Source: https://patents.google.com/patent/EP0792075A2/en
Timestamp: 2018-11-16 06:09:07
Document Index: 49423966

Matched Legal Cases: ['arts 26', 'art) 32', 'art) 33', 'arts 46', 'art 46', 'art 47', 'art 48']

EP0792075A2 - Message modification apparatus for use in a telecommunication signalling network - Google Patents
EP0792075A2
EP0792075A2 EP19970300819 EP97300819A EP0792075A2 EP 0792075 A2 EP0792075 A2 EP 0792075A2 EP 19970300819 EP19970300819 EP 19970300819 EP 97300819 A EP97300819 A EP 97300819A EP 0792075 A2 EP0792075 A2 EP 0792075A2
EP19970300819
EP0792075A3 (en )
A programmable message substitution unit PMSU (60) is provided for modifying signalling messages passing across a link (61) of a telecommunications signalling network without disrupting the link-level procedures operating over the link. In the event of a power failure or upon the detection of an operational anomaly, a bypass relay arrangement (65) is used to bypass the PMSU (60). The PMSU (60) comprises a substitution block for modifying selected messages, a database block for doing database lockups to ascertain new message parameter values to be substituted for existing ones, and a supervision block for checking the operation of the substitution block. The PMSU may be used to implement local number portability or other services.
The present invention relates to message modification apparatus for use in a telecommunications signalling network. The present invention has particular application to telecommunication signalling networks operating substantially in accordance with Signalling System No.7, whether as specified by the ITU-TS (formerly CCITT), ANSI, ETSI (for GSM), Bellcore or similar body, such a network being herein referred to as an SS7 network. The CCITT Signalling System Number 7 is specified in Recommendations Q.700-Q.716 CCITT Volume VI - Fascicle VI.7, Geneva 1989, ISBN 92-61-03511-6 which is herein incorporated by reference.
Referring to Figure 1, an SS7 network 10 is shown inter-communicating three signalling end points constituted by two service switching points SSPs 11 (between which extend speech circuits 12 of a transmission network not further illustrated) and a service control point SCP 13. The SCP serves to implement particular services (sometimes called IN, or Intelligent Network, services) in response to service requests received from an SSP, such a service request being generated by an SSP upon certain trigger conditions being met in the SSP in respect of a call that it is handling. A typical service may involve the translation of the dialled number (called party number) to a different number, the SCP returning this latter number to the SSP to enable the latter to complete call setup.
Figure 2 illustrates the SS7 architecture. Levels 1 to 3 (referenced 21, 22, 23) form the message transfer part (MTP) 24. The MTP 24 is responsible for transferring signalling information between signalling points in messages. Level 4 (not referenced as a whole) comprises circuit-related user parts, namely ISDN User Part (ISUP) 26 and Telephone User Part (TUP) 27. These user parts define the meaning of the messages transferred by the MTP 24 and provide functionality to the users of SS7 (block 29). The user parts 26 and 27 are specific to particular types of circuit-related applications as indicated by their names. In fact, the ISUP is the most important user part, the TUP being a subset of ISUP and having been largely replaced by the latter. Most inter-exchange signalling, such as between SSPs 11 in Figure 1, uses ISUP messages.
The SCCP 31 actually forms part of the transfer mechanism for non-circuit-related applications, combining with MTP 24 to provide transfer mechanisms (both connectionless and connection oriented) meeting the Open Systems Interconnection (OSI) Layer 3/4 boundary requirements. TC 30 itself comprises two elements, namely an intermediate-services part (ISP) and a transaction-capabilities application part (TCAP); ISP is only used for connection-oriented services. Users of the SCCP/TC stack include the INAP (Intelligent Network Application Part) 32 and MAP (Mobile Application Part) 33. With reference to Figure 1, messages passed between an SSP 11 (Figure 1) and SCP 13 will be INAP messages using SCCP/TC (in fact, such messages are generally concerned with real time query/response transactions for which a connectionless service is most appropriate so that only the TCAP part of TC is used). Some inter-exchange signalling may also use SCCP/TC messages where, for example, the purpose of the signalling is service related rather than circuit related. ISUP may also use the SCCP for certain messages.
