WO2016101488A1

WO2016101488A1 - Ternary content addressable memory (tcam) table search method and device

Info

Publication number: WO2016101488A1
Application number: PCT/CN2015/078586
Authority: WO
Inventors: 姜海明; 杨远田
Original assignee: 中兴通讯股份有限公司
Priority date: 2014-12-26
Filing date: 2015-05-08
Publication date: 2016-06-30
Also published as: CN105791126B; CN105791126A

Abstract

A ternary content addressable memory (TCAM) table search method and device. The method comprises: determining whether a link between a network chip and an external TCAM of the network chip is faulty or whether the external TCAM is faulty; and when the link or the external TCAM is faulty, performing table search on packets by means of an internal TCAM of the network chip.

Description

Three-state content addressable memory TCAM table lookup method and device

Technical field

This document relates to the field of communications, and in particular, to a TCAM lookup table method and apparatus for three-state content addressable memory.

Background technique

Today's network development is amazing, network traffic growth and the emergence of new services require network equipment to have wire-speed and flexible processing capabilities. A related art network chip includes an application specific integrated circuit (ASIC) and a network processor (NP). With its high-speed processing and flexible programmability, network processors have become an effective solution for data processing in today's networks. There are many different memories in the network processor, such as Static Random Access Memory (SRAM), Ternary Content Addressable Memory (TCAM), Synchronous Dynamic Random Access Memory (Synchronous). Dynamic Random Access Memory (SDRAM, etc.) stores various service items such as port tables, MAC tables, and routing tables.

The three-state content addressable memory is mainly used to quickly find an access control list (Access Control List, ACL for short) and a route. The main feature of TCAM is fast parallel search. The application on the network processor is usually that the microcode composes a key value (KEY) from the message extraction information, and sends a search command to the TCAM through the NP TCAM controller, and processes the result according to the result. Message.

The TCAM interconnects with the network chip through a channel, the physical bus, and transmits data and service information on the bus. Compared with the internal TCAM of the network chip, the TCAM interconnected with the network chip through the bus is usually called an external TCAM. The physical bus between the network chip and the external TCAM is composed of multiple links. During the operation of the device, some lanes are aged or the link quality of the bus is poor. When the TCAM writes service entries, cyclic redundancy occurs. Errors such as Cyclic Redundancy Check (CRC) or Framing. In addition, when the external TCAM is operated for a long time, fault information such as aging may occur. Once the link fails or an external TCAM If the fault occurs in itself, it will seriously affect the look-up function of the external TCAM, which in turn affects the services carried on the TCAM.

In view of the problem that the link between the external TCAM and the network chip fails in the related art or the external TCAM itself fails, thereby affecting the look-up function of the external TCAM, the related technology has not proposed an effective solution.

Summary of the invention

The present invention provides a TCAM table lookup method and apparatus for three-state content addressable memory to solve the problem that the link between the external TCAM and the network chip in the related art is faulty or the external TCAM itself is faulty, thereby affecting the external TCAM. The problem of the lookup function.

A three-state content addressable memory TCAM lookup method includes: determining whether a link between a network chip and an external TCAM of the network chip or an external TCAM is faulty; failure of the link or the external TCAM In the case, the message is checked by the internal TCAM of the network chip.

Optionally, determining whether the link between the network chip and the external TCAM of the network chip or the external TCAM is faulty includes: acquiring a fault count; determining whether the fault count reaches a preset threshold; In the case of a preset threshold, it is determined that the link or the external TCAM has failed.

Optionally, the acquiring the fault count comprises: reading the fault count in the error statistics register in the external TCAM by managing the data input and output MDIO interface.

Optionally, before the packet is checked by the internal TCAM of the network chip, the method further includes: writing a TCAM entry for the message lookup table to the internal TCAM.

Optionally, the writing of the TCAM entry for the packet lookup table to the internal TCAM includes: determining whether the service corresponding to the TCAM entry is a critical service, where the key service includes a service related to packet forwarding; In the case where the service is a critical service, a TCAM entry corresponding to the service is written to the internal TCAM.

Optionally, the network chip comprises a network processor NP, the link comprises an Interlaken link between the NP and the CPU; or the network chip comprises an application specific integrated circuit ASIC, the chain The road includes the external bus PCI-Express.

