Location identification in a communications signalling network

TECHNICAL AREA

This invention relates to location identification in a communication signaling network, and more particularly, but not exclusively, to a surveillance probe that automatically identifies its location in a signaling network that operates substantially in accordance with signaling system # 7 specified by the CCITT, such a network referred to herein as an SS7 network. The CCITT Signaling System Number 7 (CCITT signaling system no. 7) is in Recommendations Q. 700 - Q. 716 CCITT Volume VI - Bd. VI. 7, Geneva 1998, ISBN 92-61-03511-6.

BACKGROUND OF THE INVENTION

In modem communication technology, it is very common to provide two related but separate network infrastructures: a transmission network for carrying end user data traffic and a signaling network for controlling an operation of the transmission network in accordance with control signals transmitted over the signaling network. In practice, such signaling networks have fast computers connected by signaling links. Computer programs control the computers to provide a set of operating and signaling functions according to a standardized protocol. An example of such a signaling protocol is the aforementioned Signaling System No. 7 (SS7), which is widely used for controlling telephone or other data transmission networks. An SS7 network basically has different types of signaling points, namely signaling endpoints (SEP) and signaling transfer points (STP) connected by signaling links, the SEPs e.g. B. respective service switching points (SSP) of the transmission network and service control points (SCP) are assigned.

The large size and complexity of the transmission network entails a correspondingly large and complex signaling network, which is controlled by very sophisticated computer programs. The complexity of the signaling networks is increased by the need to provide redundancy to ensure that failure of a single component of the network does not result in failure of the entire network, and thereby of the associated transmission network. That's why it is z. B. in SS7 networks, it is customary to provide each SSP or SCP with at least two signaling links to corresponding constituents of a pair of geographically separated STPs.

In order to be able to perform independent monitoring of the signaling network, monitoring probes may be temporarily or permanently installed on one or more links to monitor messages flowing on the link or links. By monitoring these messages, it is possible to gain an insight into the behavior of the network and to detect errors. An example of a monitoring probe is the Hewlett-Packard 379008 Signaling Assay Kit.

When a monitoring probe is permanently or semi-permanently installed in a link, generally measures are taken to have the probe automatically send the results of its monitoring operations to a remote management station. This station may also be able to control the probe to change the focus of its monitoring activities. Of course, for the results coming from a probe to be useful to the management station, the location of the probe, expressed by the absolute identity of the connection where it is installed, must be made known to the management station. This is generally accomplished by having the installer direct this information to the management station. This can take a considerable amount of time and is error prone.

It is an object of the invention to facilitate the identification of the connection in which a monitoring probe is installed.

A method for testing telephone lines in a transmission network (as distinguished from signaling connections in a signaling network) is described in Patent Abstracts of Japan, Vol. 17, No. 301 (E-1378), June 10, 1993. Reinartz et al. Describe arrangements for testing SS7 systems in Telcom Report, Vol. 7, No. 5, September 1984, pages 279-282.

SUMMARY OF THE INVENTION

In using the present invention, a surveillance probe is generally positioned to determine its own location in the signaling network by looking for a particular type of message carrying the required information in its routing label or other routing information. The message routing label is the part of the message that shows both the source and destination points for the message and provides connection-related information for cases where more than one connection connects two signaling points. While the routing label of most messages in an SS7 network does not provide a reliable indication of the absolute identity of the connection in which the message was monitored, in the case of signaling connection test messages the routing label contains both the identity of the two points at the end of the connection in which the message was monitored, as well as the identity of the connection for that connection and another parallel connection, These pieces of information form an absolute identifier for the SS7 connection where the message was monitored.

Thus, according to the present invention, there is provided an apparatus adapted for connection to a telecommunications signaling network, the network having a plurality of signaling points connected by signaling links, the network being arranged to carry messages of a plurality of different types each message comprises both message type information and routing information, wherein the routing information for at least one message type but not all types identifies the signaling points directly connected by the link carrying the message in question and the identity of that link, the device having interface means for interfacing the device to the signaling link and is characterized by:

a monitoring device connected to the interface device for monitoring messages on the connection to which the device is interfaced, the monitoring device having connection identity detection means responsive to the presence of a message of the at least one notification type on the connection to the connection Guide information contained in the message of the at least one notification type to read and save.

The invention is in fact applicable to any device object to be connected to an existing signaling connection. If such a device itself is not a monitoring device, a suitable monitoring device must be provided.

The apparatus may include reporting means for reporting the stored routing information to a remote management station. The routing information may be sent to the management station each time any information is passed from the device to the station. Alternatively, this routing information may be sent once along with a device identifier, which is then used in all subsequent communications with the management station. This approach is preferred because it allows the management station to distinguish between multiple device objects installed in the same connection.

