PIAS: Practical Information-Agnostic Flow Scheduling for Data Center Networks

Paper Title: PIAS: Practical Information-Agnostic Flow Scheduling for Data Center Networks

Authors: Wei Bai, Li Chen, Kai Chen (Hong Kong University of Science and Technology), Dongsu Han (KAIST), Chen Tian (HUST), Weicheng Sun (Hong Kong University of Science and Technology and SJTU)

Presenter: Li Chen

Paper Link: http://conferences.sigcomm.org/hotnets/2014/papers/hotnets-XIII-final91.pdf

      Existing data center network flow scheduling schemes minimize flow completion time FCT, however, they assume a prior knowledge of flow size information to approximate ideal preemptive shortest job first and require customized switch hardware. PIAS minimizes FCT without requiring prior knowledge of flow size by leveraging multilevel feedback queue (MLFQ) that exists in many commodity switches. The goal is to have an information agnostic approach that minimizes FCT and being readily deplorable. Initially, a flow gets the highest priority and is demoted as it transfer more bytes. This is achieved by tagging packets and keeping per flow state and using switches queues.

      There is a challenge on how to choose a demotion threshold. This is addressed by modeling it as a static FCT minimization problem. The second challenge exists if there is a mismatch between traffic distribution and is mitigated by using Explicit Congestion Control ECN. 

     At the end, the system is practical and effective, information antagonistic and achieve FCT minimization, and readily deploy-able.

Questions:

 Q(  Brighten Godfrey UIUC)  How you handle the situation when you have different hardware that has different number of queues ? do you use the minimum ?

A : Yes, currently we use the minimum.

Q(  Brighten Godfrey UIUC) Do you think putting storage at switches in DataCenter and use them in the way proposed in "Revisiting Resource Pooling: The Case for In-Network Resource Sharing" paper would yield a better flow completion time ?
A: Yes, it is possible