WO2008080263A1

WO2008080263A1 - A method for measuring relative time delay of data service in optical transmitting network

Info

Publication number: WO2008080263A1
Application number: PCT/CN2006/003824
Authority: WO
Inventors: Zhiyong Yu
Original assignee: Zte Corporation
Priority date: 2006-12-31
Filing date: 2006-12-31
Publication date: 2008-07-10
Also published as: CN101336520A; CN101336520B

Abstract

A method for measuring relative time delay of data service in optical transmitting network, the relative time delay of data service is realized by transferring a timestamp identification; the timestamp identification bearing on the virtual container overhead is transmitted from the source to the sink timely and continually; after each transmission, the timestamp identification increases a timing interval; when the relative time delay is measuring, the source, after receiving a data packet, adds a current timestamp identification to said data packet immediately, after relatively processing and encapsulating, transmits the data packet to the sink; the sink receives the data packet, then relatively processes and decapsulates it, when it is output, the timestamp is extracted from the data packet, at the same time, the timestamp currently bearing on the virtual container overhead is got; the timestamp identification got from the data packet of the sink is subtracted from the timestamp identification got from the virtual container overhead to calculate the relative time delay. The present invention can provide an on-line, real-time and undamaged measure which measures the relative time delay of SDH/SONET network data service to get the relative time delay of single data packet.

Description

Method for measuring relative delay of measuring data in optical transmission network

Technical field

The present invention relates to a time delay measurement technique in an optical transmission network, and more particularly to a method for providing data service delay measurement on an SDH/SONET network optical transmission device.

Background technique

With the rapid development of data services, MSTP (Multi-service transport platform) is adopted on the transmission equipment of Synchronous Digital Hierarchy (SDH) or Synchronous Optical Network (SONET). The technology provides access to data services and has been widely used in metropolitan area networks.

The advantages of MSTP to transmit data services are mainly reflected in relatively high QoS (Quality of Service) and low cost. A more important indicator of QoS is the delay and delay jitter of the service. These indicators will become more and more important as voice and video are gradually transmitted using IP technology. Applications such as ordinary Internet browsing are generally based on the TCP/IP protocol, and the TCP/IP protocol is a Request-Respond-based mode that determines the actual available bandwidth of the user is sensitive to delay. When the transmission network delay is large, services using TCP/IP may fail to reach its maximum rate, resulting in wasted bandwidth.

As an important indicator of QoS, how to perform delay measurement has always been a topic of concern to the industry. At present, the nominal delay of the equipment is generally tested by special instruments, and the actual test is not actual. The results are often for reference only and cannot reflect the delay of the actual network operation. In actual use, users generally use the ping command to verify the actual delay of the network, but the accuracy is not high, and it is greatly affected by the software operation. It cannot be monitored from the network management in real time, and it is difficult to judge because of MSTP transmission. The delay is too large, or the data device has a problem causing the delay to increase.

Standardization organizations such as ITU-T and IEEE have now paid attention to this issue. In the new standards for data transmission networks, the content of Delay Measurement has been introduced into Ethernet OAM (Operation, Administration and Maintenance, Operation). Management keeps). The basic idea is to measure the 0AM frame by sending a dedicated delay, which carries a Time Stamp. The sink sends back the OAM frame with the timestamp, and the source end receives the time delay and confirms the two-way delay. The standard also supports sending a specific OAM frame for the measurement of the one-way delay, but because it requires the source and the sink. Synchronization in time is difficult to implement in applications, so it is mainly used to measure two-way delay.

However, in the actual network, the delay in the two directions of the data service is often different. The new test packets inserted are not exactly the same, and cannot reflect the real delay of the actual service.

Therefore, the more common methods of using network analyzers, ping commands, and OAM frame measurement delays have their own problems, and the methods of these tests do not truly reflect the true packet delay. When the service is mixed with different priority services, the test methods cannot calculate the actual delay value of each priority service in the current network.