A three-state content addressable memory TCAM look-up table device, comprising: a determining module, configured to: determine whether a link between a network chip and an external TCAM of the network chip or an external TCAM is faulty; : In case the link or the external TCAM fails, the message is checked by the internal TCAM of the network chip.

Optionally, the determining module includes: an obtaining unit, configured to: acquire a fault count; the first determining unit is configured to: determine whether the fault count reaches a preset threshold; and the determining unit is configured to: In the case where a threshold is set, it is determined that the link or the external TCAM has failed.

Optionally, the obtaining unit is further configured to: read the fault count in the error statistics register in the external TCAM by managing the data input/output MDIO interface.

Optionally, the three-state content addressable memory TCAM look-up table device further includes: a write module, configured to: write a TCAM entry for the message lookup table to the internal TCAM.

Optionally, the writing module includes: a second determining unit, configured to: determine whether the service corresponding to the TCAM entry is a key service, where the key service includes a service related to packet forwarding; To: write the TCAM entry corresponding to the service to the internal TCAM if the service is a critical service.

A computer readable storage medium storing computer executable instructions for performing the method of any of the above.

In this paper, it is determined whether the link between the network chip and the external TCAM of the network chip or the external TCAM is faulty; when the link or the external TCAM fails, the message is performed by the internal TCAM of the network chip. Checking the table solves the problem that the link between the external TCAM and the network chip in the related technology is faulty or the external TCAM itself is faulty, thereby affecting the problem of the external TCAM's look-up table function, effectively reducing the link or external TCAM failure. Impact on traffic forwarding.

BRIEF abstract

1 is a flow chart of a TCAM lookup method for a tri-state content addressable memory according to an embodiment of the present invention;

2 is a flow chart of another method for TCAM lookup of a tri-state content addressable memory according to an embodiment of the present invention;

3 is a block diagram showing the structure of a TCAM table lookup method device for a three-state content addressable memory according to an embodiment of the present invention;

4 is a structural block diagram of a judging module in a TCAM table lookup method of a three-state content addressable memory according to an embodiment of the present invention;

FIG. 5 is a structural block diagram of another apparatus for processing a TCAM table of a three-state content addressable memory according to an embodiment of the present invention; FIG.

6 is a structural block diagram of a write module in another T-state content addressable memory TCAM lookup table method device according to an embodiment of the present invention;

7 is a schematic diagram of a CPU, NP, and TCAM connection relationship for a T-state look-up memory TCAM look-up table according to an embodiment of the present invention;

8 is a flowchart of a three-state content addressable memory TCAM lookup table method applied to a CPU control plane to write a TCAM entry for a message lookup table according to an embodiment of the present invention;

9 is a flow chart of a TCAM lookup table method for a tri-state content addressable memory applied to a forwarding plane, in accordance with an embodiment of the present invention.

Embodiments of the invention

Embodiments of the present invention will be described hereinafter with reference to the accompanying drawings. It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict.

In this embodiment, a T-state content addressable memory TCAM lookup table method is provided. FIG. 1 is a flowchart of a T-state content addressable memory TCAM table lookup method according to an embodiment of the present invention, as shown in FIG. As shown, the process can include the following steps:

Step S100: determining whether a link between the network chip and an external TCAM of the network chip or an external TCAM is faulty;

Step S102: In the case that the link or the external TCAM is faulty, the packet is checked by the internal TCAM of the network chip.

The CPU accesses the external TCAM through the TCAM adapter interface of the network chip, and the network chip and the external TCAM are interconnected through the physical bus; in addition, the general NP also integrates the TCAM into the internal TCAM. Generally, the internal TCAM is much smaller than the external TCAM. In the case of the related technologies pursuing large-capacity indicators and high-speed line-speed forwarding performance, it is common practice to select an external TCAM to store services such as ACLs, and the internal TCAM is usually not used. In the event of a link or external TCAM failure, the CPU of the network chip will look up the message through the internal TCAM of the network chip.

Through the above steps, in the case that the link or the external TCAM is faulty, the internal TCAM of the network chip is used to check the message, and the external TCAM and the network chip existing in the related art are solved. The link fails or the external TCAM itself fails, which affects the problem of the external TCAM's look-up function, effectively reducing the impact of link or external TCAM failure on traffic forwarding.

