FR2741466A1 - Filtering of messages arriving at node controller in computer network for integrated circuit controller - Google Patents

Abstract

The message filter has a first filter has a number of elementary masks that operate on all incident messages having an identifier Mi coded from N bits. Each mask performs a logical AND operation to produce a set of prefiltered messages. A second filter operates on these. The second filter has a number of numeric templates that perform an exclusive OR operation on the prefiltered messages, generating second level prefiltered messages. These second level messages are combined with an OR operation to deliver n messages of acceptance or rejection. Messages are accepted if the result of the last combination is logic zero. Accepted messages are combined with an AND operation to indicate the existence of a message at the node.

Description

Incident message filtering device
in a computer network node controller
The invention relates to a device for filtering incident messages in a computer network node controller.

 When implementing computer network control protocols, an essential problem which the processor located at each network node must face is the ability to monitor incident messages circulating freely on the network, in order to retain only messages relevant to the node in question.

 In the field of integrated network controllers, for which a high level of CPU power to silicon cost ratio must be obtained, such controllers are currently implemented, in the form of network area controllers. In this type of network, a structure or message, identifier + data, is transmitted over the network. Each node, equipped with a processor or controller, must discriminate and retain relevant messages and reject irrelevant messages, based on an identifier filtering operation.

 The operating mode of the filtering operation and the processing of message data have a major effect on the workload of the central processing unit of the processor of each node of the network, taking into account, in particular, that the central processing unit above must not only manage the network control protocol, but, above all, assume a main task of transforming the transmitted data, this main task can be as complex as that consisting in conducting a frequency transform process, fast Fourier transform, on this data.

 Current network controllers have been implemented for messages coded on 8 or 16 bits. For this purpose, they most often consist of a dedicated circuit, for reasons of performance and processing speed. These circuits have, however, due to their characteristic of dedicated circuit, very little flexibility of use. In particular, when the filtering template used is very narrow, the number of messages capable of being addressed to each node is limited, due to the dedicated nature of this circuit, for effective filtering. On the contrary, when the filtering template is too wide, many admitted incident messages must then be eliminated later by software via the central unit, which causes an unnecessary workload of the latter. Another possibility may consist in use the message identifiers to read a bit memory, the bit accessed in reading indicating whether the incident message should be rejected or not.

This method however requires an initialization in relation to the incident messages which must be accepted by the node considered. For identifiers coded on 11 bits, this solution can be envisaged, the size of the bit memory reaching at most 2 kbits. The memory size increases however very quickly with the number of bits on which the identifier is coded and reaches 512 kbits for 29 bits, which is prohibitive.

 The object of the present invention is to remedy the aforementioned drawbacks, by implementing a device for filtering incident messages in a computer network node controller, in which great flexibility or flexibility of filtering at the level of each node is reached, while the complexity of the circuits used is reduced, which consequently makes it possible to reduce the surface area of silicon necessary for the production of this filtering device in the form of an integrated circuit, and therefore to improve the integration performance without significantly influencing the workload of the central unit of the node considered.

The device for filtering incident messages in a computer network node controller, object of the present invention, is remarkable in that it comprises a first filtering module comprising a plurality of n elementary masks MAk k E [O, nl] , this module operating on any incident message comprising an identifier Mi coded on N bits, from the elementary masks, a logical operation of the type
I Mj ET MAk} to generate a plurality of n prefiltered messages, first level, and a second filtering module comprising a plurality of elementary digital templates Nk, k E [O, nl] performing an operation on the prefiltered messages of first level Of type
OR exclusive
M1 AND MAk XOR I Nk to generate second level prefiltered messages. A module for combining second level prefiltered messages is provided to perform an OR type operation on all second level messages of the same rank k to deliver n messages of acceptance or non-acceptance of the original incident message, when the relation OR ((M, AND MAk) XOR (Nk) = O is verified, and a module for combining the acceptance messages makes it possible to operate on the latter an AND type operation making it possible to generate a logic signal representative of the existence of at least one acceptance message for the network node considered.

