over short time
  scales
• Can overlay networks reuse measurements collected
  by production CDNs?
• Significantly reduce the amount of measurements
  (a complementary service)
• No new infrastructure need to be deployed
• Inherit the robustness of DNS
• Easy integration with existing systems

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CDN-Driven One-Hop Source Routing
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Results

• Key findings
• DNS redirections sufficiently small
• Strong correlation to network conditions
• 50 of nodes discovered by Akamai outperform
  direct paths
• Global Internet weather-report service for
  little to no cost
• About impact
• Akamai never liked the idea

• A-J. Su, D. Choffnes, A. Kuzmanovic, and F.
  Bustamante Drafting Behind Akamai
  (Travelocity-Based Detouring), in ACM SIGCOMM
  2006.

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Relative Network Positioning via CDN Redirections

• Wide-area distributed network systems can benefit
  from network positioning systems
• P2p data sharing, multi-cast, online games
• Relative network position is sufficient for most
  applications
• Relative order is more important than absolute
  distance

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Closest Node Selection
cos_sim(A,B) lt cos_sim(A,C) gt dA,B gt dA,C
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Rank Comparison
25 CRP Top1 closely matches Meridian
20 CRP Top5 outperforms Meridian
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Latency Analysis
80 of CRP Top 5 Error lt 50ms
50 of CRP Top 5 Error lt 25ms
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Clustering
No common replica server between 2 clusters
Node D, E, F redirect to common replica X
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Central Leader Election
Node B has the largest sum of cosine similarity
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Todays Talk

• TCP congestion control
• Reusing CDNs measurements
• Net Neutrality

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Net Neutrality

• Pro net neutrality
• www.savetheinternet.com
• http//www.youtube.com/watch?vv4cYuinTGWA
• Anti net neutrality
• http//www.handsoff.org/blog/

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What is this all about?
Google, Skype Microsoft, Yahoo, etc.
ATT
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Net Neutrality Reality

• ISPs deny service to VoIP flows
• All networks with sufficient marketing power
  apply similar methods
• The problem is moving deeper into the Internet
  core
• The same is happening to p2p, gaming, and
  streaming services
• Not just about discrimination
• Entire policies may be tuned in a biased way

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Networking Research

• Give peace a chance!
• How can ISPs cooperate
• for their mutual benefits?
• How can endpoints optimize
• their local behavior while maximizing network
  performance?
• How can we provide incentives for cooperation in
  other networking domains?
• But what are we going to do if there will be no
  peace soon?

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Our Approach

• Internet Audit
• A distributed system to enable
• network accountability
• What happened, where did it happen, and who is
  responsible?
• Challenges
• Non-repudiatiable identification of
  discriminating network elements
• Detect unfair service favoring, e.g., content
  provider/ISP alliances
• Explore a range of threat models
• from open DoS attacks to using network policies
  in destructive ways

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Preliminary Results

• Problem
• Detect precise locations where queuing happens
• A key building block in detecting discriminating
  jitter-boxes
• Useful to know in general
• Overlay design (route around such spots)
• Advanced congestion control
• Fault diagnosis

S
D
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Coordinated Probing
Probe
S
D
f probe
b probe
s probe
d probe
,
,
,
4-p probing a symmetric path scenario
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Coordinated Probing
Probe
?f
?d
S
D
?s
?b
?fs
?fd
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Methodology Highlights

• Coordinated probing
• Send 4, 3, or 2 packets from two endpoints
• Quality of Measurability (QoM)
• Able to deterministically detect its own
  inaccuracy
• Self-adaptivity
• Switch among different probing schemes based on
  QoM and path properties

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Evaluation
After adding two more forward bottlenecks
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Results

• Edge vs. core
• Edge more frequently congested than the core 4.5
  times on average
• Intra-AS vs. Inter-AS
• Edge Intra-AS gt Inter-AS
• Core Intra-AS lt Inter-AS
• Time domain
• Edges congestion events clustered in time
• Core congestion events dispersed in time
• Links vs. Paths
• Links 12 congested, 3 considerably
• Paths 20 considerably congested

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Multiple Congested Points

• Probability to observe multiple congested points
  on an end-to-end path
• Grows as a power function of interval length
• Decays exponentially with the number of congested
  points

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Summary

• Congestion control
• Reusing CDNs redirections
• Net neutrality and congestion measurements
  (Ericsson, Cisco)
• Other projects
• Online traffic classification and profiling
  (Narus)
• Monitoring p2p misconfigurations

• http//networks.cs.northwestern.edu