In an optional implementation manner, determining whether the link between the network chip and the external TCAM of the network chip or the external TCAM is faulty may include: acquiring the fault count; determining whether the fault count reaches a preset threshold; When the fault count reaches a preset threshold, it is determined that the link or the external TCAM is faulty. Occasional failure of external TCAMs and links interconnected with network chips may be common, and has no impact on TCAM lookup and traffic forwarding. Because of the importance of TCAM lookup tables for service forwarding, it is also impossible and should not switch internal and external TCAMs too frequently for lookups. Only when the number of faults between the external TCAM and the network chip or the network chip itself reaches a certain threshold, it can be determined that the link or the external TCAM has a really large fault, which affects the normal lookup function of the TCAM. , which in turn affects the bearer of the TCAM to the service. Through the present embodiment, the function of switching the internal TCAM for table lookup is further optimized, and the impact of the link or external TCAM fault on the TCAM lookup function and service forwarding is effectively reduced.

Optionally, obtaining the fault count includes: reading, by using a Management Data Input/Output (MDIO) interface, the fault count in the error statistics register in the external TCAM. The CPU of the network chip can read the error status in the external TCAM by means of the CPU interface of the network chip and the corresponding MDIO address of the external TCAM. Register and error statistics registers. A fault message appears on the link and the external TCAM, and the error status register stores the associated fault information. Accordingly, the error statistics register counts the number of times the fault occurred.

Taking the Netlogic series TCAM widely used in the industry as an example, the Netlogic TCAM chip has some error status and error count of the PCS layer. Errors such as CRC can be detected in the Common Status Register of the NL11K chip, and there is a CRC error count in the RX PCS Counter register. These registers can be accessed through the out-of-band MDIO interface. By enabling the software thread, the external TCAM internal link related error status register and error statistics register are periodically read through the MDIO interface, thereby sensing the link status between the network chip and the external TCAM and the external TCAM itself. The advantage of borrowing the MDIO interface is that the MDIO signal line is an out-of-band resource, so it does not occupy the link bandwidth resources between the network chip and the external TCAM.

A method for processing a TCAM table of a three-state content addressable memory is also provided in the embodiment. FIG. 2 is a flow chart of another time processing method according to an embodiment of the present invention. As shown in FIG. 2, the process may be Including the following steps:

Step S200, writing a TCAM entry for the message lookup table to the internal TCAM;

The main feature of TCAM is fast parallel search. The application on the network processor is usually that the microcode composes a KEY (key value) from the message extraction information, and sends a search command to the TCAM through the NP TCAM controller, and processes the result according to the result. Message. Before the packet is checked by the internal TCAM of the network chip, the TCAM entry for the message lookup table is further written into the internal TCAM. That is, the control plane CPU of the network chip converts the data of the original service message sent by the upper layer service (such as ACL) into the TCAM entry for the message lookup table written to the TCAM hardware.

Steps S202 and S204 refer to step S100 and step S102 shown in FIG. 1 respectively, and details are not described herein. It is to be noted that, before the step 202, before the packet is checked by the internal TCAM of the network chip, the T-state content addressable memory TCAM lookup method provided by this embodiment further includes step S200. The TCAM entry to be used for the message lookup table is written to the internal TCAM. Writing the TCAM entry for the message lookup table to the internal TCAM is not limited to being performed before the packet is checked by the internal TCAM of the network chip, and may also be included in the judgment network chip and the external part of the network chip. Whether the link between the TCAMs or the external TCAM is out Before the fault occurs; it may also include before determining whether the link between the network chip and the external TCAM of the network chip or the external TCAM is faulty, before the packet is checked by the internal TCAM of the network chip. The internal TCAM storage space of the network chip is usually not very large, and after determining whether the link between the network chip and the external TCAM of the network chip or the external TCAM is faulty, the message is performed on the internal TCAM through the network chip. Before checking the table.

Through the above steps, the problem that the TCAM look-up table function is affected when the link between the external TCAM and the network chip or the external TCAM is broken in the related art is solved, thereby achieving the failure of the link or the external TCAM. Next, quickly switch to the internal chip TCAM of the network chip for the benefit of table lookup.

In an optional implementation, the writing of the TCAM entry for the message lookup table to the internal TCAM may further include: determining whether the service corresponding to the TCAM entry is a critical service, where the key service includes The text forwards the related service; in the case where the service is a critical service, the TCAM entry corresponding to the service is written to the internal TCAM.

