VL2: A Scalable and Flexible Data Center Network Albert Greenberg, James R. Hamilton, Navendu Jain, SrikanthKandula, Changhoon Kim, ParantapLahiri, David A. Maltz, Parveen Patel, SudiptaSengupta Microsoft Research SIGCOMM Comput. Commum. Rev., Vol 39, No. 4. (2009) , pp.51-62
Outline • Motivation • Conventional Data Center Architecture • Virtual Layer 2 (VL2) • Design • Advantage • Evaluation • Conclusion
Motivation • The network is a bottleneck to Data Center computation. • Today’s data center network has several issues: • Tree architecture • Congestion and computation hot spot • Traffic Independence • IP configuration Complexity • Migration • Tradeoff • Reliability and utilization
Design of VL2 • Location-specific IP address(LAs)(public) • For all switches and interfaces or external server • Application-specific IP addresses (AAs)(private) • For application servers • VL2 Directory System • Stores the mapping of AAs to LAs • Access control
Scale-out Topologies Aggr : Int= n:m ToR : Aggr = 1:2
Scale-out TopologiesBenefit • Risk balancing • The failure of a Int. reduces the bisection bandwidth by only 1/m • Routing is extremely simple on this topology • Random path up and random path down.
Example Randomly select Int. by ECMP Create by VL2 Agent
VL2 agent • VL2 agent’s work flow • Intercepts the ARP request for the destination AA • Converts ① to an unicast query to the VL2 directory system • Intercepts packets from the host • Encapsulates the packet with the LA address from ②. • Caches the mapping from AA to LA addresses
Advantage of VL2 • Load Balance • Randomizing to Cope with Volatility: • Building on proven networking technology: • link-state routing, • equal-cost multi-path(ECMP) forwarding, • IP anycasting, • IP multicasting • Simple Migration • Static AAs • Only need to update AAs & LAs mapping • Eliminating the ARP and DHCP scaling bottlenecks
Evaluation: testbed • 80 servers • 5 for directory system • Intermediate switches*3 • 24 10Gbps Ethernet ports(3 for Aggr) • Aggregation switches*3 • 24 10Gbps Ethernet ports(3 for Aggr, 3 for ToR) • ToR*4 • 24 1Gbps ports
Experiment objective • We test the following three objectives • Uniform high capacity • Fairness • Performance isolation
VL2 Provides Uniform High Capacity • We create an all-to-all data shuffle traffic matrix involving 75 servers. • Each of 75 servers deliver 500MB data other 74 servers - a shuffle of 2.7 TB from memory to memory. • During the run, the sustained utilization of the core links in the Clos network is about 86%. (more than 10x what the network in our current data centers can achieve with the same investment)
VL2 Provides Fairness • In the experiment before, we observe the 3 aggregate switch • We use Jain’s fairness index [15 R.Jain. The Art of Computer Systems Performance analysis, techniques for Experimental Design, Measurement, Simulation, and Modeling. John Wiley & Sons, INC, 1991.
Conclusion • VL2 provides • The simpler abstraction that all servers assigned to them are plugged into a single layer 2 switch • Hotspot free performance • A simple design that can be realized today • High utilization • Achieves high TCP fairness.
Q&A I HAVE QUESTIONS!!