WO2012088843A1

WO2012088843A1 - Method and system for bidirectional forwarding detection

Info

Publication number: WO2012088843A1
Application number: PCT/CN2011/076007
Authority: WO
Inventors: 周蕙菁
Original assignee: 中兴通讯股份有限公司
Priority date: 2010-12-29
Filing date: 2011-06-21
Publication date: 2012-07-05
Also published as: CN102064981A

Abstract

The present invention provides a method and system for Bidirectional Forwarding Detection (BFD). The method includes: a BFD local end transmits a first detection message which carries the network quality detection information(101); a BFD opposite end receives the first detection message, and transmits a second detection message which carries the network quality detection information(102); the BFD local end receives the second detection message, and detects the network quality according to the network quality detection information in the first detection message and the network quality detection information in the second detection message(103); the BFD local end reports the detection result of network quality according to preset reporting conditions(104).

Description

Bidirectional forwarding detection method and system

Technical field

The bidirectional forwarding detection (BFD) technology of the present invention specifically relates to a method and system for implementing dual-issue forwarding detection by using a BFD protocol.

Background technique

BFD provides a common low-cost fast fault detection service for various upper-layer control protocols. The upper-layer control protocol can use the services provided by BFD to determine the corresponding operations, such as re-routing. It is called bidirectional because the BFD protocol provides connectivity detection in both directions of the link through the three-way handshake mechanism. BFD can quickly detect the interface and link faults on the forwarding path, the forwarding engine fault of the node, and notify the upper layer protocol of the fault, so that the upper layer protocol can converge quickly.

Currently, BFD is only used to detect link connectivity. That is, link information obtained through BFD is either connected or disconnected. In some cases, the link usually has a small amount of packet loss, and then a large amount of packet loss, and finally the chain is broken. When there is a small amount of packet loss in the transmission, the current BFD may not be discovered. The service may be affected at this time. However, BFD needs to wait until the packet loss reaches a certain level to detect the link failure.

Summary of the invention

The technical problem to be solved by the present invention is to provide a bidirectional forwarding detection method and system for effectively preventing chain scission. To solve the above technical problem, the present invention provides a bidirectional forwarding detection method, which includes:

The two-way forwarding detection (BFD) sends the first detection packet carrying the network quality detection information to the local end; the peer end of the BFD receives the first detection packet, and sends a second detection packet carrying the network quality detection information; The BFD local end receives the second detection packet, and detects network quality according to network quality detection information in the first detection packet and network quality detection information in the second detection packet; The terminal reports the network quality detection result according to the preset reporting condition. The network quality detection information includes a message sequence number, and the method further includes:

The BFD local end determines whether to drop packets by comparing the message sequence number in the first detection packet with the message sequence number in the second detection packet. The network quality detection information includes a message sequence number, and the method further includes:

The local end of the BFD sends a plurality of first detection messages in sequence, wherein the sequence number of the message is regularly increased or decreased;

After receiving the returned second detection packet, the BFD local end compares the packet sequence number in the current received packet with the packet sequence number in the previous received packet, and calculates the number of lost packets.

The network quality detection information includes timestamp information. The method further includes: the BFD local end calculating delay or jitter according to the timestamp information and the current timestamp information in the second detection packet.

The first detection message and the second detection message use an ECHO message.

The present invention also provides a bidirectional forwarding detection system, which includes a bidirectional forwarding detection (BFD) local end and a peer end of the BFD, where:

The local end of the BFD includes: a first packet sending and receiving unit, a network quality determining unit, and a reporting unit, where:

The first packet sending and receiving unit is configured to: send a first detection message carrying network quality detection information; and receive a second detection message;

The network quality determining unit is configured to: detect network quality according to network quality detection information in the first detection packet and network quality detection information in the second detection packet;

The reporting unit is configured to: report the network quality detection result when the reporting condition is met; the opposite end of the BFD includes a second packet sending and receiving unit, and the second packet sending and receiving unit is configured to: receive the first detection report And transmitting the second detection report carrying network quality detection information Text.

