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(19) 



J 



Europaisches Patentamt 
European Patent Office 
Office europeen des brevets 



(12) 



(43) Date of publication: 

11.12.2002 Bulletin 2002/50 

(21) Application number: 01112986.3 

(22) Date of filing: 08.06.2001 



(H) EP 1 265 454 A1 

EUROPEAN PATENT APPLICATION 

(51) IntCI 7: H04Q 11/04 



(84) Designated Contracting States: 


(72) Inventors: 


AT BE CH CY DE DK ES Fl FR GB GR IE IT LI LU 


• Mordacci, Alessandro 


MC NL PTSETR 


149-43 Nynashamn (SE) 


Designated Extension States: 


• Bjdrnson, Stefan 


AL LT LV MK RO SI 


149-45 Nynashamn (SE) 


(71) Applicant: TELEFONAKTIEBOLAGET L M 


(74) Representative: HOFFMANN - EITLE 


ERICSSON (publ) 


Patent- und Rechtsanwalte 


126 25 Stockholm (SE) 


Arabellastrasse 4 




81925 Munchen (DE) 



(54) Monitoring device and method 



(57) To provide a general and effective monitoring 
equipment for an ATM communication network, it is pro- 
posed to provide an interception unit (16) to store an 
identification of at least one communication connection 
to be monitored. Further, a selection unit (20) is adapted 
to achieve a coupling to the communication connection 
to be monitored according to the information stored in 



the interception table and to further to select at least one 
cell from this communication connection. A copying unit 
(22) copies the at least one cell selected by the selecting 
unit (20) to a monitoring connection. The device for mon- 
itoring the communication connection is further integrat- 
ed into a switching equipment (12; DCS) of a packet- 
switched communication network. 




Printed by Jouve, 75001 PARIS (FR) 



EP 1 265 454 A1 



Description 

FIELD OF INVENTION 

5 [0001] The present invention relates to a monitoring device and a related method, and in particular to a device and 
method for monitoring at least one communication connection in a packet switched network. 

BACKGROUND ART 

10 [0002] The ever increasing amount of data traffic in packet switched networks leads to a demand for monitoring of 
this data traffic with the same level of security and confidentiality as known from circuit switched networks monitoring. 
In circuit switched networks, e.g., telephoning networks, it is customary to monitor communication connections from a 
remote operation center so that a network operator wishing to operate real time traffic can constantly receive information 
on the quality of the communication lines. Another application of monitoring is lawful interception, i.e. the act of inter- 
's cepting a communication on behalf of a law enforcement agency and also referred to as legal interception in the fol- 
lowing. Here, data communicated via the communication lines is copied for subsequent use, e.g.. in court proceedings. 
[0003] From the above, it is only natural that network operators will want to continue such monitoring approaches in 
packet switched networks, e.g., the ATM-based or IP-based networks. However, currently the monitoring of commu- 
nication connections in packet switched networks is accomplished on an ad hoc basis. All the solutions currently avail- 
20 able are based on stand-alone, dedicated and independent devices external to the switch equipment of the commu- 
nication networks. Typical examples are protocol analyzers, cable "sniffers", and similar devices that are used to collect 
data from communication connections. The collected data is then directly analyzed and/or registered on a media like 
a tape or disc being directly connected to the monitoring device. 

[0004] In particular for a lawful interception the storage media is sent to the law enforcement agency that requested 
25 the legal interception. Therefore, the procedure to set up such a lawful interception is lengthy and many people are 
involved. Confidentiality of the collected data is hard to achieve and the authenticity of information is also difficult to 
prove at court. 

[0005] One approach to the monitoring of communication connections for shared media networks is described in 
WO 98/33303. It is proposed to have a copy of all traffic in a selected branch of the communication network forwarded 

30 to a special test branch. This copy is achieved at the link layer according to the ISO/OSI level 2 so that some special 
purpose equipment is necessary to monitor a communication connection at the physical layer according to the ISO/ 
OSI level 1 . Further, the approach described in WO 98/33303 is restricted to a specific case where all the data traffic 
from a specific local area network is monitored and where it is not possible to isolate data traffic between network layer 
endpoints. Still further, every bridge connecting two or more networks and operating at the data link layer of the OSI/ 

35 ISO reference model or a switch connecting two or more networks and operating at the network layer of the OSI/ISO 
reference model in the path between the monitored network and the monitoring equipment must be adapted to have 
monitoring capability. Yet another disadvantage is that there is no way to take the quality of service QoS into account. 
E.g., if the monitored communication connection uses a best effort QoS class, there may occur the situation that some 
data reaches its destination endpoint but not the monitoring equipment. 

