Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04J—MULTIPLEX COMMUNICATION
  • H04J3/00—Time-division multiplex systems
  • H04J3/02—Details
  • H04J3/06—Synchronising arrangements
  • H04J3/0635—Clock or time synchronisation in a network
  • H04J3/0638—Clock or time synchronisation among nodes; Internode synchronisation
  • H04J3/0652—Synchronisation among time division multiple access [TDMA] nodes, e.g. time triggered protocol [TTP]
  • H04J3/0655—Synchronisation among time division multiple access [TDMA] nodes, e.g. time triggered protocol [TTP] using timestamps
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L43/00—Arrangements for monitoring or testing data switching networks
  • H04L43/08—Monitoring or testing based on specific metrics, e.g. QoS, energy consumption or environmental parameters
  • H04L43/0852—Delays
  • H04L43/0858—One way delays
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L43/00—Arrangements for monitoring or testing data switching networks
  • H04L43/10—Active monitoring, e.g. heartbeat, ping or trace-route

Definitions

• the invention relates to a method for operating a data network, in which network devices are present in the data network, which exchange data packets via data connections, wherein a mechanism is operated to determine at least an end-to-end latency between network devices, according to the features of the preamble of claim 1.
• Mechanisms exist in many networks, particularly data networks, to randomly determine the end-to-end latency between devices (also referred to as network devices) and / or the accessibility of devices on the network.
• the invention has for its object to improve a method for operating a data network with respect to the determination of the latencies and to avoid the disadvantages described above.
• a trigger packet is sent out as a mechanism by a network device to at least one further network device and it is determined by means of a time stamp when the trigger packet has reached this at least one further network device.
• the trigger packet is transmitted by a network device in addition to the data packets that are exchanged in the data network via the wired and / or wireless data connections and received by at least one further, for example several, preferably all network devices. If the trigger packet is received by at least one network device, a timestamp is taken with which it is determined when the trigger packet has reached the respective network device. The timestamps can be used to determine the time course that the trigger package required from network device to network device.
• the end-to-end latency between network devices can be determined.
• no additional trigger packet is sent, but a data packet itself is used as a trigger packet. If such a data packet is received by at least one network device, a time stamp is taken with which it is determined when the data packet has reached the respective network device. The timestamps can be used to determine the time course that the data packet needed from network device to network device. From this time course can be using the data packets, which requires no additional trigger packets compared to the first embodiment because the data packets themselves are used as trigger packets that determine end-to-end latency between network devices.
• a time stamp is also detected (determined) at the time of dispatch of a parcel. This timestamp can then be used together with the timestamp, which was determined at the time of receipt of the packet in the same network device, to determine the duration of the packet in this network device. Since both time stamps in a network device relate to the local clock of the same network device, the dwell time can be precisely determined. This information can be very valuable in determining causes in the case of delayed delivery of a parcel.
• the time stamp determined in the at least one further device is inserted as a partial data packet into the trigger packet and forwarded further.
• each network device receiving the trigger packet has the time stamp or times available in the at least one network device from which it was sent.
• the network device receiving this trigger packet detects receipt, it determines that time and sets a timestamp, which it inserts as a partial data packet into the received trigger packet and retransmits the trigger packet supplemented with its own timestamp.
• a timestamp can also be determined and inserted into the Tnggervers in the transmission. This forwarding can be done to a single network device, to a group of network devices or to all network devices of the respective data network.
• time stamps as partial data packets in the trigger packet
• the time stamp determined in the at least one further device is stored on this network device and provided for further network devices and / or a network management system becomes.
• time stamps of the respective network device in the trigger packet of the time stamp found in the respective network device is also or only stored on the network device, so that it is locally available and queried can. This query can be carried out by a corresponding request from another network device and / or a network management station at the network device on which the established time stamp has been collected and stored.
• the trigger packet has a certain length and this length is increased by inserting Zeitstempei.
• a place for the insertion of timestamps will exist in the trigger packet, so that the insertion of timestamps does not change the length of the trigger packet.
• the time stamp which has been detected on the respective network device is assigned further data of that network device which determines the time stamp.
• This can meta information such.
• the time profile of the data exchange of the trigger packet over the data connections involved is determined from the time stamp of a respective network device.
• the use of the trigger packet independently of the rest of the data exchange between the network devices via the data connections in the data network has the advantage that the data exchange is not delayed by the determination and transfer of time stamps.
• the trigger packets are sent, received and forwarded independently of the other data packets exchanged between the network devices.
• the timestamps detected in the participating network devices are considered to determine the duration for transmission of the trigger packet from the sending network device to the last network device receiving the trigger packet can be.
• the inventive method thus realizes an end-to-end latency determination. Alternatively or additionally, it also offers a significantly higher granularity or temporal resolution. Because with the method according to the invention, the latencies of arbitrary sub-paths down to individual path segments of the transmission media of the network can be determined. This is possible because the receive and transmit timestems of the individual network devices are collected and not accumulated in one value.
• the term "granularity" is understood to mean a precise determination of the transmission time of the trigger packets, which is required for the transmission of the trigger packets from a starting point, which can be arbitrarily selected, to an end point, which can also be arbitrarily selected specifically, when a trigger packet arrived at a network device (which is timestamped) and when it was retransmitted by that network device (which is also timestamped)
• the time between the arrival of the trigger packet on the network device and the transmission of this trigger packet depends on the processing time of at least one data packet which is also received, processed (or only forwarded) and transmitted by this network device Assemble the times of arrival of both the trigger packet and the data packet and regardless of the timing of sending both the trigger packet and the data packet together.
• the timestamp for the arrival of the trigger packet and the timestamp for the transmission of the trigger packet is a measure of how long the processing (or even the forwarding) of at least one data packet in the network device has required.
• the transmission times of a respective trigger packet can be determined between the transmission from one network device to the arrival on another network device that receives the trigger packet.
• the transmission times of the trigger packets between the network devices which are for example dependent on the type and length of a cable or which are dependent on a wireless transmission, by the detection of the timing of the trigger packets between the transmission from a network device to the reception on a subsequent network device precisely determinable. This process can be repeated as often as desired over the entire transmission path or on segments thereof, so that determination of an end-to-end latency on a predefinable partial path or the entire network path is possible at any time.
• the method according to the invention can thus be carried out alternatively or additionally in four different ways.
• trigger packets are sent out on the network and received by network devices.
• a time stamp is taken which is inserted into the trigger packet on the network device on which the trigger packet is currently located and is sent on. If the trigger packet reaches another network device, the same procedure is used there, so that further time stamps are gradually inserted into the trigger packet.
• the trigger packets exist in addition to the data packets.
• trigger packets are sent out on the network and received by network devices.
• a time stamp is taken which is stored on the network device on which the trigger packet is currently located. The same procedure is used if the trigger packet is sent out again and received by another network device.
• the timestamps are not included in the trigger packets, but they are stored on the respective network device and can be retrieved from there. This is done for example by a network management system.
• the trigger packets exist in addition to the data packets. 3. Instead of additional trigger packets, the data packets are used for the transmission of the taken time stamp.
• the data packets carry useful content in this case and additionally contain information about their reception and / or transmission on a network device.
• a time stamp is taken, which is inserted in the data packet on the network device on which the data packet is currently located, and sent on. If the data packet reaches another network device, the same procedure is used there, so that further time stamps are gradually inserted into the data packet. In this case, there are no trigger packages. In other words, this means that when a data packet arrives, which functions as a trigger packet, a time stamp is taken on a network device and / or a time stamp is emitted when a data packet is sent, which functions as a trigger packet, and inserted into the data packet.
• the data packets are used to determine the transmission time.
• the time stamps taken on the respective network devices are not inserted in the data packet, but stored in the network device on which they were just taken. This has the advantage that with the data packets the input and / or the output time can be determined on the respective network device without this information having to be inserted into the data packet. This means that the time stamp is available, but the data packet, more precisely its useful content, remains unchanged and the data packet can thus be forwarded unchanged.
• the at least one taken time stamp is available in the network device and can in turn be read by a network management system.
• a time stamp is taken on a network device and / or a time stamp is emitted when a data packet which serves as a trigger packet is sent, and taken to the network device on which the time stamp was taken. is stored.
• the invention thus relates at least to the aspect of end-to-end measurements. In general, however, the measurement does not have to be performed from the actual end (or beginning) to the actual end, but it can also be performed as a method of path segment ancestor determination, with which any partial path latencies and, in the last instance, the end-to-end Latency can be derived.
• end-to-end does not mean the actual first network device and the last network device, for example, in a line topology, but that any path segments can be defined, which are then defined by a first network device and a last network device between which there are no, at least one or preferably several network devices, so that the latency for the transmission of the trigger packets between this one and this other network device can be determined ideally, and preferably in the network devices, a timestamp is taken when a trigger packet arrives, and another time stamp is taken if that trigger packet after its processing (e.g., storage) and / or processing (or forwarding) of the received data packets leaves the network device again.