The network quality detection information includes a message sequence number;

The network quality determining unit is configured to detect the network quality according to the following manner: determining whether the packet is lost by comparing the message sequence number sent by the packet sending and receiving unit with the message sequence number received by the packet sending and receiving unit.

The network quality detection information includes a message sequence number;

The first packet sending and receiving unit is further configured to: send a plurality of first detection messages in sequence, wherein the message sequence number is regularly increased or decreased;

The network quality determining unit is configured to detect the network quality according to the following manner: after receiving the returned second detection packet, calculating, by sequentially comparing the message sequence number in the current received message with the message sequence number in the previous received message, The number of lost packets.

The network quality detection information includes timestamp information;

The network quality determining unit is configured to detect the network quality according to the following manner: calculating the delay or jitter according to the timestamp information and the current timestamp information in the second detection message.

The present invention further provides a bidirectional forwarding detection apparatus, including: a first packet transceiving unit, a network quality judging unit, and a reporting unit, wherein:

The first packet sending and receiving unit is configured to: send a first detection packet carrying the network quality detection information to the first BFD peer end; and receive the second detection of the network quality detection information returned by the first BFD peer end Message

The reporting unit is configured to: report the network quality detection result when the reporting condition is met.

The two-way forwarding detection device further includes:

And a second packet sending and receiving unit, configured to: receive a third detection packet that carries the network quality detection information that is sent by the second BFD peer end, and return a fourth detection that carries the network quality detection information to the second BFD peer end Message. The network quality detection information includes a message sequence number;

The network quality detection information includes a message sequence number;

The network quality detection information includes timestamp information;

The bidirectional forwarding detection method and system of the present invention detects network quality, such as packet loss, delay, and jitter, while detecting network switching, and is applied to all systems that need to enable BFD detection links, and the detected network quality. It can be used as a reference for upper-layer services. When the network status is unstable, but BFD has not been broken before the link is effectively prevented, the link will be taken to prevent the link from being interrupted. BRIEF abstract

1 is a schematic diagram of a bidirectional forwarding detection method according to an embodiment of the present invention;

2 is a schematic diagram of a format of an ECHO packet according to an embodiment of the present invention;

Figure 3 is a schematic diagram of an embodiment of implementing bidirectional forwarding detection using ECHO messages. Preferred embodiment of the invention

The main idea of the bidirectional forwarding detection method and system of the present invention is that in detecting the continuity of the network When detecting network quality, such as packet loss, delay, jitter, etc., the transmission quality is applied to all needs to be enabled.

In the BFD detection link system, the detected network quality can be referenced by the upper-layer service. If the network status is unstable, but the BFD has not been broken before the link is effectively prevented, the measures are taken to prevent the link from actually failing. Causes business interruption.

As shown in FIG. 1, the bidirectional forwarding detection method according to an embodiment of the present invention includes step 101-step.

104:

Step 101: The BFD local end sends a first detection packet carrying network quality detection information. Step 102: The peer end of the BFD receives the first detection packet, and sends a second detection packet carrying network quality detection information.

Step 103: The BFD local end receives the second detection packet, and detects network quality according to the network quality detection information in the first detection packet and the network quality detection information in the second detection packet.

Step 104: The BFD local end reports the network quality detection result according to the preset reporting condition. The basis for detecting network quality may be packet sequence number, timestamp information, etc., such as:

The network quality detection information includes the packet sequence number, and the BFD local end determines whether the packet is lost by comparing the number of the sent and received packets; or

The network quality detection information includes a packet sequence number, and the BFD local end sends a plurality of detection packets in sequence, and the sequence number of the message is regularly incremented or decremented, and the increment and decrement may be a message difference of 1 each. After receiving the detected test packet, the BFD local end calculates the number of lost packets by comparing the sequence number of the currently received packet with the sequence number of the received packet in the previous received packet; or

The network quality detection information includes timestamp information, and the BFD local end calculates delay or jitter according to the timestamp information and the current timestamp information in the received detection message.

