RU239864U1 - LINE CARD WITH CLIENT PORT RESERVATION FUNCTION - Google Patents

Abstract

This utility model relates to telecommunications equipment—line cards for trunk and local area networks—that ensure high fault tolerance for customer service. The technical result is a reduction in the time it takes to restore customer service in the event of a failure or degradation of a trunk or local line channel. The technical result is achieved in that a line card with a client port redundancy function is implemented in a single housing and contains a group of client ports for receiving and transmitting client signals, a group of line ports for connecting optical transceivers, a muxponder/transponder unit for packaging client streams into optical signals and reverse conversion, a group of line switches for switching trunk channels to a reserve, a group of client switches and a control device, wherein the muxponder/transponder unit is integrated into a single electrical switching unit on a single microcircuit together with a group of line switches and a group of client switches, wherein the control device for controlling the group of client switches is implemented in the form of a microcontroller placed on the same printed circuit board as the remaining elements of the circuit.

6 pp. f-ly, 3 ill.

Description

Field of technology

This utility model relates to optical transport networks (OTN), designed for transmitting large volumes of data over fiber-optic backbones. Specifically, it concerns line cards used in DCI/DWDM/OTN (Data Center Interconnect/Dense Wavelength Division Multiplexing/Optical Transport Network) equipment for multiplexing Ethernet, SDH (Synchronous Digital Hierarchy), SONET (Synchronous Optical NETwork), and DCI (Data Center Interconnect) client signals into optical channels with redundancy, thereby increasing fault tolerance. These cards are used in provider telecommunications nodes, data centers, and backbone networks where minimizing downtime during channel failures is required.

State of the art

Line cards for OTN are known that contain client and line ports, as well as control units that provide basic signal multiplexing (see, for example, US patent 20120201535 A1, 2012, which describes a card with muxponders and traffic redundancy). In such solutions, redundancy is implemented using 1+1 or APS (Automatic Protection Switching, ITU T G.873.1) schemes, but using optical switching or external modules, which results in 50-500 ms delays due to transceiver reconfiguration and command transmission over external interfaces.

Another analogue is the Infinera 7100 Series cards (SEC Filing, 2021), which integrate muxponders and switches, but failure detection and switching depend on the SDN controller, with delays of up to 100 ms and the need for external coordination.

Another alternative is the Huawei OptiXtrans E6600/E8000 line cards (2020-2023), which support muxponders with QSFP-DD DCO interfaces, 1+1 and 1:1 backbone redundancy schemes, client-side switching between muxponders/transponders, and BER degradation detection with FEC coding. These cards provide speeds of up to 400 Gbps (OTU4), telemetry (RSSI, CRC), and communication via I2C/SPI/UART/MDIO interfaces, with switching times of 50-200 ms. However, in these systems, redundancy requires SDN coordination or external modules (for example, for ODUk mapping), without full electrical integration of all functions (muxponder + switches + detection) in a single block on the board, which leads to additional delays on external interfaces and does not allow achieving electrical switching speeds below 50 ms without reconfiguring the transceivers.

A common drawback of known solutions is their dependence on optical reconfiguration and disparate components, which increases service recovery time and reduces reliability in highly loaded networks.

Disclosure of the essence of the utility model

The technical result achieved is a reduction in customer service restoration time in the event of failure or degradation of a trunk or local line channel. This is achieved through the complete integration of the muxponder/transponder and switches within a single electrical unit on a single board.

Key advantage: signals between the muxponder, transponder (or their equivalents performing the same functions), and switches (including when rerouted to a backup path) are transmitted electrically over short paths within a single board. Unlike solutions where these units are located on separate boards, there is no need for intermediate optical transmission or interaction via external interfaces. This eliminates additional delays associated with signal conversion and transmission between separate boards.

The said technical result is achieved due to the fact that the line card with the client port redundancy function is implemented in a single housing and contains a group of client ports for receiving and transmitting client signals, a group of line ports for connecting optical transceivers, a muxponder/transponder unit for packaging client streams into optical signals and reverse conversion, a group of line switches for switching trunk channels to a reserve, a group of client switches and a control device, wherein the muxponder/transponder unit is integrated into a single electrical switching unit on a single microcircuit together with a group of line switches and a group of client switches, wherein the control device for controlling the group of client switches is implemented in the form of a microcontroller placed on the same printed circuit board as the remaining elements of the circuit.

Additionally, one or more signs of failure or degradation from the group are detected in the line card: a decrease in signal level, an increase in transmission errors, a loss of frame synchronization, a loss of an electrical or optical signal.

Additionally, the line ports on the line card have a QSFP-DD design and support the installation of DCO coherent optical transceivers.

Additionally, in the line card, a group of line switches is designed to implement 1+1 and 1:1 redundancy schemes on the trunk line side.

Additionally, in the line card, the channel for exchanging states and commands is implemented through an interface selected from the group: I2C (Inter-Integrated Circuit), SPI (Serial Peripheral Interface), UART (Universal Asynchronous Receiver-Transmitter), MDIO (Management Data Input/Output).

Additionally, in the line card, the traffic switching time when the electrical redundancy implemented inside the integrated electrical unit is activated does not exceed 50 ms and is comparable to electrical switching delays.

Additionally, in the line card, a group of line ports is implemented in the form of slots for optical transceivers of at least QSFP-DD design with DCO support, ensuring the transmission of signals to trunk channels at a speed of at least 400 Gbit/s.

Additionally, the line card housing is equipped with a built-in ventilation system and allows for hot-swapping of transceivers without interrupting data transmission, with replacement time not exceeding 5 seconds.

Additionally, in the line card, a group of line switches in a configuration of at least 2x2 and a group of client switches in a configuration of at least 4x1 are integrated into a single switching unit, ensuring the redistribution of traffic between line and client interfaces without interrupting data transmission.

Line switches are controlled by an electrical switching unit, while a group of client switches is managed by a microcontroller. This approach simplifies the design and eliminates the need for optical signal switching, allowing for additional redundancy functionality for line and client signals based on software-controlled switches.

List of figures

The utility model is illustrated by drawings.

Fig. 1 shows a block diagram of a line card with port reservation in the line card muxponder mode;

Fig. 2 shows a block diagram of a line card with port reservation in the line card transponder operating mode;

Fig. 3 shows the algorithm for the operation of the client port reservation system.

Implementation of a utility model

The muxponder/transponder block (5) (hereinafter referred to as the data switch) is implemented in an integrated electrical switching unit (8) on a single microcircuit and is intended for packing client streams into optical signals (OTU4 and vice versa) using FIFO buffers.

The data switch (5) is a data recovery and multiplexer/demultiplexer chip at the L1 level (Retimer/Gearbox 800Gbps PHY (Physical layer)), supporting 4-level pulse amplitude modulation (PAM-4) or non-return-to-zero (NRZ) modulation for the receive and transmit signals of the client and line interfaces. The chip is responsible for converting the electrical interfaces of the line card in multiplexing mode, including converting PAM4 modulation, operating at higher speeds (up to 56 Gbps), to NRZ modulation (up to 28 Gbps). The 400G PAM4 retimer/multiplexer chip supports "forward" multiplexing and "reverse" demultiplexing between client (10), (11), (12), (13) and line ports (1), (2) of the chip.

The group of linear switches (3), (4) is implemented on one microcircuit of the switching unit (8) in the form of two independent switches, providing switching of the main channel to the reserve according to the 1+1 and/or 1:1 schemes with a single input and a single output port.

A group of client switches (6), (7) is located on the same microcircuit of the switching unit (8) and provides routing of the multiplexed signal to the corresponding output ports, as shown in Fig. 1 and 2.

The control device (9) is made in the form of an external general-purpose microcontroller (RISC, for example ARM Cortex-M4) with memory for storing the configuration, located on a separate board inside the same housing and connected to the integrated electrical switching unit (8) via a status exchange channel of the serial interface type (I2C, SPI, UART or MDIO).

Line ports (1) and (2) are designed as slots in a form factor that supports removable optical transceivers (QSFP28/QSFP56/QSFP-DD, compatible with DCO) for outputting signals to trunk channels at a minimum rate of 400 Gbps. This ensures instant connection without configuration, zero conversion delay, and transceiver replacement in no more than 5 seconds without service interruption.

Client ports (10), (11), (12), (13) are designed as SFP+ or QSFP type connectors for receiving and transmitting client services (Ethernet, SDH) at speeds of at least 100 Gbit/s.

The integrated electrical switching unit (8) is a single microcircuit (e.g. FPGA or ASIC) on a board that combines the muxponder/transponder unit (5), a group of linear switches (3), (4) and a group of client switches (6), (7).

The electrical switching unit (8) supports automatic hot standby (Hitless MUX) for a group of line ports (1), (2). Hitless MUX logic controls a group of line switches (3), (4), enabling secure traffic switching between the active and backup routes of the electrical switching unit's line interfaces. Intelligent switching between modes is accomplished using advanced quality criteria (FEC, BER, OSNR, CD, PMD).

