KR20030082842A - Oam processing method in atm-based mpls system - Google Patents

Abstract

PURPOSE: An OAM(Operating And Management) processing method in an ATM(Asynchronous Transfer Mode)-based MPLS(Multi Protocol Label Switch) system is provided to offer an OAM function requested between a router and a subscriber network and offer an OAM function with respect to an ATM service in the ATM-based MPLS system. CONSTITUTION: Channel information set up through an IPC(Inter Processor Communication) between an FE(Forwarding Engine)(31) and an MSC(MPLS Service Controller)(34) is stored in a table. A service type is judged from the formed channel table whenever an OAM cell is inputted to a specific channel. If the received OAM cell is an OAM cell inputted to an LSP(Label Switched Path) channel, the OAM cell is transmitted to the FE(31) through a PCI(Peripheral Component Interconnect). If the received OAM cell is an OAM cell inputted to an ATM channel, the OAM cell is transmitted to an input and output buffer switch(32) through a UTOPIA(Universal Test and Operations PHY Interface for ATM). The OAM process with respect to the LSP channel and the ATM channel is simultaneously performed in one system. Various OAM function are embodied between the FE(31) and a node of a subscriber network through the IPC from the MSC(34).

Description

OAM processing method in ATM based multiprotocol label switching (OMS) system {OAM PROCESSING METHOD IN ATM-BASED MPLS SYSTEM}

The present invention relates to an ATM OAM between a label edge router and a specific node of a subscriber network in a multi-protocol label switch (hereinafter referred to as MPLS) and an asynchronous transfer mode (hereinafter referred to as ATM) service system. The present invention relates to an OAM (OAM) processing method in an ATM based multiprotocol label switching (MPS) system that simultaneously performs operating and management and MPLS OAM processing.

MPLS is a label-based two-layer switching technology that typically provides the basis for packet or ATM networks.

In the above description, a packet network (frame network) generally means a network in which all variable-length PDUs are basic transmission units, and an ATM network means a network in which fixed-length PDUs are basic transmission units.

Thus, packet-based MPLS services perform layer 2 forwarding by labeling PDUs such as Ethernet and frame relay, whereas ATM-based MPLS services use Virtual Path Indication (VPI) / Virtual Connectivity in the header of a cell. Layer 2 switching is performed using the identifier (VCI: Virtual Connection Indication) as a label.

However, today's Internet services require lookup and forwarding for various layers. The lookup of various layers refers to a complex lookup process, which lowers the service throughput per unit time. However, the MPLS service is frequently used because service data is switched through classification of a label attached to a PDU regardless of its type, and thus high-speed switching is possible without a lookup for each layer.

According to the recommendation of the Internet Engineering Task Force (IETF), the functions of operating and management (OAM) functions in these MPLS services are as follows.

1. Determination of SLA (Service Level Agrements) QoS provided by LSP (Lable Switched Path).

-.Verify LSP connection establishment and disconnection

Error performance verification.

Delay and delay displacement verification.

-. Verify the performance of the connection.

2. Increased reliability of MPLS network.

-.LSP failure monitoring and automatic rerouting.

MPLS protection switch.

3. Reduced network operation costs.

In the case of ATM service, the OAM function is already provided according to the I.610 recommendation of the International Telecommunication Union (ITU). OAM functions in general ATM networks are classified as shown in Table 1 below.

OAM Classification Explanation Classification by hierarchy model Physical layer F1, F2, F3 ATM layer F4, F5 Classification by function Fault Management Alarm Indication Signal (AIS) Remote Defect Indication (RDI) Contimuity Check (LB) Loop (LoopBack) Performance management Forward Performance Monitoring Cell Activation / Deactivation System management

As mentioned above, IETF also mentions the function of MPLS OAM.

However, it only mentions the effects that you want to get through the OAM function, not the OAM function at the actual lower level. In the case of the ATM-based MPLS service, the OAM function for ATM service, which is already widely used as a standard, must be simultaneously supported. There is no function for this.

In addition, if there is a conventional OAM processing structure for each service, there is a problem that not only the management is complicated, but also the performance of the overall system is reduced.

