WO2012171384A1 - Method and device for implementing circuit emulation service in passive optical network - Google Patents

Abstract

Disclosed are a method and a device for implementing a circuit emulation service in a passive optical network. The method comprises: establishing a pseudo-wire link between an optical network unit and an optical line terminal; establishing a multi-protocol label switching (MPLS) tunnel between the optical line terminal and remote equipment; the optical line terminal receiving a circuit emulation service (CES) uplink data packet of the optical network unit through the pseudo-wire link, and sending the CES uplink data packet to the remote equipment through the MPLS tunnel; and receiving a CES downlink data packet of the remote equipment through the MPLS tunnel, and sending the CES downlink data packet to the optical network unit through the pseudo-wire link. Through the present invention, multi-hop pseudo-wire connection with dynamic and static labels combined can be implemented in an optical access network, a label distribution protocol is run on an optical line terminal, and an optical network unit (ONU) does not need to support a dynamic MPLS function, thereby reducing the complexity of functions of the ONU.

Description

 Method and system for implementing circuit simulation in passive optical network

Technical field

 The present invention relates to a passive optical network and a multi-protocol label switching (MPLS) technology, and more particularly to a method and system for implementing circuit simulation in a passive optical network. Background technique

 Circuit Emulation Service (CES) is a general term for transmitting Time Division Multiplex and Multiplexer (TDM) services through an asynchronous packet switching network. Traditional TDM networks, such as El, T1, etc., based on circuit-switched technology, can provide reliable quality of service, but their service types are single, expensive, and the flexibility of upgrading, extending, and interworking is poor, and with IP data. The development of the network, with its cost advantages, strong expansion and upgrade and compatibility, is becoming a major business requirement and will dominate the future network architecture. For operators, in order to maximize the return on assets and minimize operating expenses, it is highly desirable to integrate traditional multi-service networks into a single network technology. Therefore, IP data networks have become the first choice for operators.

Currently, several international standards organizations have standardized circuit simulations, including MEF (Metro Ethernet Forum), IETF (Internet Engineering Task Force), and ITU (International Telecommunications Union). Alliances, etc., the standards organizations cooperate with each other. The TDM services transparently applied by international organizations have the same application principle. The standards are basically similar, only in the specific implementation details, such as data packet encapsulation format and TDM link identifier. There are minor differences. Wherein, MEF focused on the PDH (Plesiochronous Digital Hierarchy, plesiochronous digital series of bad ¹ J) or SDH (Synchronous Digital Hierarchy, Synchronous Digital Hierarchy) traffic carried implement a circuit emulation (MEF8) over Ethernet, IETF's PWE3 working group Develop a mechanism for simulating Layer 2 network services on a Packet Switching Network (PSN). ITU standard Y.1413 is a proposal for implementing TDM on an MPLS network. It defines the format of the service carried over the MPLS network. Necessary functional requirements for TDM-MPLS network interworking. Summary of the invention

At this stage, the best carrier for the bearer circuit emulation service is IP or MPLS packet-switched network. Due to some well-known deficiencies in traditional IP networks such as traffic engineering and QoS, MPLS packet-switched networks are based on their control forwarding plane separation. And the nesting capability of the label stack, etc., to implement the circuit simulation service on the MPLS network platform, not only can a large number of value-added services, but also can shield the difference of the core network, which gradually dominates the circuit simulation business.

 With the increasing popularity of optical access networks, the need for circuit emulation in optical access networks is growing, but there is currently no MPLS implementation of circuit emulation in optical access networks.

The technical problem to be solved by the present invention is to provide a method and system for implementing circuit simulation in a passive optical network, and implementing a circuit simulation service in a passive optical network.

 In order to solve the above technical problem, a method for implementing circuit simulation in a passive optical network according to the present invention includes:

 Establishing a pseudowire link between the optical network unit and the optical line terminal, establishing a multi-protocol label switching (MPLS) tunnel between the optical line terminal and the remote device, and the optical line terminal receiving the optical network unit through the pseudowire link The circuit simulation (CES) uplink data packet is sent to the remote device through the MPLS tunnel through the MPLS tunnel; and the CES downlink data packet of the remote device is received through the MPLS tunnel, and the CES downlink data packet is passed through the pseudowire chain. The road is sent to the optical network unit.

