CA2375819A1 - Method for monitoring bit transmission quality in packet-oriented transmission - Google Patents
Method for monitoring bit transmission quality in packet-oriented transmission Download PDFInfo
- Publication number
- CA2375819A1 CA2375819A1 CA002375819A CA2375819A CA2375819A1 CA 2375819 A1 CA2375819 A1 CA 2375819A1 CA 002375819 A CA002375819 A CA 002375819A CA 2375819 A CA2375819 A CA 2375819A CA 2375819 A1 CA2375819 A1 CA 2375819A1
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- Canada
- Prior art keywords
- packets
- bit
- packet
- transmission
- transmitting
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/20—Arrangements for detecting or preventing errors in the information received using signal quality detector
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0056—Systems characterized by the type of code used
- H04L1/0061—Error detection codes
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Quality & Reliability (AREA)
- Data Exchanges In Wide-Area Networks (AREA)
- Detection And Prevention Of Errors In Transmission (AREA)
Abstract
The bit transmission quality of a connectionless switching operation such as an IP-packet switching operation is monitored by providing each packet with a checksum. This checksum only helps to determine, at the receiving end, whether or not an error has occurred during the transmission process. It is not possible to determine the number of bit errors that have occurred using this procedure. According to the invention, these problems are solved by applying the BIP calculation method used in connection-oriented switching to connectionless switching.
Description
Description Method for monitoring the bit transmission quality in packet-oriented transmission The invention relates to a method according to the preamble of claim 1.
In contemporary information processing systems, the information is transmitted in SDH (synchronous digital hierarchy) frames. The SDH transmission is a connection-oriented switching system. ATM cells or IP
(Internet protocol) cells can be inserted, for example, into the SDH frames. These must be inserted into the SDH frames at the transmitting end and removed from them again at the receiving end. In the prior art, the IP cells are incorporated in ATM cells and these are transmitted in the SDH frames. In this arrangement, the packet assembly and disassembly processes must be performed twice in each case.
To monitor the bit transmission quality, checksum calculations are periodically performed. over all data transmitted between two reference points in the case of SDH frames. For example, two switching nodes can act as reference points between which a transmission section is arranged. During this process, the bi.t error rate on the transmission section is quantified. The checksum calculations are performed independently of one another both in the transmitting and in the receiving switching node. During this process, a parity check is made via, e.g. every eighth bit in a cyclic timing pattern. At the transmitting end, the result found is entered in a bit interleaved parity (BIP) check field and supplied to the receiving switching node in the SDH frame. In the SDH frame, there are three different BIP fields which are in each case used in the path overhead, multiplex section overhead and regenerator section overhead and have different sizes. The sizes of the path and multiplex section BIPs are dependent on the size of the SDH frame and extend from 2 to n*24 bits. The regenerator section BIP always has 8 bits. At the receiving end, the transmitted check field BIP is analyzed and the bit error rate on the transmission section is quantified as determined by a comparison of this analysis with a separate checksum calculation.
The advantage of this method can be seen in that the number of bit errors which have occurred is determined.
Thus, for example, bit errors which are close together (e. g. bits 5, 7) can also be determined (burst errors).
However, the circumstance that the equipment needed for SDH frames is very expensive and complex presents problems.
In contrast to connection-oriented switching, no permanent connection is established between the transmitting facility and the receiving facility in connectionless switching. IP packet switching can be used as an example of connectionless switching. To monitor the bit transmission quality, each packet is provided with a checksum. Using this checksum, bit errors can also be determined at the receiving end.
However, the checksum only allows the detection of whether a fault has occurred during the transmission process, or not. As a consequence, the relevant IP
packet is discarded at the receiving end. This procedure does not allow the number of errors which have occurred to be determined as is the case, for example, with the BIP calculation method.
The invention is based on the object of demonstrating an approach of how the bit transmission quality can be monitored more efficiently, even in the case of connectionless switching.
On the basis of the preamble of claim 1, the invention is , achieved by the features specified in the characterizing clause.
The advantageous factor of the invention is, in particular, that the BIP calculation method known with connection-oriented switching is transferred to connectionless packet switching. This is associated with the advantage that a more detailed error pattern is presented by determining the number of bit errors which have occurred in the system. Furthermore, it is possible to detect these bit errors section by section whereas the checksum method used in the prior art only allows an end-to-end statement.
Advantageous further developments of the invention are provided in the subclaims, In the text which follows, the invention is explained in greater detail with reference to an exemplary embodiment, in which:
Figure 1 shows 2 switching nodes which terminate a transmission section, Figure 2 shows a flowchart of the method according to the invention.
Figure 1 shows a configuration in which the method according to the invention is run. Accordingly, two switching nodes RA, R$ are shown which terminate a transmission section UA. The switching nodes RA, RB are to be constructed, for example, as IP routers.
Furthermore, IP packets are to be conducted by WDM
(wave division multiplexing) via the transmission section UA. According to the present exemplary embodiment, it is assumed that the transmitting switching node is the IP router RA and the, receiving switching node is the IP router RB. As can be seen in figure 1, the transmitting IP router RA
transmits IP packets of different lengths via the transmission section UA to the receiving IP router RB.
The transmission section UA is constructed to be bidirectional but only the transmission from the transmitting IP router RA to the receiving IP router RB
is shown for clarity.
In the text which follows, the invention is explained in greater detail by means of the flowchart shown in figure 2.
In the transmitting IP router RA, the BIP calculations are performed over a number of transmitted bits within a time interval. The higher-level packet. structure does not play a role in this case, i.e. the checksum calculation is performed over the bits of a number of packets. The time interval is predetermined by two successive control packets PM. The result determined is then stored in a check field BIP together with a sequence number in a control packet PM which is quasi-periodically inserted in the stream of outgoing IP
packets. The quasi-periodic insertion is necessary since the IP packets have a variable length and their transmission cannot be interrupted. To this extent, it is not possible to insert the control packets PM
periodically. According to the invention, it is then provided to reset a counting device on insertion of a control packet PM by the IP router RA. If this counting device has reached a predeterminable threshold value, the control packet PM is inserted into the IP packet stream as next packet immediately after the current IP
packet was sent out. In the interval needed by the counting device for reaching the threshold value, the bits are counted and the BIP checksum calculation is performed (time interval).
GR 99 P 1980 - 4a -If the receiving IP router RB determines that a control packet PM has arrived, its content is compared with its own BIP calculation performed since the last time a control packet was received. Furthermore, the sequence number which is also transmitted is verified, i.e. it must be higher by 1 than the one transmitted in the last control packet PM. If this is so, the difference between the result of the locally determined BIP
calculation and the BIP check field is formed. Then the number nH of bit errors which have occurred is determined in accordance with the result. Since bit errors can average out during the checksum calculation, the value nH is a lower limit to the number of errors which have occurred.
Using the value nH determined in this manner, an estimation pE of the instantaneous bit error rate is performed. This is:
pE = nB/nR where nR = number of received bits In this process, the quantity nR can be counted precisely at the receiving end, e.g. by means of ASIC
chips. As an alternative, however, an estimate is completely adequate. Accordingly, it is then assumed that constant times would elapse between 2 control packets PM. This is equivalent to saying that the control packets PM are inserted periodically into the outgoing stream of IP packets. Thus, the same number of bits is transmitted with the same transmission rate.
According to the present exemplary embodiment, it had been assumed that the facilities RA, R$ are constructed as switching nodes between which the method according to the invention is used. However, the invention is not restricted to such a configuration. Thus, it can also be used on individual transmission sections, bounded by regenerative repeaters, of a point-to-point connection between two switching nodes. In this arrangement, the transmission sections formed by regenerative repeaters GR 99 P 1980 - 5a -form the entire link section between the transmitting and receiving facility. In this case, each regenerative repeater can carry out the BIP calculation or check and can also write the result of its own calculation back into the forwarded control packet PM. This makes it possible to estimate the bit error rate section by section. The section-by-section bit error rate estimates stored in the individual regenerative repeaters can then be read out, for example, via X.25 protocols.
In contemporary information processing systems, the information is transmitted in SDH (synchronous digital hierarchy) frames. The SDH transmission is a connection-oriented switching system. ATM cells or IP
(Internet protocol) cells can be inserted, for example, into the SDH frames. These must be inserted into the SDH frames at the transmitting end and removed from them again at the receiving end. In the prior art, the IP cells are incorporated in ATM cells and these are transmitted in the SDH frames. In this arrangement, the packet assembly and disassembly processes must be performed twice in each case.
To monitor the bit transmission quality, checksum calculations are periodically performed. over all data transmitted between two reference points in the case of SDH frames. For example, two switching nodes can act as reference points between which a transmission section is arranged. During this process, the bi.t error rate on the transmission section is quantified. The checksum calculations are performed independently of one another both in the transmitting and in the receiving switching node. During this process, a parity check is made via, e.g. every eighth bit in a cyclic timing pattern. At the transmitting end, the result found is entered in a bit interleaved parity (BIP) check field and supplied to the receiving switching node in the SDH frame. In the SDH frame, there are three different BIP fields which are in each case used in the path overhead, multiplex section overhead and regenerator section overhead and have different sizes. The sizes of the path and multiplex section BIPs are dependent on the size of the SDH frame and extend from 2 to n*24 bits. The regenerator section BIP always has 8 bits. At the receiving end, the transmitted check field BIP is analyzed and the bit error rate on the transmission section is quantified as determined by a comparison of this analysis with a separate checksum calculation.
The advantage of this method can be seen in that the number of bit errors which have occurred is determined.
Thus, for example, bit errors which are close together (e. g. bits 5, 7) can also be determined (burst errors).
However, the circumstance that the equipment needed for SDH frames is very expensive and complex presents problems.
In contrast to connection-oriented switching, no permanent connection is established between the transmitting facility and the receiving facility in connectionless switching. IP packet switching can be used as an example of connectionless switching. To monitor the bit transmission quality, each packet is provided with a checksum. Using this checksum, bit errors can also be determined at the receiving end.
However, the checksum only allows the detection of whether a fault has occurred during the transmission process, or not. As a consequence, the relevant IP
packet is discarded at the receiving end. This procedure does not allow the number of errors which have occurred to be determined as is the case, for example, with the BIP calculation method.
The invention is based on the object of demonstrating an approach of how the bit transmission quality can be monitored more efficiently, even in the case of connectionless switching.
On the basis of the preamble of claim 1, the invention is , achieved by the features specified in the characterizing clause.
The advantageous factor of the invention is, in particular, that the BIP calculation method known with connection-oriented switching is transferred to connectionless packet switching. This is associated with the advantage that a more detailed error pattern is presented by determining the number of bit errors which have occurred in the system. Furthermore, it is possible to detect these bit errors section by section whereas the checksum method used in the prior art only allows an end-to-end statement.
Advantageous further developments of the invention are provided in the subclaims, In the text which follows, the invention is explained in greater detail with reference to an exemplary embodiment, in which:
Figure 1 shows 2 switching nodes which terminate a transmission section, Figure 2 shows a flowchart of the method according to the invention.
Figure 1 shows a configuration in which the method according to the invention is run. Accordingly, two switching nodes RA, R$ are shown which terminate a transmission section UA. The switching nodes RA, RB are to be constructed, for example, as IP routers.
Furthermore, IP packets are to be conducted by WDM
(wave division multiplexing) via the transmission section UA. According to the present exemplary embodiment, it is assumed that the transmitting switching node is the IP router RA and the, receiving switching node is the IP router RB. As can be seen in figure 1, the transmitting IP router RA
transmits IP packets of different lengths via the transmission section UA to the receiving IP router RB.
The transmission section UA is constructed to be bidirectional but only the transmission from the transmitting IP router RA to the receiving IP router RB
is shown for clarity.
In the text which follows, the invention is explained in greater detail by means of the flowchart shown in figure 2.
In the transmitting IP router RA, the BIP calculations are performed over a number of transmitted bits within a time interval. The higher-level packet. structure does not play a role in this case, i.e. the checksum calculation is performed over the bits of a number of packets. The time interval is predetermined by two successive control packets PM. The result determined is then stored in a check field BIP together with a sequence number in a control packet PM which is quasi-periodically inserted in the stream of outgoing IP
packets. The quasi-periodic insertion is necessary since the IP packets have a variable length and their transmission cannot be interrupted. To this extent, it is not possible to insert the control packets PM
periodically. According to the invention, it is then provided to reset a counting device on insertion of a control packet PM by the IP router RA. If this counting device has reached a predeterminable threshold value, the control packet PM is inserted into the IP packet stream as next packet immediately after the current IP
packet was sent out. In the interval needed by the counting device for reaching the threshold value, the bits are counted and the BIP checksum calculation is performed (time interval).
GR 99 P 1980 - 4a -If the receiving IP router RB determines that a control packet PM has arrived, its content is compared with its own BIP calculation performed since the last time a control packet was received. Furthermore, the sequence number which is also transmitted is verified, i.e. it must be higher by 1 than the one transmitted in the last control packet PM. If this is so, the difference between the result of the locally determined BIP
calculation and the BIP check field is formed. Then the number nH of bit errors which have occurred is determined in accordance with the result. Since bit errors can average out during the checksum calculation, the value nH is a lower limit to the number of errors which have occurred.
Using the value nH determined in this manner, an estimation pE of the instantaneous bit error rate is performed. This is:
pE = nB/nR where nR = number of received bits In this process, the quantity nR can be counted precisely at the receiving end, e.g. by means of ASIC
chips. As an alternative, however, an estimate is completely adequate. Accordingly, it is then assumed that constant times would elapse between 2 control packets PM. This is equivalent to saying that the control packets PM are inserted periodically into the outgoing stream of IP packets. Thus, the same number of bits is transmitted with the same transmission rate.