The present invention has been proposed in order to solve the above-mentioned problems, and its object is to implement the MPLS OAM function while using the existing ATM OAM system as it is, as well as the OAM function required between the router and the subscriber network in the ATM-based MPLS system. Rather, the present invention provides an OAM processing method in an ATM-based MPS system capable of providing an OAM function for an ATM service in the same system.

1 is a functional block diagram of a label edge router in a typical multiprotocol label switching system.

2 is a functional block diagram showing a structure of a forwarding engine of an ATM-based MPLS system.

3 is a signal processing diagram schematically showing an OAM processing procedure in an ATM-based MPLS system according to the present invention.

4 is a flowchart illustrating processing of an AIS cell in an OAM processing method according to the present invention.

5 is a flowchart illustrating a process of receiving an RID cell in the OAM processing method according to the present invention.

6 is a flowchart illustrating processing at the time of CC cell reception in the OAM processing method according to the present invention.

7 is a flowchart illustrating a process of receiving an LB cell in the OAM processing method according to the present invention.

In the OAM processing method of an ATM-based MPLS system comprising a forwarding engine, an input / output buffer switch, a switch, and an MPLS service controller, as a construction means for achieving the above object of the present invention,

A first step of exchanging an IPC message with an MPLS service controller in the forwarding engine to generate a channel table in which set channel information is stored;

A second step of checking a service type of a channel table formed in the first step when an OAM cell is input to a specific channel; And

If the receiving OAM cell is the OAM cell input to the LSP channel, and forwards to the forwarding engine, and if the OAM cell input to the ATM channel to pass to the input and output buffer switch, including the third step,

OAM processing for LSP and ATM channels can be executed simultaneously in one system, and various OAM functions can be implemented between forwarding engine and subscriber network nodes through IPC message from MPLS service controller.

In addition, the IPC message between the MPLS service controller, the forwarding engine and the subscriber network node may include a forwarding engine number indicating the position of the forwarding engine in the LER system, a setting position indicating whether the channel is in the subscriber area or the channel in the switch area, and channel setting and On / off value indicating whether channel is released, channel type indicating LSP channel and ATM channel type, port number indicating physical port location in channel forwarding engine, VPI value of set channel, set channel Channel handle value, which is a channel identifier corresponding to VCI value, port / VPI / VCI, Peak Cell Rate (PCR) in the set channel, Sustainable Cell Rate (SCR) in the set channel, and set channel Cell Delay Variation (CDVT: Cell Delay Variation Torelance) information is included.

In addition, in the first step, a table is constructed by using channel identifier, port number, VPI, VCI, and channel type information included in the IPC message.In the second step, the channel handle value is input as an index when the OAM cell is input. In this case, information on a channel to which the OAM cell is applied is extracted.

In addition, the method includes a forwarding engine number in which an IPC message from an MPLS service controller indicates a forwarding engine position in the system, an OAM interval, a channel handle value, an OAM number indicating a desired OAM function, and a physical channel in which a channel is set in the forwarding engine. OAM function activation / deactivation request, OAM application section and OAM application including port number indicating port location, VPI value of set channel, VCI value of set channel, channel type value indicating whether LSP channel or ATM channel. Characterized in that to transmit information about the channel.

In addition, the method includes an OAM type indicating an OAM type being serviced on a current channel, a channel handle value indicating a corresponding channel identifier among ports / VPI / VCI, a physical port number where a channel is set in a forwarding engine, A fourth step of configuring a management table comprising a VPI value, a VCI value of a set channel, a channel type indicating whether it is an LSP channel or an ATM channel, and a timer item indicating an elapsed time since receiving the last AIS / RDI cell. The RDI / LB OAM function is characterized by managing the status of the channels being performed.

And, if the received OAM cell is an AIS cell,

A) checking whether the requested channel is a channel in use in the channel table;

B) stopping the channel if it is not in use, declaring AIS status if the channel is in use, and notifying the MPLS service controller that the status is declared;

C) after the AIS state declaration, checking whether the channel is established through the subscriber side segmenter and the PCI;

D) if the channel is established, transmitting an RDI cell, otherwise notifying the MPLS service controller that the channel setting is not made and waiting for arrival of the next AIS cell;

E) if another AIS cell is not detected within the set time during OAM, releasing the AIS status declaration for this channel, deleting this channel from the management table and reporting it to the MPLS service controller; And

F) If another AIS cell is input within the set time during OAM, the process repeats from step c) without the AIS status declaration.