The general form of a signal unit 40 is shown in Figure 3. As can be seen, a field 41 carrying message/data is encapsulated in a Level 2 framework comprising the following fields: a flag field; a backward sequence number field (BSN); a backward-indicator bit (BIB); a forward sequence number field (FSN); a forward-indicator bit (FIB); a length indicator field (LI); a spare field (SP); a check field; and a terminating flag field. The FSN, FIB, BSN, BIB and check fields provide error correction functionality at link level in a manner well understood by persons skilled in the art.
The length indicator (LI) within each message indicates the signal unit type as follows: LI = 0 means FISU; LI = 1 or 2 means LSSU; and LI = 3 or more means MSU.
Figure 3 further illustrates at 42 the basic format of an MSU; as can be seen, it comprises a service information octet SIO of 8 bits and a signalling information field SIF of 8n bits, where n is a positive integer. The SIO field includes a Service Indicator subfield that defines the user part or equivalent appropriate to the message. The SIF contains the information being transferred and will generally include a routing label 43 comprising a 14-bit destination point code indicating the destination signalling end point, a 14-bit originating point code indicating the originating signalling end point, and a 4-bit signalling link selection field for specifying a particular link in cases where two signalling points are linked by a multiple-link link set. The MTP 24 is not aware of the contents of the SIF other than the routing label.
As an example of the information that may be borne by an MSU, Figure 4 illustrates the general format of an ISUP message. As can be seen, in addition to the routing label 43, an ISUP message comprises a circuit-identification code (CIC) 44 indicating the number of the speech circuit between two exchanges to which the message refers, a message type code 45, and a number of parameters organised into three parts 46, 47, 48 according to type. Mandatory parameters of fixed length are placed in the mandatory fixed part 46. Mandatory parameters of variable length are placed in the variable mandatory part 47. Optional parameters are placed in the optional part 48. A typical ISUP message is the initial address message (IAM) which is the first ISUP message sent out when a call is being set up; the IAM will contain the required address (e.g. the digits dialled by the calling customer) and it results in a seizure of a circuit by each exchange along the route to the called-party exchange.
Figure 5 illustrates the format of another message type that may be carried in the SIF, this time an SCCP message. The message format is, in fact, very similar to that of Figure 4 but without the CIC field (as already indicated, SCCP messages generally concern non-circuit related messaging). A typical use for SCCP messages is to carry query/response messages between a SSP and an SCP, this being done in SCCP messages of the Unitdata type that utilise a connectionless service.
Figure 6 shows one embodiment of the message interceptor described in EP-A-0 669 771. The message interceptor is inserted in a link 52A, 53A, 52B, 53B with each link half 52A, 52B; 53A, 53B being terminated at a corresponding interface 50; 51 and MTP level-2 protocol engine 54; 55. The two level-2 protocol engines 54, 55 are connected through transfer circuits 56 that comprise MTP level 3 functionality 58 receiving both MSU data and link status information from the protocol engines. MSU data related to signalling network management and maintenance are identified (Service Indicator value less than 3) and handled entirely within the MTP level-3 block 58, these data being acted upon if addressed to the message interceptor itself as indicated by a match between the destination point code in the routing label and the signalling point code allotted to (and stored by) the message interceptor. MSU data related to higher levels are passed up to interception functionality (blocks 59). These blocks 59 contain the message interception functionality for selectively modifying or suppressing messages. Thus, each block 59 selectively acts on the data it receives and, where appropriate, then passes data (which may include response data) back to the MTP level-3 block 58 for transmission to the appropriate destination.
-- an input and an output to which respective portions of the link can be connected,
-- message path means extending between the input and output and comprising:
-- receive means connected to the apparatus input for receiving messages from the link and decoding them to form corresponding decoded messages including the link-level data of the messages,
-- queue means connected to the receive means for queuing decoded messages in FIFO order, and
-- transmit means for taking decoded messages from the queue means, re-coding them and passing them to the apparatus output,
-- selection means for selecting particular messages passing along the message path means according to at least one predetermined criterion, the selection means generating a modification signal in respect of each said particular message concerning a modification to be effected thereto; and
-- modification means responsive to the modification signals for effecting the desired modifications to said particular messages in passage through the message path means;
-- loopback means for connecting an output of the transmit means to an input of the receive means,
-- insertion means for inserting predetermined messages in the message path means and causing them to circulate therearound, and
-- comparison means for comparing the original form of the predetermined messages with the circulated messages after the latter have undergone at least one traverse of the message path means, the comparison means only permitting the un-bypassing of the message path means by the bypass means in the absence of unexpected differences between the compared messages.
