METHOD AND UNIT FOR THE CONTROL OF THE CELL FLOW IN A TELECOMMUNICATION SYSTEM ACCORDING TO THE ATM TECHNIQUE

Abstract: Method for the control of the cell flow in a telecommunication system in ATM technique, according to the so-called "Leaky Bucket" principle, where to each active connection (VC/VP) a current value (VLB) is associated, increased by a first quantity (INC) and decreased by a second quantity, following the arrival of an information cell relating to the connection. Said value (VLB) is compared with a reference threshold (S) to decide if the cell has to be sent or not. The decrease is equal to the product of a third quantity (DEC) and the difference between the absolute time (CLK) and the time (LST) of the previous updating of said current value (VLB). The method is implemented by means of one unit (PU) including two control units (CC, MC), an arithmetic unit (AU), a register file (RF) and an input/output unit (I/O).

Description: METHOD AND UNIT FOR THE CONTROL OF THE CELL FLOW IN TELECOMMUNICATION SYSTEM ACCORDING TO THE ATM TECHNIQUE The present invention refers to a method for t control of the cell flow in telecommunication syste employing a particular numeric technique, called A (Asynchronous Transfer Mode), for the transmission and/ communication of voice and video signals and data. In the ATM technique, data relevant to different use and services are organized as timely contiguous units wi a fix length of approximately 400 bits, called cells. Ce bits are subdivided into a field containing information be exchanged, and in a header, containing informati necessary to the cell routing through the switching netwo and other service information. The ATM technique is considered as the most promisi solution for multiplexing and switching, in the evoluti of public communication networks towards the future bro band integrated services digital network (B-ISDN), sin this technique allows a great flexibility versus t previous (circuit switching) systems. A given number of connections, called Virtual Channe (VC) and Virtual Path (VP) can be active at the same ti on an ATM link. The virtual channel is a logic associati between terminal points of a link enabling t unidirectional cell transfer on that link, while t virtual path is a logic association of virtual channe between the terminal points of a link enabling t unidirectional transfer of cells belonging to a group virtual channels existing on that link [see also CCI Rec. 1.113]. A varying number of virtual channels and/ virtual paths (VC/VP) can be associated to each user or each call, because a same ATM user could have several cal established at the same time and each virtual channel c require a special number of cells in the time unit, th obtaining a very high flexibility of the network in t management of data. In particular, the allocation of network resources c be made on the basis of what is actually required by t user, thus allowing a high effectiveness particularly the case of connections requiring variable netwo resources. However, due to the fact that the ATM technique is the asynchronous type and subject to considerable u variations by users (in a wide sense), it is necessary monitor the flow of cells sent to the switching network the ATM system to prevent the overloading of the same a particularly an overload ascribable to transmission users of a number of cells higher than that agreed with t network operator, on which basis the necessary netwo resources are allocated to the call and the accounting made for the use of the network itself. In this case it defined a "band width" higher than that agreed with t network operator. This control is called UPC (Usage Parameter Contro in ATM environment and can take place depending on one more flow parameters, generally tied to the "frequency" more particularly to the bit rate, that is to the number bits transmitted in- a given time interval. To this purpose users connected to the network can divided on the basis of the service required which can at Costant Bit Rate (CBR) or at Variable Bit Rate (VBR). I the case of CBR services the characteristic of t connection are sufficiently identified by a singl parameter, i.e. the agreed bit rate, while in the case o VBR services two parameters at least have to be considered for instance the ripple Rp bit rate (measured on a shor time period) and the medium Rm bit rate (measured on longer time period) . A method for the control of the flow in an ATM networ can be that to foresee the control or monitoring of the bi rate agreed for each CBR connection (or user) coming int the switching network and the ripple bit rate for each VB connection, excluding the cells in excess of these values This solution is acceptable for CBR connections, but results too rigid for VBR ones, compromising a great pa of the advantages of an ATM network. The solution proposed for VBR connections is therefor to eliminate exceeding cells according to given criteri which consider also the average bit rate, agreed by eac network user and the network operator, besides the rippl one. A method for the control of traffic parameters agree upon between the user and the network operator, which wa proposed in ATM environment, is the so-called "Lea Bucket". This method is shown in Fig. 6 and can b considered from the conceptual point of view as including counter CN, counting the IN input cells (with an assigne header) , and which is increased