The client port group (10), (11), (12), (13) is designed to receive and transmit data from and to the client, as well as to accommodate QSFP56, QSFP28, and QSFP-DD transceivers. Four client ports support transceivers with 100G and 200G data rates (QSFP28, QSFP56) to implement line card functionality operating in muxponder mode. Two of the four ports support modules with 400G data rate (QSFP-DD) to implement line card functionality operating in transponder mode.

The means for monitoring the channel status and collecting telemetry are implemented in the form of internal registers of the switching unit (8) for monitoring parameters (RSSI - signal level, CRC - error control, optical spectrum and TD - data telemetry).

Channel degradation detection tools are implemented directly in the transceiver, monitoring the BER and signal level. When deviations are detected, the transceiver generates an alarm signal, which is transmitted to the microcontroller (9) via the communication channel no more than 200 μs before the failure occurs. This allows the microcontroller to coordinate automatic switching without the need for external commands.

The functional control blocks include:

quality block that analyzes RSSI (Received Signal Strength Indicator) and CRC (Cyclic Redundancy Check) parameters to evaluate channels;

telemetry receiving unit that collects RSSI, CRC and optical spectrum data for predictive monitoring;

a command generation unit that generates signals based on detection to activate the redundancy logic in the switching unit (8).

The total switching delay (including detection, coordination, and switching) is no more than 50 ms, reducing customer service restoration time in the event of a failure or degradation of the trunk or local channel to electrical delays of 5-50 ms, thanks to internal hardware mechanisms, without affecting the optical medium or external interfaces. This increases reliability, response speed, and ease of use.

The device operates as follows.

The line card's primary functionality includes receiving and transmitting up to four 100G/200G channels to and from the client, combining them in muxponder mode into a single 400G channel and transmitting as a coherent signal on a standard DWDM C-Band wavelength. It also provides error recovery and receives and transmits the signal to and from the client over two 400G channels in transponder mode. Additionally, the line card features parallel redundancy for line and client interfaces through support for software-controlled switches implemented in the electrical switching unit's microchip, increasing system fault tolerance.

Optical transceivers installed in line ports (1) and (2) receive and transmit optical signals. A data switch (muxponder/transponder) (5) converts and aggregates client streams for transmission over the trunk channel. A microcontroller (control unit) (9) periodically polls status indicators and then makes decisions in accordance with preset thresholds and algorithms.

In the muxponder operating mode (Fig. 1), to increase the fault tolerance of the circuit, the line card has the ability to implement the redundancy of client ports (10), (12) by client ports (11), (13), which complements the function of redundancy of line ports (1) and (2) implemented on the side of the line ports of the electrical switching unit (8) (Fig. 1). On the client side of the electrical switching unit microcircuit there is a group of client switches (6), (7), however, their control requires an additional connection of the microcontroller microcircuit (9), in contrast to the group of line switches (3), (4) on the line side, which are controlled by the electrical data switching unit (8). To control the group of client switches (6), (7), the microcontroller (9) uses logical signals (a), (b). The microcontroller (9), in addition to controlling the group of client switches (6), (7), also allows monitoring the optical power level at the client ports (10), (11), (12), (13) via the transceivers installed in them, sending requests to the transceivers and receiving responses from them using the transceiver control interfaces (c), (d), (e), (f), which makes it possible to implement the client port redundancy functionality and increase the fault tolerance of the proposed line card. Thus, the operating algorithm of the client side of the line card is as follows: the signal received from each client port (10), (12) is fed to the electrical switching unit (8) and, via the data switch (5), is multiplexed from two streams at a rate of 200G into one signal at a rate of 400G. Then it is fed to the client port (1) or the backup client port (2). When the signal on the client ports degrades or disappears completely, a switchover to the backup client ports (11), (13) occurs, which allows data reception and transmission to be maintained without traffic loss (except for the switching time).

In the transponder mode of operation (Fig. 2) of the line card, one client port (10) 400G is used for receiving and transmitting a signal, and the remaining client port (11) is used as a backup, which increases the reliability of data reception and transmission in the event of signal degradation or its complete loss. In this mode, switching of the signal from the line ports (1), (2) is carried out by a group of line switches (3), (4) according to the same principle as in the muxponder mode of operation of the line card. Reservation of client ports and control of the group of client switches (6), (7) is carried out by the microcontroller microcircuit (9), by means of logical signals along line (a) (line (b) controls the client switch (7), which is not active in the transponder mode). The signal received from the client port (10) at a rate of 400G undergoes the FEC recovery procedure via the data switch (5) and is transmitted to the line port (1) or to the backup line port (2). In the event that the microcontroller (9) detects signal degradation on the active port (10) by means of signals coming from lines (c) and (d) (due to the fact that the group of client ports (12) and (13) does not support transceivers operating at a data reception and transmission rate of 400G in the line card transponder operating mode, they are not active, the logical lines of the microcontroller (e) and (f) are also not used), the microcontroller (9) sends a command by a logical signal from line (a) to the client switch (6), which switches the reception and transmission of the signal to the backup client port (11).