Since the one-way delay of the SDH/SONET optical transmission network is basically fixed, and is related to the node transmission delay and the fiber delay, the delay can be determined in various ways, such as the method described in the patent WO2004068750 or directly using the fiber delay plus the node. Delay, so the key to measuring the delay of carrying data services in SDH/SONET is to get its delay relative to the network. Summary of the invention

The technical problem to be solved by the present invention is to provide a method for measuring the relative delay of data services in an optical transmission network, and to solve the problem that the relative delay of the one-way data service cannot be accurately obtained in the optical transmission network.

The invention provides a method for measuring a relative delay of a data service in an optical transmission network. The source end periodically sends a time stamp identifier carried on the virtual container overhead to the sink end, and the source time stamp identifier is added one time after each transmission. The timing interval, when performing the relative time delay measurement, includes the following steps:

After receiving the data packet, the source end adds the current timestamp identifier to the data packet, performs related processing, and sends the packet to the sink end after being encapsulated;

After receiving the data packet, the sink performs related processing and decapsulation, extracts a timestamp identifier in the data packet at the time of output, and obtains a timestamp identifier that is carried on the virtual container overhead at this time;

53. Subtract the time stamp identification obtained from the virtual container overhead by subtracting the time stamp identifier obtained from the sink data packet, and calculate the relative delay of the data packet relative to the optical transmission network.

Further, the source end has a time stamp generating device, which is generated at a fixed timing interval. The stamp indicates that when the source timing continues to transmit the timestamp identifier, a count of the timing interval is incremented each time the timestamp identifier is sent. The timestamp generating device is a timer at the source end, and the timer is incremented by 1 at the frame header of each synchronous digital series SDH frame, and the value of the timestamp identifier is updated once every time the source end is sent, and is updated to be timed. The current count value of the device.

Further, the virtual container overhead of the bearer timestamp identifier is a virtual container overhead that has been defined for use.

H4, or Jl, or J2, either retain unused virtual container overhead, or the overhead of multiframe.

Further, in step S1, the step of adding a current timestamp identifier to the data packet is to add the current timestamp identifier to a reserved byte in the original data packet, or add an additional value in the data packet to the arbitrary location. byte.

Further, in step S2, the time at which the sink end extracts the timestamp identifier in the data packet at the time of output is when the first bit of the data packet is output, or when the last bit of the data packet is output.

Further, the step of obtaining the time stamp identifier on the virtual container overhead in step S2 is performed before or after the alignment of the virtual container VC members of the virtual container group VCG.

If the timestamp identifier is the smallest, the timestamp identifier in the VC member of each virtual container is the smallest. The relative delay calculated in step S3 includes the VCG delay compensation time of the virtual container group. If the timestamp identifier is taken, each VC member is taken. The time stamp in the middle identifies the maximum value, and the relative delay calculated in step 3 does not include the virtual container group VCG delay compensation time;

If the alignment is performed, the timestamp identifier takes the timestamp identifier in the VC member of any virtual container, and the relative delay calculated in step 3 does not include the virtual container group VCG delay time.

Further, in step S3, the relative time delay is calculated. If the time stamp identifier obtained from the virtual container overhead is subtracted, less than the time stamp identifier obtained from the sink packet as the subtraction, 3'j is subtracted. The complement should be used, or the resulting negative result is added to the maximum timestamp identification count value.

Further, the number of bits required for the timestamp identifier to be transmitted is determined by the timestamp identifier maximum value TSmax, which satisfies TSmax < 2 ^A TSbits - 1 , and the maximum relative delay of the corresponding time stamp identifier maximum value TSmax DMmax = TSmax x timing interval.

Further, the data packet is any data packet having a packet structure, and the data packet type includes an ATM cell, or an Ethernet frame, or a multi-protocol label switching MPLS frame, or an elastic packet ring. RPR frame, or IP packet.