According to the present exemplary embodiment, it had been assumed that the facilities RA, R$ are constructed as switching nodes between which the method according to the invention is used. However, the invention is not restricted to such a configuration. Thus, it can also be used on individual transmission sections, bounded by regenerative repeaters, of a point-to-point connection between two switching nodes. In this arrangement, the transmission sections formed by regenerative repeaters GR 99 P 1980 - 5a -form the entire link section between the transmitting and receiving facility. In this case, each regenerative repeater can carry out the BIP calculation or check and can also write the result of its own calculation back into the forwarded control packet PM. This makes it possible to estimate the bit error rate section by section. The section-by-section bit error rate estimates stored in the individual regenerative repeaters can then be read out, for example, via X.25 protocols.
Claims (11)
1. A method for monitoring the bit transmission quality in packet-oriented transmission, comprising a transmitting facility (R A) which supplies information in packets with variable length to a receiving facility (R B) via a transmission section (UA) as determined by connectionless switching, characterized in that, in the transmitting facility (R A), a check information item, which is stored in a control packet (PM), is formed bit by bit over the transmitted packets within a predeterminable time interval in accordance with an algorithm, in that the control packets (PM) are quasi-periodically inserted into the stream of packets output by the transmitting facility (R A), in that, when a control packet (PM) arrives in the receiving facility (R B), a check information item is also formed bit by bit over the packets received in the time interval in accordance with the same algorithm, in that an estimate is made with respect to the bit errors which have occurred during the transmission process in accordance with a logic operation between this check information item and the check information item transmitted in the control packet (PM).
2. The method as claimed in claim 1, characterized in that the estimation is made by dividing the number of bit errors which have occurred at a minimum (n B) by the number (n R) of the transmitted bits.
3. The method as claimed in claim 1, 2, characterized in that the number of transmitted bits (n R) is measured at the receiving end.
4. The method as claimed in claim 1, 2, characterized in that the number of transmitted bits (n R) is estimated at the receiving end by assuming a periodic insertion of the control packets (PM).
5. The method as claimed in claims 1 to 4, characterized in that the time interval is defined by the sending out of two successive control packets (PM).
6. The method as claimed in claims 1 to 5, characterized in that the validity of the control packet (PM) is decided at the receiving end by analysis of the sequence number.
7. The method as claimed in one of the preceding claims, characterized in that the packets transmit information in accordance with an Internet protocol (IP packets).
8. The method as claimed in one of the preceding claims, characterized in that the logic operation is a differentiation.
9. The method as claimed in one of the preceding claims, characterized in that the check information is provided in accordance with a BIP
(bit interleaved parity) calculation.
(bit interleaved parity) calculation.
10. The method as claimed in one of the preceding claims, characterized in that transmitting (R A) and receiving facility (R B) are constructed as switching nodes.
11. The method as claimed in one of claims 1 to 9, characterized in that transmitting (R A) and receiving facility (R B) are constructed as regenerative repeaters.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19925237.8 | 1999-06-02 | ||
| DE19925237 | 1999-06-02 | ||
| PCT/DE2000/001094 WO2000076108A1 (en) | 1999-06-02 | 2000-04-10 | Method for monitoring bit transmission quality in packet-oriented transmission |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2375819A1 true CA2375819A1 (en) | 2000-12-14 |
Family
ID=7909987
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002375819A Abandoned CA2375819A1 (en) | 1999-06-02 | 2000-04-10 | Method for monitoring bit transmission quality in packet-oriented transmission |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP1180275A1 (en) |
| CA (1) | CA2375819A1 (en) |
| WO (1) | WO2000076108A1 (en) |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4831624A (en) * | 1987-06-04 | 1989-05-16 | Motorola, Inc. | Error detection method for sub-band coding |
| US5410546A (en) * | 1993-11-01 | 1995-04-25 | Storage Technology Corporation | Apparatus and method for CRC computation over fixed length blocks containing variable length packets of data received out of order |
| JP3117000B2 (en) * | 1997-02-21 | 2000-12-11 | 株式会社デンソー | Communication system and electronic control device used therein |
-
2000
- 2000-04-10 WO PCT/DE2000/001094 patent/WO2000076108A1/en not_active Application Discontinuation
- 2000-04-10 CA CA002375819A patent/CA2375819A1/en not_active Abandoned
- 2000-04-10 EP EP00926710A patent/EP1180275A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| EP1180275A1 (en) | 2002-02-20 |
| WO2000076108A1 (en) | 2000-12-14 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |