探讨cdma1x分组网的链路负荷分担机制

一、A10报文封装原理及对报文收发顺序要求分析 在cdma1x数据业务中,PCF和PDSN的A10消息采用GRE封装. 理想情况下,PDSN和PCF都顺序接收到GRE报文.在3GPP2A.S0012-0 V2.0中说明:当接收到一个乱序的GRE报文时,应该根据RFC2890处理.在RFC2890中规定:"在当拆封者接收到一个无效序列号的数据报文时,它应该悄悄地丢弃该数据报文.当收到的数据报文的序列号小于或等于上一次成功拆封的数据报文的序列号时,收到的报文被视为序列号无效."     

基于DynamipsGUI的网络路由优化实验设计

策略路由是网络优化的常用方法。利用DynamipsGUI搭建网络环境,配置路由策略,模拟了报文大小分别为60、500和1800三种数据报文从路由器转发时,路由器根据路由策略将数据报文从不同路径转发的过程,实验结果与设计完全一致。     

IPv6高速网络环境下数据分组捕获技术的研究

针对传统的数据分组捕获技术在IPv6高速网络环境下表现出的严重分组丢失问题,采用"零拷贝"的思想设计并实现了一个适用于IPv6高速网络环境的数据分组捕获平台(HSPCP)。以Intel82541GI吉比特网卡驱动程序e1000为基础,对网络数据分组的接收流程进行改进,在内核中注册一个杂项设备,实现了其mmap和ioctl方法,并编写了与改进后零拷贝驱动相对应的用户空间报文捕获程序。通过实验将HSPCP与Libpcap进行了分组捕获效率对比测试,实验证明HSPCP相对于传统的Libpcap分组捕获方式在性能上有较明显的提高。     

基于PF_DMA的易移植零拷贝捕包方法研究

零拷贝技术是提高通用计算机报文采集性能的重要技术手段,可以增强网络数据包捕获能力,并降低系统的资源消耗。提出了一种基于PF_DMA的零拷贝报文捕获改进方法,对相关Linux内核函数进行扩展和替换,在不改变原有内核和网卡驱动代码的基础上,实现报文的零拷贝,实验结果表明,该方法保持了PF_DMA捕包的高效率,同时具有更好的通用性和可移植性。     

LTE网络测试仪——高速IP数据采集卡的设计与实现

针对LTE网络高速、海量数据的采集需求,以及现有LTE网络的IP数据采集卡的不足的问题,设计了一种多端口的千兆线速IP数据采集卡。介绍了模块化的FPGA硬件设计,给出了数据采集卡WDM驱动程序框架,提出了一种基于Windows操作系统的数据零拷贝实现方法,有效减少短包中断压力。测试应用表明,该IP数据采集卡具有较好的性能,可以广泛应用于分布式LTE网络的数据采集。     

一种VMF报文编解码工具设计

战术数据报文作为战场信息的载体,是战术指挥信息系统进行数据交互的核心。战术数据报文的模拟生成可用于训练支持、联调联试、软件测试和故障诊断等多个方面。面前我军广泛采用VMF(可变消息格式)报文。理论上,只要依据相应的VMF报文标准组装出符合要求格式的报文数据,即可实现VMF报文的模拟。但当前的模拟生成方法生成报文效率低,对原系统数据库依赖大,在应用过程中无法满足实际需要。文章提出了一种VMF报文编解码工具设计方案。     

动态层次式接入控制方法的研究

针对分布式虚拟环境中,协作对象对数据报文的传送有着不同服务要求,本文提出了一种基于协作层次的动态层次式接入控制方法.该方法将协作层次和带宽预分配结合,协作用户在加入系统时,系统将用户订购的服务质量和系统即时网络情况进行比较,从而允许或挂起.实验结果表明这种动态层次式接入控制方法能减少无效报文的转发,缓解路由器上的报文处理负荷,并且能提高系统总的网络服务效率.     

基于IPv6传感器网络的ESP压缩机制

本文通过对ESP(Encrypted Security Payloadheader)框架下的数据报文的封装及ESP头部冗余信息进行分析,提出了一种基于IPv6传感器网络的ESP头部压缩编码机制的方案,本方案在保证数据安全传输的同时,降低ESP头部增加的报文负载,减少报文传输时间,也降低了能量开销。     

用DPDK和VPP优化5G网络用户面数据报文转发

5G作为各行业数字化转型的关键基础技术，用户面需要提供高性能的数据转发能力。根据5G用户面数据转发的特点，通过分析DPDK技术以及VPP技术的原理，将两种技术相结合，实现了5G用户面网元对数据报文高速转发，并在商用网络上得到使用和验证。这种方法可以扩展到需要高速处理数据报文的其他网络设备中。     

基于网络处理器IXP2400的组播包高速转发技术

传统的IP报文的组播技术,由于在处理过程中需要把整个报文的内容报文复制多份,因此处理器需要对缓存报文的外部存储空间进行多次I/O操作,这严重制约了当前处理器,特别是网络处理器的高速报文处理能力,转发效率不高.为此,提出了一种新的技术--"零拷贝"转发技术.该技术只修改报文头,报文体不复制,减少了大量的I/O操作,提高了转发效率.     

Data aggregation in sensor networks using learning automata

One way to reduce energy consumption in wireless sensor networks is to reduce the number of packets being transmitted in the network. As sensor networks are usually deployed with a number of redundant nodes (to overcome the problem of node failures which is common in such networks), many nodes may have almost the same information which can be aggregated in intermediate nodes, and hence reduce the number of transmitted packets. Aggregation ratio is maximized if data packets of all nodes having almost the same information are aggregated together. For this to occur, each node should forward its packets along a path on which maximum number of nodes with almost the same information as the information of the sending node exist. In many real scenarios, such a path has not been remained the same for the overall network lifetime and is changed from time to time. These changes may result from changes occurred in the environment in which the sensor network resides and usually cannot be predicted beforehand. In this paper, a learning automata-based data aggregation method in sensor networks when the environment’s changes cannot be predicted beforehand will be proposed. In the proposed method, each node in the network is equipped with a learning automaton. These learning automata in the network collectively learn the path of aggregation with maximum aggregation ratio for each node for transmitting its packets toward the sink. To evaluate the performance of the proposed method computer simulations have been conducted and the results are compared with the results of three existing methods. The results have shown that the proposed method outperforms all these methods, especially when the environment is highly dynamic.     

Performance analysis of a random packet selection policy formulticast switching

This paper studies a random packet selection policy for multicast switching. An input packet generates a fixed number of primary copies plus a random number of secondary copies. Assuming a constant number of contending packets during a slot, the system is modeled as a discrete time birth process. A difference equation describing the dynamics of this process is derived, the solution of which gives a closed form expression for the distribution of the number of packets chosen. Then this result is extended to the steady state distribution through a Markov chain analysis. It is shown that the old packets have larger fanout than the fresh packets and the copy distribution of the mixed packets is determined. The packet and copy throughput taking into account the old packets have been obtained. We determined the mean packet delay as well as an upperbound for packet loss probabilities for finite buffer sizes. The asymptotic distribution of the number of packets is also given for large switch sizes under saturation by applying results from the renewal theory. Finally, simulations are done to determine the performance of the switch under mixed (unicast plus multicast) traffic     

The design and analysis of an ATM multicast switch with adaptivetraffic controller

The paper describes several improvements to a nonblocking copy network proposed previously for multicast packet switching. The improvements provide a complete solution to some system problems inherent in multicasting. The input fairness problem caused by overflow is solved by a cyclic running adder network (CRAN), which can calculate running sums of copy requests starting from any input port. The starting point can change adaptively in every time slot based on the overflow condition of the previous time slot. The CRAN also serves as a multicast traffic controller to regulate the overall copy requests. The throughput of a multicast switch can be improved substantially if partial service of copy request is implemented when overflow occurs. Call-splitting can also be implemented by the CRAN in a straightforward manner. Nonuniform distribution of replicated packets at outputs of the copy network may affect the performance of the following routing network. This output fairness problem due to underflow is solved by cyclically shifting the copy packets in every time slot. An approximate queueing model is developed to analyze the performance of this improved copy network. It shows that if the loading on each output of the copy network is maintained below 80%, the average packet delay in an input buffer would be less than two time slots     

Real-Time Traffic Scheduling and Routing in Packet-Switched Networks Using a Least-Laxity-First Strategy

In this paper, we address the problem of transmission scheduling and buffer management at a switch in a high-speed packet-switched network. Future computer networks are expected to carry bursty real-time multimedia traffic with specific time-delay requirements. We propose a technique to schedule competing packets at a switch in a packet-switched network with two objectives—(i) maximizing the number of packets that would reach their destination before their deadline has been reached (ii) minimizing the number of packets dropped in transit in the network. The method is broadly based on the popular least-laxity heuristic in real-time process scheduling and is combined with buffer management at the switch.     

