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Prepping Ethernet for new prioritization, timing tasks

Posted: 05 Jan 2012 ?? ?Print Version ?Bookmark and Share

Keywords:Ethernet? switches? TDM? MLPS?

Developers of Internet access devices are familiar with using such interