Evolving network management to bring bandwidth on demand

Jun 2, 2002 12:00 PM, Livia Schweizer

The emergence of the Sonet and synchronous digital hierarchy (SDH) standards has contributed largely to the success of optical networking technology. The two standards have proved to be reliable reference networking technologies for fault-resilient networks. Dense wave division multiplexing (DWDM) was largely inspired by SDH and Sonet and has evolved from technology for point-to-point dedicated applications to optical networking introducing flexibility, tunable lasers and fault resiliency and moving beyond the core to metro areas.

Multiple interfaces and protocols such as the Optical Internetworking Forum User Network Interface (OIF UNI), Network-to-Network Interface (NNI), the Internet Engineering Task Force Generalized Multi Protocol Label Switching (IETF GMPLS) and the International Telecommunications Union Automatic Switched Optical Network (ITU ASON) enable dynamic provisioning of pathways to allow for a new set of services requiring shorter holding times than permanently provisioned bandwidth services. These standards are opening the way for end-to-end provisioning of multi-carrier, multi-vendor, multi-technology networks.

Likewise, the network management system must evolve in order to integrate different technologies in equipment and administer coherent and end-to-end management over the permanently provisioned and automatically switched parts of the network. Ultimately service providers will have the ability to go from path provisioning to service management including service level agreement (SLA) management, policy management, inventory management, fault and performance management and billing.

Service models and network management system evolution

A carrier's optical network can support multiple types of service models:

The Permanent Provisioned Bandwidth (PPB) service model supports leased lines and private-line services; connections that traditionally fall within the category of circuit provisioning and are characterized by long holding times. In the PPB service model the network operator provides connection provisioning at the customer's request through the carrier network operation center. This is essentially the "point-and-click" type of provisioning and the control interface is either human (e.g., a customer calls a customer service representative) or handled via a customer network management system (e.g., a customer may make its request over a secure web site). PPB services are targeted for a market where the carrier's customers are unable to request connections using signaling directly from their network devices or service management applications and require connections to off-net locations and are in need of end-to-end managed services offered by (or outsourced to) carriers.

With PPB, during the provisioning process, multiple network resources are reserved and dedicated to a path.  Network resources are stored in a database to further reserve other resources. The provisioning can take some time, and the process can be either manual or semi-manual. In the semi-manual case, the network management system can be, for example, responsible for end-to-end path computation and setup.

The Bandwidth on Demand (BOD) service model supports services such as the remote backup of data servers, daily transfers to update web content, on-demand distribution between video servers and on-demand distribution of events, but it also supports carrier's carrier services. These connections fall into the category of switched connections and can be more dynamic than permanent connections while also having shorter holding times. With the PPB model, the user is required to pay the cost of the connection independent of the usage of the connection. In current data private-line services, the average utilization rate is low, and most of the bits go unused as a result of underutilization after hours and on weekends. While offices may be closed in the evenings and non-week days, the user still pays for the PPB connection. With the BOD model, service providers have the ability to take down a user's connection when it is unused and restore it when the next business day begins.

BOD service focuses on customers, such as ISPs, large intranet, and other data and SDH/Sonet networks requiring point-to-point capacities and dynamic demands, customers supporting UNI functions in their edge devices.

Switched connections are those connections initiated by the carrier's customers or by a carrier service department of the operator, directly from the customer edge devices or service management applications over the UNI and completed through the control plane (a suite of signaling and routing protocols) in the carrier's network. The time needed to set up bandwidth on demand can be less than only a few minutes. To support the dynamic connections, customer edge devices should be already physically connected to the network with adequate capacity. Entrance into the network needs to be pre-provisioned for point-to-point admission facilities. Equipment throughout the network should be set up automatically upon service request while the BOD service request should be completed only if the request is consistent with the relevant SLA and carrier's policies, comes from an authorized customer, the network can support the requested connection, and the user edge device at the other end point accepts the connection.

The OIF UNI, NNI, the IETF GMPLS and the ITU ASON are concentrating their efforts on standardization of the control plane.

The Optical Virtual Private Network (O-VPN) service model is based on a customer contract for specific network resources (O-sites, capacity between nodes, nodes' ports and links over the network, maximum quality of service (QoS)/availability level) such that the customer is able to control these resources to establish, delete and maintain connections. In effect, each customer has a dedicated optical sub-network under its own control. O-VPN service focuses on large- and medium-sized enterprises with intranets and multiple locations to connect, and on business-to-business broadband applications to be built on top of O-VPN connectivity.

Network Management Systems shall evolve to provide coherent and unified management of PPB, BOD and O-VPN services. In the BOD service model, where establishment of the connection is not part of the functions of the network management system, the connection management has to allow the network administrator to know where the connections are routed for any service model. Moreover, in BOD services the connection admission control, SLA checks and policy controls shall be provided at the connection request. Fault and performance should be managed and presented to the network administrator in a coherent and unified way. Billing of BOD and PPB is based on the bandwidth, service during, QoS, and other characteristics of the connection while O-VPN billing is based on SLA contract.

An example of BOD and O-VPN Services are shown in Figure 1.

Network management in a multi-carrier, multi-vendor, and multi-technology network

In multi-carrier, multi-vendor transport networks and in multi-technology data and transport networks, carriers need to find ways to reduce operational expenses during the setup of end-to-end optical connectivity.

The OIF UNI, NNI, the IETF GMPLS and the ITU-T ASON are defining requirements for intra-carrier, multi-vendor domain and inter-carrier interfaces and for standardizing the control plane to achieve interoperability for end-to-end service provisioning. These interfaces have different requirements; for example, in cases of trusted or un-trusted relationships where intra-carrier, multi-vendor domain is a trusted relationship, while inter-carrier interface is considered un-trusted.

These standard bodies are progressing and will reach their goal if interoperability is demonstrated and deployed in the field. OIF, for example, standardized last year the UNI1.0 interface between a client network (e.g., a data network) and a transport network (e.g., SONET/SDH) and performed an interoperability test with more than 25 vendors, including Alcatel, at Supercomm 2001. The NNI is currently being standardized: the expectation is that an NNI signaling interoperability trial will happen in mid-2002 and routing will be interoperable afterwards.

Network management systems shall evolve to provide a coherent evolution and unified management. Indeed, not all devices will have the same self-provisioning capability, and most networks will have both GMPLS and non-GMPLS enabled network elements. In these networks, the network management system will act as proxy-GMPLS device with UNI and NNI signaling protocols to act on behalf of non-GMPLS capable network elements (Figure 2).

Figure 3 shows that core and metropolitan transport networks can be supplied respectively by different vendors, a proxy-GMPLS network management system application allows the operator to demand, either via protocols or via graphical user interfaces and under carrier's control, connectivity through the core and metropolitan networks to offer a carrier's carrier service.

For fault and performance management, network planning and optimization, and for inventory management, the network management system still will be required and will need to address the introduction of automatically switched sub-networks and intelligent network elements.

This article deals in particular with the emergence of Optical Bandwidth on Demand (BOD) Services and Optical Virtual Private Networks (O-VPN) with differentiated service level agreements and flexible pricing structures; as well with end-to-end provisioning of multi-carrier, multi-vendor, multi-technology networks. All of these emerging technologies require the evolution of a coherent and unified network management system to move from connections to services.

Livia Schweizer is Product Manager of Product Strategy Network Management for Alcatel's Terrestrial Networks Division.

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