• processing e.g., storage
• processing or forwarding
• the transmission times (latencies) on any sections of the network or the entire network taking into account the processing or forwarding times of data packets in the respective network device including the transmission times on the transmission medium between the individual network devices (wired or wireless) be determined precisely.
• the network devices can be configured, for example, so that they interpret data packets of a certain type or with a certain (partial) information quasi as a trigger, so that upon arrival of such a data packet due to a specific configuration on a network device an input timestamp and / or Starting time stamp is taken.
• all incoming data packets are interpreted as a kind of trigger that determines the determination of the Initiate input timestamp and / or the output timestamp.
• data packets of the first kind can be interpreted as a kind of trigger or data packets of another type can be filtered out and nevertheless forwarded without a timestamp being taken.
• data packets having a particular VLAN priority, destination MAC address or the like may be considered as a kind of trigger from the correspondingly configured network device.
• trigger packets are transmitted on the network, preferably for at least one network device, or multiple network devices or each network device in the network, the time of arrival of the trigger packet (input time), and / or the time of sending the trigger packet (time of transmission).
• This has the advantage that parallel to the data packets that are also transmitted on the network and are forwarded by a switch, for example, need to record any additional information with respect to the time stamp, but only contain their payload content unchanged.
• it is of course possible to record a time stamp also in the data packet so that the time stamps collected and collected during the transmission can be cumulated in order to be able to determine the defined end-to-end latency on the basis thereof.
• At least one network device (or a group of similar network devices), several network devices of different types or all network devices in the network or a sub-segment of the network are addressed ,
• the inventive method described above is applicable to any network topologies (such as a ring topology or a line topology), even in the case of redundancy.
• the method according to the invention is described below and explained with reference to the figures.
• FIG. 1 shows a network in line topology
• FIG. 2 shows a network in line topology with trigger packets and a database for access via a network management system
• FIG. 4 shows an exemplary structure of a trigger packet
• FIG. 5 shows a trigger packet in the event of an error.
• FIG. 1 shows by way of example, as far as shown in detail, a network in a line topology.
• An actual start of the network is determined by the network device ED1 and an actual end of the network by the network device ED2. Between this actual end and the actual start of the network, any number of network devices, such as two switches SW1 and SW2, are present to each other via suitable transmission media (such as wired via cable or wirelessly, for example via radio, infrared or the like ) are interconnected and exchange data packets not shown. In addition to these data packets, trigger packets TP are transmitted.
• suitable transmission media such as wired via cable or wirelessly, for example via radio, infrared or the like
• each trigger packet on the left of the switch or on the left of the network device indicates that whenever such a trigger packet arrives at the input of the network device concerned, the time of arrival (receipt) is determined. So a timestamp is raised. Alternatively or additionally, the time when a trigger packet leaves the respective network device can also be determined. To one To realize the highest possible precise resolution or determination of the transmission time, both the reception time and the time of transmission are determined.
• FIG. 2 shows a network in line topology with trigger packets and a database for access via a network management system.
• the network according to FIG. 2 is based on the functioning of the network, as shown in FIG. 1, but with the difference that a network management system (NMS) is permanently connected to at least one network device (in this example the switch SW1) or temporarily usable.
• NMS network management system
• the network management system may also be permanently connected or connectable to more than one network device or all network devices residing in the network (regardless of its topology).
• the input time stamp and / or the output time stamp of the trigger packet is then stored after its detection (for example in a database, Mgmnt DB).
• the network management system can access this database and read the timestamps for every trigger packet that the respective network device has reached or left, and from this, in conjunction with the time stamps of the other network devices, the end-to-end latency for the entire network (ie from ED1 to ED2) or for certain freely selectable segments of the network (such as from ED1 to SW2 or from SW2 to ED2).
• FIG. 3 shows the case of inserting a timestamp "Inline" and in a database of the network management system.
• the time of arrival of the trigger packet is denoted by TSin and the time of transmission of the trigger packet by TSout.
• Mgmnt DB management database
• the term "trigger frame” is used in the figure itself, wherein in principle the terms “trigger frame 1 " and “trigger packet” can be used synonymously with one another If the inventive method Realized layer 2 level, the term “trigger frame” can be used, whereas the term “trigger packet” can be used when the inventive method is performed at the layer 3 level or above.
• FIG. 4 shows an example of a structure of a trigger packet, wherein it can be seen that not only the input and output timestamps of the respective network device are contained in the trigger packet, but that optionally also further data (for example metadata) can be contained in the trigger packet and transmitted ,
