FI98582C - Realization of a secure bus in a data communication network - Google Patents

Description

98582

Implementation of a certified bus in a telecommunication network

The invention relates to a method according to the preamble of appended claim 1 and to an arrangement according to the preamble of appended claim 3 for implementing a certified management or similar bus in a telecommunication network.

By management bus is meant a data transmission connection which transfers network management information, i.e. information which is intended, for example, to collect fault data or to control the functional units of the network to a certain state. In principle, the method according to the invention is suitable for implementing any bus, although in practice the transmission of management information is by far the most important conceivable embodiment of the bus.

The primary object of the present invention is to implement a certified management connection in a loop network or a so-called in a mesh network constructed of loops (there is more than one path between any two nodes in a mesh network), but the invention is generally suitable for ver-. . if the format of the bus matches the synchronization structure used in the network. Nodes connected to the bus can send their messages to the bus, '. : 25 whereby it spreads along the bus to all nodes connected to it. There must be no loops in the bus, as in this case the · · I message would be left circulating along the bus. (In this presentation, the intersections of transmission links in a telecommunications network are referred to as a node. Node-30 devices include, for example, splitter, channelization, and crossover field devices.) • · ·

The signals between the nodes of the network can be e.g.

• · *. 1J 2048 kbit / s signals according to ITU-T (formerly CCITT) recommendations G.703 / G.704, in which the frame includes 32 time-. . ·. 35 intervals (TS0 ... TS31) and 16 frames for the superframe. In the frame structure of such a 98582 2 signal, the management information can be transmitted e.g. by the service channel allocating e.g. three bits of the time slot TSO bits from the frame structure. Every other frame has a TSO frame lock flag in the time slot, 5 but every other bit bits 4-8 are free for national use, so that they can be used for the transmission of network management information.

Currently, a certified management bus is typically implemented using conditional methods implemented separately for this purpose, which means that the state of the received signal and certain status bits are monitored at the network node. When these meet certain predetermined conditions, the connection must be verified. This is described in more detail below.

Figure 1a illustrates the principle by which a management bus is typically implemented within a network node device. The node has an adder 11 to which all connections on the management bus are imported. These connections can be: 20 - a local management interface 12 in the device, to which, for example, a network management system can be connected. . directly. There may be more than one of these local management interfaces.

- Sharks passing through different useful signals Lint akana vat '· · 25 EOC 1 ... EOC N (EOC, Embedded Operation Channel or ECC, • · "": Embedded Control Channel).

• · · - connection to the node's own control block 13, where hands: receive incoming messages to the node and send responses to incoming messages.

j \ t 30 All directions shown in the figure can become messages and all these directions receive messages (i.e., • · · 1 2 traffic from the adder is bidirectional in each direction shown in figure • · • · · 2 ”). At the summation point, the channels from 11 different directions · ... · are combined. Coming from a certain direction. 35 data is further connected (transmitted) to all other • • · 98582 3 directions. Only one transmitter at a time is allowed to transmit data (if several transmitters transmit data to the bus at the same time, the signals add up and the data is corrupted).

5 Basically, the adder is a very simple device; it performs a pure logical AND operation on the management or maintenance channels connected to it. If any of the signals are in the "zero" mode, the result is zero. In practice, this means that the line sleep mode is number one. In other words, if the device does not send anything, it keeps itself in number one mode. (The line from the control block 13 to the adder is in the first state when the node has nothing to transmit, in which case it does not affect the others in any way.) The traffic is serial for the communication blocks of the devices connected to the adder 11 and the service-15 channel. At some point, the data may be in parallel format, but upon import to the adder, it must be converted to serial format.