In view of the small internal TCAM storage space of a general network chip, it is impossible to store all TCAM entries for forwarding service message lookup tables like an external TCAM. The services carried in the external TCAM are classified, corresponding to the critical service. The control plane CPU of the network chip writes the TCAM entry for the packet lookup table to the external TCAM, and then writes the internal TCAM as a backup. A key service is a service that is decisive for forwarding, such as protocol protection. If the address resolution protocol (ARP) and Open Shortest Path First (OSPF) cannot be reported, If the protocol is not processed, the forwarding service will be affected. . When the link between the external TCAM and the network chip or the external TCAM fails, the internal TCAM of the network chip is quickly switched to perform a table lookup. At this time, the backup mode in which the internal TCAM is in effect, the key services are still normal, the service is not interrupted, but the non-critical services such as QoS, flow rate limit, and flow statistics are invalid, and the internal TCAM storage space is reasonably utilized.

Through the above steps, it is determined whether the service corresponding to the TCAM entry is a critical service; when the service is a critical service, the technical means for writing the TCAM entry into the internal TCAM is not only implemented on the link or Quickly switch internals when an external TCAM fails The TCAM performs a table lookup to ensure that the forwarding of key services is not affected, and the internal TCAM storage space is effectively utilized reasonably.

When the link or external TCAM fails, the key services of the TCAM are still working normally due to switching to the internal TCAM working mode of the network chip. When obtaining the fault information, the operator or the user can be notified of an external TCAM or link problem, and the administrator can selectively perform some operations, such as replacing the external TCAM or maintaining the mode of the internal TCAM operation.

In an optional implementation, the network chip includes a network processor NP, the link includes an Interlaken link between the NP and the CPU; or the network chip includes an application specific integrated circuit ASIC, and the link includes an external bus. PCI-Express. It also includes other network chips and their bus links to the external TCAM.

In this embodiment, a three-state content addressable memory TCAM look-up table device is also provided, which is used to implement the above-mentioned embodiments and optional embodiments, and has not been described again. As used below, the term "module" may implement a combination of software and/or hardware of a predetermined function. Although the apparatus described in the following embodiments is preferably implemented in software, hardware, or a combination of software and hardware, is also possible and contemplated.

3 is a structural block diagram of a TCAM lookup device for a tri-state content addressable memory according to an embodiment of the present invention. As shown in FIG. 3, the device includes a determination module 30 and a look-up table module 32. Description.

The determining module 30 is configured to: determine whether a link between the network chip and the external TCAM of the network chip or an external TCAM is faulty; the look-up table module 32 is connected to the determining module 30, and is configured to: when the link or the external In the case of a failure of the TCAM, the message is checked by the internal TCAM of the network chip.

In an optional implementation manner, as shown in FIG. 4, the determining module 30 may further include: an obtaining unit 301, configured to: acquire the fault count; the first determining unit 302 is connected to the obtaining unit 301, and is configured to: determine Whether the fault count reaches the threshold; the determining unit 303 is connected to the first determining unit 302, and is configured to determine that the link or the external TCAM is faulty if the counting reaches a threshold.

Optionally, the obtaining unit 301 is further configured to: input and output MDIO through management data. And reading the fault count in the error statistics register in the external TCAM.

Through the apparatus provided in this embodiment, it is determined whether a link between the network chip and an external TCAM of the network chip or an external TCAM is faulty; when the link or the external TCAM fails, the network chip is adopted. The internal TCAM looks up the message and effectively solves the link failure between the external TCAM and the network chip in the related art or the failure of the external TCAM itself, which seriously affects the external TCAM lookup function, and further Affecting the problem of services carried on the TCAM, the table is checked by the external TCAM when the link and the external TCAM are working normally; in the case of a link or external TCAM failure, the TCAM is quickly switched to the internal chip of the network chip. Check the table to ensure the normal operation of the TCAM look-up table function, effectively reducing the impact of link or external TCAM failure on service traffic forwarding.

FIG. 5 is a structural block diagram of another T-state content-addressable memory TCAM look-up table device according to an embodiment of the present invention. As shown in FIG. 5, the device includes the determination module 30 and the look-up table module 32 shown in FIG. In addition, a write module 40 is included, which is described below.

