1. Improving the Freshness of NDN Forwarding States
Jianxun Cao*, Dan Pei*, Zhelun Wu*, Xiaoping Zhang*,
Beichuan Zhang†, Lan Wang‡, Youjian Zhao*
*Tsinghua University †University of Arizona ‡University of Memphis
*Tsinghua National Laboratory for Information Science and Technology (TNList)
logo
2018/11/15

2. Outline Overview of NDN routing and forwarding
Limitations and Problem Description
New Probing Strategy
Simulation Results
Conclusion
Outline
2018/11/15

3. Outline Overview of NDN routing and forwarding
Limitations and Problem Description
New Probing Strategy
Simulation Results
Conclusion
2018/11/15

4. Overview of NDN routing and forwarding
Compared with IP
NDN Routing：OSPFN, NLSR…
NDN Forwarding[1]：NACK, Interface Ranking… IP
NDN
Routing Plane
Smart
Static/ Smart
Forwarding Plane
Dumb
Stateful
In IP Internet, routers update the forwarding table (FIB) and routers forward the data according to the FIB strictly. Thus, IP Internet provides smart routing and dumb forwarding
In NDN, routing is similar to it in IP. OSPFN, NLSR…
In forwarding plane, the mechanisms, such as NACK and interface ranking, are proposed to make the network resilient and efficient. In this paper, we focus on Interface Ranking.
[1] C. Yi, A. Afanasyev, I. Moiseenko, L. Wang, B. Zhang, and L. Zhang, “A case for stateful forwarding plane,” Computer Communications, vol. 36, no. 7, April 2013.
2018/11/15

5. Overview of NDN routing and forwarding Interface Ranking
Periodical measurement
Interface Ranking
For a given prefix, to maintain the ranking metrics for interface ranking, the router periodically sends a copy of the Interest packet to all the interfaces to measure various metrics (such as SRTT) used in forwarding policies.
There are two parts in Interface ranking.
First, Periodical measurement, which means that, For a given prefix, to maintain the ranking metrics for interface ranking, the router periodically sends a copy of the Interest packet to all the interfaces to measure various metrics (such as SRTT) used in forwarding policies.
2018/11/15

6. Overview of NDN routing and forwarding Interface Ranking
Periodical measurement
Interface Ranking
Color classification is used to record an outgoing interface’s working status for each prefix.
Second, Color Classification, which is used to record an outgoing interface’s working status for each prefix.
Color
Classification
2018/11/15

7. Overview of NDN routing and forwarding Interface Ranking
YELLOW
Data Recieved
GREEN
Initialize
Periodical measurement
Data Timeout
Failure
Failure
Recovery
Interface Ranking
Color classification is used to record an outgoing interface’s working status for each prefix.
RED
There are three colors for different status.
GREEN: The interface can bring data back.
YELLOW: It’s not sure whether the interface could bring data back.
RED: The interface is down.
The changing rules among different colors are shown in the animation.
//more details
Color
Classification
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8. Overview of NDN routing and forwarding Interface Ranking
Ranking Rules
Periodical measurement
200
Interface Ranking
180
250
Based on Periodical measurement and Color classification, the ranking rules are shown as follow. (Animation)
Green is preferred than Yellow.
According to the measured metrics.
Color
Classification
330
150
2018/11/15

9. Overview of NDN routing and forwarding Interface Ranking
150
Forwarding based on
Ranking Rules
Periodical measurement
200
Interface Ranking
150
180
250
Based on the ranking rules, forwarding rules (Animation)
Choose the best Green interface.
If fails to fetch data, turn it to yellow and choose the next best Green interface.
Color
Classification
330
2018/11/15

10. Overview of NDN routing and forwarding Interface Ranking
Forwarding based on
Ranking Rules
Periodical measurement
150
Interface Ranking
180
Triggerd Probing
200
180
250
3. If there is no Green interface to choose, then start the Triggered probing component and probe to the Yellow interface one by one. Once any Yellow return data successfully, then choose this Yellow interface as the forwarding interface and turn it to Green.
Color
Classification
330
2018/11/15

11. Outline Overview of NDN routing and forwarding
Limitations and Problem Description
New Probing Strategy
Simulation Results
Conclusion
2018/11/15

12. Limitations of Interface Ranking
Periodical measurement
With the in-network cache, the uncertainty of location where Interest packets are satisfied leads to the frequent changing of network metrics.
Problem: SRTT slow-convergence.
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13. Limitations of Interface Ranking: SRTT slow-convergence
152ms
SRTT can reflect the real RTT: convergence.
SRTT can smooth the network jitter. Thus, SRTT can reflect the real RTT, which is called convergence.
Sampled RTT
152ms
179ms
151ms
153ms
149ms
150ms
SRTT
152ms
156.7ms
151.8ms
152.0ms
151.4ms
155.8ms
154.8ms
153.8ms
2018/11/15