When implementing var-20 in the above solution, the desired EOC channels must be able to be turned on or off as needed (depending on the states of the signal and the bits being monitored). This can be implemented, for example, according to Figure Ib, so that each EOC channel has its own switch SW, which is controlled on the basis of the signal and the states of the bits to be monitored. The incoming ♦ signal to the node is first routed to the channelization block MUX / DEMUX, i:: where the signal of the EOC channel is separated from the other signal and passed to the switch SW. The other time slots of the incoming signal are connected to the cross-connect block XC, from where they are switched forward. The switch control block CTR receives information about the signal status from the multiplexing block and also performs a condition of the number of bits from the cross-connect block. Based on this information, ♦ ♦ ·. * ·: It turns on the authentication connection by controlling the (corresponding) switch SW. (In the figure, only one signal is shown for simplicity. 3 5, but in the case of 98582 4 several signals, the matter is logically handled in exactly the same way.)

At the network level, the above is shown in such a way that the network management system is connected to the management bus 5 in one node, through which it can access the other nodes of the network along the management bus. This is illustrated in Figure 2, where the network shown has a main node M and eight nodes 1 to 8, and the network management system NM is connected to the node 2. Normal-10 communication connections between the nodes are marked with dashed lines and a solid line thicker than the management bus MB. In reality, the management bus thus consists of normal communication links (i.e., it runs within normal communication links), but in a logical sense it is nevertheless a network separate from normal communication links (as shown in Figure 2). At certain points in the network, there are conditional connections for the management bus (similar to Figure Ib) to turn on the authentication handover connection. In this exemplary case, the conditional switches denoted by reference numeral E are at nodes M, 3 and 4, whereby node M can connect the authentication connection in the direction of node 1, node 3 in the direction of node 7 and node 4 in the direction of node 6, if necessary.

The control bus is built into the network with its own connections. Each node defines separately where the management connections come from • · «: ·’ (which must be connected to an adder). The definitions are made by the user and are permanent. Kyt- • «· V! the fields are valid whenever the signal containing the shark channel is in order. If the signal ha - 3 0 is supposed to be faulty (eg there is a fault causing a far - end alarm or a far - end alarm is received),. the connection of the control channel to the adder is prevented so that any interference from the connection cannot interfere with traffic on the service bus via the adder.

: 3 5 In an authenticated control bus, one or more control connection points are conditional, i.e. the connection to the adder is made only if a certain predetermined condition (eg a predetermined state of one of the monitored bits) is fulfilled. Depending on the device, the condition can be tied to 5 different things.

The disadvantage of a certified management bus implemented as described above is that the user (operator) has had to separately create a system for authentication that transmits a conditional bit that remains in a normal state in a certain state and changes state at the point in the network where the abnormal situation occurs, such as the fault condition.

The object of the present invention is to alleviate the above-mentioned drawback and to provide a new, even simpler solution for implementing a management or similar bus. This object is achieved by a method according to the invention, which is characterized by what is described in the characterizing part of the appended claim 1. The arrangement according to the invention, in turn, is characterized by what is described in the characterizing part of the appended claim 3.

. The idea of the invention is to utilize the synchronization status message (SSM, defined in ITU-T standard G.704).

Synchronization Status Message) so that the condition used at the conditional switching point of the certified service bus 25 is bound to the state of this message. Thus, the invention utilizes information already used in the network for the purpose of network synchronization for a new purpose.

Thanks to the solution according to the invention, the conditional information is thus already ready in the network, and thus it is not necessary to create any conditional bit • · · [· transmission arrangement in the network separately.

«· ·

In the following, the invention and its preferred embodiments will be described in more detail with reference to Figures 3a-6d. . ·. In the examples according to the drawings 35582, Fig. 1a illustrates the implementation principle of the management bus inside the network node, Fig. Ib illustrates the implementation principle of the management bus authentication inside the network node, Fig. 5 illustrates illustrates the elements 10 of the network node with which the method according to the invention is implemented, Figures 5a ... 5d illustrate the operation of the method according to the invention in the so-called in the mesh network, and Figures 6a ... 6d show alternative interface elements for the node shown in Figure 4.