 Preferably, the method further includes: after the optical network unit is established, sending the CES uplink data message to the optical line terminal includes:

The optical network unit receives time division multiplexing (TDM) data, assembles into a TDM payload, encapsulates the TDM payload into a data packet, and configures a source media access control (MAC) address of the data packet as a MAC address of the local CES chip. Configure the destination MAC address as the MAC address of the optical line terminal, configure the VLAN ID as the VLAN ID of the pseudowire link, and configure the outer MPLS label and the inner MPLS label. The outer MPLS label is The static label switched path (LSP) forwarding label is stipulated by the optical line terminal, and the inner MPLS label is a differentiated identifier of the pseudowire link, and the CES downlink data packet is sent to the optical line terminal through the pseudowire link. Preferably, the transmitting, by the optical line terminal, the CES uplink data packet to the remote device by using the MPLS tunnel includes:

 After receiving the CES uplink data packet, the optical line terminal replaces the source MAC address of the CES uplink data packet with the MAC address of the local MPLS line card, replaces the destination MAC address with the MAC address of the remote device, and replaces the VLAN ID with The VLAN ID of the MPLS tunnel, and the outer MPLS label is replaced with the dynamic LSP forwarding label negotiated with the remote device. The CES uplink data packet is sent to the remote device through the MPLS tunnel. The yuan includes:

 After receiving the CES downlink data packet, the optical line terminal replaces the destination MAC address of the CES downlink data packet with the MAC address of the CES chip, replaces the source MAC address with the MAC address of the local MPLS line card, and sets the VLAN ID. Replace the VLAN ID of the pseudowire link with the outer MPLS label and replace it with the static LSP forwarding label, and send the CES downlink data packet to the optical network unit through the pseudowire link.

 Preferably, the method further includes: after receiving the CES downlink data packet, the optical network unit decapsulates the CES downlink data packet and sends the TDM data to the TDM port, including:

 After receiving the CES downlink data packet, the optical network unit extracts the TDM payload and recovers the clock signal, and sends the TDM payload to the TDM port according to the clock signal.

 Preferably, a system for implementing circuit simulation in a passive optical network, comprising: an optical line terminal, an optical network unit, and a remote device, where:

 The optical line terminal is configured to: establish a pseudowire link with the optical network unit, establish a multi-protocol label switching (MPLS) tunnel with the remote device, and receive a circuit simulation (CES) uplink data packet of the optical network unit through the pseudowire link. The CES uplink data packet is sent to the remote device through the MPLS tunnel; and the CES downlink data packet of the remote device is received by the MPLS tunnel, and the CES downlink data packet is sent to the optical network unit through the pseudowire link;

The remote device is configured to send CES downlink data packets to the optical line terminal through the MPLS tunnel. Preferably, the optical network unit comprises a CES chip, wherein: The CES chip is configured to receive time division multiplexing (TDM) data, assemble into a TDM payload, encapsulate the TDM payload into a data packet, and configure a source media access control (MAC) address of the data packet as its own MAC address. Configure the destination MAC address as the MAC address of the optical line terminal, configure the VLAN ID as the VLAN ID of the pseudowire link, and configure the outer MPLS label and the inner MPLS label. The outer MPLS label is The static label switching path (LSP) forwarding label agreed by the optical line terminal, the inner layer MPLS label is a distinguishing identifier of the pseudo line link, and the CES downlink data packet is sent to the optical line terminal through the pseudo line link.

 Preferably, the optical line termination comprises an MPLS line card, wherein:

 The MPLS line card is set to: Replace the source MAC address of the CES uplink data packet with its own MAC address, replace the destination MAC address with the MAC address of the remote device, and replace the VLAN ID. It is the VLAN ID of the MPLS tunnel, and the outer MPLS label is replaced with the dynamic LSP forwarding label negotiated with the remote device. The CES uplink data packet is sent to the remote device through the MPLS tunnel.

 Preferably, the MPLS line card is further configured to: receive the CES downlink data packet through the MPLS tunnel, replace the destination MAC address of the CES downlink data packet with the MAC address of the CES chip, and replace the source MAC address with its own MAC address. Replace the VLAN ID with the VLAN ID of the pseudowire link, replace the outer MPLS label with the static LSP forwarding label, and send the CES downlink data packet to the optical network unit through the pseudowire link.

 Preferably, the circuit emulation chip is further configured to: receive the CES downlink data packet, extract the TDM payload, recover the clock signal, and send the TDM payload to the TDM port according to the clock signal.

 In summary, the embodiment of the present invention can implement a multi-hop PW connection combined with a static and dynamic label in an optical access network, and the LDP runs on the OLT, and serves as both a LER and an LSR (Label Switching Router), ONU. The dynamic MPLS function is not required, and the ONU can be isolated from the MPLS network to reduce the functional complexity of the ONU, so that only the Layer 2 switching function needs to be supported, and the circuit simulation of the MPLS network can be realized. BRIEF abstract

1 is a schematic overall network diagram of a circuit emulation service according to an embodiment of the present invention; 2 is a schematic diagram of a circuit emulation message frame format according to an embodiment of the present invention;

 3 is a flow chart of a data processing method according to an embodiment of the present invention. Preferred embodiment of the invention

 The invention is in an ONU (Optical Network Unit) and an OLT (Optical Line)

A static PW (Pseudo Wire) link is established between the terminal and the optical line terminal. The OLT and the Far Equipment (FE) run LDP (Label Distribution Protocol) to establish a dynamic MPLS tunnel. At the same time, it acts as a LER ( Label Switching Edge Router), and connects a static PW link with a dynamic MPLS tunnel to implement a multi-hop PW connection combining dynamic and static tags, thereby implementing circuit simulation services.

 The circuit emulation service has two directions of sending and receiving. The ONU is in the uplink direction to the OLT, and the OLT is in the downlink direction to the ONU. The following describes the processing in two directions:

 In the uplink direction, the ONU can compress the TDM data according to the PWE3 protocol, and can use the structured or unstructured mode. The destination MAC address of the uplink packet is configured as the MAC address of the MPLS line card on the OLT, and the frame header includes the double-layer static MPLS label. The outer label is a static label (label switching path) forwarding label that is agreed with the OLT, and the inner label is used as a distinguishing identifier of different PWs. After receiving the CES uplink message, the OLT replaces the destination MAC address with the MAC address of the FE that dynamically negotiates the connection, replaces the source MAC address with the MAC address of the MPLS line card, and replaces the VLAN with the VLAN specified by the established MPLS connection. At the same time, the outer label is replaced with a dynamic LSP forwarding label negotiated with the FE, and the CES uplink packet is sent to the MPLS network.

 In the downstream direction, after receiving the CES downlink packet through the established MPLS tunnel, the OLT line card of the OLT replaces the destination MAC address of the packet with the MAC address of the CES chip on the corresponding ONU, and replaces the source MAC address of the packet with the MPLS line. The MAC address of the card is replaced with the VLAN configured with the static PW link between the ONUs. The static LSP forwarding label of the outer layer is replaced with the static outer label of the ONU, and then the packet is sent to the ONU. After the ONU receives the message, the CES chip (such as Z Ol lx of Zarlink) recovers the clock signal from the message and extracts the payload, and sends the data to the TDM port according to the clock signal.

The specific implementation method of the method and system for realizing circuit simulation of the present embodiment will be described below with reference to the accompanying drawings. The formula is explained.

 As shown in FIG. 1, the overall networking structure of the circuit emulation service of the present invention includes:

 The ONU 101 and ONU 102 are optical network units. Two are listed here as examples. The star connection between the ONU and the OLT is actually more. The number depends on the number of OLTs supported and the application requirements. The ONU 101 and the ONU 102 are at the user end, and provide a TDM interface (such as an E1/T1 interface), and include a CES chip for encapsulating, decapsulating, and recovering clocks of TDM data.

