CN101877670B - Optical fiber network media time-division multiple access method and its application traffic control method - Google Patents
Optical fiber network media time-division multiple access method and its application traffic control method Download PDFInfo
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Abstract
Description
技术领域 technical field
本发明是有关于一种光纤网络媒体分时多重访问方法及其应用的讯务控制方式,其效用在令光纤网络节点的媒体频宽访问权,能被有效且合理的在节点间分配,以改善光纤网络的节点频宽访问权不公平分配的问题,促使分时多重访问光纤网络得以适合作建构局域网、城际网或公用网络的子网络等之用,以降低网络建设成本并提升宽频使用率。The present invention relates to a time-division multiple access method for optical fiber network media and its application traffic control method. Improve the problem of unfair distribution of node bandwidth access rights in optical fiber networks, and promote time-division multiple access optical fiber networks to be suitable for constructing local area networks, intercity networks or sub-networks of public networks, etc., to reduce network construction costs and improve broadband usage Rate.
背景技术 Background technique
根据Hartley-Shannon定理(通道/信息容量定理),传输媒体的通道容量受其所使用传输媒体的频宽及信号信噪比所限制。拥有高频宽及高信号信噪比的传输媒体,自然具有较大的通道容量。比较绞线及光纤两种传输媒体,由于光纤的信噪非常低,频宽也较绞线高出很多,致使其通道容量远较绞线为高;因此,近年来通信网络的传输建设,逐步地以光纤取代绞线。According to the Hartley-Shannon theorem (channel/information capacity theorem), the channel capacity of a transmission medium is limited by the bandwidth and signal-to-noise ratio of the transmission medium used. A transmission medium with high bandwidth and high signal-to-noise ratio naturally has a large channel capacity. Comparing the two transmission media of stranded wire and optical fiber, because the signal-to-noise of optical fiber is very low, the bandwidth is much higher than that of stranded wire, resulting in a much higher channel capacity than stranded wire; therefore, in recent years, the transmission construction of communication networks has gradually Fiber optics instead of twisted wires.
媒体共享的网络自然地具有高的频宽使用率,且由于它们的网络拓扑非常简单,因此很容易达成降低建设成本的目的。各种访问控制步骤如载波感测多重访问(Carrier sense multiple access,CSMA)、载波感测多重访问/碰撞检测(Carrier sense multiple access with collision detection,CSMA/CD)、令牌环(Token ring)、令牌总线(Token bus)及分时多重访问(Time-division multipleaccess,TDMA)等等,被应用在媒体共享的网络,来作为网络节点的访问控制。Networks for media sharing naturally have high bandwidth utilization, and because their network topology is very simple, it is easy to achieve the goal of reducing construction costs. Various access control steps such as carrier sense multiple access (CSMA), carrier sense multiple access/collision detection (Carrier sense multiple access with collision detection, CSMA/CD), token ring (Token ring), Token bus and Time-division multiple access (TDMA), etc., are applied in the media sharing network as the access control of network nodes.
在计算机通信上,目前大部分的区域网络多使用Carrier Sense MultipleAccess/Collision Detection(CSMA/CD)的多重访问协定。此协定的实体层为绞线。在今日网际网络的各种服务蓬勃发展的态势下,扩大通道容量的需求压力,必然与日俱增,实体层使用绞线的区域网络,受传输距离及频宽的限制,其提高通道容量的发展不及光纤容易,且会因通道容量的提高,导致传输距离缩短,通信品质劣化的现象。故未来区域网络实体层在通道容量必须加速扩大的强烈需求下,转成以光纤取代绞线应为必然的趋势。In terms of computer communication, most of the local area networks currently use the multiple access protocol of Carrier Sense Multiple Access/Collision Detection (CSMA/CD). The physical layer of this protocol is the strand. With the vigorous development of various services on the Internet today, the demand for expanding the channel capacity is bound to increase. The regional network using twisted wires at the physical layer is limited by the transmission distance and bandwidth. The development of channel capacity is not as good as that of optical fibers. Easy, and the increase in channel capacity will lead to shortened transmission distances and degraded communication quality. Therefore, under the strong demand of accelerating the expansion of channel capacity at the physical layer of the regional network in the future, it should be an inevitable trend to replace twisted wires with optical fibers.
由于数字化的发展及服务整合的需求下,DQDB网络(Distributed-queueDual-bus,分布式队列双总线,IEEE 802.6)的协定在1990年被提出,作为达成服务整合目的的一种LAN(Local Area Networks)或MAN(Metropolitan AreaNetworks)的标准。此网络为双总线拓扑并结合分时多重访问(Time-divisionMultiple Access,TDMA)技术的应用,提供整合服务。Due to the development of digitalization and the demand for service integration, the DQDB network (Distributed-queueDual-bus, IEEE 802.6) protocol was proposed in 1990 as a LAN (Local Area Networks) for service integration purposes. ) or MAN (Metropolitan AreaNetworks) standard. This network is a dual-bus topology combined with the application of Time-division Multiple Access (TDMA) technology to provide integrated services.
此网络协定具整合等时性(如语音或多媒体讯务)及非等时性讯务(如数据讯务)的能力。由于传输媒介为光纤,具有低误码率的特性,适合高速通信服务的发展及满足高服务品质的需求。该网络采TDMA的多重访问方式,无封包碰撞问题,具有高频宽使用效率,即使在网络所提供的讯务高于通道容量时,仍可达到接近通道容量的高频宽使用效率,且因于双总线的拓扑,此网络自然地达成全双工的服务需求。This network protocol has the ability to integrate isochronous (such as voice or multimedia traffic) and asynchronous traffic (such as data traffic). Since the transmission medium is optical fiber, it has the characteristics of low bit error rate, which is suitable for the development of high-speed communication services and meets the needs of high service quality. The network adopts the multiple access method of TDMA, which has no packet collision problem and has high bandwidth utilization efficiency. Even when the traffic provided by the network is higher than the channel capacity, it can still achieve high bandwidth utilization efficiency close to the channel capacity, and because of the dual bus topology, this network naturally achieves full-duplex service requirements.
