JP2814497B2 - Signal link control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a signal link control device, and more particularly to, for example, CC
Common line signaling system N recommended by ITT (International Telegraph and Telephone Consultative Committee)
O7 level 2 signal link controller.

[Conventional technology]

To meet the demand for increasingly sophisticated and diversified communication networks with the progress of the information society, the two technological pillars of future communication network development are digitization of communication networks and control of stored programs. It is said. This will enable non-telephone services to be provided, in addition to economical and sophisticated telephone services, and the communication network will evolve toward ISDN.

The common channel signaling system uses the data link between the control system devices of exchanges, which are stored and program controlled in the above-mentioned technology flow, and provides an information transfer means for maximizing the capability of the "network". To provide. The common line signal system is a signal system in which signals are transmitted and received through a dedicated signal line different from a telephone line, and the signal line is commonly used by a large number of telephone lines.

In order to cope with the digitalization of the "network" and the integration of integrated services in the future, a new signaling system is required instead of the conventional common channel signaling system, and the CCITT has recommended it as the seventh signaling system. This is called NO7 common line signaling.

Generally, when two exchanges transmit and receive a signal, communication means (protocol) is previously determined between the exchanges, and the signal is transmitted and received in accordance with the procedure. In the common channel signaling system NO7, four hierarchies (levels) are adopted as a protocol.

Level 1 is a layer for matching the electrical and physical conditions (communication speed, transmission code format, transmission method, etc.) of the signal transfer medium, and is the most basic layer.

Level 2 is also called a signal link level, and is a layer having a function of error checking and retransmission in order to transfer a signal unit to an adjacent exchange via a signal line without error. The link is a word indicating a signal line used in level 2 and is a signal line obtained by adding a level 2 function to a physical line.

Level 3 is also called a network level, and is a hierarchy having a function of combining signaling links and sending a signaling message to a target exchange.

Level 4 is a layer also called a user part, and is a communication role provided for signal transmission / reception. At level 4, there are a plurality of communication roles (users) according to the function of signals handled such as telephone and facsimile communication.

By the way, the role of the level 2 signal link control of the common channel signaling system NO7 is to transfer a signal message to / from the opposite station via the signal data link without error. Therefore, in addition to the signal information received from the upper level 3, the signal unit also includes level 2 information necessary to guarantee the normality of the signal information.

The signal units handled by the common channel signaling method are the fill-in signal unit (FISU) and the link status signal unit (LSSU).
And significant signal units (MSUs) (signal units other than the link control signal units (LCSUs) marked with * in FIG. 2 correspond).

Conventionally, this type of NO7 signal link control has been performed within level 2 by the method shown in FIG. 3 or directly at level 3. Next, the operation will be described. The solid line in the figure Indicates the flow of the signal unit, and the dotted line Indicates a control flow.

(1) Link activation procedure At the time of link activation, a link activation command (reference numeral 46) is issued to the link state control circuit 40 from level 3 to level 2. Then, the link state is set to link establishment, and "Out of a" is transmitted to the transmission control circuit 43 by the link state signal unit (LSSU).
"Lignment" is instructed to be transmitted to the other station (reference numeral 52), and is sent to the line as a serial bit string from the error detection signal unit identification synchronization control circuit 44 in the NO7 signal format (reference numeral 63). The control circuit 41 also activates the link from the partner station, and detects whether the partner transmits a synchronization signal.

If a synchronization signal is not received from the partner station within a predetermined time (T2), a failure to start the link is reported to the level 3 through the link state control circuit 40 (reference numerals 51 and 47). Then, the level 3 takes a timing (T17) in order to start the link again, and orders the start of the link start to the level 2 again (reference numeral 46). In this way, level 3 must initiate a link up to level 2 until a link is established with the partner station.

(2) Parameter negotiation Since the parameters such as the maximum signal length, the number of outstandings, and the value of the response delay timer in the NO7 common channel signaling method are fixed, parameters cannot be determined according to each system. Therefore, when the processing capacity resource is insufficient, congestion occurs in the reception control circuit 41, the congestion state is notified to the congestion control circuit 42 (reference numeral 55), and the link is transmitted from the congestion control circuit 42 through the transmission control circuit 43 (reference numeral 56). Although the congestion is notified to the partner station by transmitting the state signal unit (reference numeral 61), the link is disconnected if the congestion is not released for a certain period (T6).

(3) Signal length display error If the value of the signal length display displayed on the received signal unit does not match the actual signal length for some reason that level 2 is not involved, the conventional NO7 common line signal The system does not specify anything.

For example, in the reception control circuit 41 that has received the signal unit (reference numeral 58), when the signal length display displayed on the reception signal unit does not match the data length of the actual reception signal unit, the reception signal unit usually receives the signal unit. Is performed. Then, it does not make a reception confirmation response to the partner station that transmitted this signal unit. Therefore, in such a case, since the reception confirmation response cannot be received at the partner station no matter how long, the link is disconnected assuming that excessive response delay has occurred. On the other hand, if a reception confirmation response is sent to the other station without discarding a signal unit whose signal length display does not match the actual signal length, the other station will not receive the signal correctly even though the reception control circuit 41 does not receive it correctly. It is determined that this signal unit has been received normally, which causes inconvenience.

Further, even though this signal unit is a significant signal unit, the value of the added signal length indication is 3 like the fill-in signal unit or the link state signal unit.
If the value is less than, the signal cannot be correctly received, and the significant signal unit is not reported to the level 3 from the reception control circuit 41. Furthermore, if the reception control circuit 41 requests retransmission when the value of the signal length display does not match the actual signal length, the cause of the mismatch between the value of the signal length display and the actual signal length is as follows. If the error is caused by a logical error existing at level 3, error control at level 2 that only detects errors occurring on the transmission path by CRC check cannot be dealt with. There is an inconvenience of falling into a state of being repeated without stopping and being unable to recover.

(4) TEST signal There is no particular signal for TEST, and when checking the line by loopback, it was confirmed that the link was activated from level 3 and the link was established for the signal returned. The level 3 normality check of the partner station while the link is in service is performed by transmitting a significance signal unit for normality check and confirming the level 3 response to the signal.

[Problems to be solved by the invention]

By the way, the conventional level 2 apparatus described above has the following disadvantages because there is no means for controlling the level 2 between the own station and the opposite station.

(1) Since the link start command is issued independently of each other, the link start fails if the partner station is not in the start wait state even after the start, and the level 2 reports the link start failure to the level 3 and the level starts. Stop the second service.

Then, at level 3, a link cannot be established unless a command is issued to level 2 to activate the link again.

(2) If the partner station continues to transmit significant signal units irrespective of the number of significant signal units that can be continuously received due to the limitation of resource processing capability, for example, the congestion state may occur. The response cannot be confirmed and the link must be disconnected.

In addition, although only several tens of bytes of data are actually sent, the maximum length of the significant signal unit is determined to be 272 bytes, so that a reception buffer must always be prepared for 272 bytes or more.

(3) If the value of the signal length indication displayed on the received signal unit does not match the actual signal length for some reason that level 2 is not involved, as described above, the link may be disconnected, Retransmission and retransmission requests may be repeated indefinitely, and cannot be recovered at level 2. Also, at level 3, it was not possible to directly judge whether level 2 was in an abnormal situation, and at level 2, there was no means to notify the current situation to the partner station.

(4) In the signal unit of the NO7 system, the "significant signal unit" is used to transfer data while the link is in service, and the "fill-in signal unit" is transmitted when the link does not transmit a significant signal unit during service. Therefore, the "link status signal unit" is used for notifying the current link and the status of the own station to the partner station. In other words, the roles of the individual signal units have all been determined.

Therefore, there has been no signal unit capable of performing intercommunication "independent of the transmission / reception state" and "without changing the transmission / reception state" as a test signal unit.

[Means for solving the problem]

According to the present invention, the first level is a hierarchy that matches the electrical and physical conditions of the signal transfer medium, and the second level is an error check or retransmission for transferring a signal unit to an adjacent exchange via a signal line without error. It is a hierarchy that has a function,
A communication protocol layer as a layer having a function of delivering the third level to a target switching center by a combination of signal links, and a layer having a communication part for transmission and reception in accordance with the function of a signal handling the fourth level The second level signal link control device of the common line signaling system configured as described above manages a control signal from a signal network function unit of the device exhibiting the third level function and controls its own signal link. Link management processor for controlling the signal link, the signal link management processor of the partner station, and the third
In order to communicate with the level, a signal length display indicating the signal length of the own signal unit and a state display indicating the link control by a combination of a specific value of the signal length display, a link control identifier designating the content of the link control, and A link control signal unit having an information field is defined, and a transmission control circuit capable of transmitting the link control signal unit without changing a current sequence number, a transmission state, or the like according to an instruction of the signal link management processor, and When receiving the signal unit, the combination of the value of the specific signal length display having the received signal unit and the state display detects that this signal unit is the link control signal unit that has designated the link control, and this link control signal unit The link control identifier and information field obtained from And a reportable reception control circuit signaling link management processor without changing the receiving state in which was provided in the signaling link controller.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a signal link control device showing one embodiment of the present invention, and FIG. 2 is a conventional NO7 signal unit (FISU, LSSU, MSU) and a link control signal unit (LCSU) defined by the present invention. FIG. 4 is a diagram showing a format (shown by a symbol *).

The signal link control method of the signal link control device of the present invention is as follows.

(1) Link activation control The link activation is instructed to the signal link management processor 1 from level 3 (reference numeral 8). Signal link management processor 1
Tells the transmission control circuit 5 to transmit a link activation signal by a link control signal unit (LCSU) (reference numeral 15).
Then, the transmission control circuit 5 issues a signal unit transmission command 29 to the error detection / signal unit identification / synchronization control circuit 6, and transmits a bit stream conforming to the format of the NO7 signal unit to level 1 (reference numeral 31).

After transmitting the link activation signal, the system waits for a link activation signal from the partner station. Upon receiving the link start signal from the partner station (reference numeral 30), the error detection / signal unit identification / synchronization control circuit 6 reports the content 26 of the signal unit and the normality of the received signal unit to the reception control circuit 3, and receives the signal correctly. The reception control circuit 3 notifies the signal link management processor 1 of the generated signal unit from the signal length indication (LI) and the link control signal identifier (LCI) to the signal link management processor 1 (reference numeral 12). Then, by actually starting the level 2 (reference numeral 13), the link starts up almost simultaneously.

(2) Level 2 parameter negotiation Generally, in the data link of NO7, the maximum signal length (maximum 2
72 bytes) and outstanding number (up to 127)
), But when it is desired to change the number of standings or the maximum signal length due to actual system constraints or the like, the signal link management processor 1 sends the setting parameters of the own station to the partner station in the information field. Before the link is established, and transmitted by the link control signal unit.

When the link control signal unit is received at the partner station, the link control signal unit is reported to the signal link management processor 1 (reference numeral 12). The signal link management processor 1 knows the parameter negotiation from the link control identifier, and resets its own transmission control circuit 5 according to the parameter of the partner station written in the information field of the link control signal (reference numeral 16).

(3) Abnormal state notification signal When the received signal unit and the actual data length do not match, the signal link management processor 1 sends the link control signal unit to the transmission control circuit 5 stating that "the procedure cannot be recovered due to NO7". (Reference 15). Then, the transmission control circuit 5 performs transmission in the NO7 format to the error detection signal unit identification synchronization control circuit 6 through the link control signal in preference to other transmission units (reference numeral 31).

The partner station delivers the signal unit reported by the error detection signal unit identification and synchronization control circuit 6 to the reception control circuit 3 (reference numeral 26). The reception control circuit 3 determines the received signal unit as a link control signal based on the signal length display and the status display, and reports it to the signal link management processor 1 (reference numeral 1).
2). The signal link management processor 1 reports an abnormal state (reference numeral 9), and resets the reception control circuit 3 and the transmission control circuit 5 so that the current sequence number matches the partner station (reference numeral 16). Thereafter, if the signal is not recovered, the signal link management processor 1 resets the link control circuit 2 (reference numeral 13) and instructs the link control circuit 2 to re-establish the link.