By adopting the method of the invention, the relative delay of the data service of the SDH/SONET network can be measured in real time without loss, and since it can provide the relative delay data of a single data packet, it can be used to monitor the delay variation of different priority services. The situation is convenient for users to compare and verify the QoS guarantee of the network. The delay data can be displayed on the network management system directly after being collected by the device. The test process is non-destructive to the business and convenient for engineering application and testing. BRIEF abstract

1 is a network model diagram for performing relative time delay measurement of a data service according to an embodiment of the present invention; FIG. 2 is a schematic diagram of an application example networking according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of an Ethernet frame in an application example according to an embodiment of the present invention. Preferred embodiment of the invention

The implementation of the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. '

The present invention proposes a method for measuring the relative delay of a unidirectional data service in real time on an SDH/SONET optical transmission network, with the aim of monitoring the delay of each service data packet relative to the SDH/SONET network in real time.

As shown in Figure 1, the networking diagram of the measurement data service delay in the optical transmission network is shown, including the source (source), the sink (sink), and the SDH/SONET light connected between the source end and the sink end. transporting network. The service data enters the source end from the receiving port (ingress), is transmitted to the sink end through the SDH network, and is sent out by the output port (egress) at the sink end.

Generally, the data service one-way delay of the MSTP (Multi-Service Transport Platform) device includes the following three parts:

(1) Receive packets from the source to send to VCG (Virtual Concatenation

Time delay of Group, virtual concatenation group;

(2) SDH network delay; (3) The delay at which the sink recovers the packet from the SDH virtual container and sends it out. Since the data service bearer layer transmitted by the MSTP device is an SDH/SONET network, the present invention utilizes a time division (TDM) based transmission mechanism of the SDH/SONET optical transport network and a rich overhead to measure the relative delay of the carried service.

First, the SDH/SONET time stamp concept is introduced. The time stamp is used to identify the time information of the system. It is timed by the SDH/SONET clock, and the time stamp is carried by the SDH frame or the SONET frame. The source is continuously and periodically through SDH/SONET. For the transmission to the sink, each time a frame is sent, a time interval is added, and the count of the time interval is used as a time stamp identifier.

When sending, in SDH/SONET, the source uses the virtual container VC (Virtual Container) overhead of the SDH frame or the SONET frame to carry the timestamp identifier as the reference time. At the same time, a timestamp identifier is added to each individual data packet of the data service (new overhead can be added to the packet or the original reserved byte in the packet) can be used as the measurement start time. When receiving, the sink uses the obtained timestamp identifier to calculate the delay. The time stamp (Time Stamp) is a general term, and is a method for representing time information. Its specific value is written here as a time stamp identifier, and the time stamp identifier can be used for recording and calculation.

Based on the test networking shown in Figure 1, the relative delay of the data traffic relative to the optical transport network (SDH/SONET) can be represented by T1. For the sake of understanding, we can use T12 to indicate the delay from the source to the packet sent to the VCG (Virtual Concatenation Group); T23 to indicate the SDH network delay; T34 to indicate the sink from the SDH virtual The delay in recovering the packet from the container and sending it out. Since the present invention calculates the relative delay, the delay of the SDH network is not included in T1, that is, T1 does not include T23. It can be considered that Τ23 is the network delay of SDH. Since there is a problem of calculating the virtual cascade compensation time at the position of position 3, the boundary of this point is relatively vague, and whether the T23 includes the position of the position 3 The compensation time needs to be treated differently.

In order to measure the relative delay of the data service, first, to establish a time stamp at the source end, at the position 1 shown in FIG. 1, the source end uses the virtual container VC overhead to transmit the timestamp identifier, and the system transmits one frame (125us), The timestamp identifier increments the count of a timed interval and, at the same time, updates the current timestamp identifier to the VC overhead. In this way, the source end periodically sends a timestamp identifier (FIG. 1, 2) carrying the reference time to the sink end, and the timestamp identifier is used to indicate the current time and time. Department The frame transmitted by the system may be an SDH frame or a SONET frame. The SDH frame is a complete frame, and VC is the payload in the SDH frame, so VC open silver is naturally included in the SDH frame.

In measuring the relative time delay of a specific data service, the following steps are included:

Step 1: After the source receives the service data packet from the receiving port (Ingress), it needs to immediately add the current time stamp to the data packet (Figure 1, location 1). After completing other processing, the data packet is encapsulated into SDH. Issued in /SONET VCG. The timestamp identifier added to the packet can either use the reserved bytes in the original packet or use the extra overhead bytes added anywhere in the packet. The timestamp identifier added here is used to indicate the start time information when starting to receive data services.