Of course, the system can provide the packet sequence number and/or the timestamp letter, packet, or other information according to the network quality management requirement, and set the different reporting conditions, such as the preset reporting threshold or the periodic reporting, so that the BFD device can The set reporting conditions report the network quality, which in turn enables the BFD device to have the network quality detection function while the network link is detected.

The detection packet can be implemented in multiple packet formats. The following is an example of using ECHO packets as an example: First, the ECHO message fields in the present invention are briefly described as follows:

As shown in Figure 2, the ECHO request packet format field description:

Version (V): 2 bit ECHO message version, specified as 1.

Message Type (PT): 8 bit, ECHO is defined as 1.

Packet Length ( Length): The length of the entire ECHO packet, in bytes.

The local discriminator (My Discriminator) is the same as the My Discriminator field in the BFD document. It is used to identify the BFD session that sends ECHO packets.

Your Discriminator is the same as the Your Discriminator field in the BFD document. If the peer packet has not been received, the field is filled with 0.

NTP timestmp (NTP timestmp): 64 bit, NTP timestamp when ECHO is sent.

Absolute timestamp represented by the NTP (Network Time Protocol) format. When the ECHO message is sent, the current timestamp is indicated, and compared with the timestamp when the receiver returns, to measure the loop delay. If the sending system cannot get this time reading, set this field to 0.

Serial Number (SN): Accumulate 1 each time an ECHO message is sent, and use it to detect packet loss and out of order. The initial value of SN is random, which prevents plaintext attacks to a certain extent.

System relative timestamp (timestamp): The timestamp is continuously monotonically increasing when transmitting, even when no ECHO message is sent. When receiving, as long as the received message sequence number is not lost, it is known that no data loss occurs. And, as long as the time difference between the messages before and after is compared, the time interval for sending the message can be determined. If the system does not support the NTP timestamp, the timestamp can be used to measure the loop delay. The initial timestamp must be chosen at random.

The service informs the BFD device to create a session and informs the BFD device of the network quality threshold (including packet loss, delay, and jitter). BFD can detect that the network quality is poor according to the network quality threshold, and a quality parameter exceeds the threshold. Then report the business.

The process of creating a session on the BFD device includes: The local end notifies the peer to support the ECHO function in the BFD negotiation; the peer also informs the local end to support the ECHO function; the session negotiation succeeds, the status of both parties is UP, and the ECHO function is enabled.

Take a BFD session as an example. Set A as the local BFD and B as the peer. For details, see BFD session detection network quality. Figure 3 shows the following steps: Step 301: A terminal provides a timer function, and the BFD application sets a timing to send an ECHO message. Before sending the first ECHO message, the A end randomly generates an SN, a timestamp, as an initial value, and each subsequent transmission. a message, monotonically increasing;

Step 302: The ECHO sending timer expires, constructing and sending an ECHO packet, and recording the sent SN sequence number, NTP time, and timestamp value;

The A-side constructs the ECHO packet, and fills in the fields according to the ECHO packet format: The local discriminator and the remote discriminator value are respectively filled in according to the actual values in the session. If the BFD packet of the B-side is not received, the remote authentication is performed. If the A port supports NTP, you need to fill in the NTP timestmp field. If it is not supported, fill in 0; SN takes the current value to be sent, and adds 1 after sending; timestamp is not necessarily absolute time, nor strict unit The rule may be the system tick value, which may be the number of milliseconds after the system is powered on, as long as the A end can recognize and the accuracy is sufficient to calculate the delay and jitter;

Step 303: The BFD session receives the ECHO packet and forwards it back to the A end according to the forwarding path.

Step 304: The A end receives the ECHO packet sent by the B end, records the timestamp at this time, records the received SN sequence number, calculates the packet loss, delay, and jitter, and reports when the threshold is exceeded.