The writing module 40 is connected to the determining module 42 and configured to: write a TCAM entry for the message lookup table into the internal TCAM before the table is checked by the internal TCAM of the network chip; the determining module 42. The look-up table module 44 refers to the determining module 30 and the look-up table module 32 shown in FIG. 3, respectively, and details are not described herein.

In an optional embodiment, as shown in FIG. 6, the writing module 40 may further include: a second determining unit 401, configured to: determine whether the service corresponding to the TCAM entry is a key service; and write the unit 402, connect To the second judging unit 401, it is set to write the TCAM entry to the internal TCAM when the service is a critical service. The key services include services related to packet forwarding.

Optionally, the above mentioned network chip and its link with the external TCAM may be an NP network processor, the link is an Interlaken link between the NP and the CPU; or may be an application specific integrated circuit ASIC. The link is a new generation bus interface PCI-Express. The currently popular network chips and their links to external TCAMs are not only NP network processors, Interlaken links; application-specific integrated circuit ASICs, next-generation bus interfaces PCI-Express, but also other network chips and their relationship with external TCAMs. Bus link.

The apparatus provided in this embodiment is used to determine whether the service corresponding to the TCAM entry is Key service; when the service is a critical service, the technical means of writing the TCAM entry into the internal TCAM not only realizes fast switching of the internal TCAM for checking the table when the link or the external TCAM fails, ensuring The forwarding of key services is not affected, and the internal TCAM storage space is effectively utilized reasonably.

A commonly used network processor to connect to the TCAM is shown in Figure 7.

The CPU accesses the external TCAM through the TCAM adaptation interface of the NP. The NP and the TCAM are interconnected by the Interlaken bus. The Interlaken physical bus is composed of multiple links, and the TCAM is also integrated inside the general NP. During the operation of the network device, the network processor microcode obtains forwarding and policy information, such as protocol protection, by checking the TCAM. The protocol packets need to be selected through TCAM matching to improve the priority and send the processing; for example, the quality of service Qos. The user configuration policy performs priority-based processing on certain types of packets. For example, traffic statistics, traffic rate limit, and so on, you need to count and limit the rate of specific packets. During the operation of the device, a certain link (lane) is aging or the link quality is poor. The TCAM write table may have errors such as cyclic redundancy check CRC or Framing (framing). In addition, if the TCAM runs for many years, there may be internal errors such as aging. In the event of such an error, the services carried on the TCAM will be affected or even cause the above services to fail.

7 is a schematic diagram of a CPU, NP, and TCAM connection relationship for a T-state look-up memory TCAM look-up table according to an embodiment of the present invention. The connection relationship between the commonly used three-state content addressable memory TCAM, the central processing unit CPU, and the network chip and its functions will be described below with reference to FIG.

The central processing unit CPU 50 is mainly responsible for completing the configuration of the network chip, such as the network processor NP and the external TCAM; and converting the original data of the service message delivered by the upper layer service (such as the ACL) into the TCAM hardware for reporting. a TCAM entry for the lookup table; a software thread running to scan the error status registration and error statistics registers in the external TCAM for determining whether the link state between the external TCAM and the NP and the operating state of the external TCAM are faulty; When the link or external TCAM fails, the dynamic switching of the NP microcode version is switched.

The external TCAM tri-state content addressable memory 52 is coupled to the network chip 54. The external TCAM 52 contains an error status register, an error statistics register for a memory link or TCAM operation failure.

The network chip 54 is connected to the central processing unit CPU 50. This embodiment is described by taking an NP network processor as an example. contain:

The microcode engine 541, which is an NP core device, is used to run microcode for all network services. Including routing lookup and other services; assembling the KEY key value for the message lookup table, sending it to the TCAM, and performing the corresponding operation according to the returned TCAM lookup table result. The NP can use a set of microcode versions for internal TCAM and external TCAM service lookups, as well as two sets of microcode. The version A microcode sends the table key value to the external TCAM for searching, and the microcode takes the external TCAM result to perform the relevant business action; the version B microcode sends the table key value to the internal TCAM for searching, and the microcode takes the internal TCAM result to execute. Related business actions. Usually, the Interlaken physical link is in good condition and runs the microcode version A. When the software thread scans to the link between the NP and the external TCAM, the microcode version is switched and the version B is loaded.