DQDB网络具有如前所述其他诸区域网络或都会网络所没有的使用特质,但因于其对非即时性(非等时性)讯务的媒体访问控制方式(Medium AccessControl,MAC),衍生出网络节点的媒体访问权分配不公平的问题。此节点间访问权不公平的分配问题,使TDMA的光纤网络上,上游节点拥有比下游节点更高的访问权。因此造成同处于此网络下,而相互具独立关系的使用者间的频宽使用权益产生争议。The DQDB network has the use characteristics that other regional networks or metropolitan networks do not have as mentioned above, but because of its Medium Access Control (MAC) for non-real-time (non-isochronous) traffic, it is derived The problem of unfair distribution of media access rights for network nodes. The unfair distribution of access rights between nodes makes the upstream nodes have higher access rights than the downstream nodes on the TDMA optical fiber network. Therefore, there is a dispute over the rights to use bandwidth between users who are under the same network but have independent relationships with each other.
在DQDB的每一网络节点(Nodes)上,当信息(Messages)产生时,会将信息分割成若干小段,并依序将每一小段当成单元(Cells)的酬载,一一存入缓冲器,等待传送。节点内的缓冲器分属分布式队列(Distributed Queues,DQ)及本地队列(Local Queues,LQ)两种。节点内属分布式队列的缓冲器,仅有一单元(53位组)的储存长度,为节点将数据写入总线空讯槽(slot)之前,暂时储存的位置,由DQSM(DQDB State Mechanism)控制其写入时机。本地队列则为单元产生后暂存的位置,最早存入队列的单元,将被移入分布式队列等待传送。一单元由本地队列进入分布式队列,到此单元被写入总线的空讯槽前的此段时间,称为分布式队列的延迟时间(DQ延迟)。一单元自被产生后,到从本地队列进入分布式队列之间的等待时间,称为本地队列的延迟时间(LQ延迟)。一节点的DQ平均延迟及LQ的平均延迟,会因该节点在此网络的位置(离讯槽产生器(Slot Generator)的远近)及其所产生讯务量的多寡,而有所变化。此种单元延迟时间随着节点离讯槽产生器的远近而变化的状况,即为前述的访问不公平现象。On each network node (Nodes) of DQDB, when a message (Messages) is generated, the message will be divided into several small pieces, and each small piece will be sequentially regarded as the payload of the unit (Cells), and stored in the buffer one by one , waiting to be sent. The buffers in the nodes are divided into two types: Distributed Queues (DQ) and Local Queues (LQ). The buffer of the distributed queue in the node has only one unit (53 bytes) of storage length, which is the temporary storage position before the node writes the data into the bus empty slot (slot), controlled by DQSM (DQDB State Mechanism) Its write timing. The local queue is the temporary storage location after the unit is generated, and the unit stored in the queue at the earliest will be moved into the distributed queue to wait for transmission. The time from when a unit enters the distributed queue from the local queue to when the unit is written into the empty slot of the bus is called the delay time of the distributed queue (DQ delay). The waiting time between when a unit is generated and when it enters the distributed queue from the local queue is called the delay time of the local queue (LQ delay). The average DQ delay and LQ average delay of a node will vary due to the location of the node in the network (the distance from the slot generator) and the amount of traffic it generates. The situation that the cell delay time varies with the distance between the node and the slot generator is the aforementioned unfair access phenomenon.
此问题在1990年前后曾引起热烈的讨论,同时很多控制演算方法被提出来改善此不公平访问的问题,这些控制方法依其使用的改进策略,可分成两大类。第一类是讯槽再使用的策略,第二类则是改善分布式队列的访问控制演算法。讯槽再使用策略需将原有的部分被动节点改成主动节点,以抹除已被读写过的讯槽,以增加总线下游节点的可用空讯槽数,通过缩短下游节点的DQ延迟时间。而第二类改善访问控制演算法的主要目的,在于使下游节点能即时的获取空讯槽,同时亦需使上游节点能不受下游节点过多的传送要求的影响,导致讯务阻塞。欲达此目的,则访问控制演算法需在频宽预留及频宽浪费两者间取得平衡。IEEE 802.6的DQDB MAC协定采用Bandwidthbalancing的演算法,以频宽预留的方式来作补偿,以改善下游节点频宽访问不公平性的问题。虽然IEEE 802.6的MAC协定采用Bandwidth balancing的演算法来作预留频宽的补偿,但访问不公平性的问题仍未被彻底解决,无法提供访问权公平合理分配的使用环境,给共用此网络的独立使用者。This problem has been discussed enthusiastically around 1990, and many control algorithms have been proposed to improve the problem of unfair access. These control methods can be divided into two categories according to the improvement strategies they use. The first type is the strategy of slot reuse, and the second type is to improve the access control algorithm of distributed queues. The slot reuse strategy needs to change some of the original passive nodes into active nodes to erase the slots that have been read and written, so as to increase the number of available empty slots for the downstream nodes of the bus, and shorten the DQ delay time of the downstream nodes . The main purpose of the second type of improved access control algorithm is to enable downstream nodes to obtain empty slots in real time, and at the same time, it is necessary to prevent upstream nodes from being affected by excessive transmission requests from downstream nodes, resulting in traffic congestion. To achieve this goal, the access control algorithm needs to strike a balance between bandwidth reservation and bandwidth waste. The DQDB MAC protocol of IEEE 802.6 adopts the algorithm of Bandwidthbalancing, and compensates in the way of bandwidth reservation, so as to improve the problem of unfair bandwidth access of downstream nodes. Although the IEEE 802.6 MAC protocol uses the Bandwidth balancing algorithm to compensate for reserved bandwidth, the problem of unfair access has not been completely resolved, and it cannot provide a fair and reasonable distribution of access rights. independent user.