at each cell input an periodically decreased by a Clock signal, whose frequenc is defined on the basis of the value agreed for the traffi parameter to be controlled. The counter output is connecte to the input of a comparator CP, receiving on the othe input a reference threshold value (stored in a TH registe being it also a function of the value agreed for th traffic parameter to be controlled) , and emitting at th output a control logic signal of a SW switch, rejecting th cell or letting it go on. Until the CN counter value is lower than the valu assigned for the threshold, cells coming from tha connection are accepted, that is routed to the network When the counter content exceeds the threshold value, th cell is rejected since the user has sent a number of cell higher than the one agreed upon. This method enables to control the agreed Bit Rate suitably fixing the decrease frequency of the counter C and the threshold value TH. In particular, in this case th "Leaky Bucket" mechanism is used to control the average Bi Rate of a VBR connection, it results that the threshol value TH is much higher than that for the control of t ripple Bit Rate of a VBR connection (or of the Bit Ra defining the connection, if this is of the CBR type), sin the user behaviour has to be averaged on a long enough ti period. However, the method described hereabove has so inconvenience and limit for use in an ATM network, due the fact that control has to be extended to all VC/ (virtual channels/virtual paths) which can be active at t same time on a given ATM link. In fact the Leaky Buck mechanism acts on the basis of the traffic parameter val agreed for the VC/VP, therefore a-.counter CN and a regist TH has to be assigned to each active VC/VP and each counter has to be decreased in a differentiate mode at t frequency defined for each VC/VP, and therefore the abo described device becomes quickly complex due to the hi number of VC/VP which can be active at the same time on link. The scope of this invention is therefore to implemen a method and a control unit capable to eliminate the abov mentioned inconveniences and limits for the forme technique. The invention consists of a method for the control o cell flow according to the so-called Leaky Bucket principl in ATM technique telecommunication system, where a curren value is associated to each active connection, increased b a first quantity and decreased by a second quantity following the arrival of an information cell relating t said connection, said value being compared with a referenc threshold to decide to send or not the cell, characterize by the fact that said decrease is equal to the product of third quantity for the difference between the absolute tim and the time of the previous updating of said curren value. The invention consists also of a unit for the contro of information cell flow in ATM technique telecommunicatio system, characterized by the fact to include: an arithmetic unit connected to an input/output uni through an internal data bus, said input/output unit bein connected to an external data bus; a register file connected to said input/output uni through said internal data bus and an internal address bus and connected to said arithmetic unit through said interna data bus; a first central controller supervising the updatin operations, and a second memory controller for the contro of the loading/storage sequence. The invention consists also of a unit at the input o an ATM technique telecommunication system for the contro of the cell flow through a unit as described above characterized by the fact to include a storage containin the so-called Leaky Bucket parameter values relevant t active connections, each address block containing a recor made of status fields, one current value field, a fiel containing the value associated to the parameter to b controlled for the relevant link and a field containing th time of the last updating of the current value field of th relevant connection. Further advantageous characteristics result from th ensuing claims. The invention shall now be described making referenc to a preferred, but not limiting, realization form, show referring to the enclosed figures, where: Fig. 1 shows a diagram of the ATM connection networ and the central unit terminations connected to the same; Fig. 2 shows a diagram of some units forming part o the exchange termination unit (ET), including a contro unit according to the invention; Fig. 3 shows more in detail the connections to th control unit according to the invention; Fig. 4 shows a construction of the control uni according to the invention; Fig. 5 shows the structure of data in the memory, and Fig. 6, already considered, shows the known contr principle of cells called Leaky Bucket. Referring to Fig. 1, an ATM switching node includes connection network SN, to which different exchan termination units (ET) are connected, receiving incomi cell flows IN/F and transmitting outgoing cell flows OUT/ correctly routed to the SN network. These input and output flows can take place through ATM link, for instance having a capacity of approximate 156 Mbit/sec. A given number of virtual channels a virtual paths, called in short hereafter VC/VP, can active on this link. An ET structure, upstream side (that is towards the network) is shown more in detail in Figures 2 and 3. includes a HTU assembly (Header processor and Translati Unit) receiving the incoming flow, processing