DE10232982A1 - HDLC time multiplexed receiver side data channel grouping recognition procedure for monitoring systems recognizes flag and characteristic bytes - Google Patents

Abstract

An HDLC (High Level Data Link Control) time multiplexed receiver side data channel set recognition procedure recognizes the flag (F) bytes and (A) (Address), (S) (Control) and (P) (Protocol) characteristic bytes in PCM (Pulse Code Modulation) frames. An HDLC (High Level Data Link Control) time multiplexed receiver side data channel set recognition procedure recognizes the flag (F) bytes and (A) (Address), (S) (Control) and (P) (Protocol) characteristic bytes in PCM (Pulse Code Modulation) frames. Independent claims are included for equipment implementing the procedure using buffer memory and a flat comparator to recognize the flag byte patterns.

Description

The invention relates to a method according to the preamble of claim 1 and an arrangement for carrying this out Method according to claim 7.

It is known to use a so-called pulse code modulation (PCM) frame structure for the rapid transmission of large amounts of data from a transmitter to a receiver, in which the data are each transmitted in a multiplicity of time channels (time slots) in time multiplex. A frequently used PCM frame structure is, for example, PCM 30 or PCM 31, with which a data stream of 2 Mbit / s can be transmitted. 1 shows schematically this PCM frame structure. Here, 32 time channels TS are combined to form a frame, the channels TS are numbered from 0 to 31. Each channel contains 1 byte or 8 bits. The step speed of the data of one channel is 64 kbit / s. By multiplexing all 32 channels, a data stream of 32 × 64 kbit / s = 2048 kbit / s is created. With the PCM 31 structure, the channel contains 0 including frame synchronization, but no traffic data. The canals 1 to 31 contain the traffic or user data. The channel is in the PCM 30 structure 0 as designed for PCM 31, the channel 16 contains, among other things, the signaling data and the so-called multiframe alignment signal, but again no traffic data. The remaining thirty channels contain the actual user or traffic data. (Digital transmission technology, PCM basics and measurement methods, Expertverlag, Oskar Heilemann, page 26)

Most of these PCM framework structures also of the possibility Utilized data signals with a data rate higher than 64 kbit / s on multiple channels distributed to broadcast. A data stream of e.g. B. 256 kbit / s then requires four time channels TS. The Location of these channels allocated to a specific data stream within the multiplex structure is arbitrary. The operators of the data connection are the chosen ones Assignments known and the selected Nesting can simply be deinterleaved at the receiving end become. It becomes difficult when such nested data traffic monitored tactically and strategically and the supervisor it is not known how in the received PCM coded Data stream of 2Mbit / s distributes the information to the usable channels are.

2 shows an example of a possible distribution of different traffic data in a PCM 30 or PCM 31 frame. In this example, six different data signals with different data rates and different distribution are distributed in the frame. For a monitoring operator (supervisor), if the channel distribution selected on the transmitter side is unknown, the possible combinations for recognizing the associated data channels are so extremely high that manual attempts are futile. The supervisor can determine a data stream of 2 Mbit / s, but has no knowledge of how many independent groups of data streams with which data rate are contained therein and how the individual data streams are arranged in the 64 kbit / s grid of the PCM frame.

It is therefore an object of the invention to show a method and an arrangement with which the receiving end automatically this for the supervisor unknown channel distribution of the PCM frame structure can be determined can, so monitoring PCM-coded data signals are also possible.

This task is carried out with regard to the Procedure based on a procedure according to the preamble of the claim 1 by its characteristic features and with regard to the arrangement solved by the features of claim 7.

Advantageous further developments result itself from the subclaims.

The invention is based on the knowledge that in such PCM-encoded data signals usually follow the data streams so-called High Level Data Link Control (HDLC) protocol can be divided into data blocks, whereby a characteristic of this HDLC protocol is that in the beginning and a so-called flag byte is provided at the end of each data block. (Lexicon of data communication, Klaus Lipinski, International Thompson Publishing, page 246)

3 shows the standardized structure of this HDLC protocol. The flags F signal the beginning and end of the protocol, they also serve for block synchronization and they consist of the characteristic bit sequence 0-1-1-1-1-1-1-0. An address byte A follows the flag byte F and contains the address of the remote station. The commands and responses are contained in a subsequent control byte S; if there are several data blocks, the sequence number is incremented. The useful data or traffic data are transmitted in the actual data block D, 2 bytes P each being provided for the identification of the internal protocol of the useful data D. At the end of the user data block D there follows a check byte C which contains the so-called cyclic redundancy check CRC as 16-bit check information and comprises the entire HDLC block with the exception of the flag bytes. Due to this HDLC-characteristic byte sequence F, A, S, P and C, it is possible to recognize the occupancy of a PCM frame with different traffic data despite the extremely fast data transmission. The data of the so as belonging together Detected data channels can then be decoded and evaluated.

The invention is illustrated below a schematic drawing of an embodiment explained in more detail. In the drawing shows:

1 a 2048 kbit / s PCM frame structure;

2 the allocation of a PCM frame with several different traffic data;

3 the HDLC protocol structure;

4 the matrix structure of the content in the PCM diagram field "TS frame";

5 Characteristic places in the PCM diagram field "TS frame" for finding grouped signals (analysis matrix)

6 a flowchart for determining the edge zones of a grouped signal and

7 the basic structure of an arrangement according to the invention for automatically executing the method according to the invention.

• 1. Auslesen einer hinreichend großen Anzahl von PCM-Rahmen und der darin enthaltenen Kanäle TS gemäß der Matrixstruktur nach 4.
• 2. Suchen nach Flags (Flag-Bytes) F mit dem Muster "0 1 1 1 1 1 1 0" innerhalb der erfaßten Matrixstruktur.
• 3. Registrieren der TS, die solche Flags enthalten; z. B. TS 7 im Rahmen 0(RO) von 4.
• 4. Automatisches Eintragen der Flags F in eine Analyse-Matrix nach 5. Diese dient dazu, eine Übersicht zu schaffen, um die Strukturen der gruppierten Signale ausfindig zu machen. Es sollen in diesem Feld die Flags und die unmittelbar folgenden, markanten TS für alle gruppierten Signale eingetragen und bewertet werden, also A, S, P und C.
• 5. Aufsuchen derjenigen und als markant oder für die Analyse als relevant zu bezeichnenden TS, die den Flags zeitlich folgend zuzuordnen sind. Diese TS, die dem Flag folgen, müssen in der Analyse-Matrix nicht notwendigerweise zusammenhängend auftreten. Sie können in folgender Konfiguration erscheinen: – Unmittelbar zusammenhängend in einem Rahmen – Mit Unterbrechung aber innerhalb eines Rahmens (verschachtelt, gruppiertes Signal) – Mit Unterbrechung im nachfolgenden Rahmen
• 6. Bewerten der Eintragungen in der Anlayse-Matrix zum Erkennen der gruppierten Signalstrukturen (5). Es sollen, soweit wie möglich, Anfang und Ende der gruppierten Signale im PCM-Rahmen erkennbar werden.

In the example chosen it is assumed that the received 2 Mbit / s data stream after a PCM 30 or PCM 31 Frame structure is transmitted on a total of 31 channels TS, namely the data signal according to the HDLC protocol 3 divided into data blocks of any length with user data streams D of any length. The bits received one after the other in rapid succession in the individual channels TS are initially in accordance with 4 read into a matrix structure as successive PCM frames. The procedure is as follows:

• 1. Reading out a sufficiently large number of PCM frames and the channels TS contained therein according to the matrix structure 4 ,
• 2. Search for flags (flag bytes) F with the pattern "0 1 1 1 1 1 1 0" within the detected matrix structure.
• 3. Register the TS that contain such flags; z. B. TS 7 under 0 (RO) of 4 ,
• 4. Automatic entry of the flags F into an analysis matrix 5 , This is used to create an overview in order to find the structures of the grouped signals. In this field, the flags and the immediately following, distinctive TS for all grouped signals should be entered and evaluated, i.e.A, S, P and C.
• 5. Search for those TS that are to be designated as distinctive or relevant for the analysis, which are to be assigned to the flags in chronological order. These TS that follow the flag do not necessarily have to be connected in the analysis matrix. They can appear in the following configuration: - Directly connected in one frame - With an interruption but within a frame (nested, grouped signal) - With an interruption in the following frame
• 6. Evaluate the entries in the analysis matrix to recognize the grouped signal structures ( 5 ). As far as possible, the beginning and end of the grouped signals should be recognizable in the PCM frame.

The evaluation is based on the Entries in the "TS frame" field over time, i.e. based on the to disposal standing frame.

• – Es wird 1 Byte A für die Adresse ADR der Zielstation (z. B. Hex 00 bis FF) verwendet.
• – Es dient 1 Byte S für das Steuerfeld STEU; es kann zur Kennung bestimmter äußerer Protokolle (z. B. Hex 00 für CiscoSLE, Hex 03 für PPP) verwendet werden; sonst hat es eine andere Bedeutung.
• – Es werden 2 Bytes P für die Kennung des inneren Protokolls, (z. B. Internet Protokoll IP), in dem sich die Nutzdaten befinden, verwendet. Um diese Protokolle ausreichend interpretieren zu können, wird im Hintergrund eine Tabelle geführt, mit der die Inhalte der TS 3 und 4 nach dem Flag verglichen werden.

The flags F form the bases for the evaluation of the following, distinctive bytes A, S, P and C. The flags are normally followed by 4 bytes, which have the following meaning:

• - 1 byte A is used for the address ADR of the target station (e.g. Hex 00 to FF).
• - 1 byte S is used for the control field STEU; it can be used to identify certain external protocols (e.g. Hex 00 for CiscoSLE, Hex 03 for PPP); otherwise it has a different meaning.
• - 2 bytes P are used for the identification of the inner protocol (e.g. Internet Protocol IP) in which the user data are located. In order to be able to interpret these protocols sufficiently, a table is kept in the background with which the contents of TS 3 and 4 are compared according to the flag.

• 7. Determine the structure of the grouped Signals in the PCM framework. To do this, the distinctive TS, the flags follow immediately, examined further below. Here comes it particularly on the location of the originally broadcast Packets (flag, ADR, STEU, protocol) in the PCM frame; when feeding There is a certain amount in the PCM framework due to the grouping "Reorganization" if you look at the continuity of the PCM framework.

• - A flag must be followed by an address ADR; if this is not immediately the case in the matrix structure in the "TS frame" field, it can be concluded that the flag is on the edge of a grouped signal, namely in the last TS of the group signal sought. An edge zone of a grouped signal has thus been determined. Finding the bytes belonging to this flag (ADR, STEU, protocol) also serves to determine the second edge zone for this grouped signal. The associated bytes must either occur in the same frame on other TS after the flag (nested, grouped signal) or in the subsequent frame on TS before the flag. There is therefore a certain limitation as to where the associated bytes will be found follows.

If the associated bytes in the subsequent frame must be Another narrowing criterion can be set up to avoid ambiguity exclude between the grouped signals; there are those TS as belonging to the viewed flag that is in the immediate vicinity of the viewed flag, however in the subsequent frame. These TS must be on the "left margin" of the grouped signal (detail I) because they are the continuation to the considered flag and therefore at the beginning of the "left Border zone "must begin. This means that the TS assignment of a grouped signal is based on 2 Frame completely detected. The two edge zones, i.e. the location of the grouped signal, is included in the analysis matrix as a result. To be more certain about the To achieve TS assignment of a grouped signal will be more Frame evaluated and registered in the same way.

• - If a flag F with the associated four distinctive channels A, S and P as connected is discovered, it somehow lies within a searched, grouped signal; you can use it first just close that this grouped signal is at least 5 TS wide. But it can also be wider and the detected signal can be in the middle or at the edges of a grouped signal. (EinzelheitII). With the "middle located "block of this broadcast consisting of flag, ADR, STEU, protocol no edge zone can be determined. To determine the marginal zones must in the following frame near the TS position of the "middle" located flags after the next Flag of this program can be searched. Depending on the location of the next one, flags discovered in this region with the distinctive, associated (4) TS in other frames, can then be recognized whether the new Constellation suitable for determining marginal zones or not. If the related TS flag, ADR, STEU, protocol in the analysis matrix does not appear contiguous, can the edge zones are determined as described above. If the new one Constellation flag, ADR, STEU, protocol occurs again coherently, can only their start and end TS are registered. Compared to the first belonging together You can only TS group based on a possible shift between these two over the Say a little more about the width of the grouped signal. The marginal zones of the grouped signal have not yet been sufficiently determined.
• - Should several groups of related, distinctive TS contiguous appear in the frame one after the other without a "separated" Group "for Find this shipment, so the situation at the end of the evaluation this program based on the entire grouping in the PCM system influenced. A possible uncertainty for a grouped signal becomes based on the reliability factors that which have neighboring signals corrected.
• - More difficult it becomes when the header block (flag, ADR, STEU, protocol) is shared in two different TS areas occurs in the same frame, that is, nested between other grouped Signals, has been arranged. In this case, there must be between other, distinctive bytes a distinction must be made between other grouped signals and possibly are also next to each other in the PCM frame. In such make have to then case decisions are made according to plausibility criteria, the overarching between neighboring groups. Based on the present Constellation is decided, which TS / grouped to which flag Signal can still be expected. This is only possible if 2 consecutive frames were assessed. The TS limits / locations of a nested, grouped signal, especially then always the clearer the more frames can be used for the evaluation. If broadcasts occur with very long data content, there are few flags including the associated, striking bytes; in such cases the number the frame to be assessed should be large. (Fall at 2048 kbps 8000 frames per second; an observation time of a few seconds might even in such cases suffice.)
• - If the field "TS frame". evaluated in this way, the structures for recognizing the grouped signals arise in a PCM frame. With short analysis times of the analysis matrix and with sometimes long-lasting individual broadcasts, structures are created that contain unassigned TS / channels. But these are then recognizable and can be interpreted accordingly in a graphic representation. The same applies to unused TS / channels. (TS numbers 1 to 4 and 20 to 31, in 4 marked with I)
• - In individual cases, ambiguities can occur in such a way that adjacent user data and header data can no longer be separated within a frame. Such cases can occur with the nested, grouped signals. Although these uncertainties lead to imprecise structures for a short time, they are of lesser importance, since the final evaluation of the structure of the grouped signals in a PCM frame is only output after a suitably selectable evaluation time, which then takes a corresponding number of frames into account in the final evaluation and individual, minority deviations then become eli miniert.
• - Everyone determined and registered result on a location of a grouped Receives signal a reliability factor, who expresses whether the result is based on separate or contiguous distinctive TS was formed. additionally becomes the number of support points (Flags) on which the result is based,

included. The striking "separately" TS is the determination of the positions unambiguous and independent of neighboring signals. You therefore get a high reliability factor. at coherently occurring, distinctive TS is the determination of the location of a grouped Signals also dependent from the neighboring signals; you get a lower reliability factor.

• – Ein PCM Datenstrom von 2 MBit/s kann derart entflechtet werden, daß gruppierte Signale in ihrer Lage erkannt werden und die Anzahl der jeweils benützten Datenkanäle offengelegt wird.
• – Die Datenrate für jedes gruppierte Signal wird ermittelt.
• – Gruppierte Signale, die verschachtelt/getrennt innerhalb des PCM-Rahmens auftreten, jedoch den Inhalt einer Sendung führen, werden erkannt und ihre Belegung der TS/Kanäle wird ausgegeben.
• – Falls die Gruppierung in dem PCM-Rahmen "dynamisch" erfolgen sollte, werden die gleichen Ergebnisse erzielt wie im statischen Zustand.
• – Die Umstellung der Gruppierung in dem PCM-Rahmen wird sofort erkannt und kann als Warnung abgegeben werden.
• – Jede Änderung in der Gruppierung wird sofort erfaßt und im Bedarfsfall gemeldet.
• – Die Zuordnungen für die gruppierten Signale erhalten Zuverlässigkeitsfaktoren, um auf eventuelle Sonderfälle aufmerksam zu werden.
• – Das Verfahren ist für PCM 30/31 einsetzbar.
• – Die Auslastung der Verkehrsverbindung ist erkennbar und kann registriert werden. (Anzahl der Einzelsendungen pro Verkehrsverbindung und Zeiteinheit einschließlich Testsequenzen).
• – Der Dateninhalt pro Verkehrverbindung kann aufgezeichnet und dekodiert werden.
• – Die Länge der Einzelsendungen pro Verkehrsverbindung wird erkannt; einschließlich eventueller Adressenänderungen.
• – Die Suche nach bestimmten Adressen kann aufgenommen werden.
• – Nicht HDLC-orientierte Datenblöcke werden erkannt und gemeldet.

When analyzed appropriately, the analysis matrix provides the following advantageous results in the overview:

• A PCM data stream of 2 Mbit / s can be unbundled in such a way that grouped signals are recognized in their position and the number of the data channels used is disclosed.
• - The data rate for each grouped signal is determined.
• - Grouped signals that appear nested / separated within the PCM frame, but carry the content of a program, are recognized and their assignment of the TS / channels is output.
• - If the grouping in the PCM frame should be "dynamic", the same results are achieved as in the static state.
• - The change of the grouping in the PCM framework is recognized immediately and can be given as a warning.
• - Every change in the grouping is recorded immediately and reported if necessary.
• - The assignments for the grouped signals are given reliability factors to draw attention to any special cases.
• - The procedure can be used for PCM 30/31.
• - The traffic load is recognizable and can be registered. (Number of individual broadcasts per traffic connection and time unit including test sequences).
• - The data content per traffic connection can be recorded and decoded.
• - The length of the individual shipments per traffic connection is recognized; including any address changes.
• - The search for specific addresses can be started.
• - Data blocks that are not HDLC-oriented are recognized and reported.