此访问权的不公平分配,影响DQDB网络各节点的分布式队列的延迟。队列是由多个缓冲器所组成,而所谓“分布式队列”是指一个队列内的单元或封包的缓冲器被分散于各节点,对DQDB网络而言,每一节点拥有一分布式队列的单元缓冲器。各节点应用相同的MAC协定,各自独立地决定储存于其分布式队列缓冲器内的单元内容被写入光纤总线上空讯槽的时机。虽然各节点是各自独立地决定其属于分布式队列的单元缓冲器的写出时间,但所应用的MAC协定必须达成分布式队列First-Come-Fist-Serve(FCFS)的服务要求。网络利用这个特色来决定各节点使用总线传送数据的秩序,也就是说,网络提供一套分布式的控制协定来控制分布式队列,使得较先申请要传送数据的节点,可以较早使用总线上的空讯槽。The unfair distribution of this access right affects the delay of the distributed queue of each node in the DQDB network. The queue is composed of multiple buffers, and the so-called "distributed queue" means that the buffers of the units or packets in a queue are scattered among the nodes. For the DQDB network, each node has a distributed queue unit buffer. Using the same MAC protocol, each node independently determines the timing when the unit content stored in its distributed queue buffer is written into the empty slot on the optical fiber bus. Although each node independently determines the writing time of its cell buffer belonging to the distributed queue, the applied MAC protocol must meet the service requirement of the distributed queue First-Come-Fist-Serve (FCFS). The network uses this feature to determine the order in which nodes use the bus to transmit data. That is to say, the network provides a set of distributed control protocols to control the distributed queue, so that the nodes that apply for data transmission earlier can use the bus earlier. empty slot.
为了解DQDB节点分布式队列延迟的特性,并通过解决访问权不公平分配的问题,有数种方法被用来作DQDB网络的分析,这些方法皆基于Bisdikian所提出近似的单一节点分析模式(an approximate single-node analytical model)。于此模式中,每一节点在有封包要传送时,均通过一个稳态产生函数(thesteady-state generation function)来产生其下游节点送达该节点的“要求传送需求”数。此节点于得到此需求数后,就能很容易地决定节点内即将被传送封包的分布式队列延迟。此种模式的分析结果证明,DQDB网络各节点的分布式队列延迟,会随着节点在网络内位置的不同而产生变化。简言之,既有的分析方法,是考量MAC的操作细节,来进行分布式队列的延迟分析。由于DQDB网络的MAC协定非常复杂,欲将此协定模式化,并通过完成队列延迟分析,是一件相当困难的事。若欲通过此种以MAC协定的操作为基础,来得到精准的DQ延迟分析,更是一件不可能达成的任务。因此,此种分析方法无法对解决访问权不公平分配的问题有所贡献。In order to understand the characteristics of the distributed queue delay of DQDB nodes and solve the problem of unfair distribution of access rights, several methods have been used for the analysis of DQDB networks. These methods are based on the approximate single-node analysis model proposed by Bisdikian (an approximate single-node analytical model). In this mode, each node uses a steady-state generation function (thesteady-state generation function) to generate the number of "transmission requests" sent to the node by its downstream nodes when there are packets to be transmitted. After the node obtains the demand number, it can easily determine the distributed queue delay of the packet to be transmitted in the node. The analysis results of this model prove that the distributed queue delay of each node in the DQDB network will vary with the location of the node in the network. In short, the existing analysis method is to consider the operation details of the MAC to analyze the delay of the distributed queue. Since the MAC protocol of the DQDB network is very complex, it is quite difficult to model this protocol and complete the queue delay analysis. It is an impossible task to obtain accurate DQ delay analysis based on the operation of the MAC protocol. Therefore, this method of analysis cannot contribute to solving the problem of unequal distribution of access rights.
从TDMA网络的角度来看,DQDB网络上的分布式队列延迟等同于TDMA网络上的等待时间。TDMA网络上的等待时间,是指节点内即将被传送的封包,进入队列内衔接总线传输系统的缓冲器后,到该封包被写入总线传输系统空闲讯槽的这段时间。此定义与DQDB网络上分布式队列的延迟是相同的。故DQDB网络上分布式队列的延迟,与TDMA网络上的等待时间,两者具有相同的性质。假如TDMA网络上的等待时间会随着网络拓扑改变,即TDMA网络节点的平均等待时间是节点位置的函数,则光纤的TDMA网络将是与生俱来地伴随着访问权分配不公的问题,两者无法分割。如果以上假设的性质能被证实其实际存在,则要完全地消除DQDB网络上访问权不公平分配的问题,将是一件不可能的事情。相反地,若以上假设的性质,其存在性无法被证实,则在TDMA网络上的等待时间被分析后,DQDB网络上访问权不公平分配的问题,应可得到适当的解决方法。From the perspective of a TDMA network, the distributed queue delay on the DQDB network is equivalent to the waiting time on the TDMA network. The waiting time on the TDMA network refers to the period from when the packet to be transmitted in the node enters the buffer connected to the bus transmission system in the queue to when the packet is written into the idle slot of the bus transmission system. This definition is the same as the latency of distributed queues on the DQDB network. Therefore, the delay of the distributed queue on the DQDB network has the same property as the waiting time on the TDMA network. If the waiting time on the TDMA network will change with the network topology, that is, the average waiting time of the nodes in the TDMA network is a function of the node position, then the optical fiber TDMA network will be inherently accompanied by the problem of unfair distribution of access rights. are indivisible. If the properties of the above assumptions can be confirmed to exist, it will be impossible to completely eliminate the problem of unfair distribution of access rights on the DQDB network. On the contrary, if the nature of the above assumptions and their existence cannot be verified, then after the latency on the TDMA network is analyzed, the problem of unfair distribution of access rights on the DQDB network should be able to obtain an appropriate solution.
对一个稳定的TDMA网络,不论所使用MAC协定为哪一种,网络承担的负载应等于使用者要求传送的负载。因此,TDMA网络上等待时间的分析,可以通过观察TDMA系统上讯槽被使用的状况来完成,而不需考虑MAC协定的控制操作细节。由此种TDMA系统使用状况的观察可知,某一节点上一个封包的等待时间的长短,直接被下一个可被应用的讯槽到达此节点的机率所影响。而这个机率,则可由网络节点的讯务分布及传输媒体的容量来决定。For a stable TDMA network, no matter which MAC protocol is used, the load borne by the network should be equal to the load requested by the user. Therefore, the analysis of the latency on the TDMA network can be done by observing the status of the slots being used on the TDMA system, without considering the details of the control operation of the MAC protocol. From the observation of the usage status of this TDMA system, it can be seen that the waiting time of a packet on a certain node is directly affected by the probability that the next available slot will arrive at this node. And this probability can be determined by the traffic distribution of the network nodes and the capacity of the transmission medium.
