Patent Description:
In an existing communications device, most solutions for performing time synchronization between devices are implemented according to a precision time protocol (Precision Time Protocol, PTP) standard of a network measurement and control system proposed by the Institute of Electrical and Electronics Engineers (Institute of Electrical and Electronics Engineers, IEEE), and the standard is also referred to as an IEEE <NUM> protocol.

A core idea of the IEEE <NUM> protocol is to use a master-slave clock mode. During synchronization, a master device periodically issues PTP packets, a slave device receives timestamp information sent by the master device. A master-slave line time delay and a master-slave time offset are calculated based on the timestamp information, and a local time is adjusted by using the time offset, so that a slave device time is kept consistent with a master device time, to implement time synchronization.

The IEEE <NUM> protocol requires that a delay between a stamping point and a physical layer medium (for example, an optical fiber) be stable and that there be no asymmetric delay change. However, in an existing network system, there is an asymmetric link delay, and a key to resolve an asymmetric delay problem is how to obtain the delay. In a plurality of current clock synchronization systems, a delay in a PHY chip is largely considered. However, internal processing, such as first in first out (First-In-First-Out, FIFO), also exists between the stamping point and an egress of a media conversion module, and a delay of the internal processing is uncertain. An existing solution is to estimate a delay of the media conversion module based on internal circuit processing. In this solution, the obtained delay may be inaccurate, resulting in relatively low synchronization performance of the <NUM> protocol.

<CIT> relates to method and system for compensated time stamping for time-sensitive network communications.

<CIT> relates to method, apparatus, and system for generating timestamp.

<CIT> relates to network time protocol precision timestamping service.

<CIT> relates to method and apparatus for aligning time references when separated by an unreliable data packet network.

This application provides a packet processing method and a network device, so as to accurately determine a delay of processing a packet by a media conversion module, and help improve synchronization performance of a <NUM> protocol.

Various specific embodiments have been defined in the respective dependent claims.

To make the objectives, technical solutions, and advantages of this disclosure clearer, the following further describes the implementations of this disclosure in detail with reference to the accompanying drawings. While the description often refers to embodiments, the embodiments of the invention are those which comprise at least all the features of an independent claim. Any embodiment which does not fall within the scope of the claims does not form part of the invention, but rather included as an illustrative example that is useful for understanding the invention.

In a mobile communications system, to ensure service quality of wireless communications, a communications network and a communications device have a strict requirement for clock synchronization. In particular, with development of a fifth-generation mobile communications technology of the mobile communications network, the mobile communications system also has a stricter requirement for clock synchronization precision. IEEE <NUM> was originally generated because precise time control is required in the industrial control field. However, because the IEEE <NUM> supports hardware stamping, the IEEE <NUM> can obtain high-precision time synchronization of a sub-microsecond µs level. In recent years, the IEEE <NUM> was introduced into a telecommunications network by the International Telecommunication Union-Telecommunication Standardization Sector (International Telecommunication Union-Telecommunication Sector, ITU-T) to provide precise time synchronization for a time division wireless system such as time division-synchronous code division multiple access (Time Division-Synchronous Code Division Multiple Access, TD-SCDMA), code division multiple access <NUM> (Code Division Multiple Access <NUM>, CDMA <NUM>), or long term evolution-time division duplex (Long Term Evolution-Time Division Duplex, LTE-TDD).

With reference to <FIG>, the following describes in detail a concept, a term, and a requirement of time synchronization, and a technical principle, a networking scenario, and a deployment consideration of the <NUM> protocol from a technical perspective.

<FIG> is a schematic diagram of a time synchronization process of an IEEE <NUM> protocol. Used packets are a synchronization (Sync) packet, a delay request (Delay_Req) packet, and a delay response (Delay_Resp) packet. A master clock sends a Sync packet to a slave clock at a moment t<NUM>, where the Sync packet carries a sending time of a t<NUM> timestamp of the Sync packet. The slave clock receives the Sync packet at a moment t<NUM>, generates a t<NUM> timestamp locally, and obtains the t<NUM> timestamp from the Sync packet. The slave clock sends a Delay_Req packet to the master clock at a moment t<NUM>, and generates a t<NUM> timestamp locally. The master clock receives the Delay_Req packet at a moment t<NUM>, and generates a t<NUM> timestamp locally. Then, the master clock adds the t<NUM> timestamp to the Delay_Resp packet, and returns the Delay _Resp packet including the t<NUM> timestamp to the slave clock. The slave clock receives the Delay _Resp packet, and extracts the t<NUM> timestamp from the packet. In this way, the slave clock obtains four timestamps. A master-slave line Delay and a master-slave time Offset can be calculated from the four timestamps. A line delay from the master clock to the slave clock is set to a delay <NUM>, and a line delay from the slave clock to the master clock is set to a delay <NUM>. A calculation process is as follows: <MAT> <MAT>.