40 

SUMMARY OF INVENTION 

[0006] In view of the above, the object of the present invention is to provide a general and effective monitoring 
equipment for an ATM communication network. 

45 [0007] According to the present invention, this object is achieved through a device for monitoring at least one com- 
munication connection in an ATM packet switched communication network, comprising and interception unit adapted 
to store an identification of the at least one communication connection to be monitored; a selection unit adapted to 
achieve a coupling to the communication connection to be monitored according to the information stored in the inter- 
ception table, and to select at least one cell from this communication connection; a copying unit adapted to copy the 

50 at least one cell selected by the selecting unit to a monitoring connection; wherein the device for monitoring a com- 
munication connection is integrated into a switching equipment of the packet switched communication network. 
[0008] Therefore, according to the present invention, the interception unit allows to isolate data traffic on a commu- 
nication connection so that only a part of the data traffic on the communication connection to be monitored may be 
forwarded to the monitoring device. Typically, this will be cells relevant to endpoints, while data related to the operation 

55 and management of the ATM communication network will not be monitored. 

[0009] Further, the operation of the selection unit and copying unit as outlined above allows for a concurrent real 
time processing of cells forwarded to an endpoint and at the same time to the monitoring device. A consequence is 
the preservation of the characteristics of the data flow both to the endpoint and also to the monitoring device through 



2 



EP 1 265 454 A1 



transparent copying. 

[001 0] Yet another decisive advantage of the inventive monitoring device and method is the integration into switching 
equipment of the ATM packet switched communication network. 

[0011] Therefore, the same administrative and technical procedures used in the ATM communication network may 
5 also be used to monitor a communication process. This allows for a lawful intercept at the same level of confidentiality 
for the monitored information that is provided by the ATM communication network for the original communication and 
therefore to fulfill monitoring requirements. 

[0012] Also, the monitoring device according to the present invention is independent on the content of the cells on 
the communication connection to be monitored and therefore does not require an adaptation for every kind of network 
10 termination and type of traffic. In other words, the monitoring device may be used for any kind of different services, e. 
g., ATM data, IP over ATM, and/or telephony over ATM. 

[0013] According to a preferred embodiment of the present invention, the monitoring device further comprises a 
terminating unit adapted to terminate monitoring connections at the switching equipment. 

[0014] Therefore, as the monitoring connection is appropriately terminated at the monitoring device, it will under no 
15 circumstances be visible to the user that a monitoring occurs. The reason for this is that due to the provision of the 
terminating unit, no ATM cells will travel in the backward direction from the monitoring device to reach the monitored 
user. Therefore, the fact that a connection is monitored will not be visible to any functional block except the monitoring 
device itself and the functional block that activated the monitoring process. Due to the provision of the terminating unit 
it is also impossible to use operation and maintenance functions to query the state of the monitoring device. 
20 [0015] According to yet another preferred embodiment of the present invention, there is provided an activation unit 
initiating the activation of the monitoring mechanism according to the present invention. 

[0016] The only data that needs to be provided by the activation unit are two connection identifiers, i.e. information 
identifying the monitored and the monitoring connection. According to the present invention, connection identifiers 
specify the physical port, the virtual circuit identifier and the virtual path identifier according to the ATM standard both 
25 for the monitored flow and for the monitoring flow. 

[0017] According to yet another preferred embodiment of the present invention, the selection unit is adapted to proc- 
ess cell header information of cells, e.g., on the communication connection to be monitored. 

[0018] Therefore, according to the present invention, the selection unit and subsequent parts of the monitoring device, 
e.g., the copying unit, are embodied to differentiate between specific parts of selected ATM cells, e.g., payload and 

30 header data. While payload data will be copied in a transparent manner, header data may be copied either unchanged 
in a transparent manner or after modification thereof. In particular, if ATM cells are discarded downstream a switch, 
the destination endpoint may usually request a retransmission of the discarded ATM cells. However, this is not possible 
for the monitoring connection as there is no means to request a retransmission for missing ATM cells which would 
reveal the monitoring process to the end user. 

35 [0019] In other words, according to the present invention it is proposed to eventually use different QoS parameters 
for the monitored connection and the monitoring connection. One example to achieve this feature in the framework of 
the ATM standard is that the monitoring device ensures that ATM cells of the monitoring connections always have the 
so-called cell loss priority CLP bit reset to zero. 

[0020] Yet another important advantage of the differentiation between payload and header data according to the 
40 present invention is that it possible to distinguish between data traffic to be forwarded to the end user and so-called 
operation and management or maintenance data which also should not be copied during the monitoring process to 
avoid revealing of the monitoring not only to an end user, but also to the network operating and maintenance system 
parts. 

[0021] According to yet another preferred embodiment of the present invention, the selection unit in the monitoring 
45 device is adapted to process cell header information at least comprising a virtual path identifier VPI and to select the 
related ATM communication connection to be monitored accordingly. 

[0022] Therefore, according to this preferred embodiment, all virtual circuits covered by the specified virtual path 
identifier may be monitored through transparent copying of the related cell payload. 

[0023] According to yet another preferred embodiment of the inventive monitoring device, there is further provided 
50 a buffer unit adapted to store cells selected from a communication connection to be monitored for subsequent copying 
to the monitoring connection. 

[0024] Therefore, according to this preferred embodiment of the present invention, cells are still processed in real 
time. Nevertheless, the provision of the buffering unit allows to delay the analysis of the cells or in other words, to 
specify a low loss but high delay profileforthe monitoring connection. This allows to achieve a better use of the network 
55 and at the same time not risking a loss of information. The reason for the better network utilization is that in modern 
multi-service networks a certain quantity of capacity is reserved for each customer/service. However, the customer/ 
service may try to use more bandwidth, as soon as it is available. In other cases the network is explicitly over-committed 
on the assumption that not all of the customers will use the maximum available bandwidth at the same time. Further, 



3 



EP 1 265 454 A1 



it is also possible to give different priorities to different customers/types of services. All of this means that the traffic 
flow is not constant, but varies around an average value. When the monitoring connection uses a low loss, high delay 
setting the ATM switch can queue the monitoring cells in a buffer and transmit them a little bit later. In this way the 
variations in bandwidth utilization are reduced and the network throughput will be nearer the theoretical maximum, 
5 whereby the better network utilization may be achieved and short-term network load fluctuations are smoothed out. 
Preferably, when congestion lasts more than the buffer capacity may handle, the ATM switch will start throwing away 
lower priority ATM cells. 

[0025] While the basic principles of the present invention as outlined above are uni-directional, the present invention 
also applies to a bi-directional monitoring. In this case the related mechanisms are applied in both directions separately. 
10 [0026] According to another preferred embodiment of the present invention there is provided a computer program 
product directly loadable into internal memory of a packet switched communication network switch and comprising 
software code portions for performing the steps according to the inventive method when the product is run on a proc- 
essor of the switch. 

[0027] Therefore, the present invention is also provided to achieve an implementation of the inventive method steps 
15 on computer or processor systems. In conclusion, such implementation leads to the provision of computer program 
products for use with a computer system or more specifically a processor comprised in, e.g., a switch in an ATM 
communication network. 

[0028] This programs defining the functions of the present invention can be delivered to a computer/processor in 
many forms, including, but not limited to information permanently stored on non-writable storage media, e.g., read only 
20 memory devices such as ROM or CD ROM discs readable by processors or computer I/O attachments; information 
stored on writable storage media, i.e. floppy discs and harddrives; or information convey to a computer/processor 
through communication media such as network and/or telephone networks and/or Internet via modems or other inter- 
face devices. It should be understood that such media, when carrying processor readable instructions implementing 
the inventive concept represent alternate embodiments of the present invention. 

25 

DESCRIPTION OF DRAWING 



[0029] The best mode of carrying out the present invention as well as preferred embodiments thereof will be described 
in the following with reference to the drawing in which 

Fig. 1 shows the basic principle underlying the best mode of carrying out the present invention and related preferred 
embodiments thereof; 



Fig. 2 shows a schematic diagram illustrating the use of the monitoring device according to the present invention 
35 together with an ATM core switch matrix; 

Fig. 3 shows a schematic diagram illustrating the interception unit to be used in the monitoring device according to 
the present invention; 

40 Fig. 4 shows a flow chart illustrating the monitoring method according to the present invention; 

Fig. 5 shows a schematic diagram illustrating the operation of a digital cross connect system; 

Fig. 6 shows a schematic diagram illustrating the use of the monitoring device according to the present invention 
45 at the input stage of the digital cross connect system shown in Fig. 6; 

Fig. 7 shows a schematic diagram illustrating the use of the monitoring device according to the present invention 
at the output stage of the digital cross connect system shown in Fig. 6; and 

50 Fig. 8 shows a schematic diagram illustrating the use of the monitoring device according to the present invention, 
both at the input stage and the output stage of the digital cross connect system shown in Fig. 6. 