Step 2: The sink receives the data packet, recovers and processes the data packet, and extracts the time stamp identifier in the data packet when outputting to the Egress output port (Fig. 1, position 4); meanwhile, the sink needs The timestamp identifier carried in the current VC overhead is solved (Fig. 1, position 3).

The time at which the timestamp identifier in the data packet is extracted may be at the time of outputting the first bit of the data packet or at the time of outputting the last bit. The time stamp identifier in the packet is extracted, and the start time information of the data service is obtained.

At the same time, the timestamp identifier included in the VC is extracted at the sink end, and since it is periodically continued during the data service transmission and processing, the timestamp identifier extracted by the sink from the VC is used to indicate the end of the data service. Time information. When extracting, it can be performed before the VC members of VCG are aligned, or after each member is aligned.

If done before alignment, the timestamp identifier can take the minimum or maximum value of each VC member. If the minimum value is taken, the relative delay T1 includes the VCG delay compensation time. The calculation of the total time delay only needs to increase the shortest path delay of the SDH/SONET network. If the maximum value is taken, the relative delay T1 does not include the VCG. Delay compensation time, calculate the total time delay only need to increase the longest path delay of the SDH/SONET network.

If the alignment is performed, the timestamp identifier can take the timestamp identifier of any VC member. The relative delay T1 does not include the VCG delay compensation time. The calculation of the total time delay only needs to increase the longest path delay of the SDH/SONET network. .

The timestamp identifier and the service data packet described above are all carried by the VCG. Among them, there are five SDH VCG members: VC-11, VC-12, VC-2, VC-3, VC-4. And SONET There are 4 VCG members: VC-11, VC-2, VC-12, VC-3. According to the standard requirements, all VC members in a VCG must be the same VC. Different VCGs can include different types of VCs, which can ensure that all data packets are encapsulated in the same VC. type container for transmission. The VC described in the present invention may be any one of them, and each VC carries an overhead and also has a reserved overhead.

The third step: using the end time stamp identifier contained in the recovered VC minus the start time stamp identifier contained in the recovered data packet, the additional delay Tl of the data packet relative to the SDH/SONET network can be obtained. When the subtraction is less than the subtraction, it indicates that the timestamp counter has overflowed, and the complement should be used or the negative result should be added to the timestamp identifier maximum value TSmax. The specific time value of the relative delay can be obtained by multiplying the time stamp difference by the set timing duration.

The time stamp identifier described above is a specific timing information, and the number of bits required to transmit the time stamp identifier (TSbits) is determined by the maximum value TSmax of the time stamp identifier, TSmax ≤ 2 ^A TSbits - 1; the maximum measurable The relative delay (DMmax) is: DMmax = TSmax* 125us, and the relative delay exceeding DMmax may result in incorrect result of the final third step subtraction.

The above-mentioned data packet is a generic term, and may actually be any packet with a packet structure, such as an ATM cell, an Ethernet frame, an MPLS (Multi-Protocol Label Switching) frame, and an RPR (Resilient Packet). Ring, flexible packet ring) Frames, IP packets, etc.

In the first step, the VC overhead for transmitting the timestamp may be a defined VC overhead (such as H4, Jl, J2, etc.), or reserved unused VC overhead, or may be composed of a multiframe method. Overhead (such as MFI (Multi Frame Indicator), etc.). When the timestamp is passed using the multiframe mode, the recovered timestamp needs to be subtracted from the multiframe time required to insert and decompose the timestamp.

When virtual concatenation technology is used, the data payload will be split and composed into VCGs, which are transmitted in SDH network through two or more paths. Because the distance between the two or more paths and the number of network elements included in the path are not the same, VCG members cannot reach the end point at the same time; the sink receiving device must compensate for the delay difference and then reassemble the payload.