the cells ATM level and transforming the cells from the ATM standa format to proprietary format internal to the node, befor these are (possibly) sent to the SN. The control of the flow at the ATM node input i carried out at this level, in cooperation between HTU and PU unit (Policing Unit), present also in the ET, having th specific task to verify the compliance of VC/VP behaviou with the parameters agreed between the user and the networ operator during the call set up phase. The non conformit or infringement can determine the elimination of the cel or its marking for further evaluation on its accessibilit in the network. The elimination and/or marking of cells infringin these parameters are actually made by the HTU since according to the invention, PU does not directly receiv the incoming cell flow, but it is connected to the HTU uni through a four-wire interface on which four signals ar exchanged, marked SP, SV, PO and EP, and through an LB bu for the communication of virtual path (VP) and virtua circuit (VC) identifiers of the incoming cell. Should the PU unit detect a non compliance, it give the answer to the HTU in due time for the cell is rejecte (or marked) by this unit, before it is sent to the network This procedure performs, from the conceptual point of view the function of the schematic arrangement, shown in Fig.6 of a controlled switch SW to reject cells in excess. The PU unit has an associated dedicated RAM memory called MPU, containing the so-called values of Leaky Bucke parameters relating to active connections. For instance matching each address, these values include the counte value and the threshold value associated to a' given link The MPU memory is able to contain, e.g. 2048 addresse (2 11 ), each including 8 bytes, totalling 16384 bytes (2 14 ) Therefore the counter, which according to the Leak Bucket method is increased, decreased and compared with threshold value, is here replaced by the content of a P register where the content of a given location of the MP memory is loaded for these operations. As it can be better noticed from Fig. 3, the interfac between HTU and PU foresees two wires for each direction and particularly two wires for SP and SV signal for th possible activation of the control procedure from HTU t PU, and two wires for EP and PO signals for acceptanc indication. Particularly, SP is the starting signal informing th PU to carry out the control on the cell identified by th VCI/VPI or other identifier, made available to the PU on LB bus (Label Bus), while SV is the validation signal; P is the output signal which communicates the result of th control to HTU, and EP is the validation output signal o PO. Matching each cell, SV and EP strobe signals are use to perform a four-phase asynchronous protocol between th HTU assembly and the PU unit, irrespective of the presenc or not of a cell to be controlled. The interface is of th general type and allows an easy coupling of the PU wit other components, in other points of the network, where th engaged band width control can be required (e.g. at t input of an ATM statistic multiplexer, etc. ) . Therefore, according to the invention, to control a VC/VP active at the same time on the ATM link, which c also be thousands on a same exchange termination unit (E of the public network, a central device is employe connected to a memory in whose addresses counter conten are allocated, each one of them being updated at t arrival of the corresponding cell. In the first model of Leaky Bucket the decrea operation of counters is made separately for each VC/ with a frequency set by the Clock dedicated to the sam However, this method has the disadvantage to have to mak in the same cell time, the decrease (updating) of counte for a number of VC/VP which cannot be foreseen befor theoretically even up to a maximum of all VC/VP active the link at the same time. According to the invention, the PU performs t control of the cell flow of all VC/VP active on the link the same time, in an independent way, performing th updating of the "virtual counter" of a single VC/VP at eac cell time, instead of a plurality of VC/VP as specifie above. This is performed making the updating of the VC/V counter only at the arrival of the cell relevant to it according to the following formula: VLB = VLB -1-INC - (CLK - LST) . DEC (1) where the variables have the following meanings: - VLB is the filling current value of the Leaky Bucke associated to the particular VC/VP. It is contained in portion (see Fig. 5) of the address location in the MP memory corresponding to the special link, from which it i drawn up for updatings, and where it is brought back afte any updating. - INC is the value by which the current value VLB i decreased when a new cell of that connection arrives Preferably this value is not a unit value, but it is alway a higher one. For instance it can reach a maximum value o (2 16 -1). - DEC is the value by which the counter is decreased a each cell time, which can be freely selected from 1 an INC. - CLK is the absolute time, which is increased by one uni with a period equal to the ATM cell duration (that is ever 2,83 μsec approx. for the 156 Mbit/s link). - LST is the time of arrival of the last cell relevant to given link. Therefore LST is assumed equal to CLK when th new cell is accepted because it does not infringe th controlled parameter, and in general (CLK-LST) indicate the time elapsed from the