Zhiqiang Shi

Token-based congestion control: Achieving fair resource allocations in P2P networks

Fair Queueing designed to achieve fair bandwidth allocations like CSFQ and Stochastic Fair BLUE, have many desirable properties for congestion control in Internet. However, such mechanisms usually supervise the bandwidth consumption of per-flow, and are good for nothing while P2P flows dominate the traffic of Internet. In this paper, we propose a Token-Based Congestion Control, which limits the access token resource consumed by every subscriber, and provides substantial fairness in P2P networks. In this congestion control system, there are three important devices: core routers, edge routers, terminals. Core routers measure congestion level, and convey it to terminals along with dataflows. Terminals label the Token- Level on sent packets according to the Congestion-Index in the transport path, and regulate the average speed of output tokens, which are the multiplication of the packet size and the Token-Level. Edge routers police the input token rate of every terminal. We present simulations and analyses on the performance of this approach at last.

MERPL: A more memory-efficient storing mode in RPL

The IPv6 Routing Protocol for Low-power and Lossy Networks (RPL) allows a node to operate in storing or non-storing mode. However, as the network size increases, non-storing RPL will introduce lots of communication overhead, while storing RPL will consume lots of memory. In this paper, we improve the storing mode in RPL by reducing the memory consumption. Our performance studies show that our scheme effectively reduces communication overhead compared with the pure non-storing mode. In addition, it makes sure that the number of routing table entry stored in a node does not exceed a pre-specified factor N. When a node stores N routing table entries, it still has enough memory to run the node program and store the collected sensor data. Even when the size of network is large, nodes near the root can still provide adequate space to store the routing table entries using our scheme, but in pure storing mode they may not.

The physical topology discovery for switched Ethernet based on connections reasoning technique

Accurate and up-to-date knowledge of topology serves as the base of a number of network management functions, such as performance monitoring and evaluation, fault detection and location, resource allocation and etc. Firstly the main achievements in topology discovery for LAN are introduced and the defects of those methods are pointed out in this paper. Then the basic theories for connections reasoning technique (CRT) based on the predication logic are proposed. This technique translates the topology discovery into a math problem of logic reasoning, so that topology of LAN can be studied by mathematic tools. A new algorithm for topology discovery based on this mechanism is proposed in this paper. Compared with current discovery algorithms, this method excels in: 1) making use of AFT more effectively in topology discovery, so the whole topology can be build up by just a part of AFTs; and 2) naturally resolving the problem of topology discovery for multiple subnet switched domain.

Congestion control with the fixed cost at the domain border

CSFQ is designed as an open loop controller to provide fair best effort service, which supervises the bandwidth consumption of pre-flow and has become helpless after P2P flows dominate the traffic of the Internet. Token- Based Congestion Control (TBCC) is based on a closed loop congestion control principle, which restricts the token resource consumed by an end-user and provides fair services with O(1) complexity. As Self-Verifying CSFQ, it is heavy load to police inter-domain traffic for lack of trust. In this paper, Token- Limited Congestion Control (TLCC) is presented, which appends inter-domain congestion control to TBCC. TLCC provides the fixed cost to the inter-domain congestion charging with O(1) complexity. By simulations, it is demonstrated that TLCC can provide stable and fair bandwidth allocation across the domain border.

A Privacy-Preserving Fuzzy Localization Scheme with CSI Fingerprint

CSI fingerprint localization is an advanced and promising technique for indoor localization, which identifies the users location by mapping his measured CSI against the servers CSI fingerprint database. This approach is highlighted due to its high granularity for location distinction and strong robustness to noise disturbances, but it also causes potential privacy leakage for the three participants in localization process: the user, the server, and the AP. Currently, there has been little research done on this issue, and the existing work often ignores the privacy concern on the AP. To fill the gap, this paper develops a privacypreserving fuzzy localization scheme with CSI fingerprint. On one hand, it leverages the property of CSI training to guarantee the randomness and independence of the users measurement in each time of localization, and uses homomorphic encryption to achieve the data transmission and measurement comparison in cipher. These operations enable our scheme to preserve the location privacy of the user and APs as well as the data privacy of the server. On the other hand, the adoption of CSI fingerprint and fuzzy logic enhances the localization accuracy greatly. Through simulation experiments performed on CRAWDAD database, the efficiency of our proposed scheme is validated.