The internal TCAM tri-state content addressable memory 542 is configured to write a TCAM entry for the message lookup table when the external TCAM or its link with the network chip fails, and check according to the table key value. Table and feedback to check the results.

TCAM interface 543, NP and TCAM adapter interface, used for NP interconnection with TCAM through Interlaken.

The CPU interface 544 is used by the CPU to access all resources in the NP through the CPU interface, including a microcode engine, a TCAM adapter interface, and an internal TCAM.

The management data input/output interface MDIO 56, the MDIO interface existing between the general NP and the TCAM, can be used to access registers in the external TCAM.

In addition, there is a physical bus between the external TCAM and the network chip, that is, the Interlaken bus, which is used to connect the TCAM interface between the external TCAM and the network chip, so that the TCAM can communicate with the network chip.

8 is a flow chart of a three-state content addressable memory TCAM lookup table method applied to a CPU control plane to write a TCAM entry for a message lookup table, in accordance with an embodiment of the present invention. As shown in FIG. 8, the process may include the following steps:

Step S600, acquiring Interlaken link running status information between the external TCAM and the network processor NP, and/or running status information of the external TCAM itself;

As shown in Figure 7, the CPU can read the TCAM internal registers through the CPU interface of the NP through the corresponding MDIO address of the TCAM. In the TCAM initialization phase, the TCAM internal related registers are configured through the MDIO interface. By enabling the software thread to run a scheduled task running on the CPU, the error status register and error statistics register of the external TCAM internal link and its external TCAM itself are read by the management data input/output MDIO interface periodically or irregularly. Obtain the Interlaken link running status information and the running status information of the external TCAM itself. The error status register in the external TCAM is used to store the Interlaken link operating status fault information and the operating status fault information of the external TCAM itself. The error statistics register in the external TCAM is used to store the count of the above errors. The advantage of using the MDIO interface is that the MDIO signal line is an out-of-band resource and therefore does not occupy the Interlaken bandwidth resources between the NP and the TCAM.

There is an MDIO interface between the general NP and the TCAM, which can access registers. For G-bit Ethernet, the serial communication bus is called Management Data Input and Output (MDIO). This bus is defined by the IEEE through several provisions of the Ethernet standard IEEE 802.3. MDIO is a simple two-wire serial interface that connects management devices (such as MAC controllers, microprocessors) to management-capable transceivers (such as multi-port Gigabit Ethernet transceivers or 10GbE XAUI transceivers) , thereby controlling the transceiver and collecting status information from the transceiver. The information that can be collected includes link status, transmission speed and selection, power down, low power sleep state, TX/RX mode selection, auto-negotiation control, loopback mode control, and the like. In addition to the features required by the IEEE, transceiver vendors can add more information gathering capabilities. Taking the Netlogic series TCAM widely used in the industry as an example, the Netlogic TCAM chip has some error status and error count of the PCS layer. Errors such as CRC can be detected in the Common Status Register of the NL11K chip, and there is a CRC error count in the RX PCS Counter register. These registers can be accessed through the out-of-band MDIO interface.

Step S602, determining whether the Interlaken link running status, and/or the running status information of the external TCAM itself is faulty;

A global fault flag is set to determine whether the Interlaken link operating status, and/or the external TCAM's own operating status information has failed. The Interlaken link and the external TCAM are perceived to be faulty by determining whether the current global fault flag is set. The global fault flag has two states: when set to 1, it indicates a fault; when set to 0, it indicates that no fault has occurred.

A software thread is a scheduled task that runs on the CPU. The TCAM internal error status register and error statistics register are scanned by turning on the software thread. When an error message is scanned and the error count reaches the threshold, a global external TCAM fault flag is set and the upper layer and the administrator are notified. Through the global tag, the control layer and the forwarding layer take corresponding actions to enter the backup state, that is, activate the internal TCAM working mode. When the administrator knows that there is a problem with the external TCAM, he or she can choose to take appropriate actions, such as replacing the external TCAM or maintaining the backup mode of the internal TCAM work.

If the global failure flag is set to 0, the process proceeds to step S604; if the global failure flag is set to 1, the process proceeds to step S606.

In step S604, the TCAM entry for the message lookup table is written into the external TCAM, and the process ends.