 The OLT 103 is an optical line terminal and is at the central office, and performs Layer 2 communication with the ONU 101 and the ONU 102 via an optical fiber. In the present embodiment, the LER and the LSR are used as the entire circuit emulation system. The OLT 103 includes an MPLS line card 104, and processes the packets sent by the ONU 101 and the ONU 102, and forwards the packets to the MPLS network 105 via the LDP protocol, and simultaneously receives the texts sent by the MPLS network 105. After being processed, the OLT 103 sends the packets to the ONUs 101 and the ONUs 102. .

 The MPLS network 105 is a network composed of any number of LSRs, and processes the LDP protocol to implement MPLS routing. The FE 106 establishes a dynamic MPLS tunnel connection with the OLT 103, processes the received and received MPLS packets, and performs circuit simulation processing. The processing method can use the method of the present invention, and the existing method can also be used, which is not limited herein.

 As shown in FIG. 2, a schematic diagram of a frame format of a circuit emulation message according to the present embodiment. In this implementation manner, processing the content of the packet includes: encapsulating and decapsulating the TDM payload on the ONU 101 of FIG. 1; At the MPLS line card 104 of 1, the MAC address of the packet header, the MPLS label, and the like are stripped and replaced.

 The encapsulation format in Figure 2 follows the ITU-T Y.1413 standard, in which the destination MAC, source MAC, VLAN tag, and Ethertype fields of the header follow the IEEE 802.3 standard, in Figure 1. When the ONU 101 is encapsulated, the destination MAC is the MAC address of the MPLS line card 104, and the VLAN ID is the VLAN ID of the pseudowire link between the ONU 101 and the OLT 103. When the 艮 line reaches the MPLS line card 104, the destination MAC is replaced with the FE 106. The MAC address, the source MAC address is replaced with the MAC address of the MPLS line card, and the VLAN ID is replaced with the VLAN ID of the MPLS tunnel on the MPLS line card, where it is replaced with the original field in the reverse direction.

The outer label of the MPLS is the LSP forwarding label. In Figure 1, the ONU101 and the OLT 103 are The static configuration field is dynamically negotiated in the MPLS network between the MPLS line card and the FE. The dynamic and static label replacement processing is performed on the MPLS line card. The MPLS inner label is used as the PW identifier. It is statically configured when it is encapsulated in the ONU. It is directly forwarded in the back-end network and is not processed.

 The PW control word and the RTP header are the encapsulation layers of the circuit emulation service, and the RTP header can be configured as needed, complying with the RFC 3550 standard.

 TDM payload data configurable length, in bytes in unstructured mode, in frame mode in structured mode (eg, one frame of E1 is 32 bytes), if the entire packet length (including FCS field) ) Less than 64 bytes, the chip automatically adds a static padding field after the payload data, so that the length reaches 64 bytes.

 FIG. 3 is a flowchart of a data processing method according to the embodiment. The data processing includes a local sending and receiving process and a remote sending and receiving process. For convenience of description, the processing method and system of the FE 106 in the network diagram of FIG. 1 are assumed to be the same as the local. In this way, only local data processing can be described. Hereinafter, the processing flow of one frame data message will be described in detail according to FIG.

 Step 301: Receive data from the TDM port of the ONU and encapsulate the data into a data packet.

 The TDM data received from the TDU port of the ONU, such as E1/T1, may optionally form a payload in a structured or unstructured manner, and the unstructured manner is to obtain data from any position of the TDM data bit stream, and to use words. The unit is the unit, and the payload is composed according to the configured length. The structuring method parses the TDM data content, framing it according to the multiframe format information carried in the frame, and composing the payload from the beginning of each frame according to the configured number of frames. After the TDM payload is formed, it is encapsulated into a data packet. The packet header includes a double-layer MPLS label. The outer label is a static LSP forwarding label, and the inner label is a PW distinguishing identifier.

 Step 302: Send the data packet to the OLT through the optical network.

 This step is for Layer 2 transmission of the optical network and does not involve the MPLS network.