分析结果显示,TDMA节点的平均等待时间是该节点讯务量的函数。当TDMA的系统容量非常大时,其节点的平均等待时间与被分析节点的讯务量成反比关系,即节点传送的讯务量愈大,其平均等待时间会愈短。根据此推论,若MAC协定具有讯务控制的能力,节点的平均等待时间将与节点在网络的位置及节点间的距离无关。换言之,若TDMA的光纤网络上,其MAC具讯务控制的操作能力,则访问权不公平分配问题就不会存在。The analysis results show that the average waiting time of a TDMA node is a function of the traffic volume of the node. When the TDMA system capacity is very large, the average waiting time of its nodes is inversely proportional to the traffic volume of the analyzed node, that is, the larger the traffic volume transmitted by a node, the shorter its average waiting time. According to this inference, if the MAC protocol has the ability of traffic control, the average waiting time of nodes will have nothing to do with the position of nodes in the network and the distance between nodes. In other words, if the MAC of the TDMA optical fiber network has the operation capability of traffic control, the problem of unfair allocation of access rights will not exist.
本发明人即是鉴于上述的分析情形,提出光纤TDMA网络的MAC协定,需通过讯务控制的操作,来决定节点的访问控制。换言之,MAC协定通过讯务控制的操作,来决定节点队列内储存的信息,可被传送到总线的时机,以期彻底地解决光纤TDMA网络的节点间访问权不公平分配的问题。In view of the above analysis situation, the present inventor proposes that the MAC protocol of the optical fiber TDMA network needs to determine the access control of nodes through the operation of traffic control. In other words, the MAC protocol determines the timing when the information stored in the node queue can be transmitted to the bus through the operation of traffic control, so as to completely solve the problem of unfair distribution of access rights between nodes in the optical fiber TDMA network.
发明内容 Contents of the invention
本发明的主要目的,是提供一种光纤网络媒体分时多重访问方法及其应用的讯务控制方式,其主要内容是MAC协定需应用讯务控制的功能来完成访问控制,才能使光纤网络的媒体访问权能有效的被公平且合理地在节点间分配,以改善光纤TDMA网络节点访问权不公平分配的问题,使该光纤TDMA网络能被采用来建构区域网络、都会网络或公用网络的子网络等等,以降低网络建设成本、提升宽频使用率及网络服务品质。The main purpose of the present invention is to provide a method for time-division multiple access of optical fiber network media and the traffic control method of its application. Media access rights can be effectively and fairly distributed among nodes to improve the problem of unfair distribution of access rights to nodes in optical fiber TDMA networks, so that the optical fiber TDMA network can be used to construct sub-networks of regional networks, metropolitan networks or public networks And so on, in order to reduce the cost of network construction, improve broadband utilization and network service quality.
附图说明 Description of drawings
图1是光纤TDMA网络的架构示意图。Figure 1 is a schematic diagram of the architecture of an optical fiber TDMA network.
图2是对应T1(n)的节点平均等待时间曲线图。Fig. 2 is a curve diagram of the average waiting time of nodes corresponding to T 1 (n).
图3是对应T2(n)的节点平均等待时间曲线图。Fig. 3 is a curve diagram of the average waiting time of nodes corresponding to T 2 (n).
图4是对应T3(n)的节点平均等待时间曲线图。Fig. 4 is a graph of the average waiting time of nodes corresponding to T 3 (n).
图5是节点间隔对第一讯务分配模式的效应曲线图。FIG. 5 is a graph showing the effect of node spacing on the first traffic allocation mode.
图6是节点间隔对第二讯务分配模式的效应曲线图。FIG. 6 is a graph showing the effect of node spacing on the second traffic allocation mode.
图7是节点间隔对第三讯务分配模式的效应曲线图。Fig. 7 is a graph showing the effect of node spacing on the third traffic allocation mode.
具体实施方式 Detailed ways
对TDMA网络而言,一个欲传送信息的节点,必须先送出“传送要求”通知整个网络,以预留空闲讯槽。预留的空闲讯槽数目对应于所送出“传送要求”的数目。当预留的空闲讯槽数目变大时,其节点平均等待时间将会因而降低。因此,如果一节点有较高的讯务量,它的平均等待时间将变小。若TDMA节点的平均等待时间,被当作评估其所拥有讯槽访问权的标准,则产生较大讯务量的节点,将拥有较多的访问权。换言之,TDMA节点间,各以其所产生讯务量的多少来相互竞争,以争取媒体的访问权。此TDMA节点的平均等待时间与其节点讯务量两者之间的关系可被推导如下。For a TDMA network, a node that wants to transmit information must first send a "transmission request" to notify the entire network to reserve a free slot. The number of reserved free slots corresponds to the number of sent "transmission requests". When the number of reserved idle slots increases, the average waiting time of nodes will decrease accordingly. Therefore, if a node has higher traffic, its average waiting time will be smaller. If the average waiting time of a TDMA node is used as a criterion for evaluating the slot access rights it has, then the nodes that generate a larger amount of traffic will have more access rights. In other words, TDMA nodes compete with each other according to the amount of traffic they generate, so as to gain access to the media. The relationship between the average waiting time of a TDMA node and its node traffic can be derived as follows.
TDMA节点的平均等待时间的推导,是基于三个网络操作条件。第一个操作条件说明被分析网络处在满载的状况。另一个操作条件限制每一“传送要求”仅可预留一空闲讯槽。第三个操作条件假设节点的访问控制操作,不能限制其“传送要求”的发送数目。因于此三操作条件,所有的节点可自由竞争,争取任一讯槽的访问权。就一稳定且含有N个节点的TDMA网络,令R代表此网络总线上讯槽的速度,T(n)代表网络内第n个节点所产生的讯务量,其中n是节点的序号,且0≤n<N。则T(n)可表示如下式:The derivation of the average waiting time of TDMA nodes is based on three network operating conditions. The first operating condition indicates that the analyzed network is fully loaded. Another operating condition restricts each "transmission request" to reserve only one free slot. The third operating condition assumes that the node's access control operation cannot limit the number of its "transfer request" sent. Because of these three operating conditions, all nodes can freely compete for access to any channel. For a stable TDMA network with N nodes, let R represent the speed of the slots on the network bus, T(n) represent the traffic generated by the nth node in the network, where n is the serial number of the node, and 0≤n<N. Then T(n) can be expressed as follows:
T(n)=r(n)/R, (1)T(n)=r(n)/R, (1)
式中r(n)是每一秒钟,第n个节点所捕捉,用以传送信息的讯槽数。In the formula, r(n) is the number of slots captured by the nth node and used to transmit information every second.