It is assumed that Delay <NUM> = Delay <NUM> = Delay. The following equations are obtained: <MAT> <MAT>.

The slave clock can adjust time of the slave clock based on a calculated offset value, so as to implement synchronization with the master clock. The foregoing calculation is based on an assumption that the link delay from the master clock to the slave clock is equal to the link delay from the slave clock to the master clock.

<FIG> is a schematic diagram of a possible application scenario according to an embodiment of this application. Specifically, <FIG> is a partial internal structural diagram of a network device. As shown in <FIG>, the network device includes an optical module, a PHY chip, a system clock, and a <NUM> protocol unit, and delays before and after the optical module are a delay <NUM> and a delay <NUM> respectively. The following first describes the modules used in <FIG>.

PHY chip (PHY chip): The PHY may be implemented by using a field programmable gate array (field programmable gate array, FPGA) or an application-specific integrated circuit (application specific integrated circuit, ASIC). The PHY may include a serdes, a bit demultiplexer (bit demultiplexer, bit demux) circuit, a first in first out buffer (first in first out buffer, FIFO buffer), a descrambling circuit, and an aggregation circuit. The PHY may be a component in a network interface card (network interface card, NIC), and the NIC may be a line card (line card, LC) or a physical interface card (physical interface card, PIC). The PHY may be connected to a media access controller (media access controller, MAC) by using a media independent interface (media independence interface, MII). The PHY chip may include one PHY or a plurality of PHYs.

Optical module: In short, the optical module is used for optical-to-electrical conversion. A transmitting interface converts an electrical signal into an optical signal. After the optical signal is transmitted through an optical fiber, a receiving interface converts the optical signal into the electrical signal.

<NUM> protocol unit: <NUM> is actually a master-slave synchronization system. In a process of system synchronization, the master clock periodically issues PTP time synchronization and time information, and the slave clock port receives timestamp information sent by the master clock port. The system calculates a master-slave line time delay and a master-slave time offset based on the timestamp information, and adjusts a local time by using the time offset, so that a frequency and a phase of a slave device time are kept consistent with those of a master device time. The <NUM> protocol can simultaneously implement frequency synchronization and phase synchronization.

System clock: Usually, the system clock is a clock system. The system clock is a circuit that includes an oscillator (a signal source), a timing wake-up device, a frequency divider, and the like. The system clock is a pulse of an entire system. Usually, a processor needs to be driven by the clock to complete instruction execution.

Usually, a timestamp generated when the network device sends a packet is completed by a service chip next preceding the media conversion module. Similarly, a timestamp generated when the network device receives a packet is completed by a service chip next following the media conversion module. In other words, actually, the timestamp generated when the network device sends the packet does not consider a time period during which the packet passes through the media conversion module, and a time of actually sending the packet should be later than the timestamp generated when the packet is sent. The timestamp generated when the network device receives the packet does not consider a time period during which the packet passes through the media conversion module. The time of actually receiving the packet should be earlier than the timestamp generated when the packet is received.

<FIG> is a schematic block diagram of a packet processing method <NUM> according to an embodiment of this application. As shown in <FIG>, the method <NUM> may be performed by a control unit in a network device. For example, the control unit may be implemented by a CPU or an FPGA. The method <NUM> includes the following steps.

A first network device receives a first packet by using a first receiving interface of a media conversion module of the first network device, where the first packet includes a first alignment marker AM.

The first network device sends a second packet by using a first sending interface of the media conversion module, where the second packet includes the first AM, and the second packet is the first packet processed by the media conversion module.