 Step 303: Perform a replacement process on a part of the field of the data message frame header.

After receiving the data packet sent by the ONU, the OLT replaces the destination MAC address with the MAC address of the remote FE of the MPLS dynamic negotiation connection (here, the MAC address of the MPLS line card on the peer OLT, the same below), and replaces the source MAC address. For the MAC address of the MPLS line card, replace the VLAN ID with the VLAN ID of the established MPLS tunnel connection configuration, and replace the static outer label with the peer PE. The dynamic LSP forwarding label of the quotient.

 Step 304: Send the processed data packet to the MPLS network.

 Step 305: Receive a data packet from the MPLS network.

 The sending and receiving of the above steps 304 and 305 is implemented through an established MPLS tunnel connection. Step 306: Processing a data packet frame header related field;

 After the MPLS line card of the OLT receives the packet through the established MPLS tunnel, replace the destination MAC address of the packet with the MAC address of the CES chip on the ONU, and replace the source MAC address of the packet with the MAC address of the MPLS line card. The ID is replaced with the VLAN ID of the static PW link configured with the ONU. The dynamic outer layer LSP forwarding label is replaced with the static outer label configured with the ONU.

 Step 307: Send the processed data packet to the ONU.

 This is consistent with the processing in step 302. Both are Layer 2 switching, and the directions are opposite.

 Step 308: Decapsulate the data packet and send the TDM data to the TDM port.

 After receiving the data packet, the ONU performs a series of protocol check on the packet header. After the verification succeeds, the ONU extracts the TDM payload from the packet, and recovers from the packet arrival rate and the timestamp information in the packet. The clock signal is output, where the clock signal is the data rate if it is unstructured, and the data rate and frame pulse are two signals if it is structured. After the payload is extracted, the data is sent to the TDM port according to the recovered clock signal.

Obviously, those skilled in the art should understand that the above modules and steps of the present invention can be implemented by a general computing device, which can be concentrated on a single computing device or distributed over a network composed of multiple computing devices. Alternatively, they may be implemented by program code executable by the computing device, such that they may be stored in the storage device by the computing device, or they may be separately fabricated into individual integrated circuit modules, or their Multiple modules or steps are implemented as a single integrated circuit module. Thus, the invention is not limited to any particular combination of hardware and software.

The above is only the embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of the present invention. within.

Industrial Applicability The embodiment of the present invention can implement a multi-hop PW connection combined with a static and dynamic label in an optical access network. The OLT runs the LDP protocol and acts as both a LER and an LSR (Label Switching Router). The ONU does not need to support dynamics. The MPLS function can isolate the ONU from the MPLS network and reduce the functional complexity of the ONU, so that it only needs to support the Layer 2 switching function to implement circuit simulation of the MPLS network.