DESCRIPTION OF PREFERRED EMBODIMENTS 



55 [0030] In the following, the best mode of carrying outthe present invention as well as preferred embodiments thereof, 
further objects and further advantages will be explained with respect to the drawings. Insofar as different features of 
the present invention are explained with respect to certain aspects thereof, it is to be understood that these features 
are combinable with each other to achieve various other modifications and variations of the present invention. 



4 



EP 1 265 454 A1 



[0031] Fig. 1 shows the basic principle underlying the best mode of carrying out the present invention and the related 
preferred embodiments. 

[0032] As shown in Fig. 1 , according to the present invention, the monitoring mechanism for the monitoring of a flow 
of ATM cells, also referred to as ATM data packets in the following, is integrated into an ATM switch. As will be outlined 
5 in more detail in the following, the monitoring device may be associated to the core switch matrix of the ATM switch 
1 0 or also to a digital cross connect used in the ATM switch 10. 

[0033] The integration of the monitoring device into the ATM switch 10 itself allows to use the same administrative 
and technical procedures used in the ATM communication network also for the monitoring of a communication con- 
nection, e.g., during transfer of a call or the exchange of data. As outlined above, this allows for a same level of 
10 confidentiality of the monitored information as provided by the network for the monitored communication process. Also, 
the integration of the monitoring device into the ATM switch 10 allows to isolate specific data traffic handled by the 
ATM switch and to consider quality of service QoS aspects during monitoring, since related information is well available 
in the ATM switch 1 0. 

[0034] Fig. 2 shows a schematic diagram illustrating the use of the monitoring device according to the present in- 
15 vention together with an ATM core switch matrix. 

[0035] As shown in Fig. 2, the ATM switch 10 divides into the core switch matrix 12 and the monitoring device 14. 

The core switch matrix 12 is adapted to map a plurality of virtual paths VP 1 VP n at the input side to a plurality of 

virtual paths VP n+1 , VP N atthe output side. Further each virtual path may divide into a plurality of virtual circuits VCI. 

[0036] In particular, the operation of the core switch matrix 1 2 insofar as the present invention is concerned may be 
20 summarized in view of the following table: 



ATM field description 


ATM switch 






Incoming cells 


Outgoing cells 


VPI 


Virtual path ID 


Used to switch cell 


May be replaced with new VPI, VCI 
value 


VCI 


Virtual circuit ID 


PTI 


Payload type indicator 


See following table 


Transparent copy 


CLP 


Cell loss priority 


Discard the cell first, if set 


Transparent copy 


HEC 


Header error control 


Discard the cell if there exists an error 
and correction is not possible 


Calculated according to ATM 
specifications 




Payload 


Ignored 


Transparent copy 



[0037] As outlined above, each ATM cell comprises a header part and a payload part. The header part divides into 
a virtual path ID VPI, a virtual circuit ID VCI, a payload type indicator PTI, a cell loss priority CLP and a header error 
control. 

[0038] Operative!^ the ATM core switch matrix uses the virtual path ID and the virtual circuit ID to switch incoming 
ATM cells to outgoing virtual paths. 

[0039] Further, the cell loss priority CLP bit marks cells that may be discarded in case there is congestion in the ATM 
network. Atthe network access point NAP it is checked that the user complies with his own contract and does not send 
more cells he is allowed to. However, the network access point NAP can choose to allow the user to send more cells 
as long as there is free capacity in the ATM network. As this may not be known in advance, the network access point 
NAP marks a certain number of cells putting the CLP bit on. In case any ATM switch experiences a congestion, the 
first step is to discard the cells having the CLP bit set. Further, the CLP bit may also be set by the user to explicitly 
point out what are the best candidates to be discarded. Discarded ATM cells may then be retransmitted for subsequent 
forwarding to the end user. 

[0040] Further, the header error control HEC will be used for error correction according to ATM specifications. 
[0041] Of particular interest for the present invention is the payload type indicator PTI that may be defined as follows: 



PTI bits 


Type of cell 


Cell destination 


Bit2 


Bit1 


BitO 






0 


0 


0 


User data, SDU=0, no congestion 


Outgoing connection 


0 


0 


1 


User data, SDU=1 , no congestion 


Outgoing connection 


0 


1 


0 


User data, SDU=0, congestion 


Outgoing connection 



5 



EP 1 265 454 A1 



(continued) 



PTI bits 


Type of cell 


Cell destination 


Bit2 


Bit1 


BitO 






0 


1 


1 


User data, SDU=1 , congestion 


Outgoing connection 


1 


0 


0 


Segment O&M cell 


Switch O&M function (if end of segment) or outgoing 
connection 


1 


0 


1 


End-to-end O&M cell 


Switch O&M function (if end system or administrative 
boundary) or outgoing connection 


1 


1 


0 


Reserved for future functions 


Should never occur 


1 


1 


1 







15 

[0042] In the above table, SDU stands for service data unit and is related to a bit of information that is transparently 
transported end-to-end by the ATM communication network. At the end system, the service data unit SDU is passed 
onto a higher layer of the protocol stack. Usually, the segmentation and reassembly sub-layer SAR of the ATM adap- 
tation layer AAL will use the SDU information bit to mark the last ATM cell of a SAR protocol data unit PDU. Because 

20 the SDU information bit is an essence end system information, it must be copied into the monitored cell. 

