EP1743453A1 - Performance measuring in a packet transmission network - Google Patents

Performance measuring in a packet transmission network

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Publication number
EP1743453A1
EP1743453A1 EP20050769213 EP05769213A EP1743453A1 EP 1743453 A1 EP1743453 A1 EP 1743453A1 EP 20050769213 EP20050769213 EP 20050769213 EP 05769213 A EP05769213 A EP 05769213A EP 1743453 A1 EP1743453 A1 EP 1743453A1
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EP
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Application
Patent type
Prior art keywords
packet
stream
terminal
packets
flow
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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.)
Withdrawn
Application number
EP20050769213
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German (de)
French (fr)
Inventor
Emile Stephan
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Orange SA
Original Assignee
Orange SA
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Publication date

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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L41/00Arrangements for maintenance or administration or management of packet switching networks
    • H04L41/14Arrangements for maintenance or administration or management of packet switching networks involving network analysis or design, e.g. simulation, network model or planning
    • H04L41/142Arrangements for maintenance or administration or management of packet switching networks involving network analysis or design, e.g. simulation, network model or planning using statistical or mathematical methods
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L43/00Arrangements for monitoring or testing packet switching networks
    • H04L43/50Testing arrangements
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00Routing or path finding of packets in data switching networks
    • H04L45/26Route discovery packet
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L43/00Arrangements for monitoring or testing packet switching networks
    • H04L43/08Monitoring based on specific metrics
    • H04L43/0852Delays

Abstract

A stream of data packets transmitted by a terminal (11) passes through network equipment (13) to which a stream-measuring unit is associated. The terminal (11) and the measuring unit are connected to a collection unit (18). Said terminal generates a stream comprising first and second packets to be transmitted to a second terminal. The measuring unit analyses one packet of the stream, the collection unit receives the description of the packet stream containing information specifying the number of the transmitted and received packets from the terminal and the measuring unit receives the description of the stream comprising the analysed packets. The collection unit (18) correlates the received descriptions packet by packet.