Applications: FIG. 2 is a schematic diagram of networking of an optical transmission network. The network is an SDH network, which includes two SDH sites, namely, Site A and Site B. There is an Ethernet service to be monitored between Site A and Site B. From the Ethernet FE (Fast Ethernet) port of Site A to the FE port of Site B, a virtual container VC-4 is used to carry the service.

In the example shown in Figure 2, the H4 byte overhead of VC-4 is used to pass the timestamp flag, and the multiframe structure is not used. Assuming that the timestamp identifier needs to be transmitted by 8 bits, TSbits = 8bits, TSmax < 2 ^A TSbits - 1 , the timestamp maximum value TSmax = 255, from DMmax = TSmax * 125us, the maximum measurable delay DMmax = 255 x 125us = 31,875ms.

' Assume that the data packet passed is an Ethernet frame, and a new overhead byte is added to the Ethernet frame to implement the timestamp identifier in the data packet. Of course, in other instances, the original reserved overhead byte in the Ethernet frame can also be used. To pass the timestamp identifier. The location of the #1 identifier is located at the frame header, and the frame carrying the timestamp is identified by adding a type field. The newly added type field is specifically used to indicate whether the time stamp is carried in the frame. In addition to the type field indicating that the frame has a time stamp, there is also an overhead of actually carrying the time stamp, and the test delay is used. Packets that are to be tested for latency need to add new overhead or use the original retention overhead. Only time-stamped packets can be tested for their delay, and the delay without adding packets is unknown. In this embodiment, the timestamp identifier uses only 8bits (as shown in Figure 3). '

Based on the SDH networking and parameter configuration above, in the example shown in Figure 2,

First, a timestamp needs to be established at the source end. A source counter can be used to generate the timestamp identifier. The source end timing continues to send the SDH frame to the sink through the SDH network. When transmitting, it is at the head of each SDH frame. Counter is incremented by 1, that is, a timing interval is added. For each SDH frame sent by point A, the H4 overhead changes once, and the time stamp value passed is the current value of the timer.

Assuming that the initial value of the counter is 1, the current time stamp in the corresponding frame is TS=100 when the 100th frame is transmitted, and the timing interval is 125us.

When performing relative delay measurement, the source can select a normal data service packet to monitor its delay condition, or it can send a dedicated data packet for measuring relative delay. In the process of transmitting the time stamp identification as the reference time, the processing flow of measuring the data service delay is as follows:

Step 1: When Point A receives an Ethernet frame from the FE port, it immediately returns Counter. The value (such as this example: TS=100) is inserted into the Ethernet frame. As shown in Figure 3, the time stamp is added to the data packet to carry the current timestamp identifier. At the same time, a new type of overhead is added, indicating that the frame carries a time stamp identifier. In this case, the new overhead is used. In other real-time modes, the original reserved overhead can also be used to carry the timestamp identifier or to carry the time stamp in the identifier frame. After GFP (Generic framing procedure) encapsulation, mapping, etc., it is sent from the SDH interface and sent to the B point as the sink end via the SDH network;

Step 2: Point B receives the VC-4 through its SDH interface, and recovers the Ethernet frame through GFP decapsulation. After corresponding processing, it is sent to the FE port of point B. When output by the FE port, the Ethernet is extracted and stripped. The timestamp identifier carried in the network frame, since the frame is the Ethernet frame received at point A in step 1, the timestamp identifier TS=100 carried in the packet is extracted, and the point B is extracted and engraved on the SDH interface. The time stamp i carried by H4 in the received VC-4. (as in this example: get TS = 135);

Step 3: Subtract the TS = 100 extracted from the VC-4 by the sink to subtract TS = 100 from the Ethernet frame. You can get 35, indicating that the extra delay of the Ethernet frame relative to the SDH network is 35 x.

Through the above three steps, you can measure the delay of a single packet relative to the transmission network.

If you need to get the full delay of the Ethernet frame, you only need to add the one-way fixed delay of the SDH network.

At the same time, the present invention can measure the relative delay of the data service of the SDH/SONET network in real time and without loss, and can provide the delay variation of the service of the different priority services of the blue control, which is convenient for the blue network to control the delay of the different priority services. The user compares and verifies the QoS guarantee of the network. ' .