The CPU converts the original data of the service packet delivered by the upper layer service (such as an ACL) into a TCAM entry for writing the TCAM hardware for the message lookup table. When the global fault flag is set to 0, it indicates that the Interlaken link and the external TCAM are not faulty, so there is no need to switch to the internal TCAM for table lookup operation. Therefore, the TCAM entry for the message lookup table is written to the external TCAM. In the subsequent forwarding service, the microcode engine extracts relevant information from the service message to form a KEY (key value), and sends a search command to the external TCAM through the TCAM controller of the NP, and processes the message according to the feedback search result.

Step S606, determining whether the upper layer service is a key service;

The services carried in the TCAM are classified and corresponding to the critical services. After the TCAM entries for the message lookup table are written to the external TCAM, the CPU control plane writes them to the internal TCAM as a backup. A critical service is a service that is decisive for forwarding, such as protocol protection. If ARP and OSPF packets cannot be sent to the CPU for processing, the protocol fails to run and the forwarding service is affected. Non-critical services, such as QOS. Flow statistics, flow mirroring, etc., do not affect the forwarding service even if they are not valid.

If the upper layer service is a key business, the process proceeds to step 608; if it is not a key service, the process is terminated.

Step S608, writing a TCAM entry for the message lookup table into the interior of the network processor NP TCAM;

When the global fault flag is set to 1, it indicates that the Interlaken link and the external TCAM have failed. Currently, the external TCAM bearer upper layer service does not apply to the external TCAM for packet lookup. The CPU converts the original data of the service packet delivered by the key service (such as the ACL) delivered by the upper layer into the TCAM entry for writing the TCAM hardware for the message lookup table. The internal TCAM of the NP has no fault. At this time, the TCAM entry for the message lookup table is written into the internal TCAM, and the KEY key value is checked, and the search command is sent to the internal TCAM through the NP TCAM controller, according to the feedback. The search results process the message.

9 is a flow chart of a TCAM lookup table method for a tri-state content addressable memory applied to a forwarding plane, in accordance with an embodiment of the present invention. As shown in FIG. 9, the process may include the following steps:

Step S700, determining whether the Interlaken link running status, and/or the running status information of the external TCAM itself is faulty;

Step S700 can refer to step S602 shown in FIG. 8 , and details are not described herein.

If the global failure flag is set to 0, the process proceeds to step S702; if the global failure flag is set to 1, the process proceeds to step S704.

Step S702, running microcode version A, ending the current process;

When the global fault flag is set to 0, it means that the Interlaken link running status and the running status of the external TCAM itself are not faulty. The NP microcode engine runs version A microcode, and sends the lookup table key value to the external TCAM for searching. The microcode performs related business operations according to the search result of finding the external TCAM feedback.

Step S704, running microcode version B;

When the global fault flag is set to 1, it indicates that the Interlaken link is operating, and/or the external TCAM itself is faulty. The external TCAM is not applicable to the message lookup table. At this time, it switches to the NP internal TCAM for table lookup operation. It is normal to use the external TCAM to perform table lookup. Only when the software scan thread scans the link or the external TCAM fails, set the fault global flag and switch to the internal TCAM for table lookup.

In the step shown in FIG. 8, the TCAM entry for the packet lookup table has been previously written to the internal TCAM for backup, and optionally, it is used to carry the critical service for the key service message. The TCAM entry for the lookup table was written to the internal TCAM for backup. The control plane performs microcode dynamic loading and switches the microcode version. The microcode engine runs version B microcode, and sends the lookup table key value to the internal TCAM for searching. The microcode performs related business operations according to the search result of finding the internal TCAM feedback.

It should be noted that the two sets of microcode version A and microcode version B in the microcode engine may be a set of microcode versions or different microcode versions.

Compared with the current link failure caused by the current NP and the external TCAM, the present embodiment provides a method for reading the TCAM internal error status register and the error statistics register through the external TCAM MDIO out-of-band interface. NP and external TCAM link status and TCAM chip issues; the control plane of the CPU writes the internal TCAM to the critical TCAM service after writing the external TCAM; when the thread senses the fault, it switches the microcode version, and works internally. The backup mode in which TCAM is in effect, the key services are still normal, and services are not interrupted. Only non-critical services such as QoS, traffic rate limit, and flow statistics are invalid. After the thread scans to the external TCAM fault, the TCAM key service still works normally due to switching to the internal TCAM working mode; in addition, the user is notified that there is a problem with the external TCAM, and the administrator can selectively perform some operations.