因于第一个操作条件及式(1),所有T(n)的和可表示如下:Due to the first operating condition and formula (1), the sum of all T(n) can be expressed as follows:
从第n个节点的角度来看,传输媒体上的讯槽可区分为三种。这三种是已使用的讯槽、已被预留的讯槽及自由讯槽。已使用的讯槽承载上游节点的信息,已被预留的讯槽用以传送下游节点的信息,自由讯槽是第n个节点可以应用的讯槽。这些自由讯槽可能已被第n个节点预留,亦可能未被预留。在一稳定网络内,自由讯槽出现在第n个节点的机率,应等于或大于第n个节点的讯务量。因第n个节点的讯务量是T(n),且此网络为满载,所以第n个节点捕捉到自由讯槽的机率亦是T(n)。From the point of view of the nth node, the slots on the transmission medium can be divided into three types. These three types are used slots, reserved slots and free slots. The used slots carry the information of the upstream nodes, the reserved slots are used to transmit the information of the downstream nodes, and the free slots are the available slots for the nth node. These free slots may or may not have been reserved by the nth node. In a stable network, the probability of a free slot appearing at the nth node should be equal to or greater than the traffic volume of the nth node. Since the traffic volume of the nth node is T(n), and the network is fully loaded, the probability of the nth node capturing a free slot is also T(n).
就一由第n个节点所产生的数据片段而言,假设此数据片段进入衔接总线的缓冲器,进入等待被传送的状况后,出现在此节点的第i个讯槽是自由讯槽。令pw(n,i)表示此数据片段被写入到第i个讯槽的机率,其中i=1,2,…,R,则pw(n,i)可以表示如下:As for a data segment generated by the nth node, assuming that the data segment enters the buffer of the connection bus and enters the state of waiting to be transmitted, the ith slot of this node is a free slot. Let p w (n, i) represent the probability that this data segment is written into the i-th channel, where i=1, 2, . . . , R, then p w (n, i) can be expressed as follows:
pW(n,i)=T(n)(1-T(n))i-1 (3)p W (n, i)=T(n)(1-T(n)) i-1 (3)
设以M(n)代表第n个节点的最大等待时间。因为第n个节点每秒钟使用r(n)个讯槽,则M(n)可以下式表示:Let M(n) represent the maximum waiting time of the nth node. Since the nth node uses r(n) slots per second, M(n) can be expressed as follows:
M(n)=R-r(n)+1 (4)M(n)=R-r(n)+1 (4)
将式(1)的r(n)代入式(4),M(n)可被整理如下:Substituting r(n) of formula (1) into formula (4), M(n) can be organized as follows:
M(n)=R(1-T(n))+1 (5)M(n)=R(1-T(n))+1 (5)
若以μ(n)表示第n个节点的平均等待时间。此平均等待时间可以下式计算:If μ(n) is used to represent the average waiting time of the nth node. This average waiting time can be calculated as follows:
将式(5)的M(n)代入式(6),第n个节点的平均等待时间可重新整理如下:Substituting M(n) of formula (5) into formula (6), the average waiting time of the nth node can be rearranged as follows:
μ(n)=[1-(1-T(n))R(1-T(n))+1(1+(R(1-T(n))+1)T(n))]/T(n)(7)μ(n)=[1-(1-T(n)) R(1-T(n))+1 (1+(R(1-T(n))+1)T(n))]/ T(n)(7)
若网络的讯槽速率R是固定的,式(7)显示第n个节点的平均等待时间,仅随着第n个节点的讯务量变化,而与节点所在位置及各节点间的距离无关,更与促成媒体共享的MAC协定无相关性存在。If the slot rate R of the network is fixed, equation (7) shows that the average waiting time of the nth node only changes with the traffic volume of the nth node, and has nothing to do with the location of the node and the distance between the nodes , and no correlation exists with the MAC protocol that enables media sharing.
对高速网络而言,R趋近于无穷大。则高速网络上的μ(n)可以推演如下:For high-speed networks, R approaches infinity. Then μ(n) on the high-speed network can be deduced as follows:
式(8)明确地表示,一高速TDMA节点的平均等待时间,与其节点讯务量成反比关系。简言之,对高速TDMA网络而言,节点讯务量愈大,其平均等待时间会愈小。此特性强烈地显示,高速TDMA网络上,一节点的平均等待时间与网络拓扑无关。换言之,高速TDMA节点的媒体访问权,随着节点的讯务量变化。因此,如果其所用MAC协定含适当的讯务控制能力,则此网络的媒体访问权,将能被有效且合理地在节点间分配。Equation (8) clearly shows that the average waiting time of a high-speed TDMA node is inversely proportional to the traffic volume of the node. In short, for a high-speed TDMA network, the greater the traffic volume of a node, the smaller its average waiting time will be. This property strongly shows that on high-speed TDMA networks, the average waiting time of a node is independent of the network topology. In other words, the media access right of a high-speed TDMA node varies with the traffic volume of the node. Therefore, if the MAC protocol used contains appropriate traffic control capabilities, the medium access rights of the network can be effectively and reasonably allocated among nodes.
因光纤网络是具高容量的高速网络,故前述的高速TDMA节点的平均等待时间与其节点讯务量成反比关系的特性,对TDMA的光纤网络而言,是其与生俱来的特性。所以若TDMA的光纤网络的MAC协定,含适当的讯务控制能力,则此网络的媒体访问权,将能被有效的在节点间作公平且合理地分配。Because the optical fiber network is a high-speed network with high capacity, the above-mentioned characteristic that the average waiting time of high-speed TDMA nodes is inversely proportional to the traffic volume of the nodes is an inherent characteristic of TDMA optical fiber network. Therefore, if the MAC protocol of the TDMA optical fiber network includes appropriate traffic control capabilities, the media access rights of this network can be effectively distributed among nodes fairly and reasonably.
为证实及说明上述的发明,本发明在此以一具讯务控制能力的MAC,应用在分时多重访问光纤网络上,进行访问控制为例,来做说明及验证。In order to prove and illustrate the above-mentioned invention, the present invention takes a MAC with traffic control capability to be applied to a time-division multiple access optical fiber network for access control as an example for illustration and verification.