A Token Based Method for Congestion and Packet Loss Control

Presently the Internet accommodates simultaneous audio, video, and data traffic. This requires the Internet to guarantee the packet loss thus to control network congestion. A series of protocols have been introduced to supplement the insufficient TCP mechanism for controlling the congestion. As such the Core-Stateless Fair Queuing (CSFQ), Token-Based Congestion Control (TBCC) were designed as open or closed-loop controller respectively to provide the fair best effort service for supervising the per-flow bandwidth consumption. In this paper, Stable Token-Limited Congestion Control (STLCC) is introduced as a new protocol which appends inter-domain congestion control to TBCC and makes the congestion control system stable. STLCC produces a congestion index, pushes the packet loss to the network edge and improves the network performance. Finally, the simple version of STLCC is introduced. It is deployable in the Internet without any IP protocols modifications and preserves also the packet datagram.

Transmission scheduling for multi-homed transport protocols with network failure tolerance

In heterogeneous network environments, the network connections of a multi-homed device may have significant bandwidth differential. For a multi-homed transmission protocol designed for network failure tolerance, such as SCTP, path selection algorithms for data transmission drastically affect performance. This article studies the effect of path bandwidth differential on the performance of retransmission strategies in multi-homing environments. It identifies that fast retransmission on an alternate path may cause receive buffer blocking when path bandwidth differential is significant and the receive buffer is limited. A theoretical model is proposed for selecting retransmission path during the fast retransmission phase, based on receive buffer and path conditions. From these observations and analysis results, this article proposes that path selection strategies for transmitting new data and retransmitted data should be decoupled. A new path selection scheme is proposed and evaluated through SCTP simulations.

An Open Conformance Test System towards the Standardization of Wireless Sensor Networks

The conformance testing on the wireless sensor networks (WSNs) is fundamental for the functional large-scale deployment and interconnection with the global Internet. The WSN protocols based on the Internet Protocol version 6 (IPv6) are the major trends of the future applications, which include IEEE 802.15.4, 6LoWPAN, and RPL. These protocols are not only diverse for various applications, but also volatile in the future. Moreover, sensor nodes are resource constrained, application related and lack the standardized test interface. Hence the corresponding conformance testing is seriously insufficient and needs urgently research. In this paper, the IPv6-based WSN protocols are analyzed and the conformance testing techniques and methods for IPv6-based WSNs are investigated towards the standardization of WSNs. A novel conformance test system for IPv6-based WSNs is designed and implemented, which is open, flexible, full featured, and practical. The conformance test system is suitable for the protocol evolution and the various hardware interfaces for the sensor nodes. The related outcomes will promote the standardization and commercialization of WSNs.

Packet Loss Control Using Tokens at the Network Edge

Presently, the Internet accommodates simultaneous audio, video, and data traffic. This requires the Internet to guarantee the packet loss which at its turn depends very much on congestion control. A series of protocols have been introduced to supplement the insufficient TCP mechanism controlling the network congestion. CSFQ was designed as an open-loop controller to provide the fair best effort service for supervising the per-flow bandwidth consumption and has become helpless when the P2P flows started to dominate the traffic of the Internet. Token-Based Congestion Control (TBCC) is based on a closed-loop congestion control principle, which restricts token resources consumed by an end-user and provides the fair best effort service with O(1) complexity. As Self-Verifying CSFQ and Re-feedback, it experiences a heavy load by policing inter-domain traffic for lack of trust. In this paper, Stable Token-Limited Congestion Control (STLCC) is introduced as new protocols which appends inter-domain congestion control to TBCC and make the congestion control system to be stable. STLCC is able to shape output and input traffic at the inter-domain link with O(1) complexity. STLCC produces a congestion index, pushes the packet loss to the network edge and improves the network performance. Finally, the simple version of STLCC is introduced. This version is deployable in the Internet without any IP protocols modifications and preserves also the packet datagram.

Smoothing the XCP sender

It is known fact that modern IP networks are adopting eXplicit Control Protocol (XCP) as the de-facto standard. In the implementation of XCP, the XCP sender outputs packets in bursts such that all the packets inside the congestion window are outputted without any interval between them. The burst not only increases the queuing delay, but also makes XCP with heterogeneous delays to be unstable. In the present paper, a Smooth XCP (SXCP) is proposed, where the interval of outputting packets at the XCP sender is no less than the round trip time divided by the congestion window. The simulations show that SXCP not only decreases the queuing delay, but also improves utilization and stability.