Method for establishing logical connections in a synchronous digital data communication network , network element and management system

IS 2 159 172 T3

DESCRIPTION

Procedure to establish logical links in a synchronous digital telecommunications network, network element and administration system.

The invention refers to a procedure for establishing logical links in a synchronous digital telecommunications network according to claim 1, as well as to a network element for a synchronous digital telecommunications network according to claim 6 and to an administration system according to claim 8 .

Data packets originating, for example, from local information networks, are transmitted via information networks to the corresponding addressees. Such data packets come especially from Internet applications, they are made according to the Internet protocol (IP) and have an IP address of the sender and another of the destination. As a transmission medium (OSI-Layer 1) for information networks in the transmission of long-range data, synchronous digital telecommunications networks are used that work according to the standards and recommendations of the SDH or SONET (SDH: Synchronous Digital Hierarchy , SONET: Synchronous Optical Network). This is inferred, for example, from RFC 1619 (W. Simpson, Request for Comments 1619, Internet Engineering Task Force, Network Working Group, May 1994), where it is proposed for point-to-point links to pack data packets into SDH Synchronous Transport Modules (STM-N), or in synchronous transport signals (STS-N) of SONET.

In digital synchronous telecommunications networks, virtual links can be connected, that is to say, links between elements of the network. This was done manually with the help of an administration system. The logical links connected once are used later for the transmission of data packets by routers of different information networks, which prepare access to the synchronous digital telecommunications network.

Since Internet applications in particular produce amounts of data that vary greatly in time (between 0 bit / s and a few Mbit / s), which must be transmitted in the form of IP data packets through the synchronous digital telecommunications network, there is the disadvantage that either large transmission capacities have to be prepared in the telecommunications network, which then remain unused most of the time, Or that bottlenecks appear when several users want to send large amounts of data at the same time.

In another concept, IP packets are first packed into ATM elements [advanced text management] and then transmitted through virtual transmission channels through a synchronous digital telecommunications network (SDH or SONET). In an article by the firm Ipsilon Networks (“IP Switching: The Intelligence of Routing, the Performance of Switching”, Ipsilon Technical White Paper on IP Switching, February 1996, which can be called up on the Internet at http // www. ipsilon. com / productinfo / wp-ipswitch. html) presents a device (IP-Switch) that combines the function of an IP router and an ATM switch. It is in the situation of identifying longer series of data packets with the same sender and destination addresses, the so-called flows by means of an address monitor, and connecting to these appropriate links internal to the device. In this way, the transmission capacity of data packets through the IP-Switch is increased, and the average connection time is shortened. There is also the drawback here that only predefined fixed logical links can be used that follow the current useful load and are either undersized or oversized.

In a theoretical article by LH Campell et al., "A Layered Approach to Network Management Control," Proceedings of the Network Operations and Management Symposium, Nom, Memphis, April 6-9, 1992, IEEE, Volume 1, January 1, 1992, pages 46-56, a multi-stage procedure is proposed for the administration of an SDH network. An administration phase designated as Path Configuration Sublayer, considers the network as a multiplicity of logical links between network elements. In this administration phase, reconfigurations of the logical links are carried out in order to manage the bandwidth. In another phase of the administration, the Traffic Configuration Sublayer, the determination of calls is carried out. In this phase, a traffic control and statistics function is also carried out. The article proposes that the results of the Traffic Configuration Sublayer control be used to optimize the existing logical links. Since the network is intended for heterogeneous services such as PSTN, ISDN and CCS, this proposal requires communication between the different communication devices and the underlying transport network. To whom a similar communication must resemble and to whom the control of heterogeneous services must resemble, the article leaves it open. In addition, the proposal requires a unitary management system for communication devices and for the elements of the transmission network. A similar unitary system of administration has not yet been available until now.

From the article by S. Kheradpi et al., “Performance Management in SONET - Based Multi Service Networks”, Countdown to the New Millenium, Phoenix December 2-5, 1991, IEEE Volume 2, December 2, 1991, pages 1406-1411 , a method for real-time bandwidth management in a SONET-based multiservice network is known. To optimize the links in the network, using virtual containers (in SONET designated as virtual tributaries), logical links are established in the network that are periodically updated. For this, as service access (Service Gateway), intelligent access units (Remote Unit) are used that count the links and data that arrive (Source Destination arrival counts) and on the basis of the count they send bandwidth demands for source / sink (Source Destination bandwidth demands) to an administration

ES 2 159 172 T3 central network. The network administration regularly updates the existing logical links based on the demands. The proposed concept foresees a single management system for the access nodes, exchange centers and elements of the underlying transport network (SONET). In addition, intelligent access nodes are needed for different services such as 64 kbps language, broadband video signals, interactive graphics, and multimedia, which carry out the counts and send the bandwidth demands to the network administration.

