OTN ASON Passing Through third-party Huawei DWDM Link Solution

1.        Background

Huawei OTN ASON network has been widely applied into various operators’ network in recent years. The advantage of OTN ASON is the large transport capacity natively with Huawei WDM combined with the flexible service grooming come with OTN. And further with the service protection scheme achieved by ASON. In most scenarios, the optical layer ASON or WSON network is built with pure Huawei NG WDM equipments such as OSN 8800/6800. While in some case, due to the investment reason, operator would like to use their legacy DWDM link resource and build OTN ASON network over the legacy network. Especially for large country, already have basic national backbone build on DWDM.

OTN ASON over third party DWDM link is a solution designed to meet such requirement. And already have some network under construction with such feature when is paper is written. In such network the ASON node is OSN8800 equipment, and the DWDM link can be BWS serial equipment link or DWDM link of other vendor.

This paper will introduce the solution design and implementation of OTN ASON over third party DWDM link.

1. 2.        Feature Introduction

To enable the ASON link launched over third party link. The third party link must meet two requests, transport the ODU frame of ASON node transparently and the fault of the third party span should be detected and trigger the reroute of ASON service. Transparent transport of ODU frame is a compulsory pre-condition for the solution, and third party span fault detection is achieved by using TCM byte alarm as ASON reroute trigger in ASON node.

2.1 Inter-connection scheme

Generally the third party link can be categorized to Huawei DWDM link and other vendors’ link. When applied on Huawei BWS link, the inter-connection scheme can be transponder with color port of ASON node WDM side connect to MUX/DEMUX board of BWS 1600G link or transponder with gray port of ASON node WDM side connect to the client port of transponder of BWS 1600G link.

Until now the transponder support gray port on WDM side include TN52,52,54NQ2.

 In scenario which ASON node connect to other vendors link, ASON node transponder can only use gray port and connect to the client port of other vendors’ transponder. Show as Figure-1

Limitation:

1, Different with ASON network with pure Huawei equipments, which the speed rate mode of the transponder in two end can be adjusted automatically between standard mode and speedup mode. When the ASON network is passing third party link, the speed rate of the transponder should be locked.

2, When ASON link pass through BWS 1600G link, the transport of ODU frame is not totally transparent, need configure the pass through of RES and GCC byte manually.

2.2 Fault detection scheme

ASON uses TCM-layer alarms to detect the status of links between the OSN 8800 ASON node connected to the third-party network and trigger rerouting based on link status. If a link between OSN 8800 equipment and equipment on the traditional WDM network is faulty, the OTU board of the downstream OSN 8800 will detect a TCM-layer alarm and report the alarm to ASON. ASON sets the status of the TE link to Down based on the TCM alarm and triggers service rerouting.

Users can specify whether the OTU board reports TCM alarms by setting the enabling status and operation mode of the TCM, and specify whether the TCM alarms on the OTU board are reported to ASON by specifying whether to enable the TCM for ASON.

TCM alarms that trigger ASON rerouting include:

SF-type alarms: ODUk_TCMn_LCK, ODUk_TCMn_AIS, ODUk_TCMn_OCI, ODUk_TCMn_TIM, and ODUk_TCMn_LTC.

SD-type alarms: ODUk_TCMn_EXC and ODUk_TCMn_DEG.

1. 3.        Solution Design- Case Study

The topology showed in figure-2 is the network implemented with ASON passing through third party DWDM link feature, in Country B. With 22 ASON nodes of OSN 8800 T64/T32. And the third party link include the existed Huawei BWS Link, and 40G link with OSN6800, and other vendors’ 10G/40G link. 

Figure-2

Generally, in each capital city have two or more ASON node to form  the national backbone mesh network.

1. 4.        Implementation

Main scenario in network implementation introduced as below:

Scenario-1 Interconnect with Huawei BWS 1600G link

The most often scenario, TN52/TN54 NQ2 grey optical port connect to 1600G SSE7/SSE8 LBFS, LBFS board have back-back connection in the link

Scenario-2  Interconnect with Huawei NG WDM  link

TN52/TN54 NQ2 grey port connect to OSN6800 TN13 LSX. LSX have back-back connection, through TX/RX to re-generate.

Scenario-3  Interconnect with Huawei NG WDM  with color port.

ND2 with color optical port, connect to MUX/DMUX of OSN6800/1600G, in the link have ND2 work in regeneration mode.

Scenario-4  Interconnect with Huawei NG WDM  40G link.

TN52/TN54 NQ2 grey port connect to TQX client port. OSN6800 by cross connection  board multiplex service to NS3, NS3 40G link can have regeneration by back plane cross connection board in intermediate site.

Scenario-5  Interconnect with other vendor  40G link.

Similar with scenario 4, third party link consist of 10G tributary board for inter connect with NQ2 in ASON node to aggregate service, and DWDM link formed by 40G transponder.

Scenario-6  Interconnect with other vendor  10G link.

Similar with scenario 1/2.

Reference：

1. Operation Guide to Huawei WDM ASON Services Passing Through a Third-Party Network V1.3, ASON R&D team, 2011-9-12

1. T  Account OTN ASON network design, 2011