A MAC-Layer Retransmission Technique for Collided Packets in Wireless Sensor Network

Efficient transmission of data for reducing collisions in sensor network is the most significant way of enhancing the network performance and achieving lifetime maximization. In this paper, we have proposed a novel data retransmission strategy for unsuccessfully transmitted packets in case of uniform and variable data rate applications. For applications with uniform data rate, a fixed number of retransmission attempts are assigned to each packet and the retransmission probability gradually reduces according to 1-Truncated Geometric Distribution after every collision. For variable data rate applications with normalized data rate $N$ , our strategy reduces the priority of the collided packets using $N$ -Truncated Geometric Distribution. After fixed unsuccessful attempts with first priority, the packets are retransmitted with reduced priority so as to avoid engaging of network resources for long duration. Moreover, our both strategies aim to improve the usual retransmission mechanism of Standard ZigBee/IEEE 802.15.4 by replacing it with our innovated scheme. The simulation shows that our proposed retransmission technique outperforms the Standard ZigBee with GTS in terms of average energy consumption, network throughput, average number of retransmission attempts and network performance.     

CPCA: An efficient wireless routing algorithm in WiNoC for cross path congestion awareness

Wireless network-on-chip (WiNoC) is a new paradigm to mitigate the long-distance transmission latency for conventional wired network-on-chip. The wireless routers in WiNoC have to handle a large number of packets which could cause data congestion, thus reducing the network performance. In this paper, we propose a novel wireless routing algorithm, called CPCA, which exploits the cross path congestion information as hints to route the packets. Under CPCA, the whole network is partitioned into sub-networks. In each subnet, the congestion information of the wireless router is propagated along the cross path. As a result, the routers in the same dimension can get the congestion degree of wireless router within the subnet. Based on the congestion information, CPCA can compute the suitable path for packets routing, which can prominently avoid the congestion aggravation in the wireless router. Experimental results show that our proposed method can effectively improve performance in terms of packets transmission latency and network throughput.     

基于Interlaken协议的高速数据流接口设计与性能分析

目前,高速网络处理系统的板级互连带宽达到了40G比特速率级,这对网络处理系统的处理速度和吞吐量提出了极大的挑战。为解决核心路由器40 Gb/sPOS线路接口板中器件间的高速数据交互难题,采用Interlaken协议对高速数据流接口设计方法进行了研究,利用高端FPGA的高速通道和IP核设计技术,完成了链路层处理芯片与转发...     

面向应急响应的高速网络流量采集设计与实现

网络安全应急响应在网络分析和追踪时需要应急采集,即捕获特定IP、端口、协议的原始分组。基于高速网络分组捕获工具PF_RING DNA,利用多核多线程并发采集与规则匹配的网络分组,并分配共享缓冲区提高分组的磁盘存储性能,同时通过对采集规则设置不同的状态,实现动态添加采集规则和人为干预采集过程。实验结果表明,在双万兆网卡的环境下,应急采集系统可以捕获并处理19.98 bit/s(3.5 Mpacket/s)的网络流量,最大应急采集速率为1 297 Mbit/s（204.9 kpacket/s）。     

网络延迟主动测量结果的被动测量校准方法

网络延迟是提供QoS保证、监控和优化网络性能的重要指标.测量网络延迟主要采用主动测量和被动测量这两种测量方法,但是这两种方法都存在一定的缺陷.以主动测量获得的延迟作为用户数据包延迟的一个估计量,用被动测量设备检测到的用户数据包信息对主动测量数据进行校准,可以实现一种有效的网络延迟测量方法.这种方法具有与协议无关、对网络流量影响小、测量方法简单、可测量单个用户流等优点.我们综合考虑了探测包间用户数据包数量和相邻探测包延迟的变化,比以往的算法更准确地反映了网络的实际状况,特别是在网络拥塞甚至存在丢包的情况下,误差更小,测量结果更精确.     

Detection method of LDoS attack based on ACK serial number step-length

Low-rate denial of service (LDoS) attack is a potential security threat to big data centers and cloud computing platforms because of its strong concealment.Based on the analysis of network traffic during the LDoS attack,statistical analysis was given of ACK packets returned by the data receiver to the sender,and result reveals the sequence number step had the characteristics of volatility during the LDoS attack.The permutation entropy method was adopted to extract the characteristics of volatility.Hence,an LDoS attack detection method based on ACK serial number step permutation entropy was proposed.The serial number was sampled and the step length was calculated through collecting the ACK packets that received at the end of sender.Then,the permutation entropy algorithm with strong time-sensitive was used to detect the mutation step time,and achieve the goal of detecting LDoS attack.A test-bed was designed and built in the actual network environment for the purpose of verifying the proposed approach performance.Experimental results show that the proposed approach has better detection performance and has achieved better detection effect.