last updating of the curren value VLB relevant to the link under consideration. A possible and preferred realization of the PU unit i given in Fig. 4. The PU unit shown in Fig. 4 includes five main units and more in particular a controller MC and a controller CC an arithmetic unit AU, a file or register file RF, and a input/output I/O unit. The central controller CC supervises updating an refresh (described here after) operations, while the memor controller MC has the function to control the loading an storage sequence to and from the MPU. The arithmetic unit AU, where updating and refres operations are actually made, includes two 16 bit records two 8x8 multipliers to make a multiplication between tw 16-bit binary numbers, and two arithmetic-logic units (ALU suitable for 32 bit arithmetic operations. The register file RF is used to contain the Leak Bucket parameters for link classes, as defined herebelow The file is made of one storage unit, where o initialization. Leaky Bucket parameters are written, rea by preset locations of the MPU. This memory is addresse through the address bus ARF and data addressed to, an coming from the same, transit on the internal data bus DBI The input/output I/O unit connects the external da bus DBE for the connection with the MPU to the intern data bus DBI, it controls the ABM address bus for the M external RAM on MC control and the ARF address bus on control. Fig. 5 shows the organization of an address block the MPU memory. Each address block or data record contai the current parameters for the execution of the contr method. Fields are the following: VLB Field: it is a 28 bit field containing the curre value of the counter indicating the Leaky Bucket fillin it is updated according to (1), at the arrival of a new A cell from the relevant connection, only if the ce complies with what agreed, or to each refresh operati relevant to that address. The VLB value is updated only when a correspondi cell arrives. In case the updating results in a negati value, VLB is assumed equal to zero. The upper limit this value is a threshold S: if the updating underw involves the overcoming of the threshold value, infringement is signalled and the VLB value is not update INC/DEC Field: it is a 16 bit read only field for t PU, containing the value associated to the parameter to controlled for the relevant VC/VP. LST Field: it is a 16 bit field and contains the C value corresponding to the last updating of the VLB valu When an infringement is detected, LST is not update according to what said above. Status Field ST: it is a 4 bit field where the n call information is stored, through the NC bit, havi value 1 for the first cell of each VC/VP, in such a w that PU initiates the VLB value at S/2; the class of th connection underway CC0-CC1 defining the threshold an increase/decrease values; and the VD bit whose functio shall be described later on. Since the increase and the decrease of the VLB valu relevant to VC/VP are made only at the arrival of th corresponding ATM cell, the result of this updatin operation depends on the time elapsing from the arrival o two consecutive cells belonging to the subject VC/VP, a indicated in (1) . The time elapsed from the arrival of th last cell is obtained as difference module-n between CL and LST, if these are represented on n bits. If a VC/VP allows too time elapse between two cells the counter generating the CLK signal could make a complet module-n count without the updating of the LST value, an therefore an overflow condition could occur, that is th subsequent cell of said VC/VP, arrived ' after a complet tour of the counter CLK, is considered as arrived after th previous one since CLK and LST values result being close and (CLK-LST) results to be small. It could occur tha users, who employ a reduced and irregular band width, tha is who send cells with a comparative low and/or irregula rithm, see their cells suppressed due to the overflo effect, with an ensuing different treatment among users and particularly punishing just the connections havin lower frequencies. The increase of counter sizes is only a partia solution of the problem, since there are some limits t this extension, and worse than that, with a very lon counter cycle, the penalization deriving from the possibl cell suppression is even higher. According to the invention, a periodical re-writing o refresh of VLB and LST values of each link is foreseen where the datum is re-written as decreased by the tim elapsed. More particularly, at each cell time, equal t 2,83 μsec (averagedly) in the example considered, the valu relevant to a VC/VP is modified according to the followin relation: VLB = VLB - (CLK - LST) . DEC (2) where the variables have the same meanings described fo This updating is made in succession for each VC/VP. other words, compared to the relation (1) , governing t control, INC is not added because no cell has arrived, b VLB is decreased by (CLK-LST) . DEC and VLB and LST valu are updated in the MPU memory, considering in this way on the time elapsed from their last updating. In pratice, in a cell time, refresh of values releva to a link is made first, applying the relation (2), an then, if a cell arrives, the actual verification is made applying the relation (1) to the parameters relevant t the VC/VP belonging to the ' cell arrived. It must be noticed that, in principle, the refres operation intervenes on the values contained in an