In addition, when the received OAM cell is an RDI cell

A) searching the management table to check whether the channel being requested is a busy channel;

B) not operating if the channel is not in use, and declaring an RDI state if it is an OAM request for the channel being used, and notifying the MPLS service controller;

C) counting time waiting for the arrival of the next RDI cell after the state declaration;

D) If the next RDI cell is not detected within the set time. Releasing the RDI status declaration, deleting the corresponding channel from the management table and reporting it to the MPLS service controller; and,

E) If the next RDI cell is detected within the set time, it is executed by repeating from step c) without the RDI state declaration.

In addition, when the received OAM cell is a CC cell

Checking whether a channel requested by the received cell is a busy channel;

If it is determined that the channel is not in use and no processing is performed, and the OAM request is made for the channel being used, checking whether the channel is established through the subscriber side segmenter and the PCI; And,

If the channel is set, the received CC cell is transmitted, otherwise it is characterized in that it comprises the step of notifying the MPLS service controller that the channel setting is not made.

And, if the received OAM cell is an LB cell,

A) checking the management table to check whether the requested channel is in use;

B) confirming whether the channel is established through the subscriber side segment and the PCI if the channel is not being used and does not perform any processing and is in use;

C) If the timer for the channel is active, check the LB cell's loopback identification (LI) field.If the LI field is 0 and the correlation tag is matched, stop the timer and then loopback to the MPLS service controller. Reporting success and performing no processing if the correlation tag does not match; And,

D) If the timer for the channel is inactive and the LI field is not 0, the loop back cell is transmitted by setting to 0.

Hereinafter, with reference to the embodiments of the accompanying drawings will be described in detail the configuration and operation of the present invention.

In the ATM-based multiprotocol label switching (MPS) system according to the present invention, the operation and management (OMM) structure has the following seven components.

1. Define ATM IPC structure for LSP channel establishment.

2. Define the LSP channel table structure.

3. Define the LER system architecture for the distinction between MPLS OAM and ATM OAM.

4. Define OAM related IPC structure.

5. AIS / RDI / LB related channel table structure.

6. MPLS OAM AIS / RDI Firmware Function Module.

7. MPLS OAM CC firmware function module.

8. MPLS OAM LB firmware function module.

All services are provided through the Label Switched Path (LSP) channel, and all F4 and F5 OAM functions may also be required only for channels that have already been set up. The LSP channel for MPLS service (hereinafter referred to as LSP channel) and the channel for ATM service (hereinafter referred to as ATM channel) are established through an IPC between the forwarding engine (FE) and the MPLS service controller.

When the IPC message corresponding to the channel establishment connection request to the switch side reassembler of FIG. 2 arrives from the MPLS service controller through the IPC channel, the message is transmitted to the forwarding engine controller through the PCI interface. The message transmitted at this time includes the information shown in Table 2 below.

SUB / SW HANDLE PHY VPI VCI TYPE

In Table 2, the SUB / SW value indicates the location where the set request channel is connected, that is, the subscriber side or the switch side.

The HANDLE value is assigned to a different value for each channel and used as a channel-specific identifier for the operator. The switch side and subscriber side may use the same HANDLE value for the same PHY / VPI / VCI, but must be separate within the same switch side or subscriber side. The MPLS LER system can dictate a total of 64000 channels in one system, with values ranging from 1 to 6400.

PHY is the physical port information where the set channel is actually located on the LER system. It is a value between 0 and 3.

The VPI / VCI value is an identifier allocated for each channel set, and the VPI / VCI can use all the values of the area provided by the ATM header.

The TYPE value indicates the type of service provided through the established channel. For example, a value of 0 indicates an ATM channel, and a value of 1 indicates an LSP channel.

When the LSP channel is set, the output direction of the input OAM cell is set to PCI, and the output direction of the input of the OAM cell through PCI becomes the subscriber network side through UTOPIA. PCI is connected to the controller of the forwarding engine. However, the input / output direction of the OAM cell input through the ATM channel is set up so that the channel is transferred from the subscriber side to the switch side or vice versa through UTOPIA. The actual channel orientation is achieved through the control of the reassembler via firmware.