Generally, the internal TCAM is much smaller than the external TCAM. In the current pursuit of large-capacity indicators and high-bandwidth line-rate forwarding performance, it is common practice to select an external TCAM to store services such as ACLs, and internal TCAMs are usually not used. Compared with related technologies, the internal TCAM space is effectively utilized for backup of TCAM entries for key service message lookup, and the thread scanning external TCAM state is enabled. When the external TCAM or bus link fails, the microcode version can be switched. Work mode switching can be performed to ensure that key business of TCAM is still running normally.

One of ordinary skill in the art will appreciate that all or a portion of the steps of the above-described embodiments can be implemented using a computer program flow, which can be stored in a computer readable storage medium, such as on a corresponding hardware platform (eg, The system, device, device, device, etc. are executed, and when executed, include one or a combination of the steps of the method embodiments.

Alternatively, all or part of the steps of the above embodiments may also be implemented by using an integrated circuit. These steps may be separately fabricated into individual integrated circuit modules, or multiple modules or steps may be fabricated into a single integrated circuit module. achieve.

The device/function module/functional unit in the above embodiment can be implemented by using a general-purpose computing device. Now, they can be concentrated on a single computing device or distributed over a network of multiple computing devices.

Industrial applicability

In the embodiment of the present invention, in the case that the link or the external TCAM is faulty, the method of checking the packet by using the internal TCAM of the network chip solves the problem that the link between the external TCAM and the network chip is faulty or The external TCAM itself fails, which affects the problem of the external TCAM's look-up function, effectively reducing the impact of link or external TCAM failure on traffic forwarding.

Claims

A three-state content addressable memory TCAM lookup method includes:

Determining whether a link between the network chip and an external TCAM of the network chip or an external TCAM is faulty;

In case the link or the external TCAM fails, the message is checked by the internal TCAM of the network chip.
The method of claim 1, wherein determining whether the link between the network chip and the external TCAM of the network chip or the external TCAM is faulty comprises:

Get the fault count;

Determining whether the fault count reaches a preset threshold;

In case the fault count reaches a preset threshold, it is determined that the link or the external TCAM has failed.
The method of claim 2 wherein obtaining the fault count comprises:

The fault count in the error statistics register in the external TCAM is read by managing the data input and output MDIO interface.
The method according to any one of claims 1 to 3, before the table is checked by the internal TCAM of the network chip, the method further includes:

A TCAM entry for the message lookup table is written to the internal TCAM.
The method of claim 4, wherein writing the TCAM entry for the message lookup table to the internal TCAM comprises:

Determining whether the service corresponding to the TCAM entry is a key service, where the key service includes a service related to packet forwarding;

In the case where the service is a critical service, a TCAM entry corresponding to the service is written to the internal TCAM.
The method of claim 5, wherein

The network chip includes a network processor NP, and the link includes between the NP and the CPU. Interlaken link; or

The network chip includes an application specific integrated circuit ASIC, and the link includes an external bus PCI-Express.
A three-state content addressable memory TCAM lookup device includes:

a determining module, configured to: determine whether a link between the network chip and an external TCAM of the network chip or an external TCAM is faulty;

The look-up table module is configured to: perform a table lookup of the packet through the internal TCAM of the network chip if the link or the external TCAM fails.
The apparatus of claim 7, wherein the determining module comprises:

Get the unit, set to: get the fault count;

The first determining unit is configured to: determine whether the fault count reaches a preset threshold;

The determining unit is configured to: determine that the link or the external TCAM is faulty if the fault count reaches a preset threshold.
The device according to claim 8, wherein

The obtaining unit is further configured to: read the fault count in the error statistics register in the external TCAM by managing the data input/output MDIO interface.
The apparatus according to any one of claims 7 to 9, further comprising:

The write module is configured to: write a TCAM entry for the message lookup table to the internal TCAM.
The apparatus of claim 10 wherein said writing module comprises:

The second determining unit is configured to: determine whether the service corresponding to the TCAM entry is a key service, where the key service includes a service related to packet forwarding;

The writing unit is configured to: when the service is a critical service, write a TCAM entry corresponding to the service to the internal TCAM.
A computer readable storage medium storing computer executable instructions for performing the method of any of claims 1-6.