1. Generic and Automatic Address Configuration for Data Center Networks
1Kai Chen, 2Chuanxiong Guo, 2Haitao Wu, 3Jing Yuan, 4Zhenqian Feng, 1Yan Chen, 5Songwu Lu, 6Wenfei Wu
1Northwestern University, 2Micrsoft Research Asia, 3Tsinghua, 4NUDT, 5UCLA, 6BUAA
SIGCOMM 2010, New Delhi, India

2. Motivation Address autoconfiguration is desirable in networked systems
Manual configuration is error-prone
50%-80% network outages are due to manual configuration
DHCP for layer-2 Ethernet autoconfiguration
Address autoconfiguration in data centers (DC) has become a problem
Applications need locality information for computation
New DC designs encode topology information for routing
DHCP is not enough - no such locality/topology information

3. Research Problem
Given a new/generic DC, how to autoconfigure the addresses for all the devices in the network?
DAC: data center address autoconfiguration

4. Outline Motivation Research Problem DAC Implementation and Experiments
Simulations
Conclusion

5. DAC Input Blueprint Graph (Gb) Physical Topology Graph (Gp)
A DC graph with logical IDs
Logical ID can be any format
Available earlier and can be automatically generated
Physical Topology Graph (Gp)
A DC graph with device IDs
Device ID can be MAC address
Not available until the DC is built and topology is collected
00:19:B9:FA:88:E2

6. DAC System Framework Malfunction Detection Device-to-logical
Physical Topology
Collection
Device-to-logical
ID Mapping
Logical ID
Dissemination

7. Two Main Challenges Challenge 1: Device-to-logical ID Mapping
Assign a logical ID to a device, preserving the topological relationship between devices
Challenge 2: Malfunction Detection
Detect the malfunctioning devices if the physical topology is not the same as blueprint (NP-complete and even APX-hard)

8. Malfunction Detection
Roadmap
Malfunction Detection
Physical Topology
Collection
Device-to-logical
ID Mapping
Logical ID
Dissemination

9. Device-to-logical ID Mapping
How to preserve the topological relationship?
Abstract DAC mapping into the Graph Isomorphism (GI) problem
The GI problem is hard: complexity (P or NPC) is unknown
Introduce O2: a one-to-one mapping for DAC
O2 Base Algorithm and O2 Optimization Algorithm
Adopt and improve techniques from graph theory

10. O2 Base Algorithm Gb: {l1 l2 l3 l4 l5 l6 l7 l8}
Gp: {d1 d2 d3 d4 d5 d6 d7 d8}
Decomposition
Gb: {l1} {l2 l3 l4 l5 l6 l7 l8}
Gp: {d1} {d2 d3 d4 d5 d6 d7 d8}
Refinement
Gb: {l1} {l5} {l2 l3 l4 l6 l7 l8}
Gp: {d1} {d2 d3 d5 d7} {d4 d6 d8}

11. O2 Base Algorithm Gb: {l1 l2 l3 l4 l5 l6 l7 l8}
Gp: {d1 d2 d3 d4 d5 d6 d7 d8}
Decomposition
Gb: {l5} {l1 l2 l3 l4 l6 l7 l8}
Gp: {d1} {d2 d3 d4 d5 d6 d7 d8}
Refinement
Gb: {l5} {l1 l2 l7 l8} {l3 l4 l6 }
Gp: {d1} {d2 d3 d5 d7} {d4 d6 d8}
Refinement
Gb: {l5} {l1 l2 l7 l8} {l6} {l3 l4}
Gp: {d1} {d2 d3 d5 d7} {d6} {d4 d8}

12. O2 Base Algorithm Refinement Gb: {l5} {l6} {l1 l2} {l7 l8} {l3 l4}
Gp: {d1} {d6} {d2 d7} {d3 d5} {d4 d8}
Decomposition
Gb: {l5} {l6} {l1} {l2} {l7 l8} {l3 l4}
Gp: {d1} {d6} {d2} {d7} {d3 d5} {d4 d8}
Decomposition & Refinement
Gb: {l5} {l6} {l1} {l2} {l7} {l8} {l3} {l4}
Gp: {d1} {d6} {d2} {d7} {d3} {d5} {d4} {d8}