[0043] Further, different cells may either be related to user data, to operation and maintenance cells being related 
to a segment of an ATM connection, an operation and maintenance ATM cell being related to an end-to-end connection 
or be of the type that is reserved for future applications which therefore never occur. ATM cells of the user data type 
may be further classified in those with no congestion and those with congestion. This classification allows for a feedback 

25 mechanism, where the overloaded party sets the congestion indicating the cell it is transmitting. When cells with the 
congestion indication will be received at the remote party, the remote party will know of the congestion status and will 
slow down its own transmission rate. 

[0044] Further, the segment related operation and maintenance cells are eitherforwarded to the operation and main- 
tenance function of the ATM switch or to an outgoing connection. End-to-end operation and maintenance cells are 
30 forwarded to the operation and maintenance function of the ATM switch, if the ATM switch is the end system or con- 
stitutes an administrative boundary or again to an outgoing connection. 

[0045] As shown in Fig. 2, the monitoring device according to the present invention cooperating with the core switch 
matrix described so far divides into an interception table 1 6 being triggered by an activation unit 1 8, further a selection 
unit 20, a copying unit 22 and a terminating unit 24. 

35 [0046] Operatively. the interception table stores an identification of the at least one communication connection to be 
connected. As shown in Fig. 3, the interception will store a relation between monitored ATM connections and monitoring 
ATM connections using connection identifiers comprising a physical port of the ATM switch 1 0 (not shown), the virtual 
path identifier VPI and the virtual circuit identifier VCI . This data necessary to set up the inventive monitoring mechanism 
will be provided by the activation unit 18. 

40 [0047] Further, the selection unit 20 shown in Fig. 2 is adapted to achieve a coupling to the communication connection 
to be monitored according to the information stored in the interception table 1 6 and to select at least one cell from this 
communication connection in compliance with the type of the cell communicated via the communication connection to 
be monitored. 

[0048] Therefore, the operation of the selection unit 20 allows to identify communication connections to be monitored 
45 usingthe virtual path ID andthe virtual circuit ID and furtherto select cells forwarded overthe communication connection 
according to the payload type indicator as summarized in the following table: 



ATM field Description 


Monitoring device 


Incoming cells on monitored 
connection 


Outgoing cells on monitoring 
connection 


VPI 


Virtual path ID 


Monitored connection? 


May be replaced with new VPI, VCI 
value 


VCI 


Virtual circuit ID 


PTI 


Payload type indicator 


Will cell be monitored? (see following table) 


CLP 


Cell loss priority 


Ignored 


Always zero 



6 



EP 1 265 454 A1 



(continued) 



ATM field Description 


Monitoring device 


Incoming cells on monitored 
connection 


Outgoing cells on monitoring 
connection 


HEC 


Header error control 


Either ignored or processed normally 


Calculated according to ATM 
specifications 




Payload 


Ignored 


Transparent copy 



[0049] As can also be seen from the above table, subsequent to the selection of a cell it will then be processed in 
the copying unit 22. 

[0050] In the copying unit 22 the cell loss priority CLP defining the behaviour in case of disregarding of a cell will be 
reset to zero, so that in case a selected cell travels through a congested ATM switch, it will be discarded first. The 
monitoring device 1 4 also comprises a terminating unit 24 adapted to terminate monitoring connections at the switching 
equipment so that data will never be transferred via the monitoring connection and the ATM switch into the ATM com- 
munication network. Further, in the copying unit 22 the header error control is either ignored or processed normally 
and calculated according to ATM specifications. Still further, the copying unit 22 is adapted to provide a transparent 
copy of the payload of a selected ATM cell to the monitoring connection. 

[0051] As is also shown in Fig. 2, the copying unit 22 may be extended by a buffering mechanism. Fig. 2 shows a 
buffer unit 26 within the copying unit 22. However, it should be noted that the specific way to implement such a buffer 
is not of particular relevance to the present invention as long as a buffering of cells going out from the copying unit 22 
to the monitoring connection is achieved, e.g., using available memory capacity in the ATM switch 10. In case the 
buffer mechanism is initiated, the monitoring may be achieved with a low loss but high delay profile on the monitoring 
connection so that the operator obtains a better use of the network and at the same time does not risk a loss of 
information. 