Finally, F4 / F5 represent the function of OAM. The two reassemblers and segments used in the present invention are Conexant's MXT4400 Ver.C commercial chips.

Fault management OAMs at F4 and F5 levels are targeted to individual channels or groups of channels, regardless of service type. That is, F4 is made of a virtual path identifier (VPI) unit, and F5 is an OAM function for each virtual connection identifier (VCI). ATM-based MPLS systems handle OAM for MPLS and ATM services simultaneously, OAM for LSP channels is handled by the forwarding engine, and OAM for ATM services is handled by I / O buffer switches.

Therefore, when setting the channel, the channel setting must be different according to the service, and the forwarding engine must also manage characteristics of different channels for each channel. That is, it means that the channel established for connection may be distinguished from an LSP channel or an ATM channel. To do this, as mentioned above, a channel table constructed based on the contents of the IPC message exchanged between the MPLS service controller and the forwarding engine is required. Once the OAM function for the established connection is required, the forwarding engine always determines the channel type through the channel table already configured, and then performs the OAM processing function corresponding to each service.

FIG. 3 schematically illustrates OAM signal processing according to the present invention. In the illustrated MPLS system, two types of OAM cells are input to a subscriber side reassembler through an LSP channel or an ATM channel. In the case of the AAL5 data cell, the reassembler assembles the packet unit and delivers the packet to the switch 33 through UTOPIA or the forwarding engine 31 through PCI. Even in the case of an ATM cell, the cell is transmitted through the same interfaces as the AAL5 packet, but there is no assembly process. If the input is an OAM cell, the possible output direction is the same as the two kinds of cells above.

Specifically, the OAM cell input through the ATM channel is regarded as a data cell and is transferred to the switch 33 through UTOPIA as it is. The OAM for the ATM channel is processed by the input / output buffer switch 32 and then input again through the switch side channel of the forwarding engine. The forwarding engine 31 considers an OAM cell input through an ATM channel to be the same as a general ATM cell, and transfers the OAM cell to the subscriber network side as it is. However, the OAM cell input to the LSP channel is transferred to the forwarding engine 31 through the PCI. As mentioned above, the output direction determination of the subscriber side input data is determined based on the content of the message upon receiving the channel connection establishment request IPC message.

The OAM function is activated in two cases. The first is a case where an OAM request is received from other nodes and corresponds to a case of receiving various OAM cells. The second case is to receive OAM function from MPLS service controller and transmit OAM cell to specific node. The request for performing the OAM is requested to the forwarding engine through an IPC message having the components shown in Table 3 below.

property Explanation Forwarding engine number Position of forwarding engine in LER system OAM section F4 (between segments), F5 (end-to-end) decisions Channel handle value Channel identifier corresponding to port / VPI / VCI (0 ~ 64000) Type of OAM Select the OAM feature you want Port number Location of the physical port where the channel is configured in the forwarding engine (0 to 3) VPI VPI value of the channel to be set VCI VCI value of the channel to be set Channel type Displays LSP channel and ATM channel type (0: ATM, 1: MPLS)

In all these cases, when the OAM is received, the channel table information of all the requested channels and the type of the OAM cell are determined to perform the corresponding OAM function. The forwarding engine accommodates various kinds of OAM requests through MPLS service controllers or LSP channels. First, it processes the request for CC and LB of the MPLS service controller and reports the processing and related situation of the AIS / RDI / LB / CC OAM function input through the LSP channel to the MPLS service controller. The MPLS service controller forwards the request for OAM through the ATM IPC.

4 is a flowchart showing an Alarm Indication Signal (AIS) OAM process in the method according to the present invention. If the OAM cell inputted into the LSP channel is an AIS cell, the AIS state is activated, and the MPLS service controller is activated through the ATM IPC. Report (S401 ~ S406), and initializes the timer and transmits the RDI cell to the subscriber network (S407 ~ S408). Next, after adding the corresponding request channel to the OAM management table, it waits for receiving the next cell (S410). If another AIS cell for the same channel is not received within the timer setting time (2.5 seconds), the set AIS state is released, the timer is stopped, and the transmission of the RDI cell is stopped, and this is reported to the MPLS service controller.

