Burst Optical/Electrical Technology on Huawei MA5600T MA5800

TDMA is used in GPON upstream direction. An ONU transmits data only within the allocated timeslots. In the timeslots that are not allocated to it, the ONU immediately disables the transmission of its optical transceiver to prevent other ONUs from being affected. The OLT then receives the upstream data from each ONU in a burst manner based on timeslots. Therefore, both OLT and ONU optical modules must support burst receive and transmit function to ensure normal running of the GPON system. Figure 2-16 shows the burst transmit function supported by ONU optical modules, and Figure 2-17 shows the burst receive function supported by Huawei MA5600T optical modules.

Ranging can be implemented to prevent cells transmitted by different ONUs from conflicting with each other on Huawei OLT MA5800. However, the ranging accuracy is ± 1 bit and the cells transmitted by different ONUs have a protection time of several bits (not a multiple of 1 bit). If the ONU optical modules do not support the burst receive and transmit function, the transmitted signals overlap and distortion occurs.

• The distance from each ONU to the OLT varies and therefore the optical signal attenuation varies for each ONU. As a result, the power and level of packets received by an OLT at different timeslots various.
• If the OLT optical modules do not support the burst receive and transmit function, an error occurs when the optical signals sent by Huawei ONU/ONT with a long transmission distance and large optical attenuation are recovered on the OLT because the optical power level is less than thethreshold (only the signals with the optical power level greater than the threshold can be recovered). Dynamic threshold adjustment enables the OLT to dynamically adjust the threshold for optical power levels based on the strengths of signals received by the OLT. This ensures that all ONU signals can be recovered.

What Is P2P Optical Access?

Definition
Point-to-point (P2P) Ethernet optical access is a mode in which P2P Ethernet optical access boards provide GE, 10GE and FE ports and coordinate with downstream devices to implement various optical access solutions for users. The solutions include FTTC/FTTB, FTTH, FTTO, FTTM and D-CCAP.

Purpose

• P2P Ethernet optical access is specially applicable to residential communities with optical fibers routed. It provides a more flexible FTTx solution, especially integrated services, including video, voice, and data for users. This feature has the following advantages:
• Higher bandwidth. The FTTH solution implemented through P2P optical access can provide a higher bandwidth for users, meeting the requirements of high-end users.

• Lower costs. P2P Ethernet optical access boards support more cascaded DSLAMs, reducing FTTC/FTTB networking costs.
• Higher reliability. P2P optical access allows a higher reliability in the DSLAM cascading scenario through features such as inter-board aggregation, smart link, and ring check.
• More flexible scenarios. The P2P Ethernet optical access boards coordinate with a variety of downstream devices (such as the DSLAM, ONT, SBU, and CBU) to implement FTTC/FTTB, FTTH, FTTO, FTTM and D-CCAP. Huawei MA5800 configured with the P2P Ethernet optical access board can not only be directly connected to access terminals but also cascade Huawei DSLAMs in order to converge a large number of users.

Alarm Clearing A_LOC on Huawei Optix OSN2500

The A_LOC on Huawei Optix OSN2500 is an alarm indicating the loss of clock in the upstream direction of the bus.

Parameters
When you view an alarm on the network management system, select the alarm. In the Alarm
Details field display the related parameters of the alarm. The alarm parameters are in the
following format: Alarm Parameters (hex): parameter1 parameter2...parameterN. For details
about each parameter, refer to the following table.

Impact on the System
When the A_LOC alarm occurs, the services carried by the board path are interrupted.

Possible Causes
The possible causes of the A_LOC alarm are as follows:
The PDH equipment interconnected to the service path is faulty.
The service type is incorrectly configured.
The service cross-connection is incorrectly configured.
The board hardware is faulty.
The cross-connect and timing board is faulty.

Procedure
Step 1 Check whether Huawei PDH equipment interconnected to the service path is faulty. If yes, take priority to remove the fault, and then check whether the A_LOC alarm is cleared.
Step 2 View the A_LOC alarm on the U2000, and then confirm the path number according to the alarm parameters.
Step 3 Check whether the service configuration of the path is correct. Make sure that the service type
at the local end is consistent with that at the remote end, and the cross-connection is correctly
configured. Then check whether the A_LOC alarm is cleared.
Step 4 If the alarm persists, check whether any hardware of the board that reports the A_LOC alarm is faulty on the U2000. If yes, perform a cold reset on the board. Then check whether the A_LOC
alarm is cleared.
Step 5 If the alarm persists, replace the board.
Step 6 If the alarm persists, perform a cold reset on the cross-connect and timing board. Then check
whether the A_LOC alarm is cleared.
Step 7 If the alarm persists, check whether the cross-connect and timing board is faulty. If yes, replace the cross-connect and timing board. Then the A_LOC alarm is automatically cleared.

How to synchronize U2000 server with more than one NTP server, and peers?

Issue Description

This case applies to situation when, when deploying U2000 server on SUN Solaris platform, in both single-server and High Availability configuration.
This solution was deployed with U2000 V100R002C01SPC100, but it will most certainly work with other versions.
Standard NTP configuration, with MSuite, allows us to configure just one time server. However client can request to have his server (servers) have more than one NTP sources configured, for redundancy purpose.
In this case we have to manually edit Solaris NTP configuration file.

Alarm Information

Null

Handling Process

In SUN Solaris OS NTP configuration file is in directory /etc/inet/ntp.conf. If it's not there, an example file exist in /etc/inet/ntp.server, which can be used as a template.
In the file we can put our lists of time servers in a format:

server X.X.X.X
server Y.Y.Y.Y
...

If we have more than one server with same STRATUM level, we can configure it as a proffered one, using keyword "prefer".

server X.X.X.X prefer

In case when we have U2000 in HA configuration, we can set master and stand-by servers as peers. This is helpful when all configured time servers will become unavailable. Both U2000 server can then configure right time between themselves. Example configuration:

peer Z.Z.Z.Z

Root Cause

Null

Suggestions

Important thing to remember is that from all time servers on the list system will choose the one with lowers (more reliable) STRATUM level. If we have few server on the same level, and no server with better value then we can use keyword "prefer" to force one servers to be used.
In configuration file we can also find server with ip address 127.127.1.0. This is LOCAL time, server's time. To make sure this time source is used as a last one, we should set its STRATUM value to less preferable. This can be done by using keyword "fudge".

server 127.127.1.0
fudge 127.127.1.0 stratum 10

Same method can by used to change STRATUM value of any real server but only to less preferable value. For instance, when server is broadcasting its time with STRATUM value of 3, we can change it locally to 4,5,6 etc, but never 0,1 or 2.

Summing up, an example file in situation when we have U2000 in HA configuration and two time servers with same STRATUM level in out network should look like this.

server 172.16.1.15 prefer
server 172.16.2.15
server 127.127.1.0
fudge 127.127.1.0 stratum 10

peer 172.16.10.10

In HA configuration each U2000 server needs to have his NTP configured separately, which means it has to have its own ntp.conf file with proper settings.

MA5600T Series Networking Protection Feature
MA5600T Series Maintenance Feature Glance
MA5600T&MA5603T&MA5608T 10G GPON Feature Glance
How to Configure the H.248-based Voice Service?
How to Login Huawei Equipment Through the Local Serial Port

Huawei GPON Frame Structure

GPON frame structure

Upstream GPON Frame
An upstream GPON frame has a fixed length of 125 μs. Each upstream frame contains the content carried by one or more T-CONTs. All Huawei ONUs connected to a GPON port share the upstream bandwidth

• All ONUs connected to a GPON port send their data upstream at their own timeslots according to bandwidth map (BWmap) requirements.
• Each ONU reports the status of data to be sent to Huawei OLT using upstream frames. Then, the OLT uses DBA to allocate upstream timeslots to ONUs and sends updates in each frame. 

Downstream GPON Frame
A downstream GPON frame has a fixed length of 125 μs and comprises physical control block downstream (PCBd) and payload. PCBd mainly consists of the GTC header and BWmap. The OLT broadcasts PCBd to all ONUs. Then, the ONUs receive the PCBd and perform operations based on the information contained in PCBd.

• The GTC header is used for frame delimitation, synchronization, and forward error correction (FEC).
• The BWMap field notifies every ONU of upstream bandwidth allocation. It specifies the start and end upstream timeslots for the T-CONTs of each ONU, ensuring that all ONUs send data using the timeslots specified by the OLT like Huawei MA5600T to prevent data conflict.

Huawei GPON Protocol Stacks

ITU-T Recommendation G.984.3 defines a new set of frame structures, which consider traditional voice, video, and Ethernet packets as payloads of Huawei GPON frames. Figure 2-10 shows the structure of GPON protocol stacks.

GPON protocol stacks involve the physical medium dependent (PMD) layer and GPON transmission convergence (GTC) layer.
PMD Layer
The GPON PMD layer corresponds to the GPON interfaces between Huawei OLTs and Huawei ONUs. Parameter values of the GPON interfaces specify the maximum reach and split ratio for a GPON system.
GTC Layer
The GTA layer is used to encapsulate payloads using ATM cells or GEM frames, and GEM frames are commonly used in GPON systems. GEM frames can carry Ethernet, POTS, E1, and T1 cells.
GTC is the core GPON layer, where media access is controlled for upstream service flows and ONUs are registered. Ethernet frame payloads are encapsulated into GEM frames and then packetized as GTC frames. These GTC frames are converted to binary codes for transmission based on interface parameters configured at the physical layer. The process is reversal on the receive end. Specifically, the receive end decapsulates the data to obtain GTC frames, GEM frames, and then payloads for data transmission.
The GTC layer is classified as TC adaptation sub-layer and GTC framing sub-layer by structure.

The TC adaptation sub-layer involves the ATM, GEM TC, and optical network terminal management and control interface (OMCI) adapters and dynamic bandwidth assignment (DBA) control module. ATM and GEM TC adapters identify OMCI channels by virtual path identifier (VPI)/virtual channel identifier (VCI) or GEM port ID. OMCI adapters

can exchange OMCI channel data with the ATM and GEM TC adapters and send the OMCI channel data to OMCI entities. The DBA control module is a common functional module, which generates ONU reports and controls DBA allocation.
On the GTC framing sub-layer, GTC frames include GEM blocks, PLOAM blocks, and embedded OAM blocks. The GTC framing sub-layer supports the following functions:
− Multiplexes and demultiplexes data. Specifically, the GTC framing sub-layer multiplexes PLOAM and GEM data into downstream TC frames based on the boundary information specified in the frame header. In addition, the GTC framing sub-layer demultiplexes PLOAM and GEM data from upstream TC frames based on frame header instructions.
− Generates frame headers and decodes data. The GTC framing sub-layer generates the TC header of downstream frames in a specified format and decodes the frame header of upstream frames. In addition, the GTC framing sub-layer terminates the embedded OAM data encapsulated into the GTC header and uses the OAM data to control this sub-layer.
− Routes data internally based on alloc-IDs. The GTC framing sub-layer routes the data sent by or to the GEM TC adapters based on internal alloc-IDs.

The GTC layer consists of plane C/M and plane U based on functions.
The protocol stacks of plane C/M include embedded OAM, PLOAM, and OMCI. Embedded OAM and PLOAM channels are used for managing PMD and GTC sub-layer functions. OMCI provides a unified system for upper-layer sub-layer management.
− Embedded OAM channels are defined in GTC frame headers for determining bandwidths, exchanging data, and dynamically allocating bandwidths.
− Dedicated space is reserved in GTC frames for format-based PLOAM channels. The PLOAM channels carry the PMD and GTC management information that does not pass through the embedded OAM block.
− OMCI channels are used for managing services.
Service flows on plane U are identified based on service flow types (ATM or GEM) and port ID/VPI. Port IDs identify GEM service flows and VPIs identify ATM service flows. In T-CONTs, bandwidths are allocated and QoS is controlled using the timeslots that can be adjusted.

Huawei GPON Networking Applications

GPON is a passive optical transmission technology that applies in FTTx solutions, including fiber to the building (FTTB), fiber to the curb (FTTC), fiber to the door (FTTD), fiber to the home (FTTH), fiber to the mobile base station (FTTM), fiber to the office (FTTO), and fiber to the WLAN (FTTW), for voice, data, video, private line access, and base station access services.
Figure 2-7 shows FTTx networking applications.

Huawei FTTx network applications in GPON access have the following in common: The data, voice, and video signals of terminal users are sent to ONUs, where the signals are converted into Ethernet packets and then transmitted over optical fibers to the OLT using the GPON uplink ports on the ONUs. Then, the Ethernet packets are forwarded to the upper-layer IP network using the uplink port on the OLT.

• FTTB/FTTC: The OLT is connected to ONUs in corridors (FTTB) or by the curb (FTTC) using an optical distribution network (ODN). The ONUs are then connected to user terminals using xDSL. FTTB/FTTC is applicable to densely-populated residential communities or office buildings. In this scenario, FTTB/FTTC provides services of certain bandwidth for common users.
• FTTD: uses existing access media at user homes to resolve drop fiber issues in FTTH scenarios.
• FTTH: The OLT such as Huawei MA5600T connects to ONTs at user homes using an ODN network. FTTH is applicable to new apartments or villas in loose distribution. In this scenario, FTTH provides services of higher bandwidth for high-end users.
• FTTM: The OLT is connected to ONUs using an ODN network. The ONUs are then connected to wireless base stations using E1. The OLT connects wireless base stations to the core IP bearer network using optical access technologies. This implementation mode is not only simpler than traditional SDH/ATM private line technologies, but also drives down the costs of base station backhaul. FTTM is applicable to reconstruction and capacity expansion of mobile bearer networks. In this scenario, FTTM converges the fixed network and the mobile network on the bearer plane.
• FTTO: The OLT is connected to enterprise ONUs using an ODN network. The ONUs are connected to user terminals using FE, POTS, or Wi-Fi. QinQ VLAN encapsulation is implemented on the ONUs and the OLT. In this way, transparent and secure data channels can be set up between the enterprise private networks located at different places, and therefore the service data and BPDUs between the enterprise private networks can be transparently transmitted over the public network. FTTO is applicable to enterprise networks. In this scenario, FTTO implements TDM PBX, IP PBX, and private line service in the enterprise intranets.
• FTTW: The OLT connects to ONUs like Huawei HG8546M using an ODN network, the ONUs connect to access points (APs) using GE for WLAN traffic backhaul. FTTW is the trend in Wi-Fi construction.