Claims

Claim 1. A method for implementing circuit simulation in a passive optical network, comprising:  Establishing a pseudowire link between the optical network unit and the optical line terminal, establishing a multi-protocol label switching (MPLS) tunnel between the optical line terminal and the remote device, and the optical line terminal passes the pseudowire link Receiving a circuit emulation (CES) uplink data packet of the optical network unit, transmitting the CES uplink data packet to the remote device by using the MPLS tunnel; and receiving the remote end by using the MPLS tunnel The CES downlink data packet of the device sends the CES downlink data packet to the optical network unit by using the pseudowire link. The method of claim 1, further comprising: after the optical network unit is configured to send the CES uplink data message to the optical line terminal, the optical network unit includes:  The optical network unit receives time division multiplexing (TDM) data, assembles into a TDM payload, encapsulates the TDM payload into a data packet, and configures a source media access control (MAC) address of the data packet as The MAC address of the local CES chip, the destination MAC address is configured as the MAC address of the optical line terminal, the virtual local area network identifier (VLAN ID) is configured as the VLAN ID of the pseudowire link, and the outer MPLS label and the inner layer are configured. a layer MPLS label, the outer MPLS label is a static label switched path (LSP) forwarding label agreed with the optical line terminal, and the inner layer MPLS label is a distinguishing identifier of the pseudo line link, by using the pseudo The line link sends the CES downlink data message to the optical line terminal. The method of claim 2, wherein the transmitting, by the optical line terminal, the CES uplink data packet to the remote device by using the MPLS tunnel includes:  After receiving the CES uplink data packet, the optical line terminal replaces the source MAC address of the CES uplink data with the MAC address of the local MPLS line card, and replaces the destination MAC address with the remote device. The MAC address, the VLAN ID is replaced with the VLAN ID of the MPLS tunnel, and the outer MPLS label is replaced with a dynamic LSP forwarding label negotiated with the remote device, and the CES is uplinked through the MPLS tunnel. A data message is sent to the remote device. 4. The method of claim 3, wherein the optical line terminal downlinks the CES Sending the data packet to the optical network unit by using the pseudowire link includes:  After receiving the CES downlink data packet, the optical line terminal replaces the destination MAC address of the CES downlink data packet with the MAC address of the CES chip, and replaces the source MAC address with the local MAC address. The MAC address of the MPLS line card, replacing the VLAN ID with the VLAN ID of the pseudowire link, and replacing the outer MPLS label with the static LSP forwarding label. The method of claim 4, further comprising: after receiving the CES downlink data packet, the optical network unit decapsulates the CES downlink data packet and sends the TDM data to the TDM. Port, including:  After receiving the CES downlink data packet, the optical network unit extracts the TDM payload, and recovers the clock signal, and sends the TDM payload to the TDM port according to the clock signal. 6. A system for implementing circuit simulation in a passive optical network, comprising: an optical line terminal, an optical network unit, and a remote device, wherein:  The optical line terminal is configured to: establish a pseudowire link with the optical network unit, establish a multi-protocol label switching (MPLS) tunnel with the remote device, and receive the optical network unit by using the pseudowire link a circuit emulation (CES) uplink data packet, the CES uplink data packet is sent to the remote device through the MPLS tunnel; and the CES network unit of the remote device is received by using the MPLS tunnel;  The optical network unit is configured to: send the CES uplink data packet to the optical line terminal by using the pseudowire link;  The remote device is configured to: send the CES downlink data packet to the optical line terminal by using the MPLS tunnel. 7. The system of claim 6, wherein the optical network unit comprises a CES chip, wherein: The CES chip is configured to: receive time division multiplexing (TDM) data, and assemble into a TDM payload, The TDM payload is encapsulated into a data packet, and the source media access control (MAC) address of the data packet is configured as its own MAC address, and the destination MAC address is configured as the MAC address of the optical line terminal. Configuring a virtual local area network identifier (VLAN ID) as the VLAN ID of the pseudowire link, and configuring an outer MPLS label and an inner MPLS label, where the outer MPLS label is a static label exchange agreed with the optical line terminal A path (LSP) forwards the label, and the inner layer MPLS label is the optical line terminal. 8. The system of claim 7, wherein the optical line terminal comprises an MPLS line card, wherein:  The MPLS line card is configured to: after receiving the CES uplink data packet, the The source MAC address of the CES uplink data packet is replaced with its own MAC address, the destination MAC address is replaced with the MAC address of the remote device, the VLAN ID is replaced with the VLAN ID of the MPLS tunnel, and the outer layer is The MPLS label is replaced with a dynamic LSP forwarding label negotiated with the remote device, and the CES uplink data packet is sent to the remote device by using the MPLS tunnel. 9. The system of claim 8 wherein  The MPLS line card is further configured to: receive the CES downlink data packet by using the MPLS tunnel, replace the destination MAC address of the CES downlink data packet with the MAC address of the CES chip, and set the source MAC address. Replace the VLAN ID with the VLAN ID of the pseudowire link, replace the outer MPLS label with the static LSP forwarding label, and send the CES downlink data packet through the pseudowire link. To the optical network unit. 10. The system of claim 9, wherein  The circuit emulation chip is further configured to: receive the CES downlink data packet, extract a TDM payload, and recover a clock signal, and send the TDM payload to the TDM port according to the clock signal.