FIG. 5 is a flowchart illustrating RID (Remote Defect Indication) OAM processing in the method according to the present invention. When RDI cells are input (S501 and S502), after checking whether the RDI state is activated (S503), the state is activated. It reports to the MPLS service controller (S505, S506). If another RDI cell is not received through the corresponding channel for the set time (2.5 seconds) by resetting the timer, the RDI state is released, the timer is stopped, and the state is reported to the MPLS service controller (S507). ~ S509).

FIG. 6 is a flowchart of processing when receiving a CC (Continuity Check) type OAM cell in the method according to the present invention. As shown in FIG. 6, no separate processing is required when receiving a CC cell, and only the received CC cell is subscribed. Send it to your network.

FIG. 7 is a flowchart illustrating a process of receiving a LB (Loop Back) OAM cell in the method according to the present invention. When the LB OAM cell is received, if the timer for the corresponding channel is active, the flowchart waits for reception of the LB OAM cell. If the LB cell's Loopback Indication (LI) field is 0, the loopback cell is looped back. If the correlation tag is matched, the loopback succeeds because the cell is generated by the forwarding engine of the LER system receiving the cell. I mean. Therefore, the timer is stopped when a correlation tag is matched and the loopback is reported to the MPLS service controller.

On the contrary, if the correlation tag does not match, no processing is performed, and if the loopback identification (LI) field is not 0, the loopback is set to 0. However, if the timer for the channel does not operate when the LB cell is received, it means that the received OAM cell is a loopback cell attempted by another node. In the mode OAM, since the LER system is terminated, the mode OAM loops back by setting the cell's LI field to 0.

This is because, as mentioned above, the scope of the OAM affected by the present invention is between the LER system and the nodes of the subscriber network. Therefore, the starting point and end point of the OAM for all LSP channels is the forwarding engine of the LER system.

As described above, the present invention has an effect of enabling the OAM function support for the LSP channel, which can promote efficient resource management, network reliability, and operation cost, even in an ATM-based MPLS system. Using a table, even if one LER system receives the same OAM cell, by separating the OAM cell for the LSP channel and the OAM cell for the ATM channel, it is possible to process both types of OAM cells.

In addition, all of the OAM function support for the LSP channels can be implemented in software (firmware), so that the function can be easily added or changed.

Claims (10)

