Opportunistic Packet Forwarding for Proactive Transport in Datacenters

Proactive transport protocols in datacenters are designed to avoid congestion by regulating flow sending rates via credit allocation. However, when a new flow starts, it takes one Round-Trip Time (RTT) before credits can be assigned to the new flow. To avoid stalling flows, modern proactive protocols allow a new flow to blast a burst of unscheduled packets at line rate during the pre-credit phase. However, sending too many unscheduled packets could cause temporary traffic spikes that lead to queue build-ups, packet losses, and retransmissions, which are particularly detrimental to short flows. In this thesis, we present the design and evaluation of Opportunistic Packet Forwarding (OPF), a building block for proactive transports designed to minimize pre-credit packet losses with negligible overhead on network switches. The key idea in OPF is to allow pre-credit packets to opportunistically take detours to avoid congested links on the shortest paths, effectively trading off packet losses for slightly increased delay. We have implemented OPF using P4 switches and integrated our implementation with Homa and NDP. Our results on a range of traffic loads show significant improvement in the 99-th percentile of flow completion time for short flows, namely, up to 60% reduction in NDP and 50% in Homa.

Name thesis:degree_name

Master of Science (MSc)

Discipline thesis:degree_discipline

Computer Science

Grantor dc:publisher.institution

Graduate Studies

Year dc:date.issued

2024

Author dc:creator

• Shani, Amir

Advisor dc:contributor.advisor

• Ghaderi, Majid

Committee members dc:contributor.committeemember

• Krishnamurthy, Diwakar
• Ye, Qiang

• Software-Defined Networking
• Programmable Switches
• Datacenter Networks

Statement dc:rights

• University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.

Language dc:language.iso

en

DOI

https://doi.org/10.11575/PRISM/46805

OAI identifier oai:identifier

oai:ucalgary.scholaris.ca:1880/119209