Description

Λ

PERFORMANCE MEASUREMENT IN A PACKET TRANSMISSION NETWORK

The present invention relates to the field of telecommunication networks and more specifically to the field of metrology packet transmission telecommunications networks. Metrology, literally "science of measurement," is developing in different areas of networks such as the characterization and modeling of traffic, traffic analysis, and the optimization of the quality of service and performance. Metrology network is also used to improve the supervision of a network. It aims in particular to provide assistance for the design of a network and for diagnosing problems detected in a network. The increasing complexity of networks and in particular that the Internet leads to ignorance of traffic and usage conditions. It becomes increasingly difficult to have real control of the network and its behavior. Typically the traffic on a network is composed of multiple packet streams. A packet flow is defined as a data exchange between two terminals of a network whose packets have common characteristics, including common characteristics of origin, destination and service. Generally, the metrology aims to identify actions to be performed on network traffic studied to gain a better understanding of trafficking. two types of measures are known. One type consists of measurements on a flow test packets. To perform these measurements called "active", is transmitted through the network studied, from a first transmitting terminal to a second terminal receiving a stream of test packets. Generally a test packet has a specific format including a first field indicating a temporal reference of the packet transmitting and a second field indicating the packet sequence number in the stream of test packets transmitted. Therefore, the receiving terminal determines a transmission delay of a test packet from the sending terminal based on the first field of the packet. The receiving terminal may also detect packet loss based on the second field of a test packet. More generally, a test packet is a packet with a known time reference emission and that we can distinguish other receiving packets to associate a time reference arrival or whether he is lost. One can thus obtain performance characteristics of a stream "from beginning to end," that is to say, the full path of the flow of test packets from the transmitter to the receiver, including measures transmission delay between the two terminals on the basis of time references known transmitting and receiving packets. This first type of measurement makes it possible to obtain performance measurements on a complete path of the stream of test packets, that is to say between the emitter terminal of the flux and the flux receiver terminal. The measurements are obtained on test packets of a flow. They are therefore qualitatively accurate. A disadvantage of this type of action is that it only provides information on the ends of the flow of test packets. It is therefore impossible to obtain information about a segment of the complete path between two network devices or between a network equipment and terminals. The information thus obtained are therefore geographically imprecise. We know a second type of measurements performed at a network equipment by analyzing the flows that pass through it. These so-called "passive" measurements can be performed either by onboard measurement units in the network equipment, or by external measurement units to the network equipment (or passive probes) dedicated to passive measures. These generally have less information than embedded measurement units. These measurement units are listening to the traffic circulating on the connections between the network equipment. This type of passive measurement, widely used in existing networks, provides volumetric flow of information through networks and equipment. A disadvantage of this type of measurement is that it provides information on network equipment that are very difficult to correlate with other information to another network equipment. Therefore, even if it is possible to obtain correlation relatively precise geometric information on a given segment, such a correlation is complex to implement, especially if the flow is sampled for analysis. Another disadvantage of this type of action is that it provides only voluméfriques flow information from network devices, including the number of analyzed packets and the sum of the sizes of the analyzed packets for a given stream. Therefore, the information obtained by such measures may prove to be qualitatively inadequate and even unreliable, especially if flows are sampled for analysis. Thus, it is interesting to obtain qualitatively accurate, that is to say on packets of a flow, and geographically specific, that is to say relating to the full path of the stream segments in existing networks. Note that the terms "network equipment" refer to an active network equipment, that is to say that performs a processing function active in the network, such as switches or routers. An active processing function in the network can also be defined as opposed to a passive treatment function performed by a particular unit of measurement. The present invention aims to provide a solution designed to meet these needs. A first aspect of the invention provides a measuring method in a network for transmitting data packets, wherein a data stream transmitted by a first terminal of packets transmitted via at least one network equipment which is associated a measuring unit stream, wherein said first terminal and said measuring unit are connected to a collection unit, said method comprising the steps of: the first device generates a packet stream, comprising a first and a second status control packet session; the measuring unit analyzes said first and / or second packet of said stream passing through the network equipment; the first terminal sends a transmitted packet stream description comprising at least the number of packets sent to the collection unit; the flow measuring unit sends a description of the stream comprising at least an information indicating the number of analyzed packets to the collection unit; and the collection unit identifies each analyzed packet flow according to the flow description for correlating, packet by packet, said descriptor stream and said packet stream description. A second aspect of the invention provides a measuring system comprising means arranged to implement the method above. A third aspect of the invention provides a collection unit comprising means arranged to implement the method above. Thanks to these features, you can get accurate information geographically and qualitatively traffic on the transmission network studied. Other aspects, objects and advantages of the invention will become apparent from reading the description of one of its embodiments. The invention will also be better understood with the aid of drawings, in which: - Figure 1 is a diagram of a network architecture according to an embodiment of the invention; - Figure 2 illustrates a network measurement method according to an embodiment of the invention; - Figure 3 illustrates a method according to an embodiment of the invention in a network architecture based on a collection unit comprising a first and a second module; - Figure 4 illustrates a format of a TCP packet header. The invention can be exploited in all areas of metrology applied to packet transmission networks. The invention proposes to combine active and passive measures to take advantage of each one. Thus, in one embodiment of the invention, two terminals (or active probes) exchange a test packet that is parsed into several points of the network, especially on the basis of timestamps of passage of the packet. The context of the invention is that any type of transmission network of fixed size packets of varying size. To illustrate the description below, the IP network, for "Internet Protocol", is taken as an example, without limiting the scope of the invention. The invention can particularly be implemented on an IP version 4 or version 6 protocol The invention is applicable to analytical methods including a selection of packets analyzed flow, such as sampling flow, or to analysis methods without selection packet stream analyzed. It is noted that in one embodiment of the invention, a measuring unit generates flux descriptions comprising information relating to the flow, while a terminal generates packet stream description comprising information relating to the packets of the flux. 1 shows a network architecture comprising a measuring system according to an embodiment of the invention. A terminal 11 and a terminal 12 are connected to the IP network 10. Terminals 11 and 12 are adapted to the generation of the stream of test packets. The IP network 10 comprises respectively referenced equipment

13, 14, 15, 16 and 17. Among these equipments, the equipments 13, 15 and 16 are each provided with a measuring unit onboard flow. The units include an export function measurements. The invention also covers a configuration in which the flow measuring unit is an external entity and listening to the traffic passing over a transmission link between the network equipment. or a terminal and an equipment. The terminals 11 and 12 as well as equipment including flow measuring units 13, 15 and 16 are connected to a collection unit 18.