• the number of time stamps in this trigger packet depends on the number of network devices, in particular on the number of terminals or the intermediary devices, such as switches.
• Such a trigger packet can, but does not have to, contain the data of the actual first network device (here ED1) or of the actual last network device (here ED2), but can, for example, also contain only the data of the network devices connected between these devices.
• FIG. 5 shows, based on the trigger packet, as shown in FIG. 4, a trigger packet in the event of an error with exemplary time specifications for the respective input and transmission time in the respective network device.
• a line topology can be used with two terminals (see FIG. 1, which shows a line topology with trigger packet).
• a trigger packet TP is transmitted by a network device ED1 and received by another network device ED2.
• the end-to-end latency can be determined by the transmission time of the trigger packet from the network device ED1 from the time of reception of the trigger packet in the network device ED2 (see FIG. 4, in the structure of the trigger packet) is) is deducted. This gives the exact end-to-end packet transit time between the network devices ED1 and ED2.
• the trigger packets can be sent independently of the network priority specified by the time synchronization protocol on a freely chosen network priority. This makes it possible to evaluate the switching of the trigger packet in the forwarding in different priority classes.
• the trigger packet from the network device ED1 to the network device ED2 mentioned in the above example has an unexpectedly high delay, it becomes possible on the basis of the invention to observe the individual delays on each step of the transmission path and thereby achieve a precise limitation of the error source.
• FIG. 5 as an example, there is an error in the network device SW2.
• the determined end-to-end latency between the network devices ED1 and ED2, at 670ns, is well above the expected latency.
• the cause of the error can now be limited to the network device SW2, since the residence time in the network device SW2 with 430 ns can be precisely determined, for example, by the network management system and significantly exceeds the assumed exemplary normal residence time in a switch of 100 ns.
• the abovementioned numerical values are purely exemplary and not restrictive.
• the illustrated meta-data is an exemplary package construction.
• these are, for example, so-called end devices (such as personal computers, sensors, actuators, industrial controls and the like), which monitor an actual start or an actual end of a network (for example in a line). or in ring topology).
• Those network devices that are arranged between these terminals usually serve the actual distribution or switching of data packets (with payload content) and send, with the exception of the inventively provided trigger packets, no new data packets to the network or change the payload of a forwarded data packet not ,
• the invention will be given again in other words:
• a "trigger packet" is sent, which ensures that individual devices, preferably each device on the transmission path, which supports the method described here, takes time stamps (eg the respective receiving and / or dispatch time) and the measured This results in a complete recording of the time history of the data switching on individual switching paths, preferably on each switching path (including the method supporting terminals) within the network the at least one receiver (device) is processed or provided for further processing (eg by passing it to a management system or by returning the packet to the initiator of the measurement).
• time stamps eg the respective receiving and / or dispatch time
• Qut-of-band Same as 1., except that the measurements and metadata are not inserted directly into the package on the device, but are cached and made available to the network participant on which they were collected ,
• the stored values may e.g. queried by a management system via a management protocol.
• mechanisms from existing time synchronization protocols such as IEEE 1588 may also be used as a "trigger packet" and to collect the timestamps.
• the time stamping method should have the highest accuracy (eg ideally, it would be helpful).
• the measurement method is suitable for use with unicasts, multicasts and broadcasts.
• the novelty of the invention is characterized by the fact that unlike existing methods such as e.g. IEEE 1588 does not aggregate the total throughput times in the trigger packet, but records the measured values for a packet separately during mediation and provides them individually. This makes it possible, for example, to determine the latency contributions that are caused, inter alia, in the mediation by individual network subscribers. In addition, this can be monitored in time slot method compliance with the timing of the transmission of individual packets and diagnosed error cases.
• IEEE 1588 does not aggregate the total throughput times in the trigger packet, but records the measured values for a packet separately during mediation and provides them individually. This makes it possible, for example, to determine the latency contributions that are caused, inter alia, in the mediation by individual network subscribers. In addition, this can be monitored in time slot method compliance with the timing of the transmission of individual packets and diagnosed error cases.
• the described measurement can, for example, take place on the basis of a reserved time slot in the context of the time-slot method.

Landscapes

• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Environmental & Geological Engineering (AREA)
• Health & Medical Sciences (AREA)
• Cardiology (AREA)
• General Health & Medical Sciences (AREA)
• Data Exchanges In Wide-Area Networks (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=60484357

Family Applications (1)

Country Status (5)

Families Citing this family (7)

Family Cites Families (14)

• 2017
  • 2017-11-21 EP EP17805158.7A patent/EP3542495A1/de active Pending
  • 2017-11-21 CN CN201780071797.6A patent/CN109997336B/zh active Active
  • 2017-11-21 US US16/341,891 patent/US11133884B2/en active Active
  • 2017-11-21 WO PCT/EP2017/079913 patent/WO2018091736A1/de active Application Filing
  • 2017-11-21 DE DE102017127431.6A patent/DE102017127431A1/de active Pending

Also Published As

Similar Documents

Legal Events