The first network device calculates a time interval T<NUM> between a time at which the media conversion module receives the first packet including the first AM and a time at which the media conversion module sends the second packet including the first AM.

The first network device receives a third packet by using the first receiving interface, and sends, by using the first sending interface, the third packet processed by the media conversion module.

The first network device uses the T<NUM> to compensate for a first timestamp at which the first network device receives or sends the third packet.

The media conversion module is an optical module. In addition to converting an optical signal into an electrical signal, the optical module may further convert the electrical signal into the optical signal.

For ease of understanding, the following uses the optical module as an example to describe the technical solutions in this embodiment of this application in detail.

It should be further understood that, when the T<NUM> is calculated in this embodiment of this application, a data stream may be input into the media conversion module, and the data stream may include a plurality of packets. A person skilled in the art understands that the data stream may be data of a physical layer, and the packet may be data of a MAC layer. The data stream may include a plurality of data blocks, and each data block in the data stream is obtained by performing physical layer encoding on an Ethernet frame stream. An alignment marker (alignment marker, AM) is periodically inserted after the physical layer encoding is performed on the Ethernet frame stream. Such a cycle may be referred to as a data cycle. The AM is also a data block. Inserting the AM into the data stream may mean that the AM is included in a packet. For ease of understanding, the following first describes in detail the data block in the data stream.

The physical layer encoding may be <NUM>-bit/<NUM>-bit encoding, or may be <NUM>-bit/<NUM>-bit encoding. When the physical layer encoding is <NUM>-bit/<NUM>-bit encoding, a quantity of bits included in one data block is <NUM>. When the physical layer encoding is <NUM>-bit/<NUM>-bit encoding, a quantity of bits included in one data block is <NUM>. In the data block of <NUM> bits, two bits may be a synchronization header. In the data block of <NUM> bits, two bits may be a synchronization header.

For example, according to a <NUM> Gigabit Ethernet (Gigabit Ethernet, GE) standard in an IEEE <NUM>. 3ba, data transmitted in one data cycle may be <NUM> data blocks. The <NUM> data blocks include the AM and <NUM> data blocks. The AM is transmitted before the <NUM> data blocks. A quantity of bits included in each of the <NUM> data blocks is <NUM>. In other words, usually, the data transmitted in one data cycle includes one AM and a plurality of data blocks, and the plurality of data blocks form a data block group. In other words, after the AM is inserted, data blocks other than the AM in the data transmitted in one data cycle are data blocks in the data block group. In the data transmitted in one data cycle, the quantity of bits included in each of the plurality of data blocks is equal to the quantity of bits included in the AM.

Optionally, steps S110, S120, and S130 may be performed only once, and the calculated T<NUM> is stored in the first network device. When the third packet needs to be sent or received, the T<NUM> may be directly used to compensate for the timestamp at which the third packet is sent or received. In other words, steps S <NUM> and S150 may be performed for a plurality of times.

Optionally, but not falling under the scope of the claims, the third packet may be the first packet. In other words, the first network device may compensate, in real time, the timestamp at which the first network device receives or sends the first packet. Specifically, if the first packet is sent by the first network device to a second network device, the first network device may add, to the first packet at the first sending interface of the media conversion module, an interval between the time at which the first packet arrives at the first receiving interface and the time at which the first packet arrives at the first sending interface, so that the second network device can calculate an accurate moment at which the first network device sends the first packet.

Optionally, the third packet may further be a packet received after the first network device receives the first packet by using the second receiving interface. To be specific, the first network device may calculate a delay in advance, and perform compensation in a subsequent packet. This example is used to describe this application in the following, but this embodiment of this application is not limited thereto.

Therefore, according to the method for measuring a delay in this embodiment of this application, a time interval before and after a packet passes through the media conversion module is recorded, and the time interval is used to correct a timestamp of sending or receiving a packet. This can accurately determine the delay of the packet through internal processing of the media conversion module, and further improve synchronization performance of a <NUM> protocol.

Optionally, in this embodiment of this application, the calculating, by the first network device, a time interval T<NUM> between a time at which the media conversion module receives the first packet including the first AM and a time at which the media conversion module sends the second packet including the first AM includes: recording, by the first network device, a first moment when receiving the first packet by using the first receiving interface and when determining that the first packet includes the first AM; recording, by the first network device, a second moment when sending the second packet by using the first sending interface and when determining that the second packet includes the first AM; and determining, by the first network device, a time interval between the first moment and the second moment as the time interval T<NUM>.