-- delay monitoring means for deriving a delay indication indicative of the delay experienced by messages passing through the message path means, and
-- delay control means for reducing this delay upon the delay indication indicating that the delay has become too large.
-- means for generating a time reference signal indicative of a current time for the apparatus,
-- timestamp means for associating a timestamp with each message received by the receive means, this timestamp being derived from the time reference signal and indicating the current apparatus time at which the message is processed by said receive means, and
-- means for generating the said delay indication as the time difference between the current apparatus time and the time value of the timestamp associated with the message at or adjacent the head of the queue means;
the delay control means taking action to reduce said delay upon the time difference exceeding a predetermined threshold. This action may include the deletion of fill-in messages and, where necessary, the deletion of operational messages (this being possible because the link-level procedures will generally cause retransmission of such messages - note that in this case, the link-level procedures are not disrupted but merely called into play to exercise their intended functionality).
. Figure 1 is a diagram illustrating the main components of a standard SS7 signalling system;
. Figure 2 is a diagram illustrating the basic architecture of the SS7 protocol;
. Figure 3 is a diagram showing the format of an SS7 message signalling unit (MSU);
. Figure 4 is a diagram of the signalling information field of an ISUP MSU;
. Figure 5 is a diagram of the signalling information field of a SCCP MSU;
. Figure 6 is a diagram of a prior art message interceptor;
. Figure 7 is a diagram showing the operational placement of the PMSU embodying the invention;
. Figure 8 is a time diagram illustrating the delay Tpmsu introduced by the PMSU;
. Figure 9 is a block diagram showing the main functional units of the PMSU;
. Figure 10 is a diagram of the substitution functional block shown in Figure 9;
. Figure 11 is a diagram of the database functional block shown in Figure 9; and
. Figure 12 is a diagram of the supervision functional block shown in Figure 9.
Best Mode of Carrying Out the Invention PMSU Overview
Figure 7 illustrates the general disposition of a programmable message substitution unit (PMSU) 60 in one channel 61 of a bi-directional link between two signalling points SP1, SP2, this channel 61 passing SS7 signalling messages in a predetermined timeslot of a framed multiplexed stream between the signalling points SP1, SP2. Messages on channel 61 are routed through the PMSU 60 and in effect enter a delay pipe subjecting them to a delay Tpmsu (see Figure 8 which depicts both a message P flowing from SP1 to SP2 along channel 61 and a return message Q flowing from SP2 to SP1 along channel 62 which does not pass through the PMSU 60 so there is no delay Tpmsu in this channel - in practice, it may be expected that both channels of a link will have a PMSU inserted). The value of Tpmsu is arranged to be of the order of 20ms (it should not be greater than 40ms to avoid exceeding the acknowledgment time limit and link bandwidth limit of current SS7 systems).
-- passes through the embedded operation channel traffic (FDL bits on T1 span);
-- locks the de-framer and re-framer of the PMSU to the recovered clock of the incoming bearer stream,
-- mimics events received on the incoming bearer stream such as loss of signal, loss of alignment, and CRC errors (CRC-6 for T1, CRC-4 for E1) on the outgoing bearer stream;
-- leaves unmodified state based procedures such as backward error correction, flow control and link alignment;
-- mimics link events such as loss of frame alignment, CRC-16 errors, aborts, long and short frames;
-- includes a bandwidth balance feature to recover idle time on the link and use it for messages whose transmission time may have increased as a result of octets inserted by the PMSU.
When the bypass relay arrangement 65 is switched in there will, of course, be no delay Tpmsu in messages passing along channel 61 (see message R in Figure 8).
