Telefonaktiebolaget Lm Ericsson (publ)

Leif M Larsson

Hans A Berghager

Hans M Nilsson

Raimo Kalevi Sissonen

Bjorn Inge Johansson

Jan S Wahlman

Eva C Westerlund

Hans K Sallberg

Kerstin E Albage

A method and a device for determining that digital information written into a memory is correctly readable before such read information, in the form of a number of coordinated bit positions, is used to control one or several functions, where the functions can be activated by a computer unit. A selected address position or positions within the memory corresponding to the stored digital information points out a first set of bits, required to control and/or initiate the functions, and a second set of bits serving as a control sum. The second set of bits is calculated taking into consideration the current set of bits corresponding to the first set of bits and a third set of bits, corresponding to the address position currently selected for readout. When the following readout of the digital information out of the memory is performed, a new control sum is calculated in the same way, taking into consideration the currently read bit positions corresponding to the first set of bits and a fourth set of bits corresponding to the address position currently selected for readout, to form a fifth set of bits. The read digital information is accepted as correct when a comparison is performed and agreement is found between the second set of bits and the fifth set of bits.

Method and device to control a memory

In a packet network for electronic transfer of data packets from one end station to another end station, there are, in the conventional way, a number of switch units. Each end station is connected to a switch unit, and the switch units perform the transfer of data packets along an established connection. The switch units are provided with switch ports on all of their connections. In these switch ports, a substitution is performed of labels of the data packets, both for data packets arriving to the switch unit and for data packets forwarded from the switch unit. The substitution prevents data packets belonging to different connections from having the same label and also offers distributed services in the data network. The data packet labels are constructed of a VPI field and a VCI field and, for data packets that arrive directly from or are sent directly to an end station, a GFC-field. In the substitution of the label of a data packet arriving to a switch unit, a table look-up is first performed in the associated switch port by way of the contents of the VPI field of the data packet. The result of the table look-up gives a direct information if the data packet belongs to a connection having a label comprising only a VPI field (VP connection), and then its contents are replaced by a record obtained in the table look-up. If the data packet has both a VPI field and a VCI field (VC connection), its VPI and VCI fields are replaced by new label portions obtained from a second table look-up.

Label handling in packet networks

A device for checking bit errors occurring in datacells, used in switching equipment which forms part of a telecommunication system, includes an error discovery unit to detect bit errors occurring within an information carrying part of a datacell, and a counter and a processor unit to note the bit error in a bit error recording unit. The error discovery unit can also be used to amend the information carrying part and/or correct the bit error.

Arrangement for bit error monitoring in switching equipment

A switch for the transfer of data packets comprises in the conventional way input ports and output ports and parallel switching planes, which are identical to each other. The switch establishes connections between input ports and output ports through the parallel switching planes. In each output port there is for each switching plane and each established connection a buffer accommodating at least one data packet. In the output port there is in addition a logical selection device for selecting data packets from the switch and from the different planes in such a way, that a data packet stream, which is as correct as possible, is obtained from the output port, and it selects in the first place data packets from a switching plane, which is the preferred plane at each instant. The selection device comprises a quality determining unit, which at each occasion determines the preferred plane by means of quality values for each plane. These quality values are determined by means of an evaluation of earlier data packets, which have arrived to the output port.

Method for handling redundant switching planes in packet switches and a

Identification of data packets in switching equipment included in a telecommunication system and known as a packet switch. A plurality of incoming links are connected to the switching equipment via first switch ports, and a plurality of outgoing links are connected to the switching equipment via second switch ports. The equipment also includes control and coupling devices required to connect an incoming link with an indicated link, where the indication of an outgoing link is initiated by signals in the form of one or more data cells occurring on an incoming link. Additional information in the form of additional bits is delivered to the data cell in the first switch port and the additional bits are given a configuration which corresponds to the address information in the data cell. The additional bits are removed in the second switch port. The additional bits include a category identification and/or a function identification.

Identification of data packets by included selected bits

The transfer of data packets are monitored in a line having various logical channels. For each logical channel there is a count value and at the arrival of a data packet, or in each time slot when the transmission on said line is time multiplexed, i.e., for each time when a packet could have arrived in a time multiplexed system, only the count value for a single channel is decremented. Then it is determined whether the received data packet, if there is one, is to be forwarded or is to be discarded by the comparison of a calculated value (F.sub.n) to a threshold value (T.sub.n) belonging to the channel to which the packet belongs. In the calculation of the value (F.sub.n), the number is used of those channels which have not been decremented after decrementing the channel to which the received packet belongs. In this way, the calculated value (F.sub.n) can be made to resemble the calculated value or level value, which is used in prior methods for handling loss of packets in a network. For each received packet this method requires only a decrementing of one count value, implying a significant saving of time and a simplification of the circuits used for carrying out the method.

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Stockholm, Sweden

Leif M Larsson