Specifically, the first network device may start a counter at the first moment. The first network device may stop the counter at the second moment, and obtain a count value N, where N is a positive integer, and a clock cycle of the counter is t. Further, the first network device may determine N * t as the T<NUM>. It should be understood that the clock cycle t of the counter may mean that the count value is increased by <NUM> at an interval of a time t.

Measuring the delay by using the counter is simple and easy to implement. The delay measurement method may be implemented by both hardware and software.

A media conversion module <NUM> of the network device in <FIG> is used as an example to describe the technical solutions in this embodiment of this application in detail. As shown in <FIG>, the media conversion module <NUM> includes at least a network interface <NUM>, a service processing unit <NUM>, and a delay measurement unit <NUM>. The media conversion module <NUM> may be configured to perform some or all of the steps or the procedures of the method <NUM> for measuring a delay in this embodiment of this application. For example, when a data stream needs to enter the inside of the media conversion module <NUM>, a processing requirement of the service processing unit <NUM> is that parallel-to-serial conversion of data usually needs to be performed by using the network interface <NUM>. For example, the network interface may be a serdes interface, and the serdes interface may be either a serializer or a deserializer. Parallel-to-serial conversion is a mainstream time division multiplexing (time division multiplexing, TDM) and peer-to-peer (peer-to-peer, P2P) serial communications technology. To be specific, a plurality of low rate parallel signals are converted into high rate serial signals at a transmit end, and high rate serial signals are transmitted through a transmission medium (an optical cable or a copper wire). Finally, the high rate serial signals are converted back into low rate parallel signals at a receive end. The data stream after the parallel-to-serial conversion may be a data stream into which an AM has been inserted. It should be understood that, inserting the AM into the data stream may be performed by the media conversion module <NUM>, or may be performed by a service chip before the data stream flows into the media conversion module <NUM>. This is not limited in this embodiment of this application. Further, a data stream that passes through the network interface <NUM> may be bypassed to the delay measurement unit <NUM>. The delay measurement unit <NUM> may identify a specific AM in the data stream. At the same time, the data stream is further processed by the service processing unit <NUM>, and before the data stream flows out of the network interface <NUM>, the data stream is bypassed to the delay measurement unit <NUM> again, and the specific AM is identified again. At moments at which the delay measurement unit <NUM> identifies the specific AM twice, the delay measurement unit <NUM> may respectively generate two pulse signals, and the two pulse signals are recorded as an FP1 and an FP2 respectively. A timer may be started inside the delay measurement unit <NUM>, and the FP1 and the FP2 are used as a start and an end of the timer. A time recorded by the timer at an end moment may be a delay during which the data stream passes through the service processing unit <NUM>. Alternatively, a high-frequency counter may be started inside the delay measurement unit <NUM>. Similarly, the FP1 and the FP2 are used as a start and an end of the counter, and a product of a value recorded by the high-frequency counter at an end moment and a cycle of the high-frequency counter may be used as a delay during which the data stream passes through the service processing unit <NUM>. Finally, the delay measured by the delay measurement unit <NUM> may be used to correct a timestamp at which the network device receives or sends some packets.

Optionally, in this embodiment of this application, the method further includes: receiving, by the first network device, a fourth packet by using a second receiving interface of the media conversion module, where the fourth packet includes a second AM; sending, by the first network device, a fifth packet by using a second sending interface of the media conversion module, where the fifth packet includes the second AM, and the fifth packet is the fourth packet processed by the media conversion module; calculating, by the first network device, a time interval T<NUM> between a time at which the media conversion module receives the fourth packet including the second AM and a time at which the media conversion module sends the fifth packet including the second AM; and receiving, by the first network device, a sixth packet by using the second receiving interface, and sending, by using the second sending interface, the sixth packet processed by the media conversion module, where a receiving direction and a sending direction of the third packet are opposite to those of the sixth packet, and the first network device uses the T<NUM> to compensate for a second timestamp at which the first network device receives or sends the sixth packet.

Similarly, the sixth packet may be the fourth packet, or the sixth packet is a packet received after the first network device receives the fourth packet by using the second receiving interface.

Specifically, the media conversion module <NUM> may be a media conversion module of a network device. A delay during which a data stream in either of the receiving direction and the sending direction of the network device passes through the service processing unit <NUM> in the media conversion module <NUM> may be measured by using the foregoing method <NUM>. For example, the any direction may be the sending direction or the receiving direction. However, a delay during which a data stream in the other direction passes through the service processing unit in the media conversion module <NUM> may be measured by using an existing delay measurement method. For example, the delay of the media conversion module may be estimated based on internal circuit processing. In actual application, the method <NUM> may also be applied in two directions of the network device, to be specific, the method <NUM> is used in both the receiving direction and the sending direction. This is not limited in this embodiment of this application.

Optionally, the receiving interface and the sending interface in this embodiment of this application may be multiplexed, to be specific, it may be understood that the first receiving interface may be the second sending interface, and the first sending interface may be the second receiving interface. A delay in one direction may be first measured, and then a delay in the other direction is measured.

In the foregoing method, a delay of internal processing of the media conversion module is used to compensate for timestamps in both the receiving direction and the sending direction. This can further improve synchronization performance of a <NUM> protocol.

Optionally, in this embodiment of this application, the third packet is a packet that is sent by a first service chip of the first network device to a second network device by using the media conversion module, and that the first network device uses the T<NUM> to compensate for a first timestamp at which the first network device sends the third packet includes: using, by the first network device, a sum of the first timestamp and the T<NUM> as a moment at which the first network device sends the third packet to the second network device, where the first timestamp is a moment at which the third packet arrives at the first receiving interface.

It should be understood that when the first network device sends the packet to the second network device, the packet first needs to be processed by using the service chip in the first network device, and then the processed packet is sent by using the media conversion module. To be specific, in this embodiment of this application, the third packet may be a packet processed by the first service chip.

The third packet is a packet that is sent by a second network device to a second service chip of the first network device by using the media conversion module, and that the first network device uses the T<NUM> to compensate for a first timestamp at which the first network device receives the third packet includes: using, by the first network device, a difference between the first timestamp and the T<NUM> as a moment at which the first network device receives the third packet, where the first timestamp is a moment at which the third packet arrives at the first sending interface.

A <NUM> clock synchronization system usually includes a master device and a slave device that exchange a packet. In this case, both the master device and the slave device may include the media conversion module <NUM>. In other words, the foregoing method <NUM> may be used to correct the timestamps of the receiving direction and the sending direction of the master device. The slave device is used as an example. The slave device may use a sum of the measured T<NUM> and the timestamp of sending a packet as a moment of sending the packet to the master device, and the slave device may also use a difference between the measured T<NUM> and the timestamp of receiving the packet as a moment of receiving the packet sent by the master device. Similarly, when sending the packet to the slave device, the master device may add the measured T<NUM> to the packet so that the slave device may calculate an accurate moment at which the master device sends the packet. In this embodiment of this application, using the method <NUM> to correct the timestamp for any direction of any device in the <NUM> clock synchronization system helps improve the synchronization performance of the <NUM> protocol.

Optionally, in this embodiment of this application, the third packet is a synchronization packet sent by a second network device to the first network device, where the synchronization packet carries a third timestamp at which the second network device sends the synchronization packet. The sixth packet is a delay request packet sent by the first network device to the second network device, where the second network device is a master device of the first network device, and the first network device is a slave device of the second network device. The method further includes: obtaining, by the first network device from the synchronization packet, a moment t<NUM> at which the second network device sends the synchronization packet; and that the first network device uses the T<NUM> to compensate for the first timestamp at which the first network device receives the third packet includes: using, by the first network device, a difference between the first timestamp and the T<NUM> as a moment t<NUM> at which the first network device receives the synchronization packet, where the first timestamp is a moment at which the synchronization packet arrives at the first sending interface; and that the first network device uses the T<NUM> to compensate for the second timestamp at which the first network device sends the sixth packet includes: using, by the first network device, a sum of the second timestamp and the T<NUM> as a moment t<NUM> at which the first network device sends the delay request packet, where the second timestamp is a moment at which the delay request packet arrives at the second receiving interface; and the method further includes: receiving, by the first network device, a delay response packet sent by the second network device, where the delay response packet carries a fourth timestamp at which the second network device receives the delay request packet; obtaining, by the first network device from the delay response packet, a moment t<NUM> at which the second network device receives the delay request packet; and calculating, by the first network device, a time offset between the first network device and the second network device based on the t<NUM>, the t<NUM>, the t<NUM>, and the t<NUM>.

It should be understood that the synchronization packet, the delay request packet, and the delay response packet in this embodiment of this application are the same as a Sync packet, a Delay _Req packet, and a Delay _Resp packet in an existing <NUM> protocol clock synchronization system. The three types of packets are all event packets, to be specific, are used to generate and communicate timing packets. For a relationship between packets, refer to <FIG> and the description of <FIG>. For brevity, details are not described herein again.

It should be further understood that the foregoing packet types are merely used as an example for description, or may also be packets of another type. This is not limited in this embodiment of this application.

Usually, the foregoing measured delay may be encapsulated in a time correction field in a PTP packet, for example, the time correction field (Correction Field) in a format of the PTP packet.

The following briefly describes a clock synchronization process by using an example in which the delay measurement method <NUM> is used for a receiving direction and a sending direction of the master device and the slave device. It is assumed that a timestamp of the Sync packet sent by the master device is t<NUM>, a delay in the sending direction measured by the master device by using the delay measurement method <NUM> is T1, a delay in the receiving direction measured by the slave device by using the delay measurement method <NUM> is T2, a timestamp at which the slave device receives the Sync packet is t2, a timestamp at which the slave device sends the Delay _Req packet to the master device is t3, a delay in the sending direction measured by the slave device by using the delay measurement method <NUM> is T3, a delay in the receiving direction measured by the master device by using the delay measurement method <NUM> is T4, and a timestamp at which the master device receives the Delay _Req packet is t4. In this case, the slave device may substitute (t1 + T1), (t2 - T2), (t3 + T3), and (t4 - T4) into the foregoing formula (<NUM>) to calculate a time offset between the master device and the slave device.

Optionally, in this embodiment of this application, the foregoing data cycle of periodically inserting the AM into the data stream may be greater than a delay of processing the data stream by the service processing unit <NUM>. In this way, two AMs identified at an ingress and an egress respectively are necessarily a same AM. Alternatively, the data cycle may be less than or equal to the delay of processing the data stream by the service processing unit <NUM>. In this case, the periodically inserted AM may be identified. For example, the AM inserted into a same data stream may be sequentially labelled from <NUM>, <NUM>,. The two identified AMs need to be the same AM, that is, AMs having a same label. Specifically, the same AM separately identified at the ingress and the egress may be a same bit or byte that separately identifies the same AM at the ingress and the egress, for example, may be a first bit. This is not limited in this embodiment of this application, provided that a same location of the same AM is used.

Optionally, the delay measurement unit <NUM> in the media conversion module <NUM> may also be a control unit outside the media conversion module <NUM>. To be specific, the data stream bypassed from the network interface <NUM> may be input to a control unit, such as a CPU, outside the media conversion module <NUM> by using another interface. The CPU records a delay during which the data stream passes through the service processing unit <NUM>.

<FIG> is a schematic block diagram of a network device <NUM> according to an embodiment of this application. The network device is a first network device. As shown in <FIG>, the network device <NUM> includes:.

Therefore, the network device in this embodiment of this application records a time interval before and after a packet passes through the media conversion module, and uses the time interval to correct a timestamp of sending or receiving the packet. This can accurately determine the delay of the packet through internal processing of the media conversion module, and further improve synchronization performance of a <NUM> protocol.

Optionally, in this embodiment of this application, the network device <NUM> further includes: a second receiving unit, configured to receive a fourth packet by using a second receiving interface of the media conversion module, where the fourth packet includes a second AM; a second sending unit, configured to send a fifth packet by using a second sending interface of the media conversion module, where the fifth packet includes the second AM, and the fifth packet is the fourth packet processed by the media conversion module; a second calculation unit, configured to calculate a time interval T<NUM> between a time at which the media conversion module receives the fourth packet including the second AM and a time at which the media conversion module sends the fifth packet including the second AM, where the second receiving unit is further configured to receive a sixth packet by using the second receiving interface, the second sending unit is further configured to send, by using the second sending interface, the sixth packet processed by the media conversion module, and a receiving direction and a sending direction of the third packet are opposite to those of the sixth packet; and a second processing unit, configured to use the T<NUM> to compensate for a second timestamp at which the first network device receives or sends the sixth packet.