This collection unit is for receiving the various information exported by the measurement units and the terminals 11 and 12 to group and correlate them to provide precise information relating to the test packets of the stream and corresponding to specific segments the full path of the flow, including performance information on packet loss or packet transmission delay. The terminals 11 and 12 may be fixed terminals. They can also be mobile terminals. In a preferred embodiment of the invention, embedded flow measurement units in equipment 13, 15, 16 are implementing gender stream analysis functions from those standards track named 'IPFIX' one implementation is distributed by the company Cisco Systems, Inc. under the name "Netflow". A type of service "IPFIX" is a global service flow analysis transiting packet transmission network equipment, including routers and IP-based switches, ATM, Ethernet or MPLS (Multiple Protocol Lable Switch) . Such a service provides an analysis of the streams entering equipment. It is also adapted to accumulate statistical measurements relating to a given flow and to export asynchronously these measurements to a collection unit 18. The export action towards the collection unit is preferably performed by encoding data to reduce the required bandwidth. Such export measures can be carried out over the water, on expiration of a timer, or on detection of an end flows. A measure can also store these measures so as to enable the collection unit 18 to download. The invention covers any other analysis function of a measuring unit providing stream information and any other method of exporting these flow information. In the following sections, for the sake of clarity and by way of example, the network equipment provided with a flow measuring unit are routers. The invention also covers a flow measuring system wherein the network equipment provided with a flow measuring unit are other network equipment, such as switches. Typically, a stream of test packets sent by the terminal 11 to the terminal 12, is identified by the following information: IP address, denoted T11_SrcAddr, and the logical port, denoted T11_SrcPort, the transmitter terminal 11; the IP address, denoted T12_DstAddr, and the logical port, denoted T12_DstPort, the receiver terminal 12; the protocol used, noted Proto_test eg TCP for "Transmission Control Protocol" UDP "User Datagram Protocol", or ICMP for "Internet Control Message Protocol". A network equipment provided with a flow measuring unit is able to provide the flow descriptions preferably comprising: a field for the number of input and output interface, respectively denoted by 'Input' and 'Output '; a field for the number of analyzed and accounted for a stream packets, denoted 'Packets'; a field for the number of bytes of the IP protocol layer corresponding to the analyzed packets flow, noted 'Bytes'; a field for passing a temporal reference of the first packet analyzed in the stream and a field for a reference time of passage of the last packet analyzed in this stream, denoted respectively 'First' and 'Last'; a field for the IP address of the next router input interface, denoted 'NextHop. When such equipment is a router, a description stream also preferably includes a field for the numbers of administrative, or AS for "Autonomous System" crossed respectively denoted 'SrcAS' and 'DstAS. A measure of a router stores data on flows that pass through that router. On receiving a packet, the measuring unit determines whether the packet belongs to a stream being analyzed. If it belongs to a stream being analyzed, the fields corresponding to the number of analyzed packets for this flow, the sum of the sizes of the analyzed packets and the time reference passage of the last analyzed packet, respectively, the fields' Packets', 'Bytes' and' Last ', are updated. If the received packet does not belong to a stream being analyzed, router measurement unit initiates an analysis to the stream by storing, among other things, a time reference of passage of the first TS packet in the field ' First '. The router the measurement unit ends analysis of a flow upon detection of the end of the stream. A measuring unit is generally adapted to export the stored data or when the end of the stream is detected, or even before the end of the current flow analysis, when a certain time has elapsed from the initiation of the flow analysis. The stored data relating to the analysis of a stream are then encoded to be exported to the collection unit 18 as stream description tickets. Several stream description tickets for Multiple studied streams can be grouped into a stream description block, as shown below. Further technical data necessary for decoding a ticket description by the collection unit 18, including a noted field 'Version' identifying a software version of the IPFIX type of service header of a ticket description flow also indicates, preferably, a time reference of the router. Fields noted 'SysUpTime' and 'UnixSecs' can be inferred when the ticket was created stream description. A note field 'FlowSequence' allows the detection of loss of stream description tickets. Table 1 below describes the header format of the exported stream description tickets, according to one embodiment of the invention.

In this table the field 'Reserved' can be used to describe information such as the sender (engine type 'and id') and a sampling method (samplingjnterval). Each stream is preferably described in a stream description ticket as detailed in Table 2 below, including in particular information relating to administrative, or AS for "Autonomous System" and on the type of service, or Tos, equivalent to a Quality of Service, or QoS.

table 2

Each stream can also be described by a ticket stream description includes only part of the information listed above. The flow description blocks grouping stream description tickets are generally sent by the measurement units to a collection unit in the form of a UDP datagram. A UDP datagram is 1464 bytes, corresponding to an Ethernet frame of 1500 bytes, can contain up to 30 stream description tickets. An IPFIX type of service implemented in the form of software, does not, in general, to analyze all the packets passing through a network equipment. The unit of measurement reduces the number of packets to be analyzed by selecting certain packets in the packet flow studied. The invention covers all packet selection like a stream. In one embodiment of the invention, the selection of packets to be analyzed is performed by sampling the flow studied. Then, the measurement units exporting flow information, as detailed in Table 2, to the collection unit 18. As previously said, the test packets are injected into the network. Indeed, the terminal 11 transmits a stream to the test packets of the terminal 12 through the network 10. The flow of test packets passes thereby through at least some of the network devices 10. When packets passing test in the network equipment provided with a measuring unit, all test packets or only a portion of the test packets of the stream are analyzed. In one embodiment of the invention, measurement units have the ability to detect certain packets among the different streams of packets passing through the network equipment which they are associated, particularly as different connection management packets. In general, the measurement units have the ability to detect session state control packets, such as a logon packet or end of session, or as a pause packet of a session. Specifically, in an IP network, such measuring units are adapted to detect TCP connection management packets. Generally, units of measure implementing an IPFIX type service have such a capability. When a measurement unit detects a package of management of a TCP connection, it exports this information in the field tcpflags 'a ticket stream description by IPFIX, as shown in Table 2 with the presence of the field tcpflags' . The following sections describe the basic principles of TCP connections. A format of a packet header according to a TCP protocol type is detailed in Figure 4. The field flag RST is 1 when the connection is reset. The flag field 'SYN' is equal to 1 when one initiates a connection. The flag field 'END' is equal to 1 when the connection is interrupted. To establish a TCP connection, the client and server exchange data and acknowledgments. The classic establishment of such a connection is made in three steps. First, the client sends a connection request message to the server. The field 'SYN' of the TCP header such a message is equal to 1 and therefore such a message is noted SYN thereafter.

