DE4213458A1 - TELECOMMUNICATION MEDIATION - Google Patents

Abstract

An ATM switching network includes a switch for protocol transparent data communications between a Source and a Destination wherein a message is divided into packets each packet comprises an Information Field and a Header where the Header carries, at least, a Destination Address and a Source address. The Destination Address is interpreted in an interpreter to the address for an output port of the switch in each successive switch in a Network of said switches. A switching network includes a plurality of such switches wherein the separate switches and the links between them may operate asynchronously. <IMAGE>

Description

The present invention relates to an ATM ver network, regarding expansion and configuration with a minimal fixed cost overhead and low Total cost is very flexible.

According to the invention, a switching or coupling Establishment of the protocol for transparent data communications between a source and a destination, where a message is divided into packets, of which each an information field and a message header (Header) comprises, the head at least one target address and a source address and where the destination address in an interpreter to the address for one Output port of the switch in each successive switching device in a network these switching devices or switching devices is interpreted.

Preferably the source address is at the destination used to the message of which the package is a part is to identify.

In addition, one of the exchange connections internally connected to access via a network to enable a resource manager, the Resource manager a control of interpretation rers, the bandwidth allocation and an emergency operation features.

Additional advantageous developments are in marked the subclaims.

In the following the invention is based on a case game explained with reference to the drawings.

Show it  

Figs. 1a and 1b, the recommended by CCITT formats for ATM cells for a subscriber network interface (UNI of User-Network Interface) and a network-network interface (NNI Network-Network Interface);

Fig. 2 is a schematic representation of a network according to the invention;

Figure 3 is a schematic representation of the path taken by a packet through a typical network.

Fig. 4 is a general schematic view of the structure of a switch or switch according to the present invention;

FIG. 5 shows in a schematic manner the switching unit of the switching device from FIG. 4; and

Fig. 6 is a schematic representation of the rate-An passungseinheit and the monitoring unit of the Ver averaging means in FIG. 4.

The switching described according to the invention or coupling device is on switching packets related, which have a fixed expansion. More normal an ATN switch works with cells that have variable dimensions. As a result, with Reference to the present invention to packages reference taken, whereas in the description reference to ATN- Cells is taken. To a large extent can in the invention the packets or cells as one another be viewed interchangeably.

To accomplish the task mentioned above, that is Network made up of a number of small integral switches facilities built. A typical extension of this Switching equipment or switching equipment be is available in 16 connections or so-called ports, from which one can be reserved for internal use. The remaining 15 connections can be used for this be connections with other similar operator facilities, with users, with a public Network or network resources such as electronic mail  to create network nodes or a database. To at least one connection in the network is connected to an operation linked to resource manager or resource manager.

To avoid the essentially fixed costs, resulting from the use of virtual connections (VCs from Virtual Circuits) result, which on request each external connection of the network that be as a network port is drawn, one by the resource manager predefined path to any other network connection. The destination or destination and source addresses will be in the VPI or VCI field of the ATM cell format, the is recommended by the CCITT. The destination address is in everyone Switch interpreted in the path, however not changed.

The physical interface of each switch facility connection, exclusively of inter be is used by a different Realized types of interchangeable units, whereby each enables a specific type of external connection light; these include, for example, optical fiber cables, Cable with twisted pairs, ribbon cable or Coaxial cable. Because different types and lengths physical transmission media different band having a wide capacity is an adjustable rate adaptation to the connections an integral part of the Switchboard structure.

The two CCITT recommended formats for ATM cells are shown in FIGS. 1 (a) and 1 (b), the fields which serve to keep the destination and source addresses being shaded.

In the proposed network shown in FIG. 2, each cell carries the destination address in the VPI field and the cell address in the VCI field. VPI means virtual path or path identifier from Virtual Path Identifier and VCI means virtual channel identifier from Virtual Channel Identifier. At the input of each switching device in the path of a connection, the target address is interpreted or evaluated for an address for an output connection on this switching device. This interpretation is provided by a memory that is managed by the resource manager.

The 12-bit VPI field of the standard cell format for the NNI interface is split into two areas. An 8-bit field that corresponds to the VPI field in the UNI version of the standard ATM cell format is used for Address a group of typically up to 150 Ver users within an area of the overall network turns; this grouping is called a mini network. The remaining 4-bit field is used between two a separate route or route provision.

The interpreters at the entrances of the mediators lungseinrichtung may only be required to ent neither the 8-bit field nor the 4-bit field depending from interpreting whether the target determination on the same mini network or another mini network; if this mechanism rather than an interpretation of the full 12-bit field is used is the memory size necessary for the interpreter, mini lubricated. Even if speed doesn't matter plays, a single interpreter can do all Inputs from a single exchange in the Time sharing can be used.

At the destination, all entrances point to the same destination address so that the sources managed by the VCI field address is used between separate and possibly nested multi-cell messages to distinguish that from the different sources Arrive simultaneously, and also a destination for an answer to provide.