Figure 9 shows the functional entities 70, 71, 72, 73 of the PMSU 60 for a single SS7 channel (a uni-directional connection in a bi-directional link). The SS7 incoming and outgoing channels are shown as tip/ring pairs 74, 75 to highlight the level 1 wiring requirements. In a physical implementation of the PMSU, the functional entities may be implemented as a distinct card, integrated on a card with other functional blocks or distributed across two or more cards. The roles of the functional entities 70-73 are summarised below:
-- provides an infrastructure to allow the various functional blocks 71-73 in the PMSU 60 to communicate with each other;
-- provides a connection path (via 76) for the PMSU 60 to share its services with other units in a network.
-- splits and terminates the SS7 channel;
-- acquires SS7 frames at level 1;
-- extracts level 3/4 protocol information from each SS7 message and modifies selected messages as required (this generally involves a database lookup to block 73 to retrieve new parameter values to be substituted for existing ones);
-- delays SS7 frames by a controlled amount and re-transmits at level 1;
-- completes external circuit via relay arrangement 65 on power fail, on command from the supervision block 72, or upon failure of the latter.
-- passively monitors both incoming and outgoing legs of SS7 channel;
-- gathers statistics on the performance of the substitution block 71 and shuts it down in the event of a fault;
-- services configuration requests and maintains a Management Information Base (MIB) for network management systems.
-- services lookup requests (primarily from the substitution block 71) and returns the result using the level 3/4 in the request as a key.
Each of the three main blocks 71 to 73 will now be considered in more detail with reference to Figures 10 to 12 respectively. In these Figures, functions performed primarily by dedicated hardware are shown in rectangular boxes whereas functions performed in software running on a program controlled processor of the PMSU are shown in rounded boxes. It will be appreciated that the split of functionality between hardware and software can be varied from that illustrated in Figures 10 to 12.
As shown in Figure 10, the line-in and line-out pairs 74 and 75 are connected to the bypass (pass thru) relay arrangement 65 of the substitution block. The relay arrangement is controlled by changeover circuitry 80 which receives inputs from several sources as will be more fully described hereinafter. At power-on or in the event of failure, the relay arrangement is in its opposite state to that illustrated in Figure 10 with the line-in pair 74 being connected to the line-out pair through a low impedance path. However, during normal operation of the PMSU, the changeover circuitry 80 places the relay arrangement 65 in its illustrated state in which the line-in pair 74 is terminated and passively monitored by a first line receiver 81, and the line-out pair is driven by a line transmitter 105.
As the framing signal of the received multiplex stream is transmitted every 125µs, it can be used as a timing source for the substitution functions. Accordingly, the de-framer 84 is arranged to output the framing signal to a timestamp block every 125µs in order to increment an internal counter of the latter. The HDLC receiver 87 acquires MTP L2 signal units (defined in Q.703) de-limited by flags and removes bits inserted for data transparency according to the procedures in Q.703. The signal units are checked by the HDLC receiver 87 against the Q.703 criteria for frame length and also that the CCITT-16 CRC check is correct; signal units that satisfy both checks are tagged as 'good' and all other signal units are tagged as 'errored'. The signal units are then packaged in a level 2 message structure which is timestamped using the time reported by the timestamp block and placed in a queue 90 for decoding.
The queue 93 of substitution-data structures is serviced by one or more database clients 95 in a FIFO fashion. If the substitution code of a substitution-data structure indicates that a database lookup is required, then the client 95 concerned requests the use of a database lookup service located on the server identified in the substitution-data structure, this lookup being effected using the signalling parameter values in the structure as database keys. Communication with the server is made using communications stack and distributed computing mechanism 96 in order to provide a secure, resilient and machine independent connection (e.g. OSF DCE running over TCP/IP). The physical layer of the connection is the local area network 70 within the PMSU which has a bus topology to eliminate single points of failure. The external connection 76 to this LAN (Figure 9) is provided to allow PMSUs to be networked together and share databases in the event of failure. Connections to database servers are managed by a database communication manager 98 which monitors the performance of the database servers and selects backup servers in the event of failure to meet lookup targets.