Then, the server returns an acknowledgment message receipt to the customer. Field

'SYN' and the field 'ACK' to the TCP header in such a message are equal to 1 and therefore such a message is noted SYN-ACK thereafter. Finally, the client responds to this message with a last acknowledgment message. The 'ACK' to the TCP header of such a message is equal to 1 and therefore such a message is denoted

ACK thereafter. After this exchange of messages, the TCP connection is established. To close a TCP connection, the client sends a connection close message to the server. The 'END' in the TCP header of such a message is equal to 1 and therefore such a message is noted FIN. The server responds to this message by sending an acknowledgment message. There is a faster procedure TCP connection close where only a message is sent: the client sends a connection close message. The field 'RST' TCP header of such a message is equal to 1 and therefore such a message is denoted RST thereafter. Generally, a unit of measure by implementing a IPFIX type service handles a particular way so that a TCP flow detected SYN marks the beginning of a stream and a RST packet, or a FIN packet detected marks the end of a stream. An embodiment of the invention takes advantage of this particular treatment. Advantageously, the flow tests generated by the terminal 11 to the terminal 12 passing through the network equipment are composed each of two test packets. Indeed, the terminal 11 initiates a TCP connection with the terminal 12 by sending a packet comprising an opening message-connexion. Then, upon receiving the acknowledgment packet corresponding to the terminal 11 closes the connection by sending a connection close packet. Therefore, such a test flow comprises a first SYN test packet and a second RST test packet. This feature of the test stream allows the collecting unit 18 to perform a simple manner correlation between different information exported by the terminal and the measuring units, respectively in the packet stream descriptions and in the flow descriptions. As described above, the flow descriptions exported by units of measure include fields for the different TCP connection management messages, noted tcpflags. Therefore, the collecting unit receiving firstly a description of flow of test packets from the sending terminal 11, and a description of flow of test packets from the destination terminal 12, and receiving on the other hand a description of test flow since the measurement units can correlate this information to obtain in a simple manner information packet by packet such as packet loss measurements on segments of the full path, that is to say between a terminal and network equipment or between two network devices. Such measures are called packet loss vectors. Indeed, a description of such flows can detect if none, one or two packets of the stream have passed and were analyzed by a unit of measurement associated with a given network equipment. If no packet flow has been analyzed, the tcpflags field 'of the stream description ticket sent by the unit of measurement associated with the equipment does not contain the SYN or RST instructions. However, if the packet's connection initiation message and / or the packet's connection closing message is analyzed by a measuring unit, the tcpflags field 'contains the SYN and / or indication RST. In such embodiment, a description of the test flow allows to deduce a flow description of test packets and beyond infer a packet loss vector on a segment of the full path. Note that the collection unit can deduce information from the values ​​contained in the tcpflags field. Thus, if the tcpflags field '

-contains the RST stated, the collection unit can be deduced that the SYN packet was not lost. Moreover, the descriptions of flows exported by measurement units also preferably fields for the time references of the first packet passage and the last packet of a flow, respectively denoted 'First' and 'Last'. The test stream comprising only two test packet, the measuring unit indicates via the two fields 'First' and 'Last' of the stream description tickets, a time reference of each of the packets of a test flow, if both packages are analyzed. The collection unit is able to simply carry out a correlation, packet by packet between the packet stream descriptions received from the terminals and descriptions stream received from the measurement units. Therefore, the collection unit can easily calculate the packet transmission times over segments of the complete path of the stream. Such delays are called vectors of instant packet transmission delay. More generally, the collection unit 18 is able to provide instantaneous following information: - information relating to the path of the packets of the stream in the network; such as a list of one or more devices by which the analyzed packets transiting; - information about equipment management the way of the flow in the network, such as a list of management addresses of one or more devices through which analyzed packets in transit; - information on the treatment of the stream in the facilities of the road, such as a list of service quality levels applied by one or more devices to the analyzed packets; or a list of administrative areas traversed by the stream; - network performance information for packet loss on a segment between a terminal and an equipment or between equipment and / or a packet transmission time on a segment between a terminal and an equipment or between two devices. In some circumstances, it may prove very useful to reiterate successively flows emitting steps of test packets by the terminal 11, flow analysis in network equipment and receiving flow from the terminal 12. in such conditions the unit. measure may provide by iteration and by correlating the information obtained at each iteration, with respect to a segment between a terminal and an equipment or between two devices, statistics on performance measures such as those defined in the IETF for "Internet Engineering Task Force "or PITU," for "International Telecommunication Union", such as: packet loss; a packet transmission delay; and a variation of transmission delay. A repetition of the measurement method is very useful also in the case where the analysis is performed on selected packets of the test stream, for example by sampling. Thus, after repetition of steps, the collection unit is able to provide, by correlation of the data obtained at each iteration, more precise and exhaustive the following information: - information relating to the path of the packets of the stream in the network ; such as a list of one or more devices by which the analyzed packets transiting; - information about equipment management the way of the flow in the network, such as a list of management addresses of one or more devices through which analyzed packets in transit; - information on the treatment of the stream in the facilities of the road, such as a list of service quality levels applied by one or more devices to the analyzed packets; or a list of administrative areas traversed by the stream; information de- network performance for packet loss on a segment between a terminal and an equipment or between equipment and / or a packet transmission time on a segment between a terminal and an equipment or between two devices. Note that the reiteration of steps turned out to be particularly advantageous in the case where the analysis is performed on selected packets of the test stream, for example by sampling. Indeed, some snapshots vectors can in this case provide incomplete information. However, if the analysis is performed on all packets of the test stream, the data listed above, can be obtained by correlation without repetition. 2 illustrates a network measurement method according to an embodiment of the invention. The stream of test packets transmitted by the terminal 11 to the terminal 12 through the equipment 13 and 15, each being provided with a flow measuring unit comprising an export function IPFIX type of flow description. In one embodiment of the invention, measurements units sample, manage and store stream descriptions in a table of flow characteristics. The structure of the table entries is similar to the structure described above in Table 2. Depending on the type of service flow analyzed, the functional level of the analysis or the type of the network equipment, this table may have additional fields or conversely, some of the already listed fields may not be filled. In a general case, a network includes a number N of equipment. The flow descriptions are sent to the collection unit 18 from one of the IP addresses of the Ei, denoted Ei_SrcAddrMgt. The packets of IP flows from the terminal 11 to the terminal 12, are thus seen as they pass in E equipment. In one embodiment of the invention, the measurement method comprises the following steps: - step 21: sending the first packet corresponding to a connection request TGP from the terminal 11 to terminal 12; - - step 22, 22 ': Introduction of the first packet to the analysis process of the flow measuring units Ei equipment; - step 23, 23 ': Creating a new entry in the table of the flow characteristics handled by the units of measure flow Ei equipment at this stage storing a time reference portion of the first packet analyzed in the field' First '; - Step 24: receiving the first connection request packet from the terminal 12 and transmission of a SYN-ACK message from the terminal 12 to the terminal 11; - Step 25: Receiving the SYN-ACK message from the terminal 11 and sends a TCP connection closing message to the RST terminal 12; - Step 26: Send the packet stream description by the terminal