为了检验光纤TDMA网络节点MAC控制方法的发明效果,一些网络工作条件的假设被提出,以便进行光纤TDMA网络的模拟。图1是揭示光纤TDMA网络的架构。图中,在讯槽产生器(slot generators)与讯槽终结器(slotterminators)之间的媒体是一条光纤。光纤上的讯槽流由讯槽产生器送出,最后沉入讯槽终结器。整个网络有N个节点。所有的节点由左而右依序编号。每一个节点的编号,亦可代表其在整个网络拓扑的节点位置。讯槽产生器将一个讯槽送上光纤的时间间隔,称为一个讯槽时间。一个讯槽在光纤上延展的距离,称为一个讯槽长度。除此之外,那些关系到邻近节点的间隔,信息的长度及节点间讯务的分配等的工作条件,叙述于后。In order to test the inventive effect of the node MAC control method in optical fiber TDMA network, some assumptions of network working conditions are put forward in order to carry out the simulation of optical fiber TDMA network. Figure 1 shows the architecture of the optical fiber TDMA network. In the figure, the medium between slot generators and slot terminators is an optical fiber. The slot flow on the optical fiber is sent out by the slot generator, and finally sinks into the slot terminator. The entire network has N nodes. All nodes are numbered sequentially from left to right. The number of each node can also represent its node position in the entire network topology. The time interval for the slot generator to send a slot to the optical fiber is called a slot time. The distance that a slot extends on an optical fiber is called a slot length. In addition, those working conditions related to the distance between adjacent nodes, the length of messages and the distribution of traffic between nodes are described later.
在一个模拟的实施例里,每一对相邻的节点间的间隔均相等,此间隔是讯槽长度的整数倍。为了确认节点平均等待时间,是否会随着节点间的间隔变化,模拟实施例的节点间间隔,将随着实施例改变,但原来的节点讯务分配,则保持不变。在所有的模拟实施例内,信息的长度保持不变,每一信息的长度,等于一个讯槽酬载的长度。节点的讯务分配,影响节点平均等待时间的变化,所以讯务分配将随着实施例改变,以检验光纤TDMA网络的“理想公平行为”的特性。In an analog embodiment, the interval between each pair of adjacent nodes is equal, and the interval is an integer multiple of the slot length. In order to confirm whether the average waiting time of nodes will change with the interval between nodes, the interval between nodes in the simulated embodiment will be changed with the embodiment, but the original traffic distribution of nodes will remain unchanged. In all simulated embodiments, the length of the messages remains constant, and the length of each message is equal to the length of a slot payload. The traffic distribution of the nodes affects the change of the average waiting time of the nodes, so the traffic distribution will change with the embodiment to test the characteristics of the "ideal fair behavior" of the optical fiber TDMA network.
为了能很容易地完成讯务控制,将应用一个基本讯务量,以作为讯务分配的根据。此基本讯务量以TB表示。TB的量,由每一实施例的讯务分配来决定。在一实施例里,任一节点的讯务量是TB的整数倍,换言之,实施例内最小的可能节点讯务量是TB。基于TB的引用,不仅易于定义各种光纤TDMA网络上的讯务分配,讯务控制操作亦能很容易地配合各种讯务分配来完成。In order to easily complete traffic control, a basic traffic volume will be used as the basis for traffic allocation. The basic traffic volume is expressed in TB . The amount of TB is determined by the traffic allocation of each embodiment. In an embodiment, the traffic volume of any node is an integer multiple of TB , in other words, the smallest possible node traffic volume in the embodiment is TB . Based on the reference of TB , it is not only easy to define the traffic distribution on various optical fiber TDMA networks, but also the traffic control operation can be easily completed in conjunction with various traffic distributions.
能完成讯务控制的MAC操作例子叙述如下。讯务控制的MAC操作是使用讯槽框来完成。在光纤上的讯槽流被分割成数个讯槽框。每一讯槽框含1/TB个讯槽。当一个讯槽框到达第n个节点,此节点可将其等待传送的信息,连续写入框内的空闲讯槽,此可连续写出的最大信息数,必须小于或等于T(n)/TB,其中T(n)是第n个节点的讯务量。此可连续写出的最大信息数目,在讯槽框到达前,将被加载到一倒数计数器。当储存在队列内的信息数大于T(n)/TB时,倒数计数器的最大值将等于T(n)/TB。否则,倒数计数器的最大值,应等于队列内的信息数。然后,每送出一信息,倒数计数器减一。直到倒数计数器归零,此节点必须立即停止信息的传送,此时队列内仍储存的信息,需等下一个讯槽框到达,才能重新启动下一个如前所述的讯务控制周期。An example of MAC operation that can accomplish traffic control is described below. MAC operations for traffic control are done using slot frames. The slot stream on the fiber is divided into several slot frames. Each slot frame contains 1/T B slots. When a slot frame arrives at the nth node, the node can continuously write the information waiting to be transmitted into the free slot in the frame. The maximum number of messages that can be written continuously must be less than or equal to T(n)/ T B , where T(n) is the traffic volume of the nth node. The maximum number of messages that can be written continuously will be loaded into a countdown counter before the slot frame arrives. When the number of messages stored in the queue is greater than T(n)/T B , the maximum value of the countdown counter is equal to T(n)/T B . Otherwise, the maximum value of the countdown counter shall be equal to the number of messages in the queue. Then, every time a message is sent, the countdown counter is decremented by one. Until the countdown counter returns to zero, the node must immediately stop the transmission of information. At this time, the information still stored in the queue needs to wait for the arrival of the next slot frame before restarting the next traffic control cycle as described above.
此网络模拟进行的目的,主要在检验光纤TDMA网络,是否符合「理想公平行为」的特性。此被检验的光纤TDMA网络,需以具有讯务控制能力的MAC协定来做访问控制。“理想公平行为”是指在不改变节点讯务量的情况下,光纤TDMA网络的节点平均等待时间,不会随着节点在网络内的相关位置改变。此相关位置包含节点的位置和节点间的间隔。因此,节点间的讯务分配和间隔,必须随着模拟的实施例改变。The purpose of this network simulation is mainly to test whether the optical fiber TDMA network conforms to the characteristics of "ideal fair behavior". The inspected optical fiber TDMA network needs to use the MAC protocol with traffic control capability for access control. "Ideal fair behavior" means that the average waiting time of nodes in the optical fiber TDMA network will not change with the relative position of the nodes in the network without changing the traffic volume of the nodes. This relative position includes the position of the nodes and the spacing between nodes. Therefore, the traffic distribution and spacing between nodes must be changed according to the simulated embodiment.
