TCP is known to perform poorly in cellular network environments. Yet, most mobile applications are explicitly built on the conventional TCP stack or implicitly leverage TCP tunnels to various cellular middleboxes, including performance-enhancing proxies, application-specific edge proxies, VPN proxies and NAT boxes.  Despite significant advances in the design of new congestion control (CC) protocols for cellular networks, deploying these protocols without bypassing the underlying TCP tunnels has remained a challenging proposition.
    This paper proposes the design of a new \emph{Application Layer Congestion Control (ALCC)} framework that allows any new CC protocol to be implemented easily at the application layer, within or above an application-layer protocol that sits atop a legacy TCP stack. It drives it to deliver approximately the same as the native performance. The ALCC socket sits on top of a traditional TCP socket. Still, it can leverage the large congestion windows opened by TCP connections to carefully execute an application-level CC within the window bounds of the underlying TCP connection. This paper demonstrates how ALCC can be applied to three well-known cellular CC protocols: Verus, Copa, and Sprout. For these protocols, ALCC can achieve comparable throughput and delay characteristics (within 3-10\%) as the native protocols at the application layer across different networks and traffic conditions. ALCC allows a server-side implementation of these protocols with no client modifications and with zero bytes overhead. The ALCC framework can be easily integrated with off-the-shelf applications such as file transfers and video streaming.

ALCC: Migrating Congestion Control to the Application Layer in Cellular Networks

  This paper presents Mir-BFT, a robust Byzantine fault-tolerant (BFT) total order broadcast protocol
  aimed at maximizing throughput on wide-area networks (WANs),
  targeting deployments in decentralized networks,
  such as permissioned and Proof-of-Stake permissionless blockchain systems.

  Mir-BFT is the first BFT protocol that allows multiple leaders to propose request batches independently
  (i.e., parallel leaders), while effectively precluding performance degradation due to request duplication
  by rotating the assignment of a partitioned request hash space to leaders.
  As this mechanism removes the single-leader bandwidth bottleneck
  and exposes a computation bottleneck related to authenticating clients even on a WAN,
  our protocol further boosts throughput using a client signature verification sharding optimization.
  Our evaluation shows that Mir-BFT outperforms state-of-the-art
  single-leader protocols
  and orders more than 60000 signed Bitcoin-sized (500-byte) transactions per second
  on a widely distributed setup (100 nodes, 1 Gbps WAN) with typical latencies of few seconds.
  Moreover, our evaluation exposes the impact of duplicate requests on parallel leader protocols which Mir-BFT eliminates.
  We also evaluate Mir-BFT under different crash and Byzantine faults, demonstrating its performance robustness.

  Mir-BFT relies on classical BFT protocol constructs, which simplifies reasoning about its correctness.
  Specifically, Mir-BFT is a generalization of the celebrated and scrutinized PBFT protocol.
  In a nutshell, Mir-BFT follows PBFT ``safety-wise'', with changes needed to accommodate novel features restricted to PBFT liveness.

JSYS 2021 May Papers Submissions

ALCC: Migrating Congestion Control to the Application Layer in Cellular Networks

Solution: Mir-BFT: Scalable and Robust BFT for Decentralized Networks

Test Submission