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Bifrost: Alibaba's Next-Generation VPC Network with High-Performance Multipath Reliable Transport#

NSDI '26 digest Program Core pick 4–6 May 2026

Abstract Paper Slides Recording

Zihao Fan (SJTU and Alibaba Cloud), Xing Li (Zhejiang University and Alibaba Cloud), Ye Yang, et al. (Alibaba Cloud), Rong Wen (Fudan and Alibaba Cloud), Shunmin Zhu (Alibaba Cloud), et al.

Play the recording: Bifrost: Alibaba's Next-Generation VPC Network with High-Performance Multipath Reliable Transport

  • Why: This is the logical endpoint of the "TCP in the guest can't survive cloud-network instability" argument: Alibaba moved reliable, multipath transport into the VPC overlay infrastructure itself, tail-latency problem included. An operational-systems paper with 26x-scale production evidence.
  • What: Next-gen VPC networking delivering reliable transport as an infrastructure service: up to 307x tail-latency reduction for Redis and 66x for Nginx, millisecond-level failure recovery, and O(100k) concurrent connections per SmartNIC.
  • How: RTT-aware multipath packet spraying across the underlay (bypasses failures, spreads elephant flows), in-place reordering in the guest for in-order delivery, delayed bitmap ACKs for end-to-end reliability, and reliability-state management engineered for SmartNIC deployment at scale.
  • Where applicable: Alibaba Cloud production (operational systems paper); requires SmartNIC-capable tunnel endpoints, so it presumes a cloud provider's level of control over the hypervisor/SmartNIC layer. The architecture — reliable multipath overlay as a tenant-transparent service — is the transferable idea.