13. O2 Base Algorithm O2 base algorithm is very slow for 3 problems:
P1: Iterative splitting in Refinement:
it tries to use each cell to split every other cell iteratively
Gp: π1 π2 π3 …… πn-1 πn
P2: Iterative mapping in Decomposition:
when the current mapping is failed, it iteratively selects the next node as a candidate for mapping
P3: Random selection of mapping candidate: no explicit hint for how to select a candidate for mapping

14. O2 Optimization Algorithm
R1: A cell cannot split another cell that is disjoint with itself.
R2: If u in Gb cannot be mapped to v in Gp, then all nodes in the same orbit with u cannot be mapped to v either.
Heuristics based on DC topology features
Sparse => Selective Splitting (for Problem 1)
Symmetric => Candidate Filtering via Orbit (for Problem 2)
Asymmetric => Candidate Selection via SPLD (Shortest Path Length Distribution) (for Problem3)
We propose the last one and adopt the first two from graph theory
R3: Two nodes u, v in Gb, Gp cannot be mapped to each other if have different SPLDs.

15. Speed of O2 Mapping
8.9 seconds
12.4 hours
8.9 seconds

16. Malfunction Detection
Roadmap
Malfunction Detection
Physical Topology
Collection
Device-to-logical
ID Mapping
Logical ID
Dissemination

17. Malfunction Detection
Types of Malfunctions
Node failure, Link failure, Miswiring
Effects of Malfunctions
O2 cannot find device-to-logical
ID mapping
Our Goal
Detect malfunctioning devices
Problem Complexity
An ideal solution
Find Maximum Common Subgraph (MCS) between Gb and Gp say Gmcs
Remove Gmcs from Gp => the rest are malfunctions
MCS is NP-complete and even APX-hard

18. Practical Solution Isomorphic Isomorphic Observations Our Idea1
Isomorphic 1
Observations
Most node/link failures, miswirings cause node degree change
Special, rare miswirings happen without degree change
Our Idea
Degree change case: exploit the degree regularity in DC
Devices in DC have regular degrees (common sense)
No degree change case: probe sub-graphs derived from anchor points, and correlate the miswired devices using majority voting
Select anchor point pairs from 2 graphs
probe sub-graphs iteratively, stop when k-hop subgraphs are isomorphic but (k+1)-hop are not, increase the counters for k- and (k+1)- hop nodes
Output node counter list: high counter => high possible to be miswired 2 2
Isomorphic … … k k
Non-Isomorphic
k+1
k+1

19. Simulations on Miswiring Detection
Over data centers with tens of thousands of devices
with 1.5% nodes as anchor points to identify all hardest-to-detect miswirings
1.5%

20. Malfunction Detection
Roadmap
Malfunction Detection
Physical Topology
Collection
Device-to-logical
ID Mapping
Logical ID
Dissemination

21. Basic DAC Protocols CBP: Communication Channel Building Protocol
Top-Down, from root to leaves
PCP: Physical Topology Collection Protocol
Bottom-Up, from leaves to root
LDP: Logical ID Dissemination Protocol
DAC manager:
handle all the intelligences
can be any server in the network

22. Implementation and Experiments
Over a BCube(8,1) network with 64 servers
Communication Channel Building (CCB)
Transition time
Physical Topology Collection (TC)
Device-to-logical ID Mapping
Logical IDs Dissemination (LD)
The total time used: 275 milliseconds

23. 46 seconds for the DCell(6, 3) with 3.8+ million devices
Simulations
Over large-scale data centers (in milliseconds)
46 seconds for the DCell(6, 3) with 3.8+ million devices

24. Summary
DAC: address autoconfiguration for generic data center networks, especially when the address is topology-aware
Graph isomorphism for address configuration
275ms for a 64-sever BCube, and 46s for a DCell with 3.8+ million devices
Anchor point probing for malfunction detection
with 1.5% nodes as anchor points to identify all hardest-to-detect miswirings
DAC is a small step towards the more ambitious goal of automanagement of the whole data centers

25. Q & A?
Thanks!