6 shows on the basis of a flow diagram the described procedure for determining the edge zones of a grouped signal.

7 shows the basic structure of an arrangement according to the invention for automatically executing this described detection method.

The arrangement includes a buffer 1 , several comparators 2 to 5 , which also act as short-term memories and which are setpoint memories 6 to 9 are assigned in which the known characteristic bit patterns of the HDLC protocol are stored. In the flag memory 6 the well-known bit sequence 0-1-1-1-1-1-1-0 is stored in the address memory 7 the address of the remote station is stored in the control memory 8th the known control bits S are stored and in the log memory 9 the two bytes P are stored for the identification of the internal protocol of the user data. There is also an analysis memory 10 , a programming unit 11 and a display device 12 intended. The individual modules are in the sense of 7 linked together.

In the clipboard 1 the individual channels TS of the time-division multiplex frames are first read continuously. The flag comparator 2 compares the bit pattern of the incoming channels with that in the flag memory 6 stored flag pattern, if a match is found, the flag comparator shares the determined channel number and frame number for each flag detected with the other comparators 3 . 4 and 5 With. The comparators 3 . 4 and 5 compare the bit patterns of those channels that follow the flag channel identified with the bit patterns of the associated setpoint memories 7 . 8th and 9 , The distinctive and HDLC-characteristic subsequent channels thus recognized are then. together with the flag channels the analysis memory 10 fed and there in the sense of 5 saved. The analysis memory 10 is given a structure that builds up the peripheral zones of the related data channels in the background. With suitable software for the program setup 11 this structure of the analysis memory 10 evaluated with regard to the marginal zones determined and the reliability factors mentioned are determined. In the display device 12 the time-division multiplex frames are finally displayed in such a way that the associated grouped data channels contained therein can be recognized. In addition, the associated data rate and the determined reliability factor can be shown. The channels identified as belonging together can then be evaluated via a decoding device (not shown).

The display result is preferred updated in adjustable time intervals, in case of deviations from the previous result, the new configuration to the data channels is continuously in shown on a new display line. With a dynamic assignment of the data channels receives you get an overview of that current and over the past Data transference.

Claims (8)

Method for detecting on the receiving side of data signals transmitted in time-division multiplexing, which on the transmitter side are divided into data blocks with a flag byte (F) at the beginning and end according to the HDLC protocol, these data blocks being transmitted on the channels of a PCM frame structure in a manner unknown to the receiving end are characterized in that, in the case of several successive PCM frames, the channels containing a flag byte (F) are determined, and from the position and sequence of the flag channels thus determined, those associated channels are determined which together each contain a data block after the HDLC protocol transmitted. A method according to claim 1, characterized in that together with the channels containing at least one flag byte (F) each part of those channels it is determined which of the flag bytes in the HDLC protocol (F) subsequent HDLC-characteristic data bytes (A, S, P) included. Method according to claim 1 or 2, characterized in that the determined channels in the form of a channel frame matrix be evaluated. Method according to one of the preceding claims, characterized characterized that the Determination of the related channels is performed several times on successive PCM frames. Method according to one of the preceding claims, characterized characterized that the in the coherent so determined Channels transmitted data blocks (D) can be decoded and evaluated. Method according to one of the preceding claims, characterized characterized that the The result of the determination of the associated channels is shown graphically. Arrangement for executing the method according to one or more of the preceding claims, characterized by an intermediate store ( 1 ), in which the successive PCM frames are read, a flat comparator ( 2 ) which compares the bit patterns of the successive channels (TS) with the known flag bit pattern, at least one further comparator ( 3 . 4 . 5 ), which compares the bit patterns of the channels following the recognized flag channel with at least one of the subsequent HDLC-characteristic bit patterns, an analysis memory ( 10 ) in which the flag channels thus recognized and the subsequent HDLC characteristic channels are stored, a programming device ( 11 ) to evaluate the content of the analysis memory ( 10 ), and a display device controlled thereby ( 12 ). Arrangement according to claim 7, characterized in that the individual comparators ( 2 to 5 ) each memory ( 6 to 9 ) are assigned in which the known HDLC characteristic bit patterns (F, A, S, PP) are stored.