1. Compare the received SN sequence number with the sent SN sequence number to see if there is any packet loss. If there is a packet loss, calculate the packet loss rate:

If the first packet is received, the current sequence number is the same as the sequence number of the first ECHO packet sent. If they are inconsistent, they may be lost packets or out of order. Packet hypothesis calculation: The current message sequence number minus the first ECHO sequence number sent is the number of packet loss; if they are consistent, it means no packet loss;

1.2 If it is a subsequent packet, it is compared with the previous received packet sequence number. If it is continuous with the previous received packet, there is no packet loss, and the currently received sequence number is updated. Otherwise, the packet loss is calculated: Current If the message sequence number is before the last received sequence number, the packet loss statistics are decremented by 1 and the currently received sequence number is not updated. The current message sequence number is not continuous after the last received sequence number, and the current message sequence number is subtracted. The value obtained by subtracting 1 from the last received message number is the number of lost packets.

2. Compare the timestamp of the received packet with the timestamp of the sending time in the packet, and calculate the network delay of the round trip of the packet:

Obtain the current NTP time or timestamp time after receiving the packet, and extract the NTP in the packet. The timestamp and timestamp, if the NTP time protocol is enabled, the NTP time is used first to calculate the delay and jitter; otherwise, the timestamp is used to calculate the delay and jitter. The current NTP time (or timpstamp) is subtracted from the NTP time (or tempstamp) difference in the text, and converted to ms. This is the ECHO sent from A, and the B-end forwarding returns the loopback time of the A end. Ignore the B-side forwarding processing time, which can be considered as the network round-trip delay. Some systems require one-way delay, and the round-trip delay can be divided by 2, that is, the estimated value of the network one-way transmission delay is obtained.

3. Each time a message is received, a delay value is calculated, and the adjacent delays are compared, and the absolute value of the difference is taken, that is, the current jitter value.

The obtained packet loss, delay, and jitter are compared with the service setting threshold. When the service reporting threshold is exceeded, the current network quality of the service is notified.

The invention can detect the link quality in real time through BFD. When the network has quality problems, it may not be very serious, there is quantitative network quality data reporting, and each service analyzes the data, and the service senses the network status as early as possible. Intervene to adjust the transmission mode or transmission rate, reduce the network burden, avoid network transmission interruption as much as possible, such as determining the corresponding measures according to their own characteristics, ignoring or mitigating the current link burden or switching to the backup link. How the business analyzes the relevant data and what measures are taken is outside the scope of the description of the present specification.

In order to implement the above method, the present invention further provides a bidirectional forwarding detection system, where the system includes a BFD local end and a peer end of the BFD, where:

The BFD local end includes: a packet sending and receiving unit, a network quality determining unit, and a reporting unit, where the packet sending and receiving unit is configured to: send a first detection message carrying network quality detection information; and receive a second detection message;

The network quality determining unit is configured to: detect network quality according to the network quality detection information in the first detection packet and the network quality detection information in the second detection packet;

The reporting unit is configured to: report the network quality detection result when the reporting condition is met;

The peer end of the BFD includes a second packet sending and receiving unit, and the second packet sending and receiving unit is configured to: receive the first detecting packet; and send the second detecting packet that carries network quality detecting information.

The network quality detection information includes a packet sequence number, and the network quality determining unit is Compare the number of sent and received packets to determine whether to drop packets.

The network quality detection information includes a packet sequence number, and the packet sending and receiving unit of the BFD local end sends a plurality of detection packets in sequence, and the message sequence number is regularly incremented or decremented, and the network quality determining unit receives After the detected packet is returned, the packet loss number is calculated by comparing the sequence number of the currently received packet with the sequence number of the packet received in the previous packet.

The network quality detection information includes timestamp information, and the network quality determining unit calculates delay or jitter according to the timestamp information and the current timestamp information in the received detection message.

The detection packet uses an ECHO protocol packet.

The method and system of the present invention use the BFD protocol to detect not only the link is disconnected, but also to timely detect and feed back the network quality status to the service, provide service reference to adjust network traffic, and take early measures to prevent service interruption.

