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【速搜问答】多级互联网是什么

问答 admin 1个月前 (04-11) 37次浏览 已收录 0个评论

汉英对照:
Chinese-English Translation:

多级互联网络(MIN ,Multistage Interconnection Network),是由大量的基本交换模块按照特定的拓扑结构相互连接构成,形成一个更大规模的能够进行信元交换的交换网络。

Min (multistage interconnection network) is composed of a large number of basic switching modules connected with each other according to a specific topology, forming a larger scale switching network that can exchange cells.

多级互联网络(MIN ,Multistage Interconnection Network),是由大量的基本交换模块按照特定的拓扑结构相互连接构成,形成一个更大规模的能够进行信元交换的交换网络。

Min (multistage interconnection network) is composed of a large number of basic switching modules connected with each other according to a specific topology, forming a larger scale switching network that can exchange cells.

简史

brief history

20 世纪 50 年代提出了多级互联网的概念,并在电话交换中得到应用。70 年代,多级互联网主要用于多处理器、多存储器的并行计算机结构中。80 年代,随着宽带 ISDN 的发展,人们开始广泛地研究它在宽带交换中的应用。

In the 1950s, the concept of multi-level Internet was proposed and applied in telephone exchange. In the 1970s, the multi-level Internet was mainly used in the parallel computer architecture of multi processor and multi memory. In 1980s, with the development of broadband ISDN, people began to study its application in broadband switching.

基本概念

Basic concepts

在 ATM 交换系统中其传输部分是由交换机构(Switching Fabric)构成的。基本交换模块的规模通常比较小,很难直接适应大型交换系统的需要。大型的实用化 ATM 交换机需要的输入输出端口多达几百条到几万条,这样规模的交换机构,必须由大量基本交换模块(交换单元)通过特定的拓扑结构互相连接起来构成。这样互相连接起来的交换单元的网络就构成了交换机构,常将其称之为交换网络。

In ATM switching system, the transmission part is composed of switching fabric. The scale of basic switching module is usually small, so it is difficult to directly adapt to the needs of large switching system. A large practical ATM switch needs hundreds to tens of thousands of input and output ports. A switching mechanism of this scale must be composed of a large number of basic switching modules (switching units) connected with each other through a specific topology. In this way, the network of interconnected switching units constitutes the switching mechanism, which is often called switching network.

在使用基本交换模块来构造交换机构的时候存在着多种不同的方式。交换机构(交换网络)的结构除了与交换单元互连的拓扑结构有关,也与其所采用的交换单元的结构有关。根据其结构的特性,交换网络可以分为两大类:

There are many different ways to use basic exchange module to construct exchange mechanism. The structure of switching mechanism (switching network) is not only related to the topology of switching unit interconnection, but also related to the structure of switching unit. According to the characteristics of its structure, switching networks can be divided into two categories

1 单级交换网络,是指在网络中信元从入线到出现的通路上只需要经过一级交换单元。

The single-stage switching network refers to a network in which only one level of switching unit is needed to pass through the channel from the incoming line to the existing channel.

2 多级交换网络,信元从入线到出线的通路上需要经过多个交换单元,需要在每个交换单元中多次为信元确定输出通路,并可能需要经过多次的排队过程。

In multi-level switching network, cells need to pass through multiple switching units from the incoming line to the outgoing line. It is necessary to determine the output path for cells in each switching unit many times, and it may need to go through many queuing processes.

单级交换网络的优点是信元在交换过程中只需要经过一次排队,因此交换时延小。但是,单级交换网络的拓展能力有限,很难构成较大规模的交换机构。多级交换网络最主要的形式就是多级互连网络(MIN)。

The advantage of single-stage switching network is that cells only need to queue once in the switching process, so the switching delay is small. However, the expansion capacity of single-stage switching network is limited, so it is difficult to form a large-scale switching organization. The main form of multi-level switching network is multi-level interconnection network (min).