BRIEF DESCRIPTION OF THE DRAWINGS

A monitoring probe incorporating the present invention will now be described by way of non-limitative example with reference to the accompanying drawings. Show it:

Fig. 1 is a schematic diagram of part of an SS7 signaling network;

Fig. 2 is a schematic block diagram of a probe used to monitor a connection of the network of Fig. 1; and

FIG. 3 is a diagram illustrating the composition of a signaling connection test message carried by the SS7 network of FIG. 1. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIG. 1, there is shown an SS7 network 10 communicatively interconnecting three signaling endpoints that are communicatively coupled by two service switching points SSP 11 (between which voice circuits 12 of a transmission network, not further illustrated) and a service control point SCP 13 can control the operation of the SSP to provide special services. The SS7 network 10 includes two pairs 14 of signaling transfer points STP and a plurality of connection sets 18 connecting the SSP, the SCP and the STP into a redundant network. Each signaling connection set 18 consists of one or more individual signaling links, the number of signaling links in a link set being chosen to provide a suitable capacity for that level of expected signaling traffic.

It is noted that an SS7 network belonging to a single transmission system operator typically has more STP pairs, SSP and SCP than shown.

Messages passing through the connections of the network may be of any one of a large number of different types depending on the nature of the call to which the message relates and on the function specified by the message. As will be described in more detail below, each message includes information that identifies its nature and a routing label that identifies the source and destination of the message.

To monitor the behavior of the SS7 network 10, monitoring probes 21 are provided. In Fig. 1, two such probes are shown. These probes are associated with respective signaling links and connected to a management station 17, which serves to collect and analyze the output signals of the probes 21. The management station 17 may also be arranged to control the configuration of each probe 21 to set up the probes to monitor particular events in the network 21. In the present example, the probes 21 and the station 17 communicate with each other via a network 19 (e.g., a local area network (LAN)) different from the SS7 network. However, it would be possible to arrange the probes 21 and the station 17 to communicate themselves via the SS7 network by connecting the probes 21 and the station 17 to their next signaling points of the SS7 network. In this latter case, information between the probes 21 and the station 17 is passed in SS7 messages which are encoded and decoded by the associated signaling points.

Fig. 2 shows in more detail the general case of connecting a monitoring probe 21 to a connection 18A of a connection set 18 extending between two signaling points 20 (eg, between the SCP 13 of Fig. 1 and one of the associated STPs). The connection set 18 of Fig. 2 has three connections, namely the monitored connection 18A and two further connections 1% and 18C. The signaling points 20 both identify these links 18A, 18B, and 18C as the first, second, and third links (LINK = 1, 2, or 3) between them.

The signaling points 20 themselves are uniquely identified in the SS7 network 10 by point codes. In the example of Fig. 2, dot codes 8 and 9 have been assigned to the signaling points 20 simply for the sake of illustration (in practice, each dot code is specified by 14 bits).

It will be appreciated that each individual connection in the network can be uniquely identified by the following triplet:

the point code of the signaling point at one end of the connection;

the point code of the signaling point at the other end of the connection;

the connection number in the connection set connecting the signaling points.

Thus, the compound 18A is uniquely identified by the triplet (8, 9, 1).

The monitor probe 21 operates to automatically ensure the absolute identity of the link 18A in which it is installed and to route this information back to the management station 17.

To ensure the absolute identity of the connection in which it is installed, the monitoring probe 21 monitors the messages on the connection to which it is connected. As noted, each message includes a routing label that holds routing information. The format of this routing label is shown at 42 in FIG. As can be seen, the routing label has 32 bits, with 14 bits assigned to represent the point code of the source signaling point (ie the signaling point sending the message), with an additional 14 bits associated with the point code of the destination signaling point, and 4 bits forming a signaling link selection (SLS) field.

Of course, the source and destination point codes in the routing label should indicate the originating point of origin and the last destination point of the message, not a start and end point of a next hop. Thus, for most types of messages in an SS7 network, reading the destination and source point codes in the routing label can not be considered to provide reliable information about the point codes of the signaling points at both ends of the link on which the message is read has been. Further, the signaling link selection field is used in most types of SS7 messages to indicate a preferred connection to be used in transmitting a message. However, there is no guarantee that this compound will actually be used in practice, as other factors may interfere with this preference.

In other words, for most types of SS7 messages, monitoring probe 21 can not ensure the absolute identity of that connection by reading the routing label of messages on the connection it is monitoring. However, for one type of message, namely signaling link test messages, the source and destination point code in the routing label of the message actually indicates the signaling points at opposite ends of the link at which the message is being monitored. Further, for such signaling connection test messages, the SLS field of the routing label actually contains the connection number of the connection carrying the message with respect to that connection and another connection in the same connection set.