14. Limitations of Interface Ranking SRTT slow-convergence
152ms
SRTT slow-convergence
50ms
When RTT varies greatly, SRTT calculated from the Sampled RTT cannot reflect the real RTT, which leads to SRTT slow-convergence.
Sampled RTT
152ms
53ms
151ms
153ms
51ms
50ms
SRTT
152ms
132.1ms
151.8ms
152.0ms
115.9ms
103ms
92.3ms
2018/11/15

15. Limitations of Interface Ranking
Periodical measurement
With the in-network cache, the uncertainty of location where Interest packets are satisfied leads to the frequent changing of network metrics.
Problem: SRTT slow-convergence.
Color Classification and Triggered Probing
The change of interface color is done at the packet-level feedback for each prefix.
When faced with burst congestions, the colors might frequently change between GREEN and YELLOW back and forth.
Problem: Probing Oscillation.
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16. Limitations of Interface Ranking Probing Oscillation
𝑅 1
𝑅 2
𝑅 3
𝑅 4
𝑅 2
𝑅 1
𝑅 3
𝑅 4
𝑅 1
𝑅 2
𝑅 3
𝑅 4
𝑅 2
𝑅 1
𝑅 1
𝑅 2
Loss Rate: 1%
𝐶𝑜𝑛
𝑅 𝑐
𝑅 1
𝑅 2
𝑅 3
𝑅 4
𝑅 𝑝
𝑅 5
𝑅 6
𝑃𝑟𝑜
For the simple topo, the interface ranking in Rc is R2->R3->R1->R4.
When the upstream link Rp-Pro results in loss rate 1%, Rc will meet the failure of fetching data from R2, thus change R2 to Yellow and choose R3, and update the interface ranking.
While, R3 will meet the failure of fetching data, thus Rc will re-choose R2.
Oscillation between R2 and R3, cause Probing Oscillation.
2018/11/15

17. Limitations of Interface Ranking
Periodical measurement
With the in-network cache, the uncertainty of location where Interest packets are satisfied leads to the frequent changing of network metrics.
Problem: SRTT slow-convergence.
Color Classification and Triggered Probing
The change of interface color is done at the packet-level feedback for each prefix.
When faced with burst congestions, the colors might frequently change between GREEN and YELLOW back and forth.
Problem: Probing Oscillation.
SRTT Slow-convergence
Out-of-date States
Throughput of Forwarding
Probing Oscillation
2018/11/15

18. Outline Overview of NDN routing and forwarding
Limitations and Problem Description
New Probing Strategy
Simulation Results
Conclusion
2018/11/15

19. New Probing Strategy Problem Approach Core idea New Probing Strategy
SRTT Slow-convergence
Adaptive SRTT Update
Dynamical Sample Frequency
Probing Oscillation
Proactive Probing
Path Backup
Probability-based Probing
Problem
Approach
Core idea
We come up with the new Probing strategy to solve the two problems.
For SRTT slow-convergence
For Probing Oscillation
2018/11/15

20. New Probing Strategy Adaptive SRTT Update
How frequently to probe the Probing packets to each GREEN interface ?
∆𝑛: the number of Interest packets between two consecutive probing.
𝜂: Normalized distance between RTT and SRTT.
𝜂= 𝑅𝑇𝑇−𝑆𝑅𝑇𝑇 𝑅𝑇𝑇+𝑆𝑅𝑇𝑇
∆𝑛 𝑖 = max( ∆𝑛 𝑚𝑖𝑛 , 1− 𝜂 𝑖 ∆𝑛 𝑖−1 ), 𝜂≥ 𝜂 𝑡ℎ𝑟𝑒𝑠ℎ𝑜𝑙𝑑 min( ∆𝑛 𝑚𝑎𝑥 , 1+𝛽 ∆𝑛 𝑖−1 ),𝜂< 𝜂 𝑡ℎ𝑟𝑒𝑠ℎ𝑜𝑙𝑑
152ms
50ms
Dynamical Sample Frequency
Back to the example.
Based on the Adaptive SRTT Update, when detect the great variation of RTT, there will be more samples, thus, the SRTT calculated is convergence.
Sampled RTT
152ms
53ms
151ms
153ms
51ms
50ms
132.1ms 62ms ms ms
SRTT
152ms
132.1ms
151.8ms
152.0ms
115.9ms
103ms
92.3ms
2018/11/15