15 ITU-T Standard G.704 defines the frame structure of a digital transmission system operating at 2048 kbit / s. According to the recommendation, bits 4-8 of every other frame are free (spare bits) and can be used e.g. to transmit the above-mentioned synchronization status messages. 20 Only one of the bits 4-8 of the frame can be used for this purpose, so a four-bit synchronization status message is generated from the selected bit (4-8) in frames 1, _ 3, 5 and 7 of the superframe and in frames 9, 11, 13 and 15. The following table shows these selected bits San1-San4; The synchronization quality levels (QL, Quality Level) indicated by the bit patterns formed by 25 (n = 4, 5, 6, 7 or 8). In the last column, the terms • · · · V · (in English) corresponding to the recommendations are used.

.. QL Sanl- Synchronization Quality (QL) Descrip- • · · * ... San4 tion • · «• · · - ---- ----- - - - *. *. 30 0 0000 Quality unknown (Existing Sync. Net- • · · work) 1 0001 Reserved 98582 7 2 0010 G.811 3 0011 Reserved 4 0100 G.812 Transit 5 0101 Reserved 5 6 0110 Reserved 7 Olli Reserved 8 1000 G.812 Local 9 1001 Reserved 10 1010 Reserved 10 11 1011 Synchronization Equipment Timing Source (SETS) 12 1100 Reserved 13 1101 Reserved 14 1110 Reserved 15 1111 Do not use for Synchronization:. : 15: As can be seen from the table, four levels of synchronization have been decided within the ITU-T and, in addition, the meaning of ^ is given to the other two levels; the other indicates that • ·. . ·. the level of synchronization is unknown and the other is that the • · · I · ”/ 20 signal should not be used for synchronization (QL = 1111).

• · ·

According to the present invention, the latter quality level (15) is utilized in the implementation of a certified management • ♦ • ”or similar bus such that when the status message changes from the state" XXXX "(" XXXX ") is different from "1111"); * ·. · In state "1111", the control bus is switched on at the conditional switching point of the network.

Figures 3a and 3b illustrate the operation of the method according to the invention 98582 8 in an annular network with a total of five nodes, denoted by reference numerals N1 to N5. The control bus MB is constructed to pass through the entire ring so that it breaks next to the main node 5 (N1) in the direction of the node N5. A condition (reference character E) is set at this breakpoint (i.e., the port leaving the node N1 in the direction of the node N5). In addition, at a normal switching point (at each port of each node), it is monitored whether the incoming connection has a vi-10 kaa, which is why the use of the connection for synchronization must be prohibited. If such a fault occurs, the bus is disconnected at this point. This measure ensures that there is no point in the bus from which messages could circulate back when the conditional connection is turned on. 15 Within each node, the internal clock quality level (QL: XXXX) is marked as the top. Below this is a node synchronization list with the selected timing source shown in italics. The synchronization method used is such that each node selects the signal with the highest quality level of the synchronization message as its timing source. If several signals, •, ·, have the same quality level, the one with the highest ·· _ club in the priority list is selected. Next to each port of the node, the \ / 25 synchronization status message sent by the node is marked with the reference "QL: xxxx". The main node N1 and node N3 have • · 1; · ‘Connected external timing sources SI and S3, respectively.

• · · ϊ.ϊ: The quality levels (QL = 0010 and QL = 0100) of synchronization status messages sent by external sources are marked above the sources. A QL value must be assigned to each source outside of loop synchronization.

: * · *: Figure 3a shows the network in its normal situation. (no defects). The master node N1 uses an external timing source • · · SI, which in this example is defined as a clock at the level QL = 0010. The master node sends this synchronization message in both directions. The submissive nodes are synchronized to a signal from the main port (Pa) with a synchronization status message QL = 0010. In this case, they forward the same quality level (QL = 0010) from port Pb and send the quality level QL = 1111 5 ("do not use for synchronization") in the direction from which they receive their timing (in the direction of port Pa).