The head of the parsed-message queue 94 effectively corresponds to the head of the delay pipe for messages passing through the PMSU. It is important that the delay through the PMSU is kept under control and, as already indicated, a suitable target value for this delay Tpmsu is 20ms. It is the responsibility of bandwidth balance block 100 to monitor the delay and take appropriate corrective action when necessary. More particularly, bandwidth balance block 100 checks if the timestamp of the message at the head of queue 94 indicates that the message was received at a time interval Tpmsu before the time currently shown by the counter of the timestamp block 88. Calling this difference Tdiff there are two cases to consider:
-- Tdiff is less than, equal to or slightly greater than Tpmsu; in this case, the message is passed to the transmit chain (blocks 101 to 105);
-- Tdiff is significantly larger than Tpmsu; this situation indicates that the delay pipe has grown owing to an increase in length of the preceding message which in turn was caused by a substitution.
The bitstream produced by the HDLC transmitter 103 is multiplexed (as a timeslot) into the appropriate framing structure (see G.704) by the re-framer 104 together with the unused timeslots and any embedded operations channel information. As with the HDLC functions, any error condition detected by the de-framer 84 (such as loss of framing or a CRC-4/6 check error) is re-created by the re-framer 104 - this an important function as the error counts gathered by the equipment at the line-in side of the PMSU must match those gathered by the equipment on the line-out side. The line transmitter 105 encodes the digital bitstream as a bipolar analogue signal according to the transmit procedures described in G.703.
If no problems are detected by the exception handler, it instructs the changeover circuitry 80 to place the relays 65 into a split / terminate configuration by sending an activate request. The changeover circuitry 80 will only service this request, however, if the supervision block 72 reports, via a supervisor status signal, that the SS7 traffic on the channel passing through the line-in to line-out ports is associated with a link that is in-service (rather than out of alignment, aligning or non-operational). Assuming the supervision status signal indicates all is well, the circuitry 80 connects line receiver 81 to de-framer 84 and switches the relay arrangement into its split and terminate position; circuitry 80 also asserts a substitution status signal.
-- a shutdown request is received by the exception handler via the PMSU LAN interface from a management station. A deactivate request is then sent to the changeover circuitry 80;
-- the database communications manager 98 can no longer establish contact with a database server which meets its performance targets. A database failure signal is sent to the exception handler 106 which in turn sends a deactivate request to the changeover circuitry 80;
-- power to the substitution block fails causing a power sense signal to the changeover circuitry 80 to be negated;
-- the supervision block 72 detects that the transformation performed between the line-in and line-out ports 74, 75 does not meet the functional and performance specifications for the PMSU and causes the supervisor status signal to the changeover circuitry 80 to be negated.
As soon as any of the conditions above arises the changeover circuitry 80 immediately releases the relay arrangement 65 and negates the substitution status signal. Database Functions
As illustrated in Figure 11, the database subsystem 73 basically comprises a database 110 and one or more database servers 111. A database lookup request from the substitution block 71 is received by one of the database servers via a network interface 112 and communications stack and distributed computing mechanism 113. Each lookup request contains a list of signalling parameters and parameter values, and the timestamp for the corresponding SS7 message to identify uniquely the transaction; each of the signalling parameter values is used in turn as a key to query a database. The responses for each of the queries are packaged in a lookup response structure together with the timestamp (transaction identifier) of the lookup request and returned to the database client via the PMSU LAN interface. Applications such as billing may require a permanent record of all translations so every lookup request / response pair is packaged in a lookup log structure and logged to disk 114 via a filesystem 115 and disk interface controller 116. Where possible, the disk subsystem should support a RAID 1 (mirrored) configuration in order to maximise the probability of data recovery in the event of a disk failure.
As shown in Figure 12, the supervision block 72 comprises two additional instantiations of the receive path of the substitution unit (the same reference numerals are used for corresponding components of the receive paths in Figures 10 and 12 but the components of two receive paths of the supervision block have been additionally labelled A and B). The main purpose of the supervision block 72 is to check that the substitution unit performs only the data transformations intended and, to this end, the block 72 further comprises a traffic comparison functional block 120 for comparing the results of decoding the SS7 channel on the line-in pair and line-out pair 75.
-- error conditions are not passed through;
-- messages experience a delay significantly less than or greater than Tpmsu;
-- a sequence of two or more messages arriving on the incoming stream has two or more messages deleted on the outgoing stream;
-- a message encoding rule has been broken on the traffic on the outgoing stream
-- an excessive number of re-transmitted messages is received on the incoming stream. (This may be due to a hardware failure in the transmitter so the unit should be taken out of service as a precautionary measure);
-- the wrong parameters of a message have been substituted (this is detectable as decoder 91A can generate the appropriate substitution code which the traffic comparison block 120 can then use to check which parameters of the corresponding message of the outgoing stream have been modified).