21. New Probing Strategy Adaptive SRTT Update
How frequently to probe the Probing packets to each GREEN interface ?
∆𝑛: the number of Interest packets between two consecutive probing.
𝜂: Normalized distance between RTT and SRTT.
𝜂= 𝑅𝑇𝑇−𝑆𝑅𝑇𝑇 𝑅𝑇𝑇+𝑆𝑅𝑇𝑇
∆𝑛 𝑖 = max( ∆𝑛 𝑚𝑖𝑛 , 1− 𝜂 𝑖 ∆𝑛 𝑖−1 ), 𝜂≥ 𝜂 𝑡ℎ𝑟𝑒𝑠ℎ𝑜𝑙𝑑 min( ∆𝑛 𝑚𝑎𝑥 , 1+𝛽 ∆𝑛 𝑖−1 ),𝜂< 𝜂 𝑡ℎ𝑟𝑒𝑠ℎ𝑜𝑙𝑑
Dynamical Sample Frequency
We design the Adaptive SRTT Updating algorithm. We use ∆𝑛 to denote the number of Interest packets between twice probing. And we define the Changing Factor of RTT as α which is calculated as follow, which describe the normalized distance between RTT and SRTT.
According to this Changing Factor, we define the stretch ∆𝑛 as this formula, which means the dynamical sample frequency.
2018/11/15

22. New Probing Strategy Proactive Probing
Path Backup
Set more than one GREEN interface to ensure some backup paths.
Probability-based Probing
The smaller the COST is, the higher the probability of the optimal choice will be.
Probing Probability Function (PPF)
𝑝 𝑖 = 1/𝐶𝑂𝑆𝑇 𝑖 1/𝐶𝑂𝑆𝑇
𝑅 1
𝑅 2
𝑅 3
𝑅 4
𝑅 1
𝑅 3
Loss Rate: 1%
𝐶𝑜𝑛
𝑅 𝑐
𝑅 1
𝑅 2
𝑅 3
𝑅 4
𝑅 𝑝
𝑅 5
𝑅 6
𝑃𝑟𝑜
35%
30%
25%
10%
There are different probabilities of different interfaces of Rc.
When Rp-Pro results in loss rate, Rc will choose outgoing interface with probability. There are 25% to choose R1. Thus, on average, Rc will jump probing oscillation within 4 oscillations.
Probing Probability (合成一页）
𝑝 𝑖 = 1/𝐶𝑂𝑆𝑇 𝑖 1/𝐶𝑂𝑆𝑇
*Path backup is explained in the paper instead of slides.
2018/11/15

23. Outline Overview of NDN routing and forwarding
Limitations and Problem Description
New Probing Strategy
Simulation Results
Conclusion
2018/11/15

24. Simulations Sub-Topology of TUNET
We use NDNSim 2.0 to evaluate our design.
A sub-topology of Tsinghua Network Topology and a larger topology
𝑟 denotes the loss rate of 𝑅 𝑝 , ranged from 1% to 10%
𝑝 denotes the loss rate of 𝑅 𝑐
𝑡 𝑑𝑎𝑡𝑎 =100𝑚𝑠
𝑡 𝑜𝑢𝑡 =120𝑚𝑠
𝑘=100𝑚𝑠
Loss rate 变化范围
Larger topology
2018/11/15

25. Simulations Sub-Topology of TUNET
SRTT Slow-convergence
First, for SRTT slow-convergence.
When RTT changes little, with our probing strategy, the probing overhead is reduced by 46.7%.
When RTT changes greatly, with our probing strategy, the time of SRTT convergence is reduced by 37.9.
Time of SRTT convergence is reduced by~37.9%
Probing overhead is reduced by~46.7%
2018/11/15

26. Simulations Sub-Topology of TUNET
Probing Oscillation (𝑝=10%)
*More simulation details and results are shown in paper.
Second, for Probing Oscillation.
When Probing oscillation occurs, with our probing strategy, probing oscillation is finished at about 4s, while NCC 17s, Best-route cannot finish.
And with our probing strategy, overhead is reduced at least 94.1%, compared to NCC and Best-route.
Loss rate ~10% 其它loss rate结果类似
The time of solving Probing Oscillation is reduced by~88.2%
The probing overhead is reduced by~94.1%
2018/11/15

27. Outline Overview of NDN routing and forwarding
Limitations and Problem Description
New Probing Strategy
Simulation Results
Conclusion
2018/11/15

28. Conclusion Limitations of the current Adaptive Forwarding Plane in NDN
SRTT Slow-convergence
Probing Oscillation
Objective: Improve the Freshness of NDN Forwarding States
Propose a new probing strategy to achieve up-to-date forwarding states to solve the above two problems
Dynamical Sample Frequency
Path Backup
Probability-based Probing
Our results show that SRTT convergence time is reduced by 37.9% and the loss rate is reduced by 75% to 94.75% with little extra overhead.
2018/11/15

29. Improving the Freshness of NDN Forwarding States
Thank you!
Improving the Freshness of NDN Forwarding States
Jianxun Cao*, Dan Pei*, Zhelun Wu*, Xiaoping Zhang*,
Beichuan Zhang†, Lan Wang‡, Youjian Zhao*
*Tsinghua University †University of Arizona ‡University of Memphis
*Tsinghua National Laboratory for Information Science and Technology (TNList)
2018/11/15