Entry Date:
July 17, 2014

Fastpass: A Centralized "Zero-Queue" Datacenter Network

Principal Investigator Devavrat Shah

Project Website http://fastpass.mit.edu/

astpass is a datacenter network framework that aims for high utilization with zero queueing. It provides low median and tail latencies for packets, high data rates between machines, and flexible network resource allocation policies. The key idea in Fastpass is fine-grained control over packet transmission times and network paths.

A logically centralized arbiter controls and orchestrates all network transfers.

Zero network queues -- Because the arbiter has knowledge of all current and scheduled transfers, it can choose slots and paths that yield the "zero-queue" property: the arbiter arranges for each packet to arrive at a switch on the path just as the next link to the destination becomes available.

Linux endpoint support -- A loadable kernel module implements a Linux qdisc (queueing discipline) that intercepts outgoing packets just before they are passed to the NIC. The qdisc sends requests to the arbiter using specialized control sockets also in the kernel module, implemented as a Fastpass transport protocol.

Arbiter -- The arbiter is implemented on the DPDK framework. The arbiter processes each request, performing two functions:

(*) Timeslot allocation: Assign the requester a set of timeslots in which to transmit this data. The granularity of a timeslot is the time taken to transmit a single MTU-sized packet over the fastest link connecting an endpoint to the network. The arbiter keeps track of the source-destination pairs assigned each timeslot.
(*) Path selection. The arbiter also chooses a path through the network for each packet and communicates this information to the requesting source.