1. B 黃冠智

2. Outline OLDI(Online Data Intensive) architecture DCTCP(Datacenter TCP)
D3(Deadline Driven Delivery) Protocol
D2TCP(Deadline-Aware Datacenter TCP)
Congestion avoidance algorithm
Simulation
Q&A

3. OLDI application Tree-based structure, divide-and-conquer algo
Soft-real-time constraints(300 ms latency)

4. OLDI application Problems： Sols:
Maintain deadline will affect respond quality
Fan-in burst cause congestive packet drops and TCP retransmits
Sols:
Over-provision the network link bandwidths(high cost)
increase the network’s time budget(degrades respond quality)

5. OLDI application
Datacenter network also carry background flow which push control information and data to the node
Long-lived flows cause switch buffer to high utilization
Package drop feedback
Fair-share protocol

6. OLDI(Online Data Intensive) architecture DCTCP(Datacenter TCP)
D3(Deadline Driven Delivery) Protocol
D2TCP(Deadline-Aware Datacenter TCP)
Congestion avoidance algorithm
Simulation
Q&A

7. DCTCP AQM(Active Queue Management) scheme
Using CE(Congestion Encountered) bit to control transmission rate
ECN does not have suffice to solve fan-in burst problem
Aggregates one-bit ECN feedback and multiple RTTs to form multiple-bit metric

8. OLDI(Online Data Intensive) architecture DCTCP(Datacenter TCP)
D3(Deadline Driven Delivery) Protocol
D2TCP(Deadline-Aware Datacenter TCP)
Congestion avoidance algorithm
Simulation
Q&A

9. D3 Protocol
The bandwidth request for the next RTT is piggybacked on the data packets of the current RTT
Switch grant as much of the request as possible
Far-deadline requests arriving slightly ahead of near-deadline requests

10. D3 Protocol
Challenges
Requires custom switch ASICs (high cost low vol)
Cannot coexist with legacy TCP

11. The DC Network Protocol Should
Meet OLDI deadlines, especially in fan-in-burst-induced congestion
Achieve high bandwidth for background flows
Work with existing switch hardware
Be able to coexist with legacy TCP

12. OLDI(Online Data Intensive) architecture DCTCP(Datacenter TCP)
D3(Deadline Driven Delivery) Protocol
D2TCP(Deadline-Aware Datacenter TCP)
Congestion avoidance algorithm
Simulation
Q&A

13. D2TCP
Meet OLDI deadlines, especially in fan-in-burst-induced congestion
Deadline-aware
Achieve high bandwidth for background flows
Work with existing switch hardware
Be able to coexist with legacy TCP

14. Congestion avoidance algorithm
𝑓 is the fraction of packets that were marked with CE bits in the most recent window
𝑔 is the weight given to new samples
d is the deadline imminence factor
P is the penalty function applied to the window size
W is congestion window

15. Congestion avoidance algorithm
𝛼 ≤ 1 and therefore, 𝑝≤ 1
d > 1 (near-deadline
flows incur lower penalty)
d < 1 (far-deadline
flows incur higher penalty)
d = 1 behavior matches DCTCP

16. Determining d
𝑇𝑐 is the time needed for a flow to complete transmitting
D is the time remaining until its deadline expires

17. OLDI(Online Data Intensive) architecture DCTCP(Datacenter TCP)
D3(Deadline Driven Delivery) Protocol
D2TCP(Deadline-Aware Datacenter TCP)
Congestion avoidance algorithm
Simulation
Q&A

18. Simulation

20. TCP DCTCP D3 D2TCP

21. Background flows discuss

22. Missed deadline under tight deadline