In the above-described PMSU, the nature of the modification to be effected by the message modification block 99 is indicated by the substitution code stored in the substitution-data structure formed for each message to be modified. However, the use of such a code is not necessary in situations where the required substitution is implicit in the other information contained in the substitution-data structure - for example, in the simple case of changing the value of given field (such as the Called Party field), then the inclusion of Called Party parameter in the substitution-data structure may be used to indicate that the modification required is a direct substitution of one value of the Called Party parameter for another. In other cases, such as when the originating and destination point codes of a message are to be swapped, it would be possible to store the substitution code with the corresponding parsed message structure in queue 94 and have message modification block 99 effect the required swap as soon as it is able (the block 99 scanning the messages in queue 94 to ascertain which require modification).
In fact, viewing the database clients 95 and message modification block 99 as together forming modification means for implementing message modifications, and considering the message decoder as having a functional entity serving as selection means for selecting the messages to be modified, the operation of the selection means and message modification means can be generalised to the selection means passing the modification means a modification request signal (the substitution-data structure in Figure 10) that includes an indication of the required modification. The modification means acts upon the modification request to effect any necessary database lookup and then modify the appropriate message in queue 94.
Apparatus insertable in a signalling link (61,62) between two signalling points (SP1,SP2) for modifying selected messages that are passing over the link in accordance with a link-level protocol, said protocol having state-based procedures that use link-level data carried by the messages; said apparatus comprising:
-- an input (74) and an output (75) to which respective portions of said link can be connected,
-- message path means (71) extending between said input and output and comprising:
-- receive means connected to said input for receiving (81) said messages from the link and decoding (91) them to form corresponding decoded messages including the link-level data of the messages,
-- queue means (94) connected to said receive means for queuing said decoded messages in FIFO order, and
-- transmit means (101,105) for taking decoded messages from said queue means, re-coding them and passing them to said output,
-- selection means (91,92) for selecting particular said messages passing along said message path means according to at least one predetermined criterion, said selection means generating a modification signal (93) in respect of each said particular message concerning a modification to be effected thereto; and
-- modification means (99) responsive to said modification signal for effecting the desired modifications to said particular messages in passage through said message path means;
Apparatus according to claim 1, further comprising bypass means (65) for selectively providing a direct connection between said input and said output to bypass said message path means and pass said messages unmodified through said apparatus.
Apparatus according to claim 2, further comprising a supervision unit (72) for comparing the flow of messages through said input and said output in order to detect abnormal operation of said apparatus, said supervision being operative upon detecting such abnormal operation, to cause the bypass means to bypass said message path means.
Apparatus according to claim 2, further comprising test means (106) for testing the operation of the message path means when said bypass means is bypassing said message path means, said test means comprising:
-- loopback means for connecting an output of said transmit means to an input (82) of said receive means,
-- insertion means for inserting predetermined messages in said message path means and causing them to circulate therearound, and
-- comparison means for comparing the original form of said predetermined messages with the circulated messages after the latter have undergone at least one traverse of said message path means, said comparison means only permitting the un-bypassing of said message path means by said bypass means in the absence of unexpected differences between the compared messages.
Apparatus according to claim 1, wherein said modification means is operative to modify said particular messages whilst the latter are passing as decoded messages through said queue means.
Apparatus according to claim 1 or claim 5, wherein said modification signal is passed from the selection means to said modification means separately from the said particular message concerned, said modification signal including an identifier which is also associated with the said particular message concerned, and said modification means using said identifier to associate the modification signal with the message to be modified.
Apparatus according to claim 6, wherein said receive means associates a timestamp with each message, said timestamp constituting said identifier.
Apparatus according to claim 1, wherein said modification signal includes the existing value of a parameter carried by the corresponding said particular message, said modification means including:
-- database lookup means operative to effect a database lookup using said existing parameter value to derive a new parameter value, and
-- substitution means for substituting said new parameter value for said existing parameter value in said corresponding particular message.