Optionally, in this embodiment of this application, the first calculation unit <NUM> is specifically configured to: record a first moment when receiving the first packet by using the first receiving interface and when determining that the first packet includes the first AM; record a second moment when sending the second packet by using the first sending interface and when determining that the second packet includes the first AM; and determine a time interval between the first moment and the second moment as the time interval T<NUM>.

Optionally, in this embodiment of this application, the first calculation unit <NUM> is specifically configured to: start a counter at the first moment; stop the counter at the second moment, and obtain a count value N, where N is a positive integer and a clock cycle of the counter is t; and determine N * t as the T<NUM>.

Optionally, in this embodiment of this application, the third packet is a packet that is sent by a first service chip of the first network device to a second network device by using the media conversion module. The first processing unit <NUM> is specifically configured to: use a sum of the first timestamp and the T<NUM> as a moment at which the first network device sends the third packet to the second network device, where the first timestamp is a moment at which the third packet arrives at the first receiving interface.

Optionally, in this embodiment of this application, the third packet is a packet that is sent by a second network device to a second service chip of the first network device by using the media conversion module. The first compensation unit <NUM> is specifically configured to: use a difference between the first timestamp and the T<NUM> as a moment at which the first network device receives the third packet, where the first timestamp is a moment at which the third packet arrives at the first sending interface.

Optionally, in this embodiment of this application, the third packet is a synchronization packet sent by the second network device to the first network device, where the synchronization packet carries a third timestamp at which the second network device sends the synchronization packet. The sixth packet is a delay request packet sent by the first network device to the second network device, where the second network device is a master device of the first network device, and the first network device is a slave device of the second network device. The network device further includes: a first obtaining unit, configured to obtain, from the synchronization packet, a moment t<NUM> at which the second network device sends the synchronization packet, where the first processing unit <NUM> is specifically configured to use a difference between the first timestamp and the T<NUM> as a moment t<NUM> at which the first network device receives the synchronization packet, the first timestamp is a moment at which the synchronization packet arrives at the first sending interface, the second processing unit is specifically configured to use a sum of the second timestamp and the T<NUM> as a moment t<NUM> at which the first network device sends the delay request packet, and the second timestamp is a moment at which the delay request packet arrives at the second receiving interface; a third receiving unit, configured to receive a delay response packet sent by the second network device, where the delay response packet carries a fourth timestamp at which the second network device receives the delay request packet; a second obtaining unit, configured to obtain, from the delay response packet, a moment t<NUM> at which the second network device receives the delay request packet; and a third calculation unit, configured to calculate a time offset between the first network device and the second network device based on the t<NUM>, the t<NUM>, the t<NUM>, and t4.

Optionally, in this embodiment of this application, the media conversion module is an optical module.

The network device <NUM> in this embodiment of this application may correspond to the first network device in the method embodiment of this application. In addition, the foregoing and other operations and/or functions of the units in the network device <NUM> are respectively intended to implement the corresponding procedures of the method <NUM> in <FIG>. For brevity, details are not described herein again.

<FIG> is a schematic block diagram of a network device <NUM> for measuring a delay according to an embodiment of this application. The network device <NUM> is a first network device. As shown in <FIG>, the network device <NUM> includes a network interface <NUM>, a memory <NUM>, and a processor <NUM>. The network interface includes: a receiving interface and/or a sending interface, configured to receive or send a packet. The memory is configured to store an instruction. The processor is configured to: control a first receiving interface of a media conversion module of the first network device to receive a first packet, where the first packet includes a first alignment marker AM; control a first sending interface of the media conversion module to send a second packet, where the second packet includes the first AM, and the second packet is the first packet processed by the media conversion module; calculate a time interval T<NUM> between a time at which the media conversion module receives the first packet including the first AM and a time at which the media conversion module sends the second packet including the first AM; control the network interface to receive a third packet by using the first receiving interface, and control the network interface to send, by using the first sending interface, the third packet processed by the media conversion module; and use the T<NUM> to compensate for a first timestamp at which the first network device receives or sends the third packet.

