The stability of Congestion Control Algorithms (CCAs) is critical to maintaining consistent network performance, particularly as modern networks increasingly rely on Active Queue Management (AQM) and packet scheduling techniques. Although prior work has studied CCA behavior under steadystate conditions, less attention has been paid to transient states; moments of rapid change that significantly affect responsiveness, latency, and fairness. In this paper, we investigate the stability of CCAs under AQM-controlled bottlenecks, focusing on realworld scenarios with default system configurations. We evaluate the widely deployed CUBIC CCA with an emphasis on two algorithms: Flow Queue Controlled Delay (FQ-CoDel), which uses deterministic dropping, and Flow Queue Proportional Integral controller Enhanced (FQ-PIE), which uses probabilistic dropping. These differing designs reveal nuanced interactions during load shifts, highlighting trade-offs in link throughput and queue delay. The goal is to deepen the understanding of CCAAQM dynamics under practical conditions. Our results show that FQ-PIE adapts faster in transient conditions, while both FQ-CoDel and FQ-PIE provide stronger long-term stability.

This paper demonstrates a new dimension in packet programming and processing by leveraging New IP technology since applications are sensitive to different types of network constraints. For instance, emerging industry operations, manufacturing, and autonomics are limited by the stochastic quality of services and inflexible address structures. Instead, they require efficiency and deterministic networks. In this paper, we propose a programmable data plane for New IP packet processing and show how network headers could evolve in the future. We demonstrate the implementation of New IP stack to encompass three goals: (1) address customization: applications and routers can forward packets between hosts with different address formats. (2) design an end-to-end model to meet service delivery guarantees: routers implement various in-network New IP contracts as described by the applications. (3) Rapid experimentation of the New IP components. With New IP, developers can describe packet processing functionalities without depending on the specifics of the underlying hardware. Our implementation of New IP stack uses the existing toolsets and capabilities of the Linux platform, such as eXpress Data Path (XDP) and Traffic Control (TC) subsystem. It consists of an end-to-end solution with a new network stack on the host side and a corresponding packet processing and forwarding engine on the network. It is validated using Network Stack Tester (NeST), a lightweight tool built on Linux network namespaces.

The design of a transport protocol for high precision industrial networks is a complex problem since the industrial applications are resource-critical, time-critical, session-less, and safety-critical. These requirements make existing end-to-end transport mechanisms unsuitable for use in the industry verticals that require control-systems type communication. This paper proposes a lightweight, connection-less, and reliable protocol called TinTin. It utilizes the in-network capabilities to compensate for end device constraints. The mechanisms adopted in TinTin aim to reduce the communication overheads associated with well-known connection-oriented protocols. This paper discusses the design considerations of TinTin in detail and presents an early stage proof-of-concept implementation of TinTin with New IP.

BBR, a congestion control algorithm proposed by Google, regulates the source sending rate by deriving an estimate of the bottleneck’s available bandwidth and RTT of the path. The initial version of BBR, called BBRvl, was found to be unfair, getting higher than the fair share of bandwidth when co-existing on bottleneck links with other congestion control algorithms. It also does not perform as well with networks having routers with shallow buffers. To overcome these concerns, a newer version, called BBRv2, has been proposed. Our goal in this paper is to understand the differences between the two versions and examine the primary reasons behind the improvement in performance of BBRv2. We present an experimental evaluation of BBRvl and BBRv2, evaluating their fairness across connections using the same protocol (intra-protocol fairness) and using different protocols (inter-protocol fairness) as well as delay and link utilization. From experiments with shallow and deep buffers, BBRv2 is most effective when it uses Explicit Congestion Notification (ECN), but fairness issues continue to exist in BBRv2 when ECN is disabled. A concern for BBRv2 is that it is somewhat complex to deploy in Wide Area Networks (WAN) because of the dependency with the DCTCP-style reduction of the congestion window, which is primarily usable in low-feedback delay Data Center Networks.

The problem of bufferbloat arises due to the presence of large unmanaged buffers and leads to high queuing delays and significant degradation in the performance of time-sensitive and interactive Internet applications. Recently, a new smart queue management system called Common Applications Kept Enhanced (CAKE) has been introduced in Linux 4.19 to tackle the problem of bufferbloat in home Internet gateways. One of the integral parts of CAKE system is COBALT (CoDel and BLUE Alternate), a queue discipline which is a combination of Controlled Delay (CoDel) and BLUE algorithms. Although CAKE is a part of the Linux kernel, a detailed discussion on the design of COBALT is missing. In this paper, we discuss the design of COBALT and compare its performance with CoDel. Additionally, we propose a simulation model for COBALT in ns-3 and test its correctness by comparing the results obtained from it to those obtained from the Linux model. Our evaluation shows that COBALT offers substantial benefits in terms of curtailing queue delays when unresponsive flows exist.

Bufferbloat problem arises due to buffering of large amounts of data in queues, owing to the large size of these queues. Bufferbloat being a relatively new phenomenon meant that earlier queue management algorithms did not specifically address this problem. Despite this issue, there is merit in analysing and evaluating old queue management algorithms which have helped alleviate the undesirable performance issues that arose due to persistently full buffers. One of the earliest and most significantly studied Active Queue Management (AQM) algorithms is Random Early Drop (RED). RED helps to keep the average size of the queues low and allow occasional bursts of packets through the queue. Once the number of packets queued crosses a minimum threshold, incoming packets are dropped with a random probability. However, the resulting average queue length is quite sensitive to the level of congestion and the RED parameter settings. Adaptive RED (ARED) solves most of the issues faced by RED with minimal changes and leaves its basic idea intact. The ARED algorithm regularly adapts the value of the maximum dropping probability and ensures that the queue length stays within the targeted range. Despite its ability to resolve the inherent problems in RED, ARED went largely unnoticed for several years, until the issue of Bufferbloat arose. Although ARED predates Bufferbloat, its fundamental design makes it an effective solution to handle Bufferbloat. This discovery led to the implementation of ARED in Linux and in network simulators like ns-3. Besides Linux, FreeBSD is one of the most popular open source operating systems. Although RED is supported in FreeBSD, ARED is not. Since ARED is one of the viable solutions to tackle Bufferbloat, this paper discusses the design and implementation of ARED in FreeBSD. We also detail the challenges faced during the implementation, and validate through real testbed experiments that our implementation in FreeBSD exhibits ARED's key characteristics.