特点

characteristic

1 MIN 通常由一些相同的基本交换模块构成,基本交换模块通过特定的拓扑结构互连。基本交换模块的规模可以很小,使用规模较大的基本交换模块可以减少 MIN 的级数。

1 min is usually composed of the same basic switching modules, which are interconnected by a specific topology. The size of the basic switching module can be very small, and the number of min can be reduced by using the larger basic switching module.

2 允许信元并行地穿过 MIN。、

2 allow cells to pass through min in parallel. 、

3 在 MIN 中,信元的传输通路上至少需要经过两个以上的基本交换模块,信元经过的基 4 本交换模块的数量就是 MIN 的级数。

In min, there are at least two basic switching modules in the transmission path of a cell. The number of basic switching modules that the cell passes through is the number of min.

4 入线到出线的全连通性,即任何入线输入的信元都可道德任何一条出线。者要求在 MIN 中的任何一条入线与任何一条出线之间至少存在一条通路。

4. Full connectivity from incoming line to outgoing line, i.e. any incoming cell can be connected to any outgoing line. It is required that there is at least one path between any incoming line and any outgoing line in min.

5 MIN 内部资源的共享。MIN 中的所有资源,包括基本交换模块、内部链路和通路等,都能被多个 ATM 连接中的信元传输所共享,而不是为某一个连接或通路所专用。

5 min internal resource sharing. All the resources in min, including basic switching modules, internal links and paths, can be shared by cell transmission in multiple ATM connections, rather than being dedicated to a particular connection or path.

MIN 最早用于电路交换网。20 实际 70 年代中期,MIN 应用到并行计算机系统中。MIN 的主要优点是其规则性和良好的拓展能力,它是构成 ATM 交换机构最主要也是应用最广泛的方式。

Min was first used in circuit switching network. In the mid-1970s, min was applied to parallel computer system. The main advantages of min are its regularity and good expansion ability. It is the most important and widely used way to form ATM switching mechanism.

路由选择

Routing

ATM 交换需要实现的基本功能包括了排队功能和路由选择。其中排队功能在基本交换模块中实现,而路由选择则是在交换机构中需要实现的。在这里所讨论的路由选择,是指在交换机构内部(即在 ATM 中)如何选择一条从入线到出线的通路的过程。

The basic functions of ATM switching include queuing and routing. The queuing function is implemented in the basic switching module, while routing is implemented in the switch architecture. The route selection discussed here refers to the process of how to select a path from the incoming line to the outgoing line within the switching mechanism (that is, in ATM).

在 MIN 中,路由标签(Routing Tag)是用来表示信元传输通路的一种方式。首先,我们采用统一的方式对 MIN 中所有交换单元的每一条出线都分配一个地址编号。N×N 的交换单元,对出线进行编制需要比特。当所有信元从入线到出线穿过一个 MIN 时。每经过一个交换单元,都把信元在该交换单元上所选择的出现地址纪录下来。在整个信元传输通路上,个交换单元所选择的出现地址串联起来所构成的一串数字,就成为路由标签。

In min, routing tag is a way to represent cell transmission path. First of all, we use a unified way to assign an address number to each outgoing line of all switching units in min. N × n switching unit, it needs bit to program the outgoing line. When all cells pass through a min from the incoming line to the outgoing line. Every time a cell passes through a switching unit, the occurrence address selected by the cell on the switching unit is recorded. In the whole cell transmission path, a string of numbers formed by concatenation of the address selected by each switching unit becomes the routing label.

在 MIN 中路由标签可以用来标示穿越 MIN 的一条内部的传输通路。给定了一条入线和一个路由标签,路由标签在 MIN 中被用作路由选择的表示工具。

In min, routing label can be used to mark an internal transmission path through min. Given an incoming line and a routing label, the routing label is used as a representation tool for routing in min.