It should be understood that, in this embodiment of this application, the processor <NUM> may be a CPU. The processor <NUM> may further be another general-purpose processor, a digital signal processor (Digital Signal Processor, DSP), an application-specific integrated circuit (Application Specific Integrated Circuit, ASIC), a field programmable gate array (Field Programmable Gate Array, FPGA) or another programmable logic device, a discrete gate or a transistor logic device, a discrete hardware component, or the like. The general-purpose processor may be a microprocessor, or the processor may be any conventional processor or the like.

The memory <NUM> may include a read-only memory and a random access memory, and provide an instruction and data to the processor <NUM>. A part of the memory <NUM> may further include a non-volatile random access memory. For example, the memory <NUM> may further store information about a device type.

In an implementation process, content in the foregoing methods can be implemented by using a hardware integrated logic circuit in the processor <NUM>, or by using instructions in a form of software. The content of the method disclosed with reference to the embodiments of this application may be directly performed by a hardware processor, or may be performed by using a combination of hardware in the processor and a software module. A software module may be located in a mature storage medium in the art, such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory, an electrically erasable programmable memory, a register, or the like. The storage medium is located in the memory <NUM>, and the processor <NUM> reads information in the memory <NUM> and completes the content in the foregoing methods in combination with hardware of the processor <NUM>. To avoid repetition, details are not described herein again.

In a specific implementation, a first calculation unit, a second calculation unit, a third calculation unit, a first processing unit, a second processing unit, a first obtaining unit, and a second obtaining unit in the network device <NUM> may be implemented by the processor <NUM> in <FIG>, and sending units and receiving units in the network device <NUM> may be implemented by the network interface <NUM> in <FIG>.

A person skilled in the art may use different methods to implement the described functions for each particular application, but it should not be considered that the implementation goes beyond the scope of the embodiments of this application.

Some or all of the units may be selected depending on actual requirements to achieve the objectives of the solutions of the embodiments.

When the functions are implemented in the form of a software functional unit and sold or used as an independent product, the functions may be stored in a computer-readable storage medium. Based on such an understanding, the technical solutions of this application essentially, or the part contributing to the prior art, or some of the technical solutions may be implemented in a form of a software product. The computer software product is stored in a storage medium, and includes several instructions for instructing a computer device (which may be a personal computer, a server, or a network device) to perform all or some of the steps of the methods described in the embodiments of this application. The foregoing storage medium includes: any medium that can store program code, such as a USB flash drive, a removable hard disk, a read-only memory (Read-Only Memory, ROM), a random access memory (Random Access Memory, RAM), a magnetic disk, or an optical disc.

Claim 1:
A packet processing method, wherein the method is performed by a first network device, the first network device comprising a media conversion module and a service chip, wherein the media conversion module is an optical module and is configured to convert an incoming signal received from a second network device from an optical signal type into an electrical signal type and provide the incoming signal to the service chip and is further configured to convert an outgoing signal received from the service chip from the electrical signal type to the optical signal type and send the signal to the second network device, and wherein the service chip is configured to perform time stamping of incoming and outgoing packets, and wherein the method comprises:
receiving (S110), from the second network device by using a first receiving interface of the media conversion module, a first packet, wherein the first packet comprises a first alignment marker, AM, wherein the first packet is included in a first data stream obtained by performing physical layer encoding on a first Ethernet frame stream and the first AM is periodically inserted after the physical layer encoding is performed on the first Ethernet frame stream;
sending (S120), to the service chip by using a first sending interface of the media conversion module, a second packet, wherein the second packet comprises the first AM, and the second packet is the first packet processed by the media conversion module;
calculating (S130), by the first network device, a receiving time delay T<NUM> between a time at which the media conversion module receives the first packet comprising the first AM and a time at which the media conversion module sends the second packet comprising the first AM; and
receiving (S140), by using the first receiving interface of the media conversion module, a third packet and sending, by using the first sending interface of the media conversion module, the third packet after processing by the media conversion module, and determining (S150) a moment at which the first network device receives the third packet based on the receiving time delay T<NUM> and a first timestamp generated by the service chip when the third packet is received.