[0052] A more detailed explanation how a differentiation between those cells that may be monitored and those that 
may not be monitored using the packet type indication data comprised in the cell is summarized in the following table: 



PTI bits before monitoring 


Monitorable ATM cell? 


PTI bits after monitoring 


Bit2 


Bit1 


BitO 


Bit2 


Bit1 


BitO 


0 


0 


0 


Yes 


0 


0 


0 


0 


0 


1 


0 


0 


1 


0 


1 


0 


0 


0 


0 


0 


1 


1 


0 


0 


1 


1 


0 


0 


No 




1 


0 


1 


End-to-end O&M cells 


1 


0 


1 


1 


1 


0 


No, reserved values that should never occur 




1 


1 


1 





45 

[0053] As can be seen from the above table, cells having a packet type indicator bit pattern according to the first four 
rows, may be forwarded to the monitoring connection by the copying unit 22. As can be seen from the shaded bits in 
lines 3 and 4, those bits being related to discarding of a cell will always be set to zero to avoid a revealing of the 
monitoring process. 

50 [0054] Further, cells having a PTI bit pattern of (1 , 0, 0) may not be copied. The reason for this is that cells having 
this PTI bit pattern are segment management cells being only meaningful within the network. End systems cannot 
exchange segment management O&M cells among themselves. Besides, as copied, they would confuse the segment 
O&M function at the next ATM switch. 

[0055] Still further, cells having a packet type indication of (1 , 0, 1) are related to end-to-end operating and mainte- 
55 nance cells. In some communication networks they may be used to transport end user information and therefore may 
also be monitored. Otherwise, the communication network will use them. In the latter case they should not be monitored 
because they could cause interference with the operating and maintenance cells introduced by the management of 
the monitoring connection. 



7 



EP 1 265 454 A1 



[0056] The further packet type indication PTI bit patterns according to the last two rows should never occur as they 
are reserved for future applications. 

[0057] In the following, an operation of the monitoring device will be summarized in view of the flow chart shown in 
Fig. 4. 

5 [0058] As shown in Fig. 4, initially the interception table shown in Fig. 3 is set up for subsequent evaluation whether 
a communication connection is to be monitored in step S2. If this is not the case, the procedure may branch back, e. 
g., to update the interception table for further communication connections to be monitored and subsequent repetition 
of the interrogation step S2. 

[0059] As shown in Fig. 4, in the affirmative case of step S2, cells are selected from the connection to be monitored 
10 according to the cell type, as explained above, in step S3. Then, a copy of the selected cells is forwarded to the 

monitoring connection in step S4 before the procedure goes back to step S2 to detect further monitoring requests. 

Here, either the monitoring of an already selected communication connection may be continued through selection of 

further cells or the monitoring could be switched to a different communication connection to be monitored. Further. 

while Fig. 4 shows a feedback from step S4 to step S2, alternatively the procedure may as well branch to step S1 
15 according to the present invention. 

[0060] In the following the application of the present invention to a digital cross connect system will be explained 

with respect to Figs. 5 to 8. Heretofore, first a short review of the function of a digital cross connect system will be given 

first with respect to Fig. 5. 

[0061] As shown in Fig. 5, a digital cross connect system manipulates digital input signals, but does not handle 

20 signaling messages or perform call processing. In Fig. 5, the letters A, B, C, R denote specific communication 
channels, and Z designates idle time slots. One function of the system shown in Fig. 5 is called cross connection and 
relates to the redirection of channels from one facility interface to another. A further function is related to the rearrange- 
ment of time slots (also referred to as grooming), and the placement of multiple lower speed signals onto a higher 
speed trunk is referred to as multiplexing. The removal of idle time slots is referred to as concentration and allows to 

25 improve the use of available communication capacity. 

[0062] Contrary to the arrangement in Fig. 2, where the inventive monitoring device is operated in combination with 
a core switching matrix, the monitoring device may as well be operated in corporation with the digital cross connect 
system as shown in Figs. 6 to 8. Typically, the monitoring device may be assigned to the input stage of the digital cross 
connect system as shown in Fig. 6, at the output stage of the digital cross connect system as shown in Fig. 7, or both 

30 at the input stage and the output stage of the digital cross connect system as shown in Fig. 8. Heretofore, the selection 
unit 20 is connected to the different input/output lines of the digital cross connect system to detect communication 
connections to be monitored. Further, after triggering through the selection unit in case of identification of a communi- 
cation connection to be monitored, the copying unit 22 will copy related cells from the input/output lines of the digital 
cross connect system. As shown in Figs. 6 to 8, also in this preferred embodiment of the present invention, the buffering 

35 mechanism outlined above with respect to Fig. 2 is applicable. The same applies to the termination of the monitoring 
connection at the terminating unit 24. 

