White Paper Challenges in Managing Optical Transport Networks

Introduction

The growth of numerous multimedia applications such as Telepresence, Video share applications, mobile broadband applications and cloud computing has resulted in increasing network traffic and bandwidth requirements both for the consumers and application providers alike. With the increase in packet traffic a solution was needed where both TDM and packet traffic can be supported in a single transport element and also services can be directly mapped onto transport technology. Most of the applications require bandwidth on demand instead of permanent connections. Though the traditional SONET/SDH/DWDM solutions offer good bandwidth with high quality of Service with predictable protection and restoration capabilities, they lack in dynamic provisioning and flexibility in multiplexing services. Besides SONET/SDH networks required considerable amount of operational expenses for managing the networks and the circuits were not used efficiently hence keeping the costs high. This forces the service providers to look for new transport technologies that support very high bandwidth rates with high QoS while containing costs so the cost per GB bandwidth is still affordable. This led to the development of new standards for “Optical Transport Network” that provides flexibility to multiplex various services and also package the services efficiently on top of optical transport. In addition standards for automatic provisioning and restoration (ASON) have been developed that will reduce the provisioning time to activate the services and reduce operational costs for managing the transport network. 

Market Drivers
The advances in mobile broadband and new video streaming technologies led to proliferation of multi-media applications to the consumers. The bandwidth demands have now increased tremendously with more and more users signing up for FiOS and high bandwidth cable modem access services. The service providers now face the challenge of offering bundled triple play/quad play services with reduced cost. This has led to deployment of high bandwidth core networks with high quality of Service and stringent SLAs. Following are major market drivers to come up with new transport technology and management standards that will meet today’s requirements as well as be ready for tomorrow’s demands. 

• WDM systems can support higher bit rates and SONET/SDH structures cannot support that high bit rates. A new technology that can switch and multiplex multiple payloads and efficiently utilize the wavelengths is needed to meet the demands of today’s market.
• CapEx costs have to be reduced to offer low cost high bandwidth solution.  This requires that the overall hardware/software COGS need to be reduced by reducing the processing within transport elements to carry and process payloads.
• Proprietary implementation for error corrections, OAM functions and operational procedures should be reduced or eliminated so a multi-vendor networks can be deployed.
• Existing technologies are inadequate to monitor payload as a whole. It is difficult to correlate facility errors to payloads and services. Better monitoring at the payload level is required. A new technology that can transport Ethernet or SONET payload as a whole is required.  
• Management of transport nodes in general has been very complex and it is vendor specific. End to end provisioning of transport network is a manual process and needs to be carried out with lot of planning.
• Network Planning, Topology and discovery are very specific to NEs and it is difficult for operator to understand unless NE details are known.
• Differences in NE behaviors for the same situations such as automatic protection, network fault restoration make it difficult to repair faults and restore services
• Lack of interoperability between vendors makes it difficult to plan for multi-carrier/multi-vendor networks.

• Due to this complexity the operational expenses has been very high which adds to the cost of per Gb bandwidth. Better standards are needed that will enable automatic end to end provisioning and restoration. 

ITU-T, Telcordia, IETF, OIF and various other standard forums have been working on the standards for next generation technologies. The OTN standards have gained popularity and the vendors have started implementing OTN systems. To address management complexities, standards for Automatic Switching of Optical Nodes (ASON) have been developed.

Optical Transport Network
Optical Transport Network standardization efforts were started to address some of the issues faced by service providers in deploying transport networks. The major issues were ability to support higher bandwidth rates, switching and multiplexing of various services and monitoring at service/payload level. OTN has the following advantages over traditional optical transport:

• Supports higher bandwidth rates (2.5 G to 40G per wavelength)
• Provides efficient packing of each wavelength
• Dynamic multiplexing of services
• Visibility of packet content for better monitoring
• Supports both packet and circuit(TDM) traffic
• Automatic restoration to recover from network faults
• Support for multiple technologies (WDM, Sonet/Sdh, Ethernet, MPLS, Microwave radio links)
• Multi-carrier, Multi-vendor interoperability due to support for standardization
• Processes OAM similar to SONET networks

Telecom Equipment Manufacturers have already started to develop OTN systems and the initial systems are ready to be deployed. Service providers are already thinking of migration from traditional optical networks to OTN based deployments. The network management solutions for OTN network management need to be developed in order to complete and manage the OTN deployments.