Further, the delay data can be directly displayed on the network management device, and the test process is non-destructive to the business, facilitating engineering application and testing.

It can be seen from the above that the purpose of testing each actual data packet relative to the one-way delay of the SDH/SONET network is achieved by this method, and the delay of each data packet of the actual service can be indicated. The situation is beneficial to compare the actual delay of each priority service. Industrial applicability

The invention provides a method for measuring the relative delay of a data service in an optical transmission network, and uses the time stamp identification to realize the relative delay of the data service, and can measure the relative time of the data service of the SDH/SONET network in real time without loss. Delay, because it can provide relative delay data of a single data packet, it can be used to monitor the delay variation of different priority services, facilitate user comparison, and verify the QoS guarantee of the network. The delay data can be displayed on the network management device after being directly collected by the device. The test process is non-destructive to the business and convenient for engineering application and testing.

Claims

Claim

A method for measuring a relative delay of a data service in an optical transmission network, characterized in that: the source end periodically sends a timestamp identifier carried on the virtual container overhead to the sink end, and the source end time stamp identifier is sent after each transmission. Add a timing interval. When performing relative delay measurement, include the following steps:

S2: After receiving the data packet, the sink performs related processing and decapsulation, extracts a timestamp identifier in the data packet at the time of output, and acquires a timestamp identifier that is carried on the virtual container overhead at this time;

Knowledge, calculate the relative delay of the data packet relative to the optical transport network.

2. The method according to claim 1, wherein the source end has a time stamp generating device that generates a time stamp identifier at a fixed timing interval, and each time the source end timing continuously transmits the time stamp identifier. The stamp identifies a count of a timed interval.

3. The method according to claim 2, wherein the time stamp generating means is a timer at the source end, the timer is incremented at the frame header of each synchronous digital series SDH frame, and the source end transmits each Once, the value of the timestamp identifier is updated once and updated to the current count value of the timer.

4. The method according to claim 1, wherein the virtual container overhead of the bearer timestamp identifier is a defined virtual container overhead H4, or J1, or J2, or the unused virtual container overhead is reserved. , or the overhead of multiframe.

5. The method of claim 1, wherein in step S1, the step of adding a current timestamp identifier to the data packet is to add the current timestamp identifier to a reserved byte in an original data packet. , or add extra bytes in the packet anywhere.

The method according to claim 1, wherein, in step S2, the time at which the sink end extracts the timestamp identifier in the data packet when outputting is when the first bit of the output packet is selected, or When the last bit of the packet is output.

7. The method of claim 1, wherein the step of identifying the time stamp on the virtual container overhead in step S2 is performed before or after the alignment of the virtual container VC members of the virtual container group VCG. If the timestamp identifier is the value of the timestamp identifier in the VC member of each virtual container, the relative delay calculated in step S3 includes the VCG delay compensation time of the virtual container group, and the time stamp identifier is taken as each VC member. The time stamp in the middle identifies the maximum value, and the calculated relative delay in step 3 does not include the virtual container group VCG delay compensation time;

If the alignment is performed, the timestamp identifier takes the timestamp identifier in the VC member of any virtual container, and the relative delay calculated in step 3 does not include the virtual container group VCG delay compensation time.

8. The method according to claim 1, wherein the relative time delay is calculated in step S3, if the time stamp identifier obtained from the virtual container overhead is subtracted, less than the slave data packet obtained as the subtraction number. For the timestamp identifier, the subtraction should use the complement, or add the resulting negative result to the maximum timestamp identifier count value.

The method according to claim 1, wherein the number of bits required to be transmitted when the time stamp is transmitted is determined by a time stamp identification maximum value TSmax, and both satisfy TSmax < 2 ^A TSbits - 1 . Corresponding time stamp identification maximum value TSmax maximum relative delay DMmax = TSmax χ timing interval.

10. The method according to claim 1, wherein the data packet is any data packet having a packet structure, and the data packet type comprises an ATM cell, or an Ethernet frame, or a multi-protocol label switching MPLS frame. , or resilient packet ring RPR frames, or IP packets.