[0063] While in the above, the present invention has been described with reference to drawings and figures of the 
best mode and preferred embodiments of the invention, it should be noted that clearly the present invention may be 
implemented using variations and modifications thereof which will apparent and can be readily made by those skilled 
40 in the art without departing from the scope and spirit of the present invention. Typically, the functionalities described 
above may be realized in software, in hardware, or a combination thereof. 

[0064] Accordingly, it is not intended that the scope of claims appended hereto is limited to the description as set 
forth herein, but rather that the claims should be construed so as to encompass all features of the present invention 
as described above, including all features that would be treated as equivalent thereof by those skilled in the art to which 
45 the present invention pertains. 



Claims 

50 1. Device for monitoring at least one communication connection in an ATM packet switched communication network, 
comprising: 

an interception unit (1 6) adapted to store an identification of the at least one communication connection to be 
monitored; 

55 

a selection unit (20) adapted to achieve a coupling to the communication connection to be monitored according 
to the information stored in the interception table, and to select at least one cell from this communication 
connection; 



8 



EP 1 265 454 A1 



a copying unit (22) adapted to copy the at least one cell selected by the selecting unit (20) to a monitoring 
connection; wherein 

the device for monitoring a communication connection is integrated into a switching equipment (12; DCS) of 
5 the packet switched communication network. 

2. Device according to claim 1 , characterized in that it is associated to a core switch matrix (12) provided in the 
switching equipment. 

10 3. Device according to claim 1 . characterized in thatii is associated to a digital cross-connect system (DCS) provided 
in the switching equipment. 

4. Device according to one of the claims 1 to 3, characterized in that it further comprises a terminating unit (24) 
adapted to terminate monitoring connections at the switching equipment (10). 

15 

5. Device according to one of the claims 1 to 4. characterized in that it further comprises an activation unit (18) 
adapted to initiate the monitoring of communication connections. 

6. Device according to one of the claims 1 to 5, characterized in thatlhe selection unit (20) is adapted to process 
20 cell header information of cells. 

7. Device according to claim 6, characterized in thatthe selection unit (20) is adapted 

to process cell header information at least comprising a virtual circuit identifier (VCI) and 
to select related ATM communication connections to be monitored. 

25 

8. Device according to claim 7, characterized in thatthe selection unit (20) is further adapted 
to process cell header information comprising a virtual path identifier (VPI) and 

to select related ATM communication connections to be monitored. 

30 9. Device according to claim 7 or 8. characterized in that the selection unit (20) is further adapted to select cells in 
communication connections to be monitored according to a cell type indication (PTI). 

10. Device according to one of the claims 1 to 9, characterized in thatXhe copying unit (22) is adapted to achieve 
transparent copying of cell payload. 

35 

11. Device according to claim 10, characterized in thatXhe copying unit (22) is further adapted to copy communication 
control related data of selected cells transparently or after modification thereof. 

12. Device according to one of the claims 1 to 11 , characterized in that it further comprises a buffer unit (26) adapted 
40 to store selected cells before copying to the monitoring connection. 

13. Method of monitoring at least one communication connection in an ATM packet switched communication network, 
comprising the steps: 

45 storing an identification of the at least one communication connection to be monitored in an interception table 

(16); 

achieving a coupling to the communication connection to be monitored for subsequent monitoring according 
to the information stored in the interception table (16); 

50 

selecting at least one cell from the communication connection to be monitored according to the cell type; 

copying the selected at least one cell to a monitoring connection; wherein 

55 the method of monitoring is executed in a switching equipment (1 0) of the ATM packet switched communication 

network. 

14. Method according to claim 13, characterized in that it further comprises a step of terminating monitoring connec- 



9 



EP 1 265 454 A1 



tions at the switching equipment (1 0). 

15. Method according to claim 13 or 14, characterized in that the at least one communication connection to be 
monitored is selected through processing of cell header information. 

16. Method according to claim 15, characterized in that \X comprises the steps 

processing cell related header information at least comprising a virtual circuit identifier (VCI) and 
selecting related ATM communication connections to be monitored. 

17. Method according to claim 16, characterized in thatW further comprises the steps 
processing cell related header information comprising a virtual path identifier (VPI) and 
to select related ATM communication connections to be monitored. 