addres of the MPU memory different from the one being the objec of the control operation. Occasionally, it can occur t make a refresh operation in the same cell time, followed b a control operation on the values relevant to the sam VC/VP, or contained in the same MPU address. In this case the result of the two subsequent updatings of VLB is equa to the one which can be obtained with a single updating applying only the relation (1), and therefore the refres operation is completely transparent to the user of the AT network. If a 2 n address MPU memory was foreseen, the complet updating of all VC/VPs should take place after 2 n cel times or CLK increases. Due to the fact that VC/VPs activ at the same time on a same link could be even more tha 2000, n can have to be higher than 11; preferably, the CL counter, and therefore LST, are selected of the 16 bi length, that is each one of the variables CLK and LST is 1 bit long. With this choice the upper limit of the MP maximum dimension, which is 2 * --° addresses maximun, result far beyond practical requirements for use. To prevent overflow it is sufficient to perform th refresh operation with an intervention frequency not highe than the overflow cycle time (equal to 2 16 cell time), an therefore the device runs for whichever equipment of th MPU memory not higher than the above mentioned maxim dimension. Preferably, according to the invention, VC/VPs acti at the same time on the link are subdivided into classes groups and the classification of VC/VP into one class indicated by the CC value (Connection Class) contained the MPU at the address corresponding to the VC/VP. T class is selected during the link establishment phase a therefore the CC value can be programmed according to t final contract stipulated with the user. Also DEC value programmable according to the final contract with the use On the contrary, the INC value and the threshold value can be programmed according to the class. It is th possible to save space in the memory, because an INC val and an S value for each VC/VP have not to be stored in t MPU, but only the CC value to identify the relevant class. In this case DEC is proportional to the Bit Rate on wants to control and INC corresponds to the number of equ intervals into which the link band width is divided a therefore it depends on the minimum value of band widt which can be allocated and controlled. For instance, havi INC represented on 16 bits we can discriminate among Bi Rates differing of about 2 kbit/s. An alternative realization is to maintain the I value programmable according to the contract stipulate with the user, while the DEC value is made programmabl according to classes. In this case INC is proportional t the Bit Rate to be controlled and DEC corresponds to t width of intervals into which the link band width i divided, and therefore it conforms to the minimum ba width we can allocate and control, that is DEC = corresponds to a 2 kbit/s band width, for the 156 Mbit/ link, if the maximum dimension of INC (and therefore DEC) is equal to 16 bits. As an indication, without limiting the scope of t invention, the number of classes has been selected equal 4, therefore the CC value results represented on 2 bits C and CCO, as shown in Fig. 5. According to the invention, the PU unit can programmed to operate in Single Mode (SM) or in Parall Mode (PM) , through polarization of the S/PM input shown Fig.3. SM operation has been described herein before. On the contrary, the operation in PM, the PU unit contro an indication coming from the outside. This indicati comes to the EPOK and EEP inputs represented with dott lines in Fig.3. The information relevant to the non acceptance of t cell due to events out of the subject PU control (e. infringement of parameters controlled by other PU or othe type units), is given to the EPOK input, while the signa validating EPOK is given at the EEP input. The PU evaluates the EPOK signal only if it has no detected the violation i.e. when it supplies at the outpu PO=l. In this case, if the PU finds EPOK=0, i correspondence of the EEP rising edge, it stores VD=1 i the status field ST of the MPU memory (see Fig. 5), at th address relevant to the VC/VP, which the considered cel belongs to, otherwise it stores VD=0. Therefore: if PO=l and EPOK=l, it results VD=0; if PO=l and EPOK=0, it results VD=1; if PO=0, EPOK is not considered and VD is no modified. Each time PU is activated by HTU to perform the cel control (SP=1 in correspondence of the rising edge SV) , i updates the VLB value according to the VD value stored i the MPU memory in the following way: 1. with VD=0, PU applies the formula (1) , as in Singl Mode operation; 2. with VD=1, PU updates VLB without increasing th value of INC quantity, since it has already made thi increase on the arrival of the preceeding cell of the sam VC/VP, which was rejected by HTU due to events independen from the PU under consideration. Therefore the formula (2 is applied, and therefore we can talk of refresh li algorithm. The refresh operation is not affected by t Single/Parallel Mode operation, and in the Parallel Mode is performed as previously described. Though the invention has been described maki particular reference to preferred realization forms a application methods, it is not limited to what describe but extends to cover all the obvious variations and/ modifications which shall be evident to the technicians this field.