11 to the collection unit 18; - step 27, 27 ': end detection flow upon receipt of the RST packet and recording a time reference passage of this last packet in the' Last 'by units of measurement; - step 28, 28 'Export flux descriptions by the measuring units Ei equipment to the collection unit 18; - Step 29: Receive the last connection close packet by the terminal 12; - Step 30: Send the packet stream description by the terminal

12 to the collection unit 18; - Step 31: Aggregation and correlation data for this stream by the collection unit 18; - Step 32: Production of relatifves information vectors in the facilities of the path of the stream or segments of the path taken by the packets of this flow or concerning the complete path through the collection unit. The following sections describe each step of the measuring method mentioned above. In step 21, the terminal 11 requests the opening of a TCP connection with the terminal 12. It sends a TCP message with the SYN field has the value 1, to the terminal 12. The terminal 11 stores a reference time, denoted T11_SYN_time relating to the packet transmitting time. The characteristics of the test streams are: - T11_SrcAddr; - T11_SrcPort; - T12_DstAddr; - T12_DstPort. - TCP Protocol. In step 22, 22 ', the packet sent during the preceding step is submitted to the process of analyzing each network device through which it passes, if it is selected. In step 23, 23 ', the analysis process which is presented the first package detects the beginning of a new TCP connection, by controlling the value of the' SYN 'of the TCP header of the packet. So it creates an entry in the flow characteristics table for this connection. Then, in one embodiment of the invention, the process assigns a value to the different fields of the table entry. Thus, it assigns a time reference of the arrival time of packet field 'First' of the table entry. And it affects the number of octets of the IP packet to the field 'Bytes' of the entry in the table. It assigns the value 1 to the field 'Packets' of the table entry. It assigns the value corresponding to the SYN flag tcpflags field 'of the table entry. It affects the value of the field T11_SrcAddr 'SrcAddr' of the entry in the table. It affects the value of the field T11_SrcPort 'SrcPort' of the entry table entry. It affects the value of the field T12_DstAddr 'DstAddr' of the entry in the table. It affects the value of the field T12_DstPort 'DstPoif the table entry. It assigns a value corresponding to TCP field 'Proto' of the entry in the table. In step 24, the terminal 12 receives a TCP connection open request. It stores a time stamp of arrival of the packet in the T12_SYN_time field. Then responds by sending a packet comprising a

-message- acceptance -of the TCP connection. Such message is a packet whose header includes the field 'SYN' equal to 1 and the field 'ACK' equal to 1. In step 25, the terminal 11 receives the acceptance message from the opening TCP connection. It responds to this message by sending a packet including a reset connection closing message. It stores a time reference of the transmission of this packet in the T11_RST_time field. In step 26, the terminal 11 produces a packet stream description of this stream and sends it to the collection unit 18. This description preferably contains the following information: - T11_SrcAddr; - T11_SrcPort; - T12_DstAddr; - T12_DstPort; - Protocol; - T11_SYN_time; - T11_RST_time; - tcp_flags; - T11_AS; - T11_Tos. In the case where the terminal 11 exports the descriptions under IPFIX format type, the description sent to the collection unit is detailed in the following table.