The source address is only 12 of the 16 bits of the VCI Use the field. The remaining four bits do not have any directly related to the network, but you can for one  of different purposes between a pair of Network endpoints are used.

One of the uses for the remaining four Bit is one of up to 16 virtual ones Circuits that operate simultaneously between a special Network source address and destination address are set up, to identify. This requires signaling protocol between the endpoints, the transparent is led through the network.

A second use for the remaining four Bit is to control a 4-way multiplexer. For this application, the four bits are divided into two 2-bit Fields split, the multiplexer target and sources provide auxiliary addresses.

In FIGS. 1a and 1b, payload format fields and fields for header error control and 48 octet information fields are additionally shown.

The illustration in FIG. 3 shows a route through a typical network configuration.

To the possibility of a short-term overload the connection lines in the network must be minimized each switch input port with a bandwidth control mechanism provided that the average Short-term bandwidth to one from the resource manager supplied value limited. This function is called Monitoring (policing).

Is the short-term average bandwidth that the Connection assigned is exceeded, then it is likely that cells will be deleted or ver go lore. However, to trim bandwidth to avoid peaks that re from burst-like sources an input queue is provided. The queue exit is related to the Bandwidth restricted so that the cells only get lost if the queue overflows.

This is often required in private data networks Feature is the ability to connect from a single port  to transmit data to a group of network connections. This feature is called multicasting.

Some of the values in the 8-bit VPI field can be used Identification of a group of addresses in the network be applied. These values are of two types: Local and global. A value selected for local multicast refers to a group of goals on one Mini net. In this case, the number of destination addresses the mini net can lead to the number of provided local multicast addresses reduced. A Value selected for Global Multicast focus on a group of destination addresses located somewhere in the Network can lie. In this case the number is from Destination addresses that are kept in every mini network can, by the number of Global Multi provided cast addresses reduced.

VPI values selected as multicast addresses are in each switching center as interpreted those for destination addresses, however the Interpreter addresses for two or more output deliver connections to the switching center. In in this case, duplicate copies of the cell become internal half of the switching device generated. The of a multicast value in the 8-bit VPI field Address group can ent the source address as a destination hold (for example, if a single multicast value is used to define a group of users kidneys that usually communicate with each other). Around to avoid the formation of unwanted address loops the address of the source connection of a ver averaging device from the interpreted group of Switchboard connections deleted.

A block diagram of the switching structure is shown in FIG. 4, while in FIG. 5 the switching unit and in FIG. 6 the rate adjustment and monitoring unit are shown.

All have VPI values defined as multicast Priority access to the interpreted operator output connections. A CPI value can also be considered as "Multicast" can be defined if only one target is addressed is to gain priority access.

In general, the interpretation extends either the 8-bit VPI field or the 4-bit VPI field, however, the rate adjustment unit uses the full one 12-bit field to address a 1-bit wide memory ren, the emergency operation "Emergency Mode" identified. At emergency operation set at a switching connection the bandwidth control is deactivated, so that use the full range of the physical medium can be detected.

A 4096 × 1 bit memory is provided by the sources address addressed that is in the VCI field of a cell becomes. Is the addressed bit set and emergency operation at this connection by the resource manager released, emergency operation is on this connection set. After a short timeout, if there are no further "emergency operation" cells on the connection received, a fallback mode is generated, i. H. the Standard mode restored.

Sources with the ability to initiate emergency operation are two addresses assigned, the second for fallback mode operation is provided.

All necessary for the emergency operation Chen cells would be defined as multicast to the Switch output ports access priority too win.

The use of an emergency operation leads easily significant deterioration in manageability for all other data that have the same connection Share lines in the network, so that this characteristic extremely is economical to use.  

The functionality of the network is monitored, by the average short-term expansion of competitive or conflict resolution queues is examined within each mediation statistical multiplexing, as well as queues in the rate adapts units for adjusting the rate of the mediation outputs and monitoring of the inputs are provided. This information regarding the "Short-Term Average Size "of the queues is stored in a memory of the Mediation microprocessor saved and available Query by the resource manager via the Switching connection available, the internally indicated is closed.

The resource manager is typically an application program execution, an operator instruction solution or a personal computer that is connected to one of the Network connections is connected, he features like Histograms can provide the function on a Switching device and its connections, routes tracking, identification of heavily polluted persons connections, network schemes and identification of Show sources that use emergency operation. The operating middle or resource manager is able to network by reconfiguring routes, by changing the Connections assigned bandwidth and by release or decommissioning certain features such as one Priority (single destination multicast) and emergency mode to control.

Every switching device works synchronously, by using a local clock generator internally. There is no need for synchronization across the network. The asynchronous nature of the Transport mechanism together with the queues, through the rate adjustment and monitoring mechanism all connections are permitted moderate differences in clock speed between the ver  communication facilities, while the characteristic of the band broad allocation provides for large differences. In Similarly, the physical transmission working medium asynchronously. For example a connecting to the public network Have a rate based on the public Network is locked, but is independent of the rate in the final exchange of the private network.

Without explaining the function of each part of the block diagrams of FIGS . 4, 5 and 6 in detail, it should be mentioned here again that from these figures the basic connection between the switching device, signaling unit, the microprocessor for the administrator control, the rate and protocol adjustment as well as the connections. In Fig. 5 the various queues with addressing on the input side and output handling on the output side of the waiting queues and the control via a microprocessor are shown schematically. A corresponding overview with regard to the queues for the rate adjustment and monitoring unit is given in FIG. 6.

The characteristics of the system described can be summarize as follows.

Preferably the source address is used as the destination used to identify the message from the the package is part.

One of the operator connections is internal connected that he has a switching network or coupling network access to a resource manager allowed.

Information about the function of the operator establishment is achieved by the average Short-term length of all queues is monitored, to determine the bandwidth and the corresponding Information is used for on-demand access saved the resource manager.  

The control of the interpreter, the bandwidth assignment and an emergency operating feature are through rendered the resource manager.

The packages have a fixed length and that Format recommended by the CCITT for ATN cells. The destination address is in the VPI field and the source address is managed in the VCI field.

The 8-bit VPI field used for the UNI format Cells is defined for the address targets in one local network of switches used and it becomes the four more bits of the NNI format used to identify which one or several local networks ver the required destination is bound.

The source address uses 12 bits of the 16 bit VCI field, and deliver the remaining four bits two 2-bit fields for the source and destination addresses a 4-way multiplexer.

There are also facilities for rate adjustment seen at different transfer rates various physical to the switching equipment to allow switched on media.

At each input connection of the switching device device are devices for managed bandwidth control tion provided, these devices an on Waiting queue of limited maximum length which is a portion of input bandwidth transitions permitted beyond the stipulated value.

The bandwidth control is from the emergency operation feature on a special input connector except Operation set and by interpreting certain values a source address activated and after a period of time deactivated again.

A source that has an emergency address, is assigned a second address for normal use net.  

Some of the target address values are used to to define a group of targets in the network so that the interpretation of the target address value in a be agreed switching facility in more than one Output connection of the switching device, the is addressed, can result in copies of the Packets are sent to each of the addressed ports with such packets being access priority to the output ports of the operator have.

The connecting lines between the individual Switching facilities work in relation to each other asynchronous.

Claims (14)

1. Switching device transparent to the protocol Data communications between a source and one Destination where a message is divided into packets by each with an information field and a header, where the head has at least one destination address and one Source address carries and the destination address in an Inter preter in each successive mediation establishment in a network of this intermediary on the address for an output connection of the Switching device is interpreted. 2. Switching device according to claim 1, in which the source address at the destination to identify the destination is used, of which the package is part. 3. Switching device according to claim 1 or 2, in which one of the switch ports internally connected to through an intermediary Network access to a resource manager to provide. 4. Switching device according to claim 3, in which Information regarding the function of the operator direction is provided by the average Short-term length of all queues for determining the Bandwidth is monitored, and the information on Access by the resource manager as required is saved. 5. Switching device according to claim 4, in which a control of the interpreter, the bandwidth assignment and an emergency operating characteristic of the company funds managers are provided.   6. Switching device according to a previous one Claim in which the packets are of fixed length and in a format approved by the CCITT for ATM cells is recommended, and in which the destination address from the VPI field and the source address from the VCI Field is led. 7. Switching device according to claim 6, in which the 8-bit VPI field used for the UNI format of cells is defined for the address provisions in one local network of switches used and in which the additional four bits of the NNI format can be used to identify with which one or more local networks the Destination is connected. 8. Switching device according to claim 6 or 7, in which the source address 12 bits of the 16-bit VCI Field and in which the remaining 4 bits two 2-bit fields for the source and destination addresses a 4-way multiplexer. 9. Switching device according to one of the preceding the claims, comprising a device for providing a rate adjustment to different transmission advise on various connected physical To enable media. 10. Switching device according to a previous one Claim in which a facility for managed Bandwidth control on each input port of the Switching device is provided and in which the device for bandwidth control an input queue upstream of limited maximum length, which allows a portion of input bandwidth transitions exceed the set value.   11. Switching device according to claim 10, in which is the emergency operating feature the bandwidth control on a special input port out of order sets and by interpreting certain values one Source address is activated, as well as after a time period is put out of operation again. 12. Switching device according to claim 10, in which a source with an emergency address, a second address is assigned for normal operation. 13. Switching device according to a previous one Claim in which some of the target address values ver a group of goals in the network diffine that the interpretation of the target address value in a certain switching facility can have more than one output terminal of the switch is addressed and that copies of the package to each of the addressed connections are sent, such Packets access priority to the output ports of the Have switching center. 14. switching network, comprising several switching devices according to one of the preceding claims, in which the connecting lines between these Switching devices asynchronously with respect to each other work.