Thus, the function of reserving client ports (10), (11), (12), (13) is performed by the hardware component using software. The hardware component is: the microcontroller (9), a group of client switches (6), (7), and four client ports (10), (11), (12), (13) on which switching will be organized. The software component is the embedded software (hereinafter referred to as the firmware) for controlling the microcontroller (9).

The operating principle of the redundancy function for increasing the fault tolerance of client ports (10), (11), (12), (13) (Fig. 3) is based on the constant polling by the microcontroller (9), located on the line card board, of the transceivers installed in the active (10), (12) (or (10) in the transponder mode) and backup (11), (13) (or (11) in the transponder mode) ports that receive and transmit a signal on the client side of the line card. In the event of any disturbances in the active channel leading to degradation of the signal power, an alarm message is sent to the control network and a switchover to the backup data reception and transmission channel is performed. The result of each action of the microcontroller (9) or the VPO is recorded and stored in the electronic log of the device's operation. Before commencing operations, the microcontroller (9) queries client ports (10), (11), (12), and (13) for installed transceivers. It also checks their compatibility with the software and components installed on the line card. To pass this check, the transceivers must support optical power request commands that comply with the CMIS or SFF8636 specifications. At this stage, the operating route has not yet been selected, and the value stored in the Res variable is -1. To select the operating route, after completing the transceiver checks, the microcontroller (9) checks the incoming optical power level from them, comparing it with the previously set minimum threshold. If the optical power exceeds the specified threshold, the microcontroller (9) selects the ports specified by default, setting the value of the Res variable to 0, and compares the optical power, adding the hysteresis value to it, on the main ports (10), (12) (or (10) in the transponder mode) with the optical power on the backup ports (11), (13) (or (11) in the transponder mode) in order to select the most powerful signal. If the optical power value on the backup ports (11), (13) (or (11) in the transponder mode) is higher, the microcontroller (9) rebuilds the working route to the backup client ports (11), (13) (or (11) in the transponder mode) and the value of 1 is set in the Res variable. After selecting the ports, the microcontroller (9) software sets the working route and again repeats the optical power checking cycle.

The client port redundancy system algorithm is universal and works with any software-controlled switches, microcontrollers capable of controlling switches and reading optical power levels at the transceiver input, as well as ports that support any transceivers that comply with the CMIS or SFF8636 specifications.

The proposed line card differs from existing analogs by the presence of a built-in electrical switching unit (8), providing flexible redirection of input signals via a group of client switches (6), (7) to the output interfaces of the microcircuit, via a group of linear switches (3), (4). Thus, there is no rigid binding of groups of input and output signals, which enables the dynamic redundancy of line ports of the QSFP56-DD format, as well as client ports QSFP28, QSFP56, QSFP56-DD and increases their fault tolerance. Client and line signals, multiplexed and switched by the line card, comply with IEEE 802.3 (CAUI-4 and 400GAUI-8) recommendations and provide a data transfer rate of up to 400 Gbps.

CAUI-4 and 400GAUI-8 are high-speed electrical ports with retimed signal recovery support, standardized within the IEEE 802.3bm (for 100G/200G), 802.3bs (for 400G), and 802.3ck (extension for 400G/800G) specifications. These ports support data transmission at rates of 100, 200, and 400 Gbps by aggregating multiple lanes with signal timing correction, which is critical for minimizing jitter and ensuring signal integrity in high-speed systems. A key requirement of the standards is to provide a reliable chip-to-module channel that guarantees compatibility between the PHY device (electrical switching unit (8)) located on the line card and the connected client optical module (e.g. QSFP56-DD DCO or QSFP28).

Example of a customer service recovery sequence

Step 1. Monitoring the channel status

The microcontroller polls the key channel parameters at a specified frequency (in accordance with the monitoring policy):

RSSI (Received Signal Strength);

BER (bit error rate);

CRC (checksum errors).

Step 2. Detecting degradation or failure

The system compares current indicators with preset thresholds. An event is triggered when any of the following conditions are met:

RSSI drops below the critical level (for example, -30…-40 dBm);

BER exceeds the acceptable threshold (e.g. 10 ^-6 );

the number of CRC errors or other failures exceeds the limit for the control interval.