Table 3 In step 27, 27 ', the analysis process which is presented the latest package detects the end of a TCP connection, by controlling the value of the' RST 'in the TCP header of the packet. If no entry exists for this flow, the analysis process creates a new entry in the table of flow characteristics. If an entry already exists for this flow and the process increases the value of the 'byte' of the table entry of the number of bytes of the packet. It increases the value of the field 1 'Packets' of the table entry. Then, the entry is new or not, assigns a temporal reference of the arrival time of packet field 'Last' of the table entry. Finally, a description of flow is generated and sent to the collection unit. The "entry in the corresponding table is then preferably released. The table below shows a table of the input flow characteristics of E network equipment for a given test flow. The source AS and is rated A TAS destination is denoted B.

Table 4 In step 28, the measurement units prepare a stream description. These flux descriptions can also be grouped in blocks of flow descriptions before being sent to the collection unit. The flow descriptions are sent to the collecting unit from the address Ei_SrcAddrMgmt. The destination address of this packet is Ei_DstAddrMgmt. The present invention also includes the configuration in which the measuring units store the flow descriptions and the collection unit downloads them when desired. In step 29, the terminal 12 receives a connection message end packet from the terminal 11. On receiving this packet, it stores a reception time reference in T12_RST__time. In step (30), the terminal 12 sends to the collection unit description stream of test packets. This description contains the following information: - T11_SrcAddr; - T11_SrcPort; - T12_DstAddr; - T12_DstPort; - Protocol; - T12_SYN_time; - T12_RST_time; - tcp_flags; - T12_AS; - T12_Tos. In step 31, the collection unit 18 includes the flow descriptions received from the measuring units and the packet stream descriptions received from terminals. The following table details the information thus gathered. Table 5 In step 32, in one embodiment of the invention, depending on the configuration of the collection unit, the latter may provide: - path information packets flow in the network; - information about equipment management the way of the flow in the network; - information on the treatment of the stream in the facilities of the road; - network performance information for packet loss on a segment between a terminal and an equipment or between equipment and / or a packet transmission delay on a segment between a terminal and an equipment or between two equipment and / or to a variation of packet transmission delay. It can also calculate the packet transmission delays and packet loss on the full path of the flow, as shown in the examples described in the following sections. In one embodiment of the invention, the collection unit provides NextHop vectors "End to end" in gathering the information NextHop SYN and RST packets from step (31).

Table 6 In one embodiment of the invention, the collection unit provides management interface vectors by grouping the package management interface information and RST SYN test flow from step 31.

Table 7 The corresponding final vector is {T11_AddrMgmt, ...

Ei_AddrMgmt, E + 1_AddrMgmt T12_AddrMgmt}. In one embodiment of the invention, the collection unit provides AS vectors by grouping the AS information SYN and RST packets analyzed and identified by the collection unit, from step 31 . AS the source of the stream and AS destination of flows are respectively described in the fields exported by the terminals, and Src_AS Dst_AS. A unit of measurement exports for a given Ei, the previous AS in the path and the next AS in the path that is to say the AS NextHop flow. The case described below turns out to be very useful in an IP network to a path flows through several different AS. Knowledge of the list of AS traversed by a stream enables a cross-domain diagnosis. The table below contains information on AS SYN packets and RST to produce vectors AS relating to segments of the path of the flow.

Table 8 The corresponding final vector is {T11_AS, ..., Ei-1_AS, Ei_AS, E + 1_AS, E + 2_AS, ..., T12_AS). In one embodiment of the invention, the collection unit provides vectors Tos (or QoS) by grouping information and RST SYN packet, as detailed in the table below. Tos field is one of the few fields that network equipment is allowed to change. This field determines the quality of processing the packet in the queues network equipment. This is important information including cross-domain for the establishment of marking devices of the quality of services.

Table 9 The final vector is {T11_Tos, ..., Ei_Tos, E + 1_Tos, ...} T12_ToS. The collection unit can also calculate a transmission delay of a vector packet of the "end to end" according to the following equations: T12_SYN_time - T11_SYN_time; T12_RST_time - T11_RST_time. The loss and delay vectors are complementary. A packet observed by T12 calculates a transmission delay as shown in the table below.

table 10

On the other hand, an unobserved package calculates a loss. A loss of a SYN packet between Ei + 1 and the terminal 12 is detected as illustrated by the table below.

table 11

In the case illustrated above, the terminal 11 sends a TCP connection initiation message to the terminal 12. The corresponding packet is observed by the network equipment Ei, Ei + 1 ... This message is clearly not received by the terminal 12. thus, the terminal 11 does not receive a corresponding acknowledgment message. Thus the SYN message is retransmitted by the terminal 11. Upon receipt of this second message SYN, the network equipment believe that a new connection, so a new stream is to be treated. A new entry in the table of flow characteristics is created. In the case illustrated by the table below, a loss of a RST packet between Ei network equipment and Ei + 1 is detected. This loss is confirmed by the fact that the RST packet is not received by T12.