18. Method according to claim 1 6 or 1 7, characterized in that it further comprises the step of selecting cells in com- 
munication connections to be monitored according to a cell type indication (PTI). 

19. Method according to one of the claims 13 to 18, characterized in that it further comprises the step for achieving 
a transparent copy of cell payload. 

20. Method according to one of the claims 13 to 19, characterized in that it further comprises a step to copy com- 
munication control related data of selected cells transparently or after modification thereof. 

21. Method according to one of the claims 13 to 20, characterized in that it further com prises a step to buffer selected 
cells before copying these cells to the monitoring connection. 

22. Computer program product directly loadable into the internal memory of a packet switched communication network 
switch , comprising software code portions for performing the steps of one of the claims 1 3 to 21 , when the product 
is run on a processor of switch. 



10 



EP 1 265 454 A1 



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EP 1 265 454 A1 




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EP 1 265 454 A1 



Internal interception table 



.16 



Monitored 
connection 
identifier 


Monitoring 
connection 
identifier 


Port 


VPI 


VCI 


Port 


VPI 


VCI 


* • • 


• • » 


• # ♦ 


• • * 


• « • 


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1 


32 


32 


3 


20 


21 


• • • 


• • « 


• • • 


• • • 


• • • 


» * • 



FIG. 3 



13 



EP 1 265 454 A1 




SI 



Setup / update 
interception table 




Select cell(s) from 
connection to be monitored 
according to cell type 



S4 

Copy selected cell(s) 
to monitoring connection 



FIG. 4 



14 



EP 1 265 454 A1 



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EP 1 265 454 A1 



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EP 1 265 454 A1 



European Patent 
Office 



EUROPEAN SEARCH REPORT 



Application Number 

EP 01 11 2986 



DOCUMENTS CONSIDERED TO BE RELEVANT 



Category 



OtaJfcm of doeumarct wilfri indication. where appropriate, 
of relevant passages 



Relevant 
to claim 



CLASSIFICATION OF THE 
APPLICATION <faLCI.7) 



US 5 887 000 A (KUDO HIRQYUKI ET At) 
23 March 1999 (1999-03-23) 



* figure 13 * 

* column 7, line 14 - column 9, line 7 * 

US 5 742 765 A (6HUFRAH SALMAN ET At) 
21 April 1998 (1998-04-21) 

* column 6, line 34 - line 50 * 

EP 0 763 941 A (ALCATEL NY) 

19 March 1997 (1997-03-19) 

* column 5, line 35 - column 6 S line 11 * 

* column 7, line 1 - line 12 + 



The present search report has been drawn up for all claims 



1-8,10, 
11, 

13-17, 
19,20,22 
9,12,18 
21 



9,18 



12,21 



H04Q11/04 



TECHNICAL FIELDS 
SEARCHED (lnr.CI.7) 



H04Q 



PBaoe- at Beanch 

THE HAGUE 



Date of completion of the searati 

12 November 2001 



ExamJner 

Seal fa, A 



CATEGORY OF CITEt) DOCUMENTS 

X :: partlou any relevant if taken atone 

Y : partial 'arty relevant If combined wttn another 

document erf the same category 
A : technological background 
O : non-written clsc&osure 
P : intermediate document 



T : theory or principle underlying the invention 
E : earlier patent document, but published on, or 

i»tler ma fling data 
D : document cited ir the .application 
L : document ched for other reasons 

& : member oftne same patent' family, corresponding 
document 



19 



EP 1 265 454 A1 



ANNEX TO THE EUROPEAN SEARCH REPORT 
ON EUROPEAN PATENT APPLICATION NO. 



EP 01 11 2986 



This annex lists the patent family members relating to the patent documents cited In the above-mentioned European search report. 
The members are as contained in the European Patent Office EDP ftte on 

The European Patent Office is In no way liable for these particulars which are merely given lor the purpose of information. 

12-11-2001 



Patent document 
cited in search repo rt 



Publication 
date 



Patent family 
members) 



Publication 
date 



US 5887000 



23-03-1999 JP 



8037527 A 



US 5742765 



21-04-1998 NONE 



06-02-1995 



EP 0763941 


A 


19-03-1997 US 


5640512 A 


17-06-1997 






AU 


715139 B2 


20-01-2000 






AU 


6442496 A 


20-03-1997 






CA 


2185365 Al 


15-03-1997 






EP 


0763941 A2 


19-03-1997 






HZ 


299348 A 


24-04-1997 



uj For more detail about this annex sgq Officii Journal of the European Patent Office, No 12/8? 



20