Figure 3b shows a situation where a fault has occurred in the connection between nodes N1 and N2. When Node N2 detects this fault, it selects a new timing source. 10 Since it receives the quality level QL = 1111 from the second direction (from node N3), it cannot use this direction for timing either, in which case it enters the internal timing mode and starts transmitting the quality level QL = 1011. The next node (i.e., node N3) receives this quality level from port Pa, whereby it changes the external source S2 to its timing source because the quality level QL = 0100 provided by this is better than the quality level received from port Pa, and port Pb cannot be used for timing (QL = 1111 ). Node N3 starts transmitting the quality level QL = 0100 in both directions. Node N2 sync-20 is cloned to the signal from node N3 because the quality level it contains is better than its internal quality level. (QL = 1011), at which point it starts transmitting the quality level QL = 1111 in the direction of node N3. Node N4 also accepts the quality level sent by node N3 because it receives quality level QL = 1111 from port Pb: 25. Thus, the node N4 forwards the quality level * *. · QL = 0100 to the node N5, which synchronizes in the direction of the port Pb • · because the quality level QL = 0010 is obtained from there. Then • · · · # node N5 returns the quality level QL = 1111 to node N1 and forwards the quality level QL = 0010 to node N4. The rest of the nodes in loop 30 do the same, i.e. forward the quality level QL = 0010 «· * from port Pa and return the quality level QL = 1111 to port Pb.

• · · This has led to the situation shown in Figure 3b.

• · *. * ·: When Node N1 detects that the quality level sent to it by Node N5 changed to QL = 1111 (i.e., Node N5 uses this authentication direction for its synchronization because there is a fault in one of the 98582 10 main directions), it switches on the control bus in the direction of node N5.

Figure 4 illustrates the elements of a single network node that are relevant to the invention. Node N comprises several parallel interface units IU1 ... IU, through which the node connects to the network (the interface can be e.g. a 2 Mbit / s PCM interface according to the above recommendations, as shown in the figure), and a control unit CU common to several interface units. Each interface unit 10 comprises at its input a channelization block (i.e. a multiplexing / demultiplexing block) 81, which is connected via a switch SW to the internal bus IBUS. On this bus, a logical AND operation takes place for the signals connected to the bus (in normal mode, the pull-up resistors keep the bus in state one as long as one of the signals connected to the bus directs the bus to zero state). As discussed above, in order to implement a certified bus, the desired shunt channels must be able to be turned off or on as appropriate. This can be implemented according to Figures Ib, so that each control channel has its own switch SW, which is controlled, ·, from the control unit control block 82. The EOC control channel II 1 _ ·· _ is thus separated from the rest of the signal in the channelization blocks 81 and the control block -; . * 25 The coronation status message changes from "XXXX" to "1111" ("XXXX" is different from "1111"). The control block of the synchronization status • · ·: message value is received from the channelization block 81, which • 4 · · generates a value from the bits selected for this purpose. In Fig. 4, it is assumed that only the port corresponding to the IU1 of the interface-30 is set to a condition, so that only this port transmits a synchronization status message. value for control bus connection control (in other ports • · · 9 · · this value is only transmitted for synchronization use).

‘The control unit CU comprises an adder 83 from the node control block 13 and the network management system NM.

t I

• I

98582 11 for connecting the control channel in a corresponding manner by means of a switch SW to the adder 11 (cf. Fig. 1). The network access system is connected by means of a communication connection (typically a serial connection such as V.11) to a serial port SP at the input of the control unit 5, which in turn is connected to an adder 83.

Figures 5a ... 5d illustrate the operation of the method according to the invention in the network according to Figure 2. Figure 5a shows the network in the normal state with the switches of all 10 conditional switching points open. In the situation of Fig. 5b, a fault occurs in the main loop A between the nodes M and 2. When a fault is detected, nodes M and 2 disconnect the bus for a faulty connection. In a manner similar to that of Figures 3a and 3b, the nodes of the main loop 15 synchronize in the opposite direction. When the Node M detects that the quality level sent to it by the Node 1 changed to the level QL = 1111, it switches on the control bus in the direction of the Node 1. In the situation of Figure 5c, a fault also occurs in the sub-loop C, whereby the nodes (6 and 20 8) on both sides of the fault disconnect. The condition at the end of the loop in the node 3 is triggered when the synchronization •, · received from the node 7. the status message changes from QL = 0010 to QL = 1111.