Table 12 Thus, the segment Ei - Ei + 1 full path that lost packet is identified. Note that when a stream is analyzed by sampling instant vectors supplied by the collection unit are less accurate and less numerous. Indeed, in such conditions, a test packet is not systematically analyzed by all routers. However, for each test flow, measurements of "end to end" are always available. Furthermore, the TCP type connections cross the "firewall walls" (in English, "Firewall") IP network. Thus, the present invention based on a TCP protocol type provides measurements on roads crossing of firewalls. In some cases, it is advantageous to introduce a collecting unit comprising two modules in the network architecture described above. For example, if a module of a collection unit is adapted to receive and manage descriptions of streams emitted by the units of measure, but is not adapted to receive packet stream descriptions from the terminals. Deputy was then another module to receive the packet stream descriptions. 3 illustrates a method according to an embodiment of the invention in a network architecture based on a collection unit comprising a first and a second module. The method then comprises the following steps: - Step 302: Sending the terminal 11 and the second module 301 a copy formatting request message test stream description between the terminals 11 and 12, corresponding to a measurement start , by the first module 300; - step 21: sending the first packet corresponding to a TCP connection request from the terminal 11 to terminal 12; - step 22, 22 ': Introduction of the first packet to the analysis process of the flow measuring units Ei equipment; - step 23, 23 ': Creating a new entry in the table of the flow characteristics handled by the units of measure flow Ei equipment at this stage storing a time reference portion of the first packet analyzed in the field' First '; - Step 24: receiving the first connection request packet from the terminal 12 and transmission of a SYN-ACK message from the terminal 12 to the terminal 11; - Step 25: Receiving the SYN-ACK message by the terminal 11 and sends a TCP RST closing message

- destination of the terminal 12; - Step 26: Send the packet stream description by the terminal 11 to the first module 300; - step 27, 27 ': end detection flow upon receipt of the RST packet and recording a time reference passage of this last packet in the' Last 'by the measurement units; - step 28, 28 'Export flux descriptions by the measuring units Ei equipment to the second module 301; - Step 29: Reception of connection close packet by the terminal 12; - Step 30: Send the packet stream description by the terminal 12 to the first module 300; - step 303: Transmission over water flow descriptions between terminals 11 and 12 by the second module 301 to the first module 300; - step 304: Aggregation and correlation data for this stream by the first module 300; - step 305: Production of vector information relating to the facilities of the path of the stream or path segments taken by the packets of this flow or concerning the complete path by the first module 300. Preferably, in a configuration wherein the collection unit comprises two modules 300 and 301, the module 300 of the collection unit comprises an input filter for filtering only the information related to the relevant stream. In one embodiment of the invention, a stream description ticket also includes a TTL field 'for Time To Live. Such information is conventionally included in a field of a stream packet. By exporting this information, the collection unit is able to schedule easily Ei equipment on the path of the flow. The present invention proves to be very beneficial in all fields of metrology packet transmission networks, including the network dimensioning, as well as commissioning and maintenance of the network and to control the quality of Service provided. Indeed, upon detection of transmission problems "end to end" an embodiment of the invention locates very quickly or the full path segments that are causing problems, based very accurate and reliable measures. In addition, the measurements provided are available and usable very quickly. In addition, an embodiment of the invention is very simple to implement in existing networks. It is further noted that it is easy to deduce from this description an embodiment of the present invention in which a terminal transmits the flow of packets to a plurality of terminals. Thus, the measurement method according to an embodiment of the invention can be easily applied to a multi-destination transmission or multicast 'in English. In such a case, it is possible to provide that some or all of the receivers of the transmitted packet stream terminal sends a packet stream description received in the collection unit. In the case where the collection unit receives multiple packet stream descriptions received, it may for example derive the number of receiving terminals which have actually received the broadcast stream multicast. In another embodiment of the present invention, the function of the collection unit as stated above can be advantageously completed by a plurality of entities arranged in a hierarchical architecture. In such an architecture, a collection unit comprises a plurality of collection units and a central entity. The terminal and the measuring unit are then connected to at least one of the collection entities. Thus, for example, a terminal may send descriptions stream packets to a collection of entities and a measuring unit can send flow descriptions to another collection entity. Then, each of these collection entities may then transmit the received descriptions to the central entity, which identifies each analyzed packet flow according to the flow description for correlating, packet by packet, the flow description and the description of flow thus received packets.