Step 3: Deciding to Switch

The control algorithm performs the following actions:

analyzes the availability of backup resources (lines, transceivers, routes);

evaluates their current state (signal quality, load, status);

selects the optimal backup path or device based on priorities (minimum latency, maximum bandwidth, reliability);

generates switching commands for actuators.

Step 4. Performing the switch

Commands are sent to line and client switches. If a data switch is present, internal flow switching is performed.

Step 5. Verifying the restored channel

The restored channel is checked using RSSI and CRC indicators. If the results are unsatisfactory:

alternative backup is in progress;

An operator alert is generated.

Step 6. Recording events

Device:

records the following information in the event log: time, reasons for switching, resources involved, verification results;

Updates the service status in the management interface.

Examples of parameters and threshold values

The following approximate parameters can be used as a basis for setting up the monitoring and control system:

1. Signal Strength Detection Threshold (RSSI)

Value range: from - 30 to - 40 dBm.

Note: The specific threshold value is determined by the type of transceiver used and the communication quality requirements of the specific network.

2. Threshold values for transmission errors

Bit error rate (BER): > 10 ^-6 .

Checksum (CRC) errors: number of errors > N during the check interval T.

Note: The N and T parameters are set by the monitoring policy and depend on the acceptable level of losses for the service and the requirements for transmission reliability.

3. Telemetry polling period

Value range: from 100 to 1000 ms.

Note: The choice of interval is determined by a compromise between the required speed of fault detection and the permissible load on the control device.

4. Target service switching time

Value: < 50 ms (approximately).

Note: Actual switching time depends on the speed of the switches, the complexity of the control algorithms, and the delays in the data exchange channels between the system components.

Implementation options

The design of the line card provides for the following options for the technical implementation of key components:

1. Linear ports

Line ports support transceivers of various form factors, including QSFP28, QSFP56, QSFP-DD (with DCO compatibility), and SFP/SFP+ for lower-bandwidth solutions. The choice of a specific form factor is determined by the required bandwidth and the type of connected equipment.

2. Switching elements

Switching elements can be implemented in two alternative ways:

hardware implementation based on relay or optical switches, ensuring high reliability and minimal switching time;

logical implementation using ASIC or FPGA, providing flexibility in customizing switching algorithms and the ability to integrate additional signal processing functions.

3. Data switch

The data switch features flexible configuration and software control capabilities, allowing it to be tailored to specific network infrastructure requirements.

Management and control algorithms

The control logic includes modules for monitoring, analysis (comparison with thresholds), decision-making (selection of a backup path) and execution of switching commands, as well as a module for verifying the result.

The given example of the sequence of actions, together with the approximate parameters, demonstrates the achievement of the stated technical result - a reduction in the time to restore customer service in the event of failure or degradation of the main or local linear channel, due to the integration of a muxponder/transponder and switches on a single board and automatic control.

Claims (7)

1. A line card with a client port redundancy function, implemented in a single housing and containing a group of client ports for receiving and transmitting client signals, a group of line ports for connecting optical transceivers, a muxponder/transponder unit for packing client streams into optical signals and reverse conversion, a group of line switches for switching trunk channels to a reserve, a group of client switches and a control device, characterized in that the muxponder/transponder unit is integrated into a single electrical switching unit on a single microcircuit together with a group of line switches and a group of client switches, wherein the control device for controlling the group of client switches is implemented in the form of a microcontroller placed on the same printed circuit board as the other elements of the circuit. 2. A line card according to paragraph 1, characterized in that the line ports have a QSFP‑DD design and support the installation of coherent optical transceivers DCO. 3. A line card according to paragraph 1, characterized in that the group of line switches is intended for implementing 1+1 and 1:1 redundancy schemes on the side of the trunk line. 4. A line card according to paragraph 1, characterized in that the channel for exchanging status and commands is implemented through an interface selected from the group: I2C, SPI, UART, MDIO. 5. A line card according to paragraph 1, characterized in that the traffic switching time upon activation of the electrical backup implemented inside the integrated electrical unit does not exceed 50 ms and is comparable with electrical switching delays. 6. A line card according to paragraph 1, characterized in that the group of line ports is designed in the form of slots for optical transceivers of at least QSFP‑DD design with DCO support, ensuring the transmission of signals to trunk channels at a speed of at least 400 Gbit/s. 7. A line card according to paragraph 1, characterized in that the housing is equipped with a built-in ventilation system and ensures hot replacement of transceivers without interrupting data transmission, while the replacement time does not exceed 5 seconds.