In the OAM processing method of an ATM-based MPLS system including a forwarding engine, an input / output buffer switch, a switch, and an MPLS service controller, A first step of storing channel information set through the interprocessor communication (IPC) of the forwarding engine and the MPLS service control period in a table form; A second step of determining a service type from a channel table formed in the first step each time an OAM cell is input to a specific channel; And If the receiving OAM cell is the OAM cell input to the LSP channel, and if the OAM cell input to the ATM channel, and if the OAM cell input to the ATM channel including the third step of transmitting to the input / output buffer switch through UTOPIA, The ATM-based MPLS system is characterized in that it simultaneously executes OAM processing for LSP and ATM channels in one system, and implements various OAM functions between the nodes of the forwarding engine and the subscriber network through IPC from the MPLS service controller. How to handle OAM. The method of claim 1, IPC between the MPLS service controller and the forwarding engine and the subscriber network nodes Forwarding engine number indicating the position of forwarding engine in the system, setting position indicating whether it is channel of subscriber area or switch area, setting / release value indicating channel setting and channel release, LSP channel and ATM channel type Displayed channel type, port number that indicates the physical port location where the channel is set in the forwarding engine, VPI value of the set channel, VCI value of the set channel, channel handle value corresponding to the port / VPI / VCI, That includes information about the peak cell rate (PCR) on the set channel, the sustained cell rate (SCR) on the set channel, and the cell delay variation (CDVT) on the set channel. OAM processing method of ATM-based MPLS system characterized by. The method according to claim 1 or 2, In the first step, a channel table is configured using channel identifier, port number, VPI, VCI, and channel type information included in the IPC message. In the second step, OAM cell extraction method using the channel handle value as an index, extracting information on the channel to which the OAM cell will be applied OAM processing method of the ATM-based MPLS system. The method of claim 1 wherein the method is IPC message from MPLS service controller forwarding engine number indicating forwarding engine position in LER system, OAM section, channel handle value, OAM number indicating desired OAM function, location of physical port where channel is set in forwarding engine Including a port number indicating the number, the VPI value of the set channel, the VCI value of the set channel, the channel type value indicating whether the LSP channel or ATM channel, OAM processing method of the ATM-based MPLS system, characterized in that to transmit information on the OAM function activation / deactivation request, OAM application interval and OAM application channel. The method of claim 1 wherein the method is OAM type that indicates the type of OAM currently being serviced on the channel, channel handle value indicating the corresponding channel identifier among port / VPI / VCI, physical port number where channel is set in the forwarding engine, VPI value of the set channel, set channel And a fourth step of constructing a management table comprising a VCI value of L, a channel type indicating an LSP channel or an ATM channel, and a timer item indicating a time elapsed since the reception of the last AIS / RDI cell. OIS processing method of the ATM-based MPLS system, characterized in that the AIS / RDI / LB OAM function to manage the status of the channel. The method of claim 1, wherein the method is performed when the received OAM cell is an AIS cell. A) checking whether the requested channel is a channel in use in the channel table; B) stopping the channel if it is not in use, declaring AIS status if the channel is in use, and notifying the MPLS service controller that the status is declared; C) after the AIS state declaration, checking whether the channel is established through the subscriber side segmenter and the PCI; D) if the channel is established, transmitting an RDI cell, otherwise notifying the MPLS service controller that the channel setting is not made and waiting for arrival of the next AIS cell; E) if another AIS cell is not detected within the set time during OAM, releasing the AIS status declaration for this channel, deleting this channel from the management table and reporting it to the MPLS service controller; And F) If another AIS cell is input within the set time during OAM, OAM processing method of the ATM-based MPLS system, characterized in that the step is repeated from step c) without the AIS state declaration. The method of claim 1, wherein when the received OAM cell is an RDI cell, A) searching the management table to check whether the channel being requested is a busy channel; B) not operating if the channel is not in use, and declaring an RDI state if it is an OAM request for the channel being used, and notifying the MPLS service controller; C) counting time waiting for the arrival of the next RDI cell after the state declaration; D) If the next RDI cell is not detected within the set time. Releasing the RDI state declaration, deleting the corresponding channel from the management table, and reporting it to the MPLS service controller; And, E) If the next RDI cell is detected within the set time, OAM processing method of the ATM-based MPLS system, characterized in that is executed in the step of repeating from step c) without the RDI state declaration. The method of claim 1, wherein the received OAM cell is a CC cell, Checking whether a channel requested by the received cell is a busy channel; If it is determined that the channel is not in use and no processing is performed, and the OAM request is made for the channel being used, checking whether the channel is established through the subscriber side segmenter and the PCI; And, If the channel is set, transmitting the received CC cell; otherwise, notifying the MPLS service controller that the channel is not configured. The method of claim 1, wherein the received OAM cell is an LB cell, A) checking the management table to check whether the requested channel is in use; B) confirming whether the channel is established through the subscriber side segment and the PCI if the channel is not being used and does not perform any processing and is in use; C) If the timer for the channel is active, check the LI field of the LB cell. If the LI field is 0 and the correlation tag is matched, stop the timer and report that the loopback was successful to the MPLS service controller. Otherwise do nothing; And, D) If the timer for the channel is inactive and the LI field is not 0, the OAM processing method of the MPLS system, characterized in that the step of transmitting a loop back cell. In an ATM-based MPLS system including a forwarding engine, an input / output buffer switch, a switch, and an MPLS service controller, A first step of storing channel information set through the interprocessor communication (IPC) of the forwarding engine and the MPLS service control period in a table form; A second step of determining a service type from a channel table formed in the first step each time an OAM cell is input to a specific channel; And If the receiving OAM cell is an OAM cell input through the LSP channel, a computer-readable recording medium that records a program that executes the third step of transferring the forwarding engine through PCI to the input / output buffer switch through UTOPIA if the OAM cell is input through the ATM channel. .