Automatic Switched Optical Network
Automatic Switched Optical Networks concept is being developed to improve resource and connection management within optical networks. Traditionally it required manual provisioning of the cross connects for the entire network to enable a service. Depending on the SLAs,  the protection paths have to be pre-planned and all cross connects need to be manually provisioned. With the ASON standards automatic end to end provisioning is made easier and also dynamic bandwidth on demand services can be offered. Automatic restoration from network faults can also be achieved instantly The aim is to automate the end to end cross connect provisioning using GMPLS control plane communications between the network elements. ASON tries to provide a common information model for the transport network so the dependency on vendor specific information or behavior is greatly reduced or eliminated. The ASON standards address the following:

• Resource Management
• Automatic connection management and end to end path computation
• Connection protection/restoration
•  Bandwidth on demand requirements
• Customer initiated connection requests, scheduled or time of day services
• Topology discovery
• Traffic Engineering

The ASON architecture proposes layered architecture for the management of optical networks. It consists of management plane (MP), Control Plane (CP) and Transport Plane (TP).
Management Plane provides Element management, Network management and Service management functions including FCAPS, service provisioning, and service monitoring. The management plane interacts with control plane using a common information model that represents the resources, links, connections, and bandwidth. The Control Plane implements control functions such as connection control, call control, routing, link resource manager, termination and adaptation functions and discovery agent. The transport plane contains transport resources and is responsible for resource provisioning. Figure below illustrates the relationship between the ASON architectural components (ref G.7718-Y1709 ITU-T standards).

The scope of control plane functions and the management view of the element management functions and interfaces as per ITU-T G.7718 y 1709 are illustrated in the figure below. The management plane will implement the FCAPS functions, end to end provisioning of static cross connects, billing, and interactions with control plane for automatic end to end provisioning and restoration.

Management Challenges
The deployment of transport networks involved high operational costs as the NOC operators were required to undergo training to understand the transport network element, their provisioning and behavior. Each vendor’s equipment had their own way of cross connect provisioning, NE specific behavior for fault management, protection and recovery The network planners need to plan both working path and protection path for every service and pre provision all cross connects. Dynamic changes were very difficult and service activation, monitoring and maintenance were quite complex.

The OTN and ASON standards were developed to reduce the complexity of service provisioning and increase the interoperability between multiple vendors so a multi-carrier, multi-vendor network can be deployed easily with high QoS and relatively lower cost. This requires:

 

• All the vendors of OTN network elements to comply with the standards proposed by ITU_T and IETF
• Common Information model and interfaces proposed by ASON should be used in control plane and management plane
• All interoperability requirements should be specified by a common forum and efforts should be made to have the vendors conform to standard interfaces. This effort is already undertaken  by OIF.
• The service providers should insist on interoperability conformance by vendors prior to deployment.

The ASON standards have proposed to delegate end to end automatic provisioning using control plane. Migrating from a traditional management solution to hybrid management plane – control plane solution brings additional challenges:

 

• Maintain consistency between management plane and control plane for topology, link status and resources information
• Resynchronization of information when communication between management plane and control plane communication restored or when changes occur in the network
• Ensure consistent management policy across multi-vendor/multi-domain network
• Synchronization and coordination between management plane initiated provisioning vs. control plane initiated automatic provisioning
• Smooth migration from a traditional management to hybrid management and also providing backward compatibility to existing deployments
• Accurate fault analysis of transport plane failures and timely restoration

The control plane and transport plane are implemented within equipment. The vendors typically have a tendency to add proprietary implementation to standards interfaces to differentiate or increase the value. If products are developed for control plane and management plane that comply with the above requirements, it will reduce the cost of development for equipment vendors and enable interoperability between vendors while reducing management complexities. 

OTN Management Solution

The primary objective for ASON based management solution is to reduce complexities in provisioning and enabling flexibility to support bandwidth on demand and scheduled  time of day services. Any management solution for managing OTN networks should support these objectives. The OTN management solution should support control plane interactions for automatic provisioning to comply with the ASON standards.

The deployment configuration for OTN solution is provided in the figure below. The Management Plane interacts with Control plane using NMI-A interface and transport plane using NMI-T interface. The end to end provisioning for a service involves following type of connections:

• Permanent Connection (PC): This is similar to existing static cross connect provisioning and the EMS determines the working path and protection path and establishes permanent cross connect provisioning for the service in each node without control plane involvement. Here the EMS is aware of the topology and the circuit availability based on constant interaction with the network element. This is a manual process and may take weeks to complete the provisioning process.
• Switched  connection (SC): These are the connections established by the client systems to establish a connection for a service on demand. This is accomplished by client systems requesting a connection via control plane, use the bandwidth and tear down the connection when the service ends.
• Soft Permanent Connection (SPC): In this case the connections are established based on a schedule. The connections are requested by management plane for a service requesting time of day services or a scheduled service. The management plane requests control plane of an ingress node to set up end to end provisioning for a service. The management plane establishes the connections between client systems and ingress/egress nodes.

For supporting these services the management plane uses NMI-A interface to interact with control plane and NMI-T interface to interact with transport plane. The transport plane interactions are same as traditional management interface to a Network element which uses TL1, SNMP or XML interfaces. The NMI-A interface depends on the implementation approach for control plane. In a distributed control plane implementations interface such as XML, REST or CORBA can be used.    