Apparatus according to claim 1, wherein said modification signal comprises a swap indication indicating that the value of two parameters carried by the corresponding said particular message are to be swapped, said modification means being responsive to said swap indication to swap the relevant parameters of the said particular message concerned.
Apparatus according to claim 1, wherein said modification signal comprises a predetermined-modification indication indicating that the value of a particular parameter carried by the corresponding said particular message is to be modified to a predetermined value, said modification means being responsive to said predetermined-modification indication to set the said particular parameter of the said particular message concerned to said predetermined value.
Apparatus according to claim 1, further comprising bandwidth balancing means (100) comprising:
-- delay monitoring means for deriving a delay indication indicative of the delay experienced by messages passing through said message path means, and
-- delay control means for reducing said delay upon said delay indication indicating that the delay has become too large.
Apparatus according to claim 11, wherein said delay monitoring means comprises:
-- timestamp means (88) for associating a timestamp with each message received by said receive means, this timestamp being derived from said time reference signal and indicating the current apparatus time at which the message is processed by said receive means, and
-- means for generating said delay indication as the time difference between the current apparatus time and the time value of the timestamp associated with the message at or adjacent the head of said queue means;
Apparatus according to claim 12, wherein said messages passing over the link include fill-in messages, said delay control means being operative upon said delay indication indicating that said delay has become too large, to delete the message at the head of said queue means where said message is a said fill-in message, deletion of this message being accompanied by adjustment of the link-level data of the next message in said queue means.
Apparatus according to claim 12, wherein said messages passing over the link include fill-in messages, said delay control means being operative upon said delay indication indicating that said delay has become too large, to delete a said fill-in message, if present, in said queue means upstream of its head, such deletion being accompanied by advancement of the timestamps of the messages in said queue means ahead of the deleted message.
Apparatus according to claim 12, wherein said delay control means is operative upon said delay indication indicating that said delay has become too large, to delete the message at the head of said queue means, reliance being placed on the link-level procedures operated on the link to cause message retransmission.
Apparatus according to claim 1, wherein said receive means is operative to decode said messages to make selected parameters contained in said messages directly available without further processing of the messages.
Apparatus according to claim 1, wherein said predetermined criterion used by the selection means comprise at least one predetermined value of at least one parameter carried by said messages, said predetermined criterion being programmable from externally of said apparatus.
EP19970300819 1996-02-26 1997-02-07 Message modification apparatus for use in a telecommunication signalling network Withdrawn EP0792075A3 (en)
GB9604379A GB9604379D0 (en) 1996-02-26 1996-02-26 A method of providing a service in a switched telecommunications system and a message interceptor suitable for use in such method
GB9615998A GB9615998D0 (en) 1996-02-26 1996-07-30 Message modification apparatus for use in telecommunication signalling network
EP0792075A2 true true EP0792075A2 (en) 1997-08-27
EP0792075A3 true EP0792075A3 (en) 1998-11-11
EP19970300819 Withdrawn EP0792075A3 (en) 1996-02-26 1997-02-07 Message modification apparatus for use in a telecommunication signalling network
JPH1127342A (en) * 1997-06-30 1999-01-29 Nec Corp Method and system for matching network information
GB0129672D0 (en) * 2001-12-12 2002-01-30 Ibm Method and system for preserving message order when parallel processing messages
EP0669771A1 (en) 1994-02-25 1995-08-30 Hewlett-Packard Company Message interceptor for a signalling network
NL9200391A (en) * 1992-03-03 1993-10-01 Nederland Ptt Device for effecting a modification in a stream of transmission cells.
"CCITT.", vol. VI, 1989, GENEVA., ISBN: 92-61-03511-6
JPH09247235A (en) 1997-09-19 application
GB9615998D0 (en) 1996-09-11 grant
US5905724A (en) 1999-05-18 grant
EP0792075A3 (en) 1998-11-11 application
US5475732A (en) 1995-12-12 Common channeling signaling network maintenance and testing
US5926482A (en) 1999-07-20 Telecommunications apparatus, system, and method with an enhanced signal transfer point
US5089954A (en) 1992-02-18 Method for handling conversational transactions in a distributed processing environment