 The device for filtering incident messages in a network node controller, object of the present invention, finds application in the production of computer network node controllers in the form of integrated circuits.

It will be better understood on reading the description and observing the drawings below, in which
- Figure 1 shows, in the form of functional blocks, a device for filtering incident messages in a computer network node controller, in accordance with the object of the present invention
- Figure 2 shows a functional layout diagram at bit level of the incident message filtering device in a computer network node controller, as shown in Figure 1
- Figure 3 gives an exemplary embodiment of the filtering operation performed by the device object of the invention, in the non-limiting case where the identifiers of the incident messages are coded on 12 bits.

 A more detailed description of the device for filtering incident messages in a computer network node controller in accordance with the object of the present invention will now be given in conjunction with FIG. 1.

 The above figure shows a block diagram, functional block, of the filtering device according to the present invention.

According to the above-mentioned figure, this device comprises a first filtering module 1 comprising a plurality of n elementary masks, denoted MAk where k represents the index of each elementary mask, k E [O, nl]. For any incident message comprising an identifier Mi coded on N bits, the coding bits of the identifier, as represented in FIG. 1, bearing the reference j with j E [O, Nl], the first filtering module 1 operates, from MAk elementary masks, a logical operation of the type
(M, ET MA,) where the operator AND indicates the logical operator AND.

The first filtering module 1 thus makes it possible to generate a plurality of n prefiltered messages, of first level, these first prefiltered messages of first level being designated in FIG. 1 by mlk. Each of the first level prefiltered messages checks the previous relationship.

It is understood in particular that the above-mentioned logical AND operation is carried out bit by bit between the bits of the same weight of the identifier Mi of each incident message and each elementary mask of rank k.

 The filtering device according to the invention also comprises a second filtering module 2 receiving the aforementioned first level prefiltered messages and comprising a plurality of elementary digital templates, denoted Nk with k E [O, n-l].

The second filtering module 2 performs an exclusive OR type operation on the first level prefiltered messages m, k verifying the relationship
(Mi AND MA, XOR I Nk the operation of the exclusive OR type being by convention designated by XOR or e.

The second filtering module 2 makes it possible to generate second level prefiltered messages each verifying the aforementioned relationship, these messages being designated by m2k.

It is understood of course that the operation of the exclusive OR type is carried out between each prefiltered message of first level mlk and each elementary digital template
Mk, this operation also being carried out bit by bit for the corresponding weight bits of each of them.

 The filtering device, object of the present invention, then comprises a module 3 for combining second level prefiltered messages, m2k, these combination means performing an OR type operation on all of the second level messages of rank k, that is to say finally over the set of N bits constituting the aforementioned second level prefiltered messages, as will be described in more detail in the description, later. The module 3 for combining the second level prefiltered messages delivers n messages of acceptance or non-acceptance of the original incident message, each acceptance message being noted ma.k. Acceptance of this original incident message is acquired when the following relation is verified OR ({Mi and MAk) XOR (Nk /) O.

 When the left member of the previous relation is equal to 1, the message mo k corresponds to a non-acceptance of the incident message for the corresponding filtering rank k.

The filtering device according to the invention finally comprises, as shown in FIG. 1, a module 4 for combining the acceptance messages ma, this combination module operating on the above-mentioned messages an AND type operation making it possible to generate a signal logical, noted
Hit, representative of the existence of at least one acceptable incident message for the network node considered, this acceptable message having satisfied the filtering criterion as defined by the device represented in FIG. 1.

 It is understood of course that, for a given incident message of identifier Mi, this message is subject to filtering according to the n masks and filtering templates and that, when all the messages ma k, acceptance messages, verify the relationship recently mentioned, this being equal to O, the original incident message corresponds to one of the filtering criteria defined by the filter masks and by the filtering templates, which then makes it possible, thanks to the signal Id, to cause the central unit located at the network node to admit this message for the node in question.

 A more detailed description of the device for filtering incident messages in a computer network node controller in accordance with the object of the present invention will now be given in conjunction with FIG. 2, this description corresponding to a bit-level functional diagram of the device as shown in Figure 1.