NOCVue OTN Solution

NOCVue is a scalable management platform for developing Carrier-Grade EMS solutions.  NOCVue follows industry standard protocols and interfaces to communicate with Network Elements and Operations Support and Network Management Systems.  It provides a state-of-the-art graphical user interface with intuitive, consistent and flexible views for supported management functions.  NOCVUe supports multiple operating systems and multi-databases.  Out-of-the-box support includes the core FCAPS capabilities required for a typical carrier grade EMS and NMS solution.  The platform accelerates time to market and reduces development costs by incorporating many Carrier-Grade requirements in its core. OTN/ASON management requirements can be easily incorporated into NOCVue platform. The section below describes the NOCVue solution for managing OTN networks. NOCVue high level architecture is provided  in the figure below.

NOCVue supports N-Tier architecture to support scalability, extend-ability and modularity needed for any carrier grade Management application.

Management Application Server: 

• Can be deployed in a 1+1 High Available mode or clustering mode..
• Supports interfaces for communicating with a wide variety of clients based on Java Swing, Web client, North Bound OSS clients and 3^rd party application clients.
• Hosts FCAPS applications and technology specific solutions like Optical, Metro-Ethernet and WiMAX etc.
• For OTN management an application for end to end provisioning and connection management of optical networks based on ASON requirements G.7718 y.1709 can be added. The topology, inventory, fault and performance monitoring modules can use data collected at the NMI-T interface as shown in the figure below.   For connection management the application can interact with OTN module in the NSE to send requests and receive responses and notifications from control plane. The traffic engineering database can be modeled and created by interacting with control plane.
• NOCVue provides north bound interface based on TMF standards. Specific interfaces based on MTNM v3.5, TMF 608, TMF 814 standards can be easily plugged in to NOCVue solution.

Network Service Engine: 

 

• Hosts the standard device specific management capabilities like Fault, Performance data collection, Software Upgrades, Provisioning etc. Vendor specific customization can be implemented on top these standard capabilities.
• Can be deployed on multiple servers based on network segregation or based on the services provided by NOCVue.  This allows NOCVue to simultaneously manage hundreds of thousands of network elements per deployment.
• Has a wide variety of built-in protocol adapters such as SNMP, XML, HTTPS, TL1 for communicating with Network Elements.  This will meet the NMI-T interface specified in ASON standards.  Additional protocol support can be easily plugged in to the solution.
• For NMI-A interface XML based interface using the data model specified in ITU-T G 7718 series recommendations can be used. NOCVue platform already supports XML. The specific data model needs to be incorporated. 

NOCVue Control Plane:

• NOCVue control plane solution is provided as a middleware that can be embedded in an Network Element for distributed CP implementation or used as a proxy outside the element to help migrate from older network deployments. The control plane incorporates control plane functions such as connection management, topology, link resource manager, inventory, bandwidth availability, and routing. Control plane supports UNI for interfacing with clients and XML to interface with management plane. It provides south bound adaptation layer to interface with TP. NOCVue control plane architecture is provided in the Figure below.
• The NOCVue control Plane supports XML to interface with Management Plane, UNI and TP. Most of the Network Elements today support XML or Netconf based interface. So providing XML based middleware will be easier to support most of the vendors. Additional protocols can be easily supported by developing protocol adapters.   

Conclusion
The ASON standards specify the requirements for automated end to end provisioning and reduce the complexities in managing optical networks. With the distributed control plane approach the provisioning can be much faster as the Network Elements are aware of the topology, availability of resources and the current traffic engineering information for efficient routing. The end to end provisioning can be achieved in seconds as opposed to months that used to take with the network operators provision each device manually. Additionally flexibility can be introduced to offer bandwidth on demand and scheduled time of day services which most of the multi media applications today need.
NOCVue being a flexible platform with most of the protocol adapters already built in,  a OTN management solution can be easily developed in a short timeframe. Additionally a control plane solution can be easily offered along with EMS/NMS solution to increase the interoperability between equipments and management systems. Common database model can be used between EMS and Control plane and the integration efforts can be reduced tremendously. The control plane software can be easily plugged into the equipment software as a module and with XML based interface it can easily interact with other modules within transport plane. Developing a control plane software in house will take a long time and in addition one needs to worry about integrating with client software and management plane. A combined single vendor solution not only offers a quick solution to equipment vendors and also provides a one shop solution for the management challenges. 

 

About Velankani

Velankani is an Engineering and Consulting services company focused on providing full product life cycle development and support for enterprise and Carrier-Grade products for the telecommunications industry.  Velankani offers its customers a portfolio of products, resources and service quality that they need to secure a competitive edge in a global market.  Our mission is to enable telecommunications product vendors the ability to meet their time and cost constraints while exceeding their performance and quality expectations.

With its corporate headquarters in Piscataway, NJ, and a 22 acre technology campus in Bangalore, India, housing over 500,000 square-foot of office space.  Velankani has the facilities and human resources needed to complete a full range of systems integration and software and hardware development projects for its growing clientele.

Velankani is ISO 9001 certified company and it follows all the standard practices in term of process improvements.

For further details, please visit our websites: www.velankani.com and www.nocvue.com

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