另一方面,式(8)所表示,由分析产生的节点平均等待时间,将被使用来确认模拟的结果。若以Drms表示分析和模拟的节点平均等待时间两者间的均方根误差,则Drms可被定义如下:On the other hand, the average waiting time of nodes generated by the analysis, represented by Equation (8), will be used to confirm the simulation results. If D rms is used to represent the root mean square error between the average waiting time of the analyzed and simulated nodes, then D rms can be defined as follows:
式中μs(n)和μ(n)分别代表模拟和分析所得的第n个节点的平均等待时间。In the formula, μ s (n) and μ (n) represent the average waiting time of the nth node obtained from simulation and analysis respectively.
在以下所有显示模拟结果的图中,水平轴的数目,代表节点的序号。因为节点的序号是离散的数字,所以所有图内的曲线是由小线段组成。在纵轴的节点平均等待时间的单位是以讯槽时间表示。In all the following figures showing simulation results, the number on the horizontal axis represents the ordinal number of the node. Because the serial numbers of nodes are discrete numbers, all curves in the graph are composed of small line segments. The unit of the average waiting time of nodes on the vertical axis is expressed in slot time.
为了了解光纤TDMA网络的节点讯务量,对节点平均等待时间,及“理想公平行为”等两者的影响,模拟用到三种讯务分配模式。此三种讯务分配模式中,每一节点的讯务量,均是TB的整数倍。因为光纤是单方向传送信息,且所有节点的信息,皆未送出此模拟网络,故在所有的讯务分配模式里,第(N-1)个节点均未产生讯务。在第一个讯务分配模式里,令T1(n)表示第n个节点的讯务量,则T1(n)可定义如下:In order to understand the traffic volume of the nodes in the optical fiber TDMA network, the impact on the average waiting time of the nodes, and the "ideal fair behavior", three traffic distribution modes are used in the simulation. In the three traffic allocation modes, the traffic volume of each node is an integer multiple of TB . Because the optical fiber transmits information in one direction, and the information of all nodes is not sent out of the simulated network, in all traffic distribution modes, the (N-1)th node does not generate traffic. In the first traffic allocation mode, let T 1 (n) represent the traffic volume of the nth node, then T 1 (n) can be defined as follows:
T1(n)=(N-n-1)TB,n=0,1,...,N-2(10)T 1 (n)=(Nn-1)T B , n=0, 1, . . . , N-2(10)
在此定义里,靠近讯槽产生器的节点拥有最大的讯务量。其他节点的讯务量,随着节点序号的增加而降低。基于此定义,在一个讯槽框内,第n个节点可捕捉的最大讯槽数是(N-n-1)。因为此网络是满载,所以In this definition, the nodes closest to the slot generator have the greatest amount of traffic. The traffic volume of other nodes decreases as the node number increases. Based on this definition, within a slot frame, the maximum number of slots that the nth node can capture is (N-n-1). Because the network is fully loaded, the
故对应于第一个讯务分配模式,一个讯槽框所含的讯槽数(F1)为:Therefore, corresponding to the first traffic allocation mode, the number of slots (F 1 ) contained in a slot frame is:
F1=1/TB=N(N-1)/2 (12)F 1 =1/T B =N(N-1)/2 (12)
根于第一个讯务分配模式,其对应的模拟结果显示于图2。此模拟的网络含四十个节点。图中实线代表由分析计算而得的节点平均等待时间的变化,虚线代表由模拟而得的节点平均等待时间的变化。两条曲线几乎完全重垒。两曲线所代表的节点平均等待时间的均方根误差计算如下;Based on the first traffic allocation model, the corresponding simulation results are shown in Fig. 2. This simulated network contains forty nodes. The solid line in the figure represents the variation of the average waiting time of nodes obtained from the analysis and calculation, and the dotted line represents the variation of the average waiting time of nodes obtained from the simulation. Both curves are almost completely heavy base. The root mean square error of the average waiting time of nodes represented by the two curves is calculated as follows;
此均方根误差值趋近于零,该结果不但证实本文对节点平均等待时间推论的正确性,同时亦确认对光纤TDMA网络模拟的精准性。The root mean square error value is close to zero. This result not only confirms the correctness of the deduction of the average waiting time of nodes in this paper, but also confirms the accuracy of the simulation of the optical fiber TDMA network.
在第二个讯务分配模式里,节点讯务量随着节点序号,依序增加。令T2(n)代表第n个节点的讯务量,T2(n)的量可以下式定义:In the second traffic allocation mode, the traffic volume of nodes increases sequentially with the node serial number. Let T 2 (n) represent the traffic volume of the nth node, and the volume of T 2 (n) can be defined as follows:
T2(n)=(n+1)TB,n=0,1,...,N-2 (14)T 2 (n)=(n+1)T B , n=0, 1, . . . , N-2 (14)
在此定义里,靠近讯槽产生器的节点讯务量最小。其他节点的讯务量,随着节点序号的增加而变大。基于此定义,在一个讯槽框内,第n个节点可捕捉的最大讯槽数是(n+1)。一个讯槽框所含的讯槽数F2与F1相同,同为(N(N-1))/2。图3显示具有第二个讯务分配模式的网络,其节点平均等待时间的变化。图中实线及虚线分别代表分析与模拟的节点平均等待时间的变化。两条曲线几乎完全重垒。两曲线所代表的节点平均等待时间间的均方根误差为0.047958。若以n1及n2分别表示图2及图3的节点序号,再对图2及图3的变化进行比较。比较结果显示:不管n1是否与n2相等,只要T1(n1)与T2(n2)相等,则n1与n2的节点平均等待时间必会相等。这种现象表示,当光纤TDMA网络的MAC协定,具有讯务控制能力时,每一节点的平均等待时间,只与节点本身的讯务量有关,而与节点所在的网络位置无关。In this definition, the nodes closest to the slot generator have the least amount of traffic. The traffic volume of other nodes increases with the increase of the node serial number. Based on this definition, within a slot frame, the maximum number of slots that the nth node can capture is (n+1). The number of slots F 2 contained in a slot frame is the same as that of F 1 , which is (N(N-1))/2. Fig. 3 shows the variation of the average waiting time of the nodes for the network with the second traffic allocation mode. The solid line and dotted line in the figure respectively represent the change of the average waiting time of the nodes in the analysis and simulation. Both curves are almost completely heavy base. The root mean square error between the average waiting time of nodes represented by the two curves is 0.047958. If n 1 and n 2 represent the node numbers in Figure 2 and Figure 3 respectively, then compare the changes in Figure 2 and Figure 3 . The comparison results show that no matter whether n 1 is equal to n 2 or not, as long as T 1 (n 1 ) is equal to T 2 (n 2 ), the average waiting time of nodes n 1 and n 2 must be equal. This phenomenon shows that when the MAC protocol of the optical fiber TDMA network has traffic control capabilities, the average waiting time of each node is only related to the traffic volume of the node itself, and has nothing to do with the network location of the node.