Claims

1. A method of measuring in a network for transmission of data packets, wherein a stream of data packets transmitted by a first terminal (11) passes via at least one network equipment (13) which is associated a measuring unit stream, wherein said first terminal, and said measuring unit are connected to a collection unit (18), said method comprising the steps of: the first device generates a packet stream, comprising a first and second control packets d session state; the measuring unit analyzes said first and / or second packet of said stream passing through the network equipment; the first terminal sends a transmitted packet stream description comprising at least the number of transmitted packets (26) to the collection unit; the flow measuring unit sends a stream description (28,28 ') including at least information indicating the number of analyzed packets to the collection unit; and the collection unit (18) identifies each packet of the stream analyzed according to the flow description for correlating, packet by packet, said descriptor stream and said packet stream description issued.
2. The method of claim 1, wherein at least one second terminal (12) connected to the collection unit (18) receives the packet flow and sends a description of flow of received packets, including the number of received packets, to the collection unit; and wherein the collection unit identifies each analyzed for correlating packet, packet by packet, the description stream and the packet stream descriptions.
3. The method of claim 1 or 2, wherein the terminal is a mobile terminal.
4. A method according to any preceding claim, wherein the first packet is a start packet of the connection and the second package is a closed package of the connection.
5. A method according to any preceding claim, wherein the telecommunications network is a network based on an IP protocol type, for Internet Protocol; wherein the connection is a TCP connection, for Transmission Control Protocol '; and wherein the first packet is a SYN packet and the second packet is a RST packet or a FIN packet.
6. A method according to any preceding claim, wherein the collection unit (18) determines a relative loss of packets in a segment between the first terminal equipment and by correlation (32) the number of transmitted packets and the number of analyzed packets.
7. A method according to any one of claims 2 to 6, wherein the collection unit (18) determines a relative loss of packets in a segment between the equipment and the second terminal by correlating (32) the number of packets analyzed and the number of packets received.
8. A method according to any one of claims 2 to 7, wherein the packet stream descriptions (26,30) further comprises a time reference of the transmission by the first terminal and / or receipt by the second terminal, of each packet of the stream, and the flow descriptions
(28,28 ') further comprises a time reference of the passage through the equipment of the first and last analyzed packet, and wherein the collection unit (18) determines a transmission delay of said first and last analyzed packets on a segment between a terminal equipment and by correlation (32) of said time references of the packets.
9. A method according to any preceding claim, wherein a plurality of network devices (13,15,16) are provided with respective measurement units, and wherein the collection unit (18) provides the least one of the following instantaneous information: information relating to the path of the packets of the stream in the network; information about equipment management the way of the flow in the network; information relating to the processing flow in the facilities of the road; performance information relating to a packet loss on a segment between a terminal and a device or between two devices; performance information relating to a packet transmission delay over a segment between a terminal and a device or between two devices; performance information relating to a variation of packet transmission delay over a segment between a terminal and a device or between two devices.
10. The method of claim 9, wherein the measuring unit provides iterative steps of the method according to claim 1 at least one statistic of the following steps on a segment between a terminal and a device or between two devices: - a packet loss; - a packet transmission delay; and - a change in transmission delay.
11. A method according to any preceding claim, wherein the measuring unit analyzes a subset of packets of the stream selected from among the packets of the stream received by the device.
12. The method of claim 11, wherein the subset of packets is selected by sampling the packet stream.
13. The method of claim 11 or 12, wherein the measuring unit provides by iteration of the method steps according to claim 1 and by correlating the information obtained at each iteration with respect to a segment between a terminal and an equipment or between two devices, at least one statistic of the following: packet loss; a packet transmission delay; and - a change in transmission delay.
14. The method of claim 13, further wherein comparing the statistic with instant information obtained by the process according to claim 9, to determine relatively quickly changes.
15. A method according to any one of claims 11 to 14, wherein the measuring unit provides by iteration of the method steps according to claim 1 and by correlating the information obtained at each iteration at least one of the following relatively detailed information: - information about the way the packets flow in the network; - information about equipment management the way of the flow in the network; - information on the treatment of the stream in the facilities of the road; performance information on. a packet loss on a segment between a terminal and a device or between two devices; - performance information relating to a packet transmission delay over a segment between a terminal and a device or between two devices; performance information relating to a variation of packet transmission delay over a segment between a terminal and a device or between two devices.
16. The method of claim 15, wherein the relatively precise information further is compared with the instantaneous information obtained by the process according to claim 9, to determine relatively quickly changes.
17. A method according to any preceding claim, wherein the measurement unit is included in the equipment.
18. A method according to any preceding claim, wherein the collection unit (18) comprises a first module (300) for collecting the packet stream descriptions and a second module (301) for collecting the flow descriptions ; wherein the second module (301) transmits the flow descriptions to the first module (300); and wherein the first module correlates, packet by packet, the flow descriptions and the packet stream descriptions.
19. A method according to any preceding claim, wherein the collection unit (18) comprises a plurality of collection units and a central entity, the terminal and the measuring unit being connected to at least one of said collection of entities; and wherein the collection entities transmit the flux descriptions and packet stream descriptions received at said central body, said central entity identifying each analyzed packet flow according to the flow description for correlating, packet by packet, the description flow and packet stream description.
20. A measurement system in a data packet transmission telecommunications network comprising means arranged to implement a method according to any one of claims 1 to 19.
21. Collection unit comprising means arranged to implement a method according to any one of claims 1 to 19.
EP20050769213 2004-05-07 2005-05-03 Performance measuring in a packet transmission network Withdrawn EP1743453A1 (en)

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