Figure 5d shows a fault in the second sub-loop (B).

. '. The nodes (5 and 6) at the ends of the failed connection are 25 re-bus the bus for a faulty connection.

• · 'The condition at the end of the loop in node 4 is triggered when the state of the synchronization status message received from the node ϊ · ί 6 changes from • «· l .:: state QL = 0010 to QL-1111.

Figures 6a ... 6d show different options for implementing a single, conditionally connected connection unit. Figure 6a shows a figure. 4 corresponding solution, where fault and status information is obtained • · · directly from the multiplexing block and separate switches • · * · 'met SW are used, through which the control channel signal is connected: 35 to adder 11, if necessary 12 98582 signal is connected from the multiplexing block to cross-connect block 91 (not shown) in Figure 8), from which they are further forwarded. Figure 6b shows another alternative in which the entire signal (all time slots) is applied from the channelization block to the cross-connect block 92, from where the EOC channel is connected (if necessary) to the adder 11 and the other channels to other desired locations. The QL value is still obtained from the channelization block. Figures 6c and 6d show alternatives in which the control block 82 controlling the switch SW receives the signal fault information and the QL value 10 from a separate fault database 93, and not directly from the channelization block. The implementation of Figure 6c corresponds in another respect to the implementation shown in Figure 6a and the implementation of Figure 6d to the implementation of Figure 6b.

Although the invention has been described above with reference to the examples according to the accompanying drawings, it is clear that the invention is not limited thereto, but can be modified within the scope of the inventive idea set forth above and in the appended claims. If, for example, the recommendations change in such a way that the corresponding information is also obtained with bit patterns other than QL = 1111, such a second bit pattern can, of course, be used in the same way to implement management bus authentication.

Only one example of the basic structure of the apparatus has been presented above, and a person skilled in the art can vary this structure in many ways without deviating from the timing according to the invention.

• <i • · «« 1 «1 ···:::« • · * ♦ • · · «M •« «« · · • · • · t «<'I t ·

Claims (4)

A method of realizing a secured bus, in particular a control bus, in a telecommunications network comprising a plurality of nodes connected to transmission links, in which network synchronization status messages according to Recommendation G.704 are used, indicating the relationship between the quality level of a signal and the synchronization, according to which the procedure 10 network is provided with a bus (MB), which transmits information outside the utility traffic, such as connecting information to the network control, and - at least in a node, a conditional access point (E) is used, that the bus is switched to pass through said access point only if a predetermined condition connected to the conditional connection is fulfilled, characterized in that the state of the synchronization status message is used as said condition, so that the synchronization status message indicates that a state indicates the question if the signal should not be used in synchronization, the control bus is connected to go through it! , conditional access point. • · 25 2. A method according to claim 1, characterized in that said coupling is performed where the synchronous * status message transfers from state "XXXX" which is different than "1111" to state "1111". . • 3. Arrangements for the realization of a bus, T: 30 in particular a control bus, in a telecommunication network, *. which includes a plurality of nodes connected to »# ι ·. 'transmission links, according to which arrangement in' ·; - in the network, synchronization status message is transmitted; countries according to recommendation G.704, which synchronization <35 status messages indicate a signal's quality level in relation to the synchronization, - in the network a bus (MB) is realized, which bus transmits information outside the utility traffic, as connected to the network control. and, at least one node in the network has a conditional switching point (E) for the bus, so that the bus is coupled to pass through this switching point only if a predetermined condition connected to the conditional coupling is fulfilled, characterized in that coupling means ( 82, SW, 92) of said conditional access point are responsive to said synchronization status message so that the switching means switches on the bus as the synchronization status message transfers to a given predetermined state. 4. Arrangement according to claim 1, characterized in that when the synchronization status message Transfers to state "1111" from some other state, the switching means performs the bus pointing connection. • · ♦ · ··· ♦ · ♦ • · «• · • ·« 1 «• · · • · · • · · •» • · · • · ♦ • «♦ ♦ • · •»