从以上两模拟结果的比较,可以预测,当网络讯务是平均分布时,各节点的平均等待时间,将会彼此相等。为检验此预测,假设第三个讯务分配模式是均匀分布。令T3(n)代表第三个讯务分配模式里,第n个节点的讯务量,则对所有的节点而言,T3(n)=1/(N-1)=TB。每一讯槽框内含K(N-1)个讯槽,其中K是一正整数。在一讯槽框内,每一节点可捕捉的最大讯槽数为K。在本模拟里,所选择的K等于2。均匀分布的讯务分配模拟结果如图4。From the comparison of the above two simulation results, it can be predicted that when the network traffic is evenly distributed, the average waiting time of each node will be equal to each other. To test this prediction, assume that the third traffic allocation pattern is a uniform distribution. Let T 3 (n) represent the traffic volume of the nth node in the third traffic allocation mode, then for all nodes, T 3 (n)=1/(N−1)=T B . Each slot frame contains K(N-1) slots, where K is a positive integer. In a slot frame, the maximum number of slots that each node can capture is K. In this simulation, K was chosen equal to 2. Figure 4 shows the simulation results of evenly distributed traffic distribution.
在图4内,实线及虚线分别代表分析与模拟的节点平均等待时间的变化。两条曲线几乎完全重垒。两曲线所代表的节点平均等待时间间的均方根误差为0.003766。所有节点的平均等待时间几乎相同。此与预测的结果相符。In Fig. 4, the solid line and the dotted line represent the variation of the average waiting time of nodes in analysis and simulation respectively. Both curves are almost completely heavy base. The root mean square error between the average waiting time of the nodes represented by the two curves is 0.003766. The average waiting time for all nodes is almost the same. This is consistent with the predicted results.
以下的模拟,用以检视邻近节点间的间隔,对节点平均等待时间的影响。在之前的三个模拟实施例,节点间的间隔,皆是一个讯槽长度。以后的模拟实施例里,节点间的间隔,皆增为三个讯槽长度,而其他的工作条件,则维持与之前的三个实施例相同。图5、图6和图7是分别对应到三个讯务分配模式,且节点间的间隔为一个和三个讯槽长度的模拟结果。The following simulation is used to examine the effect of the distance between adjacent nodes on the average waiting time of nodes. In the previous three simulation examples, the interval between nodes is the length of one slot. In the subsequent simulation embodiments, the interval between nodes is increased to three slot lengths, while other working conditions remain the same as the previous three embodiments. Fig. 5, Fig. 6 and Fig. 7 are simulation results respectively corresponding to three traffic distribution modes, and the interval between nodes is one and three slot lengths.
在图5、图6和图7这三张图里,实线代表邻近节点间的间隔,为一个讯槽长度的模拟结果,虚线代表邻近节点间的间隔,为三个讯槽长度的模拟结果。两条曲线几乎完全重垒。对应到图5、图6和图7,每图内两曲线所代表的节点平均等待时间间的均方根误差,分别为0.001235,0.03755和0.000176。每一均方根误差值,均趋近于零。此代表节点平均等待时间,不会受节点间隔的大小影响。In Figure 5, Figure 6 and Figure 7, the solid line represents the interval between adjacent nodes, which is the simulation result of one slot length, and the dotted line represents the interval between adjacent nodes, which is the simulation result of three slot lengths . Both curves are almost completely heavy base. Corresponding to Figure 5, Figure 6 and Figure 7, the root mean square error between the average waiting time of nodes represented by the two curves in each figure is 0.001235, 0.03755 and 0.000176 respectively. Each root mean square error value tends to zero. This represents the average waiting time of nodes and will not be affected by the size of the node interval.
以上的模拟结果显示:MAC协定具有讯务控制能力的光纤TDMA网络,它的节点平均等待时间与网络拓扑无关。因此,通过本发明的方法,光纤网络的媒体访问权,能被有效且合理的在节点间分配,而得以改善光纤网络访问时间不公平的问题。改善后的光纤TDMA网络适合被采用来建构都会网络、区域网络或公用网络的子网络,以降低网络建设成本、提升宽频使用率及通信品质。The above simulation results show that the average waiting time of nodes has nothing to do with the network topology in the optical fiber TDMA network with the traffic control capability of the MAC protocol. Therefore, through the method of the present invention, the media access rights of the optical fiber network can be effectively and reasonably allocated among nodes, thereby improving the problem of unfair access time of the optical fiber network. The improved optical fiber TDMA network is suitable to be used to construct sub-networks of urban networks, regional networks or public networks to reduce network construction costs, improve broadband utilization and communication quality.
综上所述,本发明实施例确能达到所预期的使用功效,又其所揭露的具体功能,不仅未曾见诸于同类产品中,亦未曾公开于申请前,诚已完全符合专利法的规定与要求,于是依法提出发明专利的申请,恳请惠予审查,并赐准专利,则实感德便。To sum up, the embodiment of the present invention can indeed achieve the expected use effects, and the specific functions disclosed by it have not only been seen in similar products, but also have not been disclosed before the application, and have fully complied with the provisions of the Patent Law. Therefore, I filed an application for an invention patent in accordance with the law, and I sincerely appreciate the convenience of reviewing and granting the patent.
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