One of ordinary skill in the art will appreciate that all or a portion of the above steps may be accomplished by a program instructing the associated hardware, such as a read-only memory, a magnetic disk, or an optical disk. Alternatively, all or part of the steps of the above embodiments may also be implemented using one or more integrated circuits. Correspondingly, each unit in the foregoing embodiment may be implemented in the form of hardware, or may be implemented in the form of a software function module. The invention is not limited to any specific combination of hardware and software.

The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. In view of the present invention, various other modifications, equivalents, improvements, etc., should be made without departing from the spirit and scope of the invention. It is included in the scope of protection of the present invention.

Industrial applicability

The bidirectional forwarding detection method and system of the present invention detects network quality, such as packet loss, delay, and jitter, while detecting network switching, and is applied to all systems that need to enable BFD detection links, and the detected network quality. It can be used as a reference for upper-layer services. When the network status is unstable, but BFD has not been broken before the link is effectively prevented, it will prevent the link from being interrupted and cause traffic interruption. It has strong industrial applicability.

Claims

Claim

1. A two-way forwarding detection method, the method comprising:

The two-way forwarding detection (BFD) sends the first detection packet carrying the network quality detection information to the local end; the peer end of the BFD receives the first detection packet, and sends a second detection packet carrying the network quality detection information;

The BFD local end receives the second detection packet, and detects network quality according to network quality detection information in the first detection packet and network quality detection information in the second detection packet; The terminal reports the network quality detection result according to the preset reporting condition.

2. The bidirectional forwarding detection method according to claim 1, wherein the network quality detection information includes a sequence number, and the method further includes:

The BFD local end determines whether to drop packets by comparing the message sequence number in the first detection packet with the message sequence number in the second detection packet.

3. The bidirectional forwarding detection method according to claim 1, wherein the network quality detection information includes a "^ text number, the method further includes:

The method of detecting the bidirectional forwarding according to claim 1, wherein the network quality detection information includes timestamp information; the method further includes:

The local end of the BFD calculates the delay or jitter according to the timestamp information and the current timestamp information in the second detection packet.

The bidirectional forwarding detection method according to any one of claims 1 to 4, wherein the first detection message and the second detection message use an ECHO message.

6. A two-way forwarding detection system, the system comprising a bidirectional forwarding detection (BFD) local end and a The opposite end of the BFD, where:

The reporting unit is configured to: report the network quality detection result when the reporting condition is met; the opposite end of the BFD includes a second packet sending and receiving unit, and the second packet sending and receiving unit is configured to: receive the first detection report And sending the second detection message carrying network quality detection information.

7. The bidirectional forwarding detection system according to claim 6, wherein

The network quality detection information includes a message sequence number;

8. The bidirectional forwarding detection system according to claim 6, wherein

The network quality detection information includes a message sequence number;

9. The bidirectional forwarding detection system according to claim 6, wherein

The network quality detection information includes timestamp information;

The network quality determining unit is configured to detect network quality in the following manner: according to the The timestamp information and the current timestamp information in the second detection packet calculate delay or jitter.

The bidirectional forwarding detection system according to any one of claims 6-9, wherein the first detection message and the second detection message use an ECHO message.

11. A bidirectional forwarding detection apparatus, comprising: a first packet transceiver unit, a network quality judging unit, and an upper unit, wherein:

12. The bidirectional forwarding detection apparatus of claim 11, further comprising:

And a second packet sending and receiving unit, configured to: receive a third detection packet that carries the network quality detection information that is sent by the second BFD peer end, and return a fourth detection that carries the network quality detection information to the second BFD peer end Message.

13. The bidirectional forwarding detection apparatus according to claim 11, wherein

The network quality detection information includes a message sequence number;

14. The bidirectional forwarding detection apparatus according to claim 11, wherein

The network quality detection information includes a message sequence number;

15. The bidirectional forwarding detection apparatus according to claim 11, wherein

The network quality detection information includes timestamp information;

The bidirectional forwarding detection apparatus according to any one of claims 11 to 13-15, wherein the first detection message and the second detection message use an ECHO message.