构成

constitute

现代的多级互联网大都由多个 2×2 交叉连接单元构成。每个 2×2 交叉连接单元都有两个输入端和两个输出端,把这两个输入端和两个输出端平行连接或交叉连接起来,即可控制交叉连接单元。

Modern multi-level Internet is mostly composed of multiple 2 × 2 cross connection units. Each 2 × 2 cross connection unit has two input terminals and two output terminals. If the two input terminals and two output terminals are connected in parallel or cross connected, the cross connection unit can be controlled.

图中示出了一个 8×8 的多级互联网,它有 8 个入端和 8 个出端。12 个交叉连接单元分为 3 级,每级 4 个。级与级之间的这种很规则的连接方法,一般叫做“蝶形连接”。“蝶形连接”只是级间连接的方法之一。级间连接方法不同的多级互联网常有其各自不同的名称,如 Benes 网、Omega 网、Banyan 网等等。

The figure shows an 8 × 8 multi-level Internet with 8 in and 8 out terminals. The 12 cross connect units are divided into 3 levels, with 4 in each level. This very regular connection method between levels is generally called “butterfly connection”. “Butterfly connection” is only one of the methods of inter stage connection. Multi level Internet with different connection methods often has different names, such as Benes network, Omega network, banyan network and so on.

图 1 8X8“蝶形连接”的多级互联网

Figure 1 multi level Internet with 8×8 “butterfly connection”

一个多级互联网的入端数和出端数总是相等的,并且可以表示成 N=2M 的形式(N 为出、入端数,M 为级数)。

The number of in and out terminals of a multi-level Internet is always equal, and can be expressed in the form of n = 2m (n is the number of out and in terminals, M is a series).

2×2 交叉连接单元是一个电子器件或光器件,在有些情况下它可能相当复杂。例如在 ATM 交换中,可能要求这个交叉连接单元具有存储 ATM 信元和对其信头进行分析处理的功能。由于技术的进步,已经可以把整个 8×8 甚至 16×16 多级互联网,包括各个交叉连接单元及其连线,集成到一块晶片上了。

The 2 × 2 cross connect unit is an electronic or optical device, which may be quite complicated in some cases. For example, in ATM switching, the cross connect unit may be required to store ATM cells and analyze their headers. Due to the progress of technology, the entire 8 × 8 or even 16 × 16 multi-level Internet, including cross connection units and their connections, can be integrated into a single chip.

原理

principle

多级互联网的作用是通过对各个交叉连接单元的控制来完成入端和出端之间的各种连接,使每个入端上的信息都可以送到任何一个出端上去,但是实际上仍有内部阻塞的可能。例如,当入端 0 和出端 0 相连时,入端 1 不能找到和出端 1 连接的路径。

In fact, all kinds of information can be sent to and out of the Internet through a multi-level cross connection. For example, when the in end 0 is connected to the out end 0, the in end 1 cannot find the path to connect with the out end 1.

消除或减少内部阻塞的办法之一是增加多级互联网的级数,理论上讲,至少有 2M-1 级(M 足够大时)的多级互联网才有可能无内部阻塞。但还没有人用实际设备证明达到 2M-1 级时就确实可以作到无内部阻塞。

One of the ways to eliminate or reduce internal congestion is to increase the number of levels of multi-level Internet. Theoretically speaking, a multi-level Internet with at least 2m-1 level (when m is large enough) can have no internal congestion. However, no one has proved with actual equipment that no internal blockage can be achieved when 2m-1 level is reached.

多级互联网的研究和一些数学分支(主要是拌队论和组合论)密切相关。排队论用来研究多级互联网中的信息阻塞和延迟问题。组合论和多级互联网之间的密切关系可以由简单事实看出:一个多级互联网中的入端和出端之间的连接关系,等价于组合论中的重排问题。

The research of multi-level Internet is closely related to some branches of Mathematics (mainly team theory and combinatorial theory). Queuing theory is used to study information blocking and delay in multi-level Internet. The close relationship between combinatorial theory and multi-level Internet can be seen from simple facts: the connection between the in end and out end in a multi-level Internet is equivalent to the rearrangement problem in combinatorial theory.


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