The monitor probe 21 may therefore perhaps ensure the absolute identity of the link it is monitoring by detecting signaling link test messages on the link and reading the routing label from such messages.

3 shows the relevant message formats for signaling connection test messages. Thus, at 40, the general format of an SS7 Message Signal Unit (MSU) is shown and, as can be seen, an MSU has the following fields:

an 8-bit flag field;

a 7-bit reverse sequence number field (BSN);

a backward indicator bit (BIB);

a 7-bit forward sequence number field (FSN);

a 6-bit connection indicator field (LI);

a spare 2-bit field (SP);

an 8-bit service information octet (SIO);

a signaling information field of 8n bits, where n is only an integer equal to 2 or greater;

a 16-bit test field; and

an 8-bit tail flag.

Signaling connection test messages are included in the signal information field of an MSU. The format of a signaling connection test message is shown at 41 in FIG. A signaling connection test message has the following fields:

a 32-bit routing label;

a 4-bit header code H0;

a 4-bit header code H1;

a replacement 4-bit field;

a 4-bit length indicator; and

a test structure of 8m bits, where m is an integer.

The format of the routing label of the signaling connection test message 41 has already been described above with reference to the format 42.

Only for signaling test messages, the service indicator of the MSU (ie the first 4 bits of the SIO field) is set to 0001 and the header code H0 is set to 0001. By searching for messages with these settings, the monitoring probe 21 can identify signaling connection test messages.

Further information regarding signaling connection test messages may be obtained by reference to the CCITT recommendations mentioned above.

Returning to a consideration of the monitor probe 21 of Figure 2, the probe is interfaced with the connector 18A through a network interface (NI) 22 which uninterruptedly reads the messages on the link. The output of the network interface 22 is connected to a monitoring circuit 23. The monitoring circuit 23 performs predetermined monitoring operations (e.g. Recording all messages coming from a particular signaling point) and stores the results of their monitoring operations in a data memory 24. The nature of the predetermined monitoring operation may be fixed or may be preprogrammed by the management station 17 by messages routed through the network 19, through an interface 26 of the probe to a control unit 28 serving to provide the monitoring operation 23 needed for the monitoring operation suitable to program.

The data stored in the memory 24 is routed periodically to the management station 17 after being formatted in a report generator 25 whose output is connected to the interface 26. The generation of reports is controlled by the control unit 28 and z. At predetermined intervals or in response to a request message obtained by the control unit 28 from the management station 17.

An identifier for identifying the probe 21 is stored in the memory 32. This probe identifier is read by the report generator 25 each time a report is generated, and the probe identity is included in each report sent to the management station 17. In this way, station 17 knows the origin of the report.

The previous general operation of the probe 21 is standard and can be easily implemented by those skilled in the art.

In order to provide automatic detection of the absolute identity of the connection in which it is installed by the probe 21, the monitoring circuit 23 of the probe is provided with a signaling connection test detection circuit 30 which operates after initially installing the probe to cause the monitoring circuit thereto . to respond to the presence of a signaling connection test message on link 18 by reading the routing label of that message and by storing the contents of the tag in a link ID store 31. Once the absolute identity of the connection 18A has been determined by the probe 21, the control unit 28 is informed by a signal on a line 29 from the detection unit 30. Thereafter, the control unit 28 causes the report generator 25 to send a message to the management station 17 which includes both the probe identity and the absolute connection identification information from the memory 31.

After the management station 17 has forwarded the absolute connection identifier together with the probe identity, it can subsequently associate the monitoring data sent to it by the probe with the corresponding connection (it is recalled that the monitoring data will be routed with the probe identity).

Prior to detection of the absolute connection identity by detection circuit 30, the normal monitoring operation of circuit 23 may be inhibited, although this is not essential. Further, it is also possible to arrange the detection circuit 30 to detect the absolute connection identity not only at initial installation of the probe 21, but also at periodic intervals or on a continuous basis. In this case, the management station 17 need only be informed again about the absolute connection identity should the latter change.

It is also noted that it is not essential that an initial message be sent from the probe 21 to the management station 17 which associates the probe identity with the absolute connection identity, since the latter information is sent in each monitoring data report sent by the probe to the management station that can be included.

In general, the management station 17 will of course receive reports from a plurality of probes 21. The station 17 can therefore hold a look-up table in which it stores all the probe identities along with their associated absolute connection identifiers.

If an operator at the management station 17 now wants to send an instruction to a particular monitor probe 21 (eg, to reprogram its monitor operation), the operator need only specify the connection he is interested in, the monitor station itself being automatic referring to its look-up table can determine the identity of the corresponding probe.

It will be appreciated that the use of the term "probe" with respect to the monitoring probe 21 has no particular significance, except that a device is being viewed looking into a network to extract information of interest. Further, as indicated above, the present invention may be applied to devices other than monitoring probes.