(4) Test signal unit for data link In the test for the data link, first, the transmission path is physically turned back at the place to be tested, and a transmission command of the link control signal unit is transmitted from the signal link management processor 1 to the transmission control circuit 5.
(15), and transmits a link control signal unit for testing. Then, the transmitted signal unit is looped back so that the signal can be correctly received by the error detection signal unit identification and synchronization control circuit 6 (reference numeral 26), and the transmitted link control signal unit is correctly reported to the signal link management processor 1 (reference numeral 26). Reference numeral 12) is performed by confirming whether or not the transmitted signal contents match.

In the normality check of level 3, first, the state of level 3 is transmitted to the partner station as a link control signal unit through the signal link management processor 1 (reference numeral 15). On the receiving side, any state of the link is reported to the signal link management processor 1 as a link control unit.
By notifying the contents of the information field that has received the reception report to the level 3 (reference numeral 9), the state of the partner station can be known. In this way, the level 3 periodically knows the state of the partner station from each other, so that the normality check of the level 3 of the partner station can be performed regardless of the link state and without affecting the level 2 sequence number. I can do it.

〔The invention's effect〕

As described above, according to the present invention, the level 3 load can be reduced by providing the signal link management processor and the level 2 device capable of transmitting and receiving the link control signal unit for communication of the signal link management processor. The effect is that the functions that can be supported by the signal link control can be addressed to level 2.

[Brief description of the drawings]

FIG. 1 is a block diagram of a signal link control device showing one embodiment of the present invention, FIG. 2 is a diagram showing a format of a link control signal unit defined by the present invention and an existing signal unit, and FIG. It is a block diagram which shows a signal link control apparatus. 1 ... Signal link management processor, 2,40 ... Link state control circuit, 3,41 ... Reception control circuit, 4,42 ... Congestion control circuit, 5,43 ... Transmission control circuit, 6,44 ... Error detection signal unit identification synchronization control circuit, 7,45 ... Reception MSU signal unit, 8 ... Signal link control signal, 9 ... Signal link status report signal, 10 ... Setting / notification link control signal unit, 11,48 ... Transmission MSU signal unit, 12 ... Reception link control signal unit, 13,46 ... Level 2 link status control signal, 14,47 ... Level 2 link status report signal, 15 ... Transmission link control signal unit, 16 …… Sending / receiving circuit and congestion control circuit parameter setting signal 17,49 …… Signal link state signal unit 18,50… Reception start instruction, etc. 19,51… Receiving side abnormal state notification, 20,52 …… Signal link status signal unit transmission instruction, etc. 21,53 …… Transmission Abnormal status notification, etc. 22,54 …… Receive reverse sequence number notification, etc. 23,55… Busy state detection notification, etc. 24,56 …… SIB signal indication, 25,57 …… Transmission forward sequence number notification, etc. 26,58… Reception signal unit, 27,59… Normal / abnormal signal unit reception notification, 28,60… Signal unit transmission completion / incomplete notification, 29,61… Transmission signal unit, 30,62 ... Received signal bit stream, 31,63 ... Transmitted signal bit stream.

Claims (1)

(57) [Claims] 1. A first level is a hierarchy for matching electric and physical conditions of a signal transfer medium, and a second level is error checking and retransmission for transferring a signal unit to an adjacent exchange via a signal line without error. Hierarchy with the function of
A communication protocol layer serving as a layer having a function of delivering the third level to a target switching center by a combination of signal links and a layer having a communication function for transmitting and receiving according to the function of a signal handling the fourth level; The second level signal link control device having a common line signaling system, wherein a control signal from a signal network function unit of the device exhibiting the third level function is managed and its own signal level is controlled. And a signal length indication representing the signal length of the own signal unit and a specific value of the signal length indication to communicate with the signal link management processor and the third level of the partner station. A link having a status display indicating link control, a link control identifier designating the contents of the link control, and an information field. A control signal unit is defined, a transmission control circuit capable of transmitting the link control signal unit without changing a current sequence number, a transmission state, or the like according to an instruction of the signal link management processor. Detecting from the combination of the value of the specific signal length indication and the status indication of the received signal unit that this signal unit is the link control signal unit that has designated the link control, and the link control obtained from this link control signal unit. A reception control circuit capable of reporting an identifier and an information field to the signal link management processor without changing a current sequence number or a reception state.