 As shown in the above figure, it is indicated that the first filter module 1 is formed by a plurality of n planes of AND logic gates, each AND logic gate operating, of course, at bit level.

 In FIG. 2, each logic gate plane is shown successively superimposed, in the vertical plane, for the rank j of each bit j E [O, N-l].

 Of course, and in order not to overload the drawing, each door plan in fact comprises N AND type doors, the N doors for each plane being symbolized by the arrow substantially orthogonal to the plane of the sheet for each plane, for j E [Y, N-1].

 Thus, only one door AND is represented by door plane, this door carrying the reference ETk.J for the door plane of rank k with of course k E [O, n-l].

 Furthermore, it is indicated that the first filtering module 1 comprises a plurality of n programmable registers, the programmable register of rank k thus constituting the corresponding filter mask MAk with k E [O, n-l].

Each logic gate ETk.j thus receives on a first input the bit of rank j of the identifier Mi of each incident message, as well as on a second input the bit of rank j of the mask MAk of corresponding rank k. Each logic gate ETk, i thus delivers a first level prefiltered elementary message referenced m ,, l.

 Similarly, upon observation of FIG. 2, it can be seen that the second filtering module 2 is constituted by a plurality of n plans of logical OR exclusive gates, each plane of gates comprising an OR gate exclusive at bit level. In the same way as in the case of the first filter module 1, the second filter module comprises, for each plane of exclusive OR gates, N corresponding exclusive OR gates. A single exclusive OR door is represented by door plan in order not to overload the drawing, each exclusive OR door plan being symbolized by a double arrow for j E [O, n-l]. Thus, for the row of exclusive OR gates of row k, only one exclusive OR gate is represented, bearing the reference XORk. Similarly to the first filter module 1, it is indicated that, advantageously, the filter templates Nk are constituted by programmable registers of N bits. Thus, any XORkj exclusive OR gate of rank k belonging to the bit plan of rank k receives on a first entry, the elementary prefiltered first level message mXkj corresponding, and, on a second entry, the bit of rank j delivered by the template filtering Nk of corresponding rank k. Of course, the exclusive OR gates of the same rank k, that is to say belonging to the same bit plane k, receive, on the one hand, the elementary prefiltrB message of first level d order j on a first entry, and, on the other hand, on a second entry, the bit of row j corresponding for j E tO, N-1].

 As shown in FIG. 2, each exclusive OR door plan of rank k thus delivers N second level prefiltered elementary messages, bearing the reference m2kj with j E [O, N-l].

 With regard to the module 3 for combining the second level pre-filtered messages m2k and the corresponding elementary messages, the aforementioned messages 2.j, it is indicated, as shown in FIG. 2, that this can advantageously consist of a plurality of n logic gates of the OR type with N inputs, each logic gate of the OR type being denoted OUk.

 As shown in the same FIG. 2, it is indicated that an input of each logical OUk gate is interconnected at the output of an exclusive OR gate at the bit level constituting an exclusive OR gate plane of corresponding rank k, the OUk gate receiving thus on its N entries the set of elementary second level pre-filtered messages m2k.j with j E [O, Nl] for the exclusive OR door plane of corresponding rank k. The OUk gate then delivers a message of acceptance or non-acceptance of the incident message, the message ma k previously mentioned in the description. This message of course verifies the relationships previously indicated.

 Finally, the module 4 for combining the acceptance messages a. is, as represented in FIG. 2, constituted by an AND logic gate with n inputs, each input of the aforementioned logic gate, as represented in FIG. 2, being connected to the output of a logic gate of the OUk type with k E [O, nl]. The aforementioned AND gate thus receives all the acceptance messages ma, k for k E (0, nl]. It delivers the logic signal representative of the existence of at least one incident message acceptable for the network node considered , this logic signal being noted Id.

 Recall that when Id = O, the incident message satisfies one of the filtering criteria of rank k constituted by the mask MAk and the template Nk, as mentioned previously.

 In general, it is indicated that the number of bits on which the message identifier Mi is coded can be any and of course preferably greater than 16. In an advantageous embodiment, this number N was equal to 29.

 Of course, the operating mode of the filtering device previously described in the description in conjunction with Figures 1 and 2 is independent of the number N above.

 An example of operating mode in which the number of bits N is arbitrarily taken equal to 12 so as not to unnecessarily overload the drawings and the corresponding description, will now be described in conjunction with FIG. 3.

In accordance with FIG. 3 above, it is proposed to admit to the network node considered any incident message whose identifier Mi is of the form
lOlXXXXOlXXX.

By definition, all incident messages whose weight bits 11, 10, 9 and 4, 3 correspond to those defined above, while all the other bits have the value
X = O or 1, will be accepted as incident messages from the same family of incident messages specific to the network node considered.

 Of course, for the aforementioned family, the MAk filter mask and the Nk filter mask satisfy specific criteria, which will be explained below.

 As will be seen in FIG. 3, each MAk filter mask comprises a series of N bits for which each weight bit corresponding to the weight of the significant bits of the identifier Mi of the incident messages of the same family of messages incidents, these incident messages being discriminated by the corresponding value of the bits of the same weight, is placed at the value 1. Thus, for the identifier Mi represented in FIG. 3, it is understood that the bits of the same weight of the mask MAk given, c that is to say the bits of weight 11, 10, 9 and 4, 3 are set to the value 1.

In addition, each bit of weight corresponding to the weight of the insignificant bits of the identifier of the incident messages of this same family of incident messages, is set to the value 0. Thus, for an incident message Mi as shown in FIG. 3, the weight bits 8, 7, 6, 5, 2, 1, 0 of the MAk filter mask of corresponding index are set to the value 0.

Similarly with regard to each elementary digital filtering template Nk, these include a series of
N bits. Each bit of weight corresponding to the weight of the significant bits of the identifier of the incident messages of the same family of incident messages discriminated by the corresponding value of the bits of the same weight is set to the corresponding value. Thus, bits 11, 10, 9 and 4, 3 of the filtering mask of rank k Nk have respectively the value 1, 0, 1, O, 1, that is to say the value of the bits of the same weight of the identifier Mi of the incident message or of the family of incident messages of FIG. 3. In addition, each bit of weight corresponding to the weight of the insignificant bits of the identifier Mi of the incident messages of this same family of incident messages is placed to the value 0. Thus, the bits of weight 8, 7, 6, 5, 2, 1, O of the elementary filtering mask of rank k Nk are set to the value 0.

 As will be observed by way of example in FIG. 3, for an incident message whose identifier has the value ID1 represented in FIG. 3, the plurality of first level prefiltered messages is represented by the operation bit to bit delivering the expression ID1 AND MAk in which the logical AND operation is performed for the bits of equal weight between ID1 and MAk.

The operation performed on all of the first level prefiltered messages Mlkj by the second filtering module from the given rank k filtering template Nk, as represented in FIG. 3, by the exclusive OR operation carried out bit by bit between each elementary first level filtering message mlki and the filtering template
Corresponding Nk delivers all of the N elementary second level filtering messages m2kj. One of these messages, as shown in FIG. 3, being different from 0, the incident message whose identifier is ID1 is rejected, the OR type operation carried out on all of the second level filtering messages being equal to 1, the corresponding acceptance message ma k being equal to 1.

 On the contrary, in the case of an incident message whose identifier is ID2 as shown in FIG. 3, whose significant bits 11, 10, 9 and 4, 3 are indeed equal to the corresponding weight bits of the family defined by the identifier Mi and therefore at least one elementary filtering template of rank k Nk as shown in FIG. 3, the exclusive OR operation carried out bit by bit on the set of elementary first level pre-filtering messages m1ki generates a set N elementary second level prefilter messages m2kj all equal to O, the acceptance relation being satisfied and the logic signal Id is then equal to O indicating the existence of an original incident message whose identifier satisfies the filter criteria.

 With regard to the connection between the message filtering device, object of the present invention, and the processor or central unit of the network node considered, it is indicated that the logic signal representative of the existence of the incident message of acceptable origin for the network node in question, can act directly on the aforementioned processor to make an interrupt call, which then causes the acceptance of the incident message on the network input port. Rapid interrupt call methods can thus be used, the current context of the central unit being saved and a specific register which can be used to admit the relevant incident message thus detected. The processing of incident messages is thus carried out in a manner particularly fast insofar as the workload of the central unit has thus been transferred to the device which is the subject of the present invention.

 It is also understood, of course, that the rank k of each filter mask and of each elementary filter mask Nk can be arbitrary insofar as the global operations of logical AND type, of exclusive OR type and of OR type carried out by the first, second and third modules are in parallel.

 Of course, for a large number of messages and finally for a great flexibility of use of the filtering device object of the present invention, the number n of filter masks and the corresponding number of filtering templates can be greater than 3 or 4 , which allows a very great flexibility of use.

 Finally, it is indicated that all of the circuits necessary for implementing the device which is the subject of the present invention can be produced using 0.6 pm CMOS technology.

Claims (8)

 1. Device for filtering incident messages in a computer network node controller, characterized in that it comprises  - first filtering means comprising a plurality of n elementary masks MAk k E tO, nl], said first filtering means operating on any incident message comprising an identifier Mi coded on N bits, from the elementary masks, a logical operation of the type  I M1 AND MAk} to generate a plurality of n prefiltered messages, first level  - second filtering means comprising a plurality of elementary digital templates Nk, k E (O, nl] performing on said first level pre-filtered messages an operation of the exclusive OR type I Mj AND MAk) XOR I Nk} to generate pre-filtered messages second level  means for combining said second level prefiltered messages, performing an OR type operation on all of the second level messages of rank k in order to deliver n messages of acceptance or non-acceptance of the original incident message, when the acceptance of this message is acquired, the relationship  OR ((Mi AND MAk) XOR (Nk) = O is checked ;;  means for combining said acceptance messages operating on said acceptance messages an AND type operation making it possible to generate a logic signal representative of the existence of at least one acceptance message for the network node considered.  2. Device according to claim 1, characterized in that said first filtering means are formed by a plurality of n planes of AND logic gates, each door plane comprising an AND gate at bit level.  3. Device according to claim 1 or 2, characterized in that said second filtering means are formed by a plurality of n planes of logic gates Exclusive OR, each door plan comprising an exclusive OR door at bit level.  4. Device according to one of claims 1 to 3, characterized in that said masks MAk and said filtering templates Nk are constituted by programmable registers of N bits.  5. Device according to one of claims 2 to 4, characterized in that said means for combining second level prefiltered messages are constituted by a plurality of n logic gates of the OR type with N inputs, one input of each logic gate being interconnected at the output of an exclusive OR gate at bit level constituting an exclusive OR gate plan of the plurality of n logical gate plans Exclusive OR constituting the second filtering means, each logical OR type gate delivering an acceptance message or non-acceptance of the original incident message.  6. Device according to one of claims 1 to 4 in combination with claim 5, characterized in that said means for combining said acceptance messages are constituted by a logic gate of the AND type with n inputs, each input of this gate AND type logic being connected to the output of an OR type logic gate delivering a row k message of acceptance or non-acceptance of the original incident message, said AND type logic gate delivering said logic signal representative of the acceptance or non-acceptance of the original incident message for the network node under consideration, through the existence of at least one acceptance message of rank k.  7. Device according to one of the preceding claims, characterized in that each elementary filter mask MAk comprises a series of N bits, each bit of weight corresponding to the weight of the significant bits of the identifier of the incident messages of the same family of incident messages, discriminated by the corresponding value of the bits of the same weight, being placed at the value 1, each bit of weight corresponding to the weight of the non-significant bits of the identifier of the incident messages of this same family of incident messages being placed at the value 0.  8. Device according to one of claims 1 to 7, characterized in that each elementary digital filtering template Nk comprises a series of N bits, each bit of weight corresponding to the weight of the significant bits of the identifier of the incident messages, discriminated by the corresponding value of the bits of the same weight, being placed at said value, each bit of weight corresponding to the weight of the insignificant bits of the identifier of the incident messages of this same family of incident messages being placed at the value 0.