Claims: CLAIMS 1. Method for the control of the cell flow in an A technique telecommunication system, according to the s called Leaky Bucket principle, where to each acti connection (VC/VP) is associated a current value (VLB increased by a first quantity (INC) and decreased by second quantity, following the arrival of an informati cell relating to said connection, said value being compar with a reference threshold (S) to decide to send or not t cell, characterized by the fact that said decrease is equ to the product of a third quantity (DEC) for the differen between the absolute time (CLK) and the time (LST) of t previous updating of said current value (VLB) . 2. Method according to claim 1, characterized by t fact that said updating occurs only on the arrival of a n cell relevant to said connection, if this did not cause infringement. 3. Method according to claim 1, characterized by t fact that the value of said threshold (S) is variable. 4. Method according to claim 1, characterized by t fact that the value of the first quantity (INC) variable. 5. Method according to claim 1, characterized by t fact that the value of the third quantity (DEC) variable. 6. Method according to claims 3, 4 and 5 characterized by the fact that the values of the thresho (S) and of the first quantity (INC) can be programme according to the connection class and said value of th third quantity (DEC) can be programmed according to th connection. 7. Method according to claims 3, 4 . and 5 characterized by the fact that the values of said threshol (S) and of the third quantity (DEC) can be programme according to the connection class and said value of th first quantity (INC) can be programmed according to th connection. 8. Method according to whichever claim 1 to 7 characterized by the fact that said current value (VLB) i periodically decreased by a fourth quantity, with a intervention frequency lower than the overflow cycle tim of the counter defining the difference between sai absolute time (CLK) and time (LST) of the previous updatin of said current value (VLB). 9. Method according to claim 8, characterized by th fact that said fourth quantity is equal to the product o said third quantity (DEC), for the difference between th absolute time (CLK) on the moment of the periodica decrease and the time (LST) of the previous updating o said current value (VLB). 10. Method according to whichever claim 1, 3, 6 an 7, characterized by the fact that said current value (VLB) is assumed firstly as one half of said threshold value (S) on the arrival of a first information cell relevant to sai connection. 11. Method according to whichever claim 1 to 9, characterized by the fact that said current value (VLB) i updated following the arrival of an information cel relevant to said connection without being increased by sai first quantity (INC) according to the value of a fift quantity (VD) and of a sixth quantity (S/PM) . 12. Method according to claim 11, characterized by th fact that said fifth quantity (VD) is a binary value whic can be modified. 13. Method according to claim 11, characterized by th fact that said sixth quantity (S/PM) is a binar programmable value. 14. Unit for the control of the information cell flo in an ATM technique telecommunication system, characterize by the fact to include: an arithmetic unit (AU) connected to an input/outpu unit (I/O) through an internal data bus (DBI), sai input/output unit being connected to an external data b (DBE); a register file (RF) connected to said input/outp unit (I/O) through said internal data bus (DBI) and internal address bus (ARF), and connected to sa arithmetic unit (AU) through said internal data bus (DBI) a first central controller (CC) supervising t updating operations, and a second memory controller (M for the control of the loading/storage sequence. 15. Control unit according to claim 14, characteriz by the fact of being connected to means (HTU) suitable perform the processing of the cell flow of the A technique telecommunication system through a four-wi interface and a bus (LB) for the exchange of virtual pa (VP) and virtual circuit (VC) indicators of the incomi cell, and a dedicated RAM memory (MPU) containing t current parameters for the execution of the control metho 16. Input unit of an ATM technique telecommunicati system for the control of the cell flow through a unit (P according to claims 14 to 15, characterized by the fact include a storage (MPU) containing the so-called Lea Bucket parameter values relevant to active connection each address block containing a record made of stat fields (ST), one current value field (VLB), an (INC/DE field containing the value associated to the parameter be controlled for the relevant link (VC/VP) and a fie (LST) containing the time of the last updating of t current value field (VLB) of the relevant connection. 17. Unit according to claim 16, characterized by t fact that said status field /ST) is made of 4 bits whe are stored the new call (NC) information, the class of t connection (CCO-CCl) underway defining said thresho values (S) and increase/decrease (INC/DEC) values, and o bit (VD) recording the infrigement of parameters controlle by different units of said control unit (PU) .

Inventors: BALBONI GIANPAOLO, COLLIVIGNARELLI MARCO, CONIGLIARO SALVATORE, BALBONI, GIANPAOLO, COLLIVIGNARELLI, MARCO, CONIGLIARO, SALVATORE
Applicants: ITALTEL SPA, ITALTEL SOCIETA' ITALIANA TELECOMUNICAZIONI S.P.A.
Application year: 1992
Main classification: H04L12
IPC codes: H04L12