One mission of the invention is to present a procedure with which a synchronous digital telecommunications network can better adapt to the data traffic, variable in time. Other missions of the invention consist of presenting a network element and an administration system for a synchronous digital telecommunications network, which are appropriate for carrying out the procedure.

The mission is resolved with respect to the procedure, by means of the characteristic notes of claim 1, with respect to the network element by means of the characteristic notes of claim 6, and with respect to the administration system by means of the characteristic notes of claim 8.

An advantage of the invention is that in the transmission of data packets the existing transmission capacities can be better utilized, and that on average the amount of transmission is greater than hitherto. An additional advantage is that commercial IP routers can be used, and that for a user who wants to forward data packets through the telecommunications network, no modifications are necessary in his apparatus.

In a particularly advantageous embodiment, a control of the sender addresses was additionally carried out. In this way a charging for the transmitted data packets is made possible.

According to another advantageous embodiment of the invention it is possible to assign a higher priority in transmission to data packets with predetermined sender or recipient addresses, for example to all data packets from or to a single predetermined user.

An example of embodiment of the invention is described below with the help of Figures 1 to 2b. Shows:

Figure 1 Two local communications networks (LANs) linked by a synchronous digital telecommunications network.

Figure 2a A configuration of a telecommunications network in the event of high data traffic between nearby users.

Figure 2b A configuration of a telecommunications network in case of high data traffic between remote users.

In figure 1 two local information networks LAN1, LAN2 are represented which are linked to each other by means of a synchronous SDH digital telecommunications network, and which can exchange data packets through the telecommunications network. The access of the information networks to the SDH telecommunications network is formed by routers RTR1, RTR2. Each of these is linked to a network element NE1, NE2 of the telecommunications network. Between these two network elements NE1, NE2 there is a logical link through the SDH network, through which the data packets to be transmitted are transported. If data packets are to be transmitted from the first local information network LAN1 to the second local information network LAN2, they will be packed in the first network element NE1 in synchronous transport modules or in subunits of such synchronous transport modules, the called virtual VC-N containers (in case of SDH) or virtual VT tributaries (in case of SONET), and they are transmitted to the second network element NE2, where they are unpacked and tracked to the second router RTR2. Alongside the SDH and SONET systems, digital synchronous telecommunications networks in the sense of the invention must also be considered as transmission systems of the Plesiochroonic Digital Hierarchy (PDH).

A logical link is generated (frequently also referred to as a virtual link), in which two network elements periodically exchange subunits of synchronous transport modules, and here the subunits are interconnected without repackaging, in other intermediate network elements located in the SDH network. telecommunications. The virtual links are established by a central management system of the SDH synchronous digital telecommunications network, and have a fixed transmission capacity, that is, they are permanent virtual links.

A fundamental idea of ​​the invention consists in providing in the telecommunications network a control of the destination addresses of the data packets to be transmitted, from this, determining the volume of traffic between the individual elements of the telecommunications network, and On the basis of the traffic volume, determine an optimized configuration of logical links, with which the network is updated. In this way, the network adapts to the current volume of traffic, making the best use of the transmission capabilities of the network. This procedure is offered especially in IP data packets from Internet applications, but it can also be applied to data packets that are made according to other protocols, preferably OSI level 3, such as the IPX protocol from Novell. Inc.

It is especially advantageous to control the destination addresses in at least a part of the network elements of the synchronous digital telecommunications network. For this, the network elements have means for controlling the destination addresses, for example, an IP address monitor. Furthermore, it is advantageous to carry out the determination of the traffic volume and the investigation of an optimized configuration in a central management system of the telecommunications network. The network elements communicate to the administration system, the

ES 2 159 172 T3 results of the control of the destination addresses, from which the management system can determine the traffic volume. Through the interfaces (for example, a Q interface), through which the administration system is linked to the network elements, instructions are then communicated to the network elements, referring to logic links to be connected by the elements. network. In this way, the administration system establishes the logical links in accordance with the optimized configuration in the network.

It is advantageous to periodically determine an optimized configuration and periodically update the logic links. This can be carried out in each case following the application, for example, daily, hourly or also every minute (pseudo on line).

Figures 2a and 2b show three elements CC1 - CC3 of the synchronous digital telecommunications network, in an example of embodiment of the invention, the first and second network elements being physically linked to each other, as well as the second and third. , for example, by means of waveguides (glass fibers) or coaxial cables. However, the figure does not show the phasic connections. The links drawn are logical links. Each of the three network elements is linked by an interface with a central TMN management system. From this they can receive instructions on which logic links to connect internally. A router RTR1-RTR3 is connected to each of the three network elements CC1 CC3, which forms the access from a local information network, not shown, to the telecommunications network. The router sends data packets coming from the local information network connected to it, which are determined for a recipient in another local information network, to the network element connected to it, where the data packets are packed into subunits. synchronous transport modules, and are transmitted to another network element, through one of the logical links.

According to the invention, in each of the transmitting network elements, before the packing of a data packet, a control of the destination address takes place. The result of this control is followed in the form of an MTL communication to the central administration system TMN. Here also the results of the checks of various data packets to be transmitted can be gathered and sent as an MTL communication to the TMN management system.

In the configuration shown in figure 2a, between every two neighboring network elements, there are two logical links, while between the two remote network elements CC1 and CC3, there is no logical link. This configuration is suitable for high data traffic volumes between CC1 and CC2 elements as well as nearby CC2 and CC3 network elements. The traffic between remote elements of the network, for example, data packets that must be sent from CC1 to CC3, have to be unpacked in CC2, fed to the connected router RTR2, there they are checked and returned to CC2 from where later, they can be transmitted to CC3 .

In the three network elements, a control of the destination addresses of all data packets to be transmitted by the respective network element takes place. The result of all the controls is communicated to the central TMN administration system as MTL communications. The TMN management system finds out the current traffic volume from these communications and determines from it an optimized configuration with which the logic links in the telecommunications network are then updated, relaying the management system to the network elements. , ANW instructions referring to the logic links that each network element must connect.

If reinforced data traffic now appears between the remote network elements CC1 and CC3, the TMN management system determines that for an optimized configuration a logical link is necessary between the network elements CC1 and CC3, and sends to each of the elements CC1 - CC3 network, an ANW instruction to connect the corresponding link, that is, to interconnect a virtual container representative of the logic link to be established, from the first CC1 network element, to the network element CC2, for the third CC3. The optimized configuration for data traffic between elements CC1 and CC3 remote from the network is represented in figure 2b. Thanks to the optimization, the data throughput for IP packets is increased, and the times of passage through the telecommunications network are reduced.

From the IP routers, a similar optimization will not be possible since they do not have any knowledge of the network topology. On the contrary, the routers automatically recognize and use or handle the new or no longer existent logic links, for example, they follow the so-called interrogation procedure. Therefore, the routers can use to route, the telecommunication network, dynamically optimized by the procedure according to the invention, after short recognition times.

It has also been proven with advantage that commercial routers in telecommunications network accesses can be used with interfaces in common use, for example, with interfaces E1, E3, E4, T1, T3, DS1, DS3, OC-na or STM- n. Also no modifications are necessary to the user's devices.

It is favorable to carry out the control of the destination addresses in crossover connectors whose task is to connect logical links in a synchronous digital telecommunications network.

A further development of the invention consists in controlling not only the destination addresses of the data packets, but also the sender addresses. In this way, a billing can be made for each sender of the data packet transmission, for example, by simply counting the transmitted data packets.

Following another refinement of the invention, preference is given to selected data packets following predefined criteria, that is, they are treated with a higher priority. Such criteria can

ES 2 159 172 T3 be in particular the sender or destination addresses. In this way, a more secure and faster data link can be made available to selected users who, for example, pay a higher rate.

Another development of the invention provides that when determining the optimized configuration, experiences with cyclically occurring traffic situations are also taken into account. Such experiences can be acquired, for example, by statistical evaluation over long periods of time, or also from the typical behavior of individual users. Thus, for example, from observations it can be known that two users always perform data compensation on Sunday night with a large volume of data traffic. The transmission capacity regularly required for this transaction is thus automatically made available by the administration system, already shortly before the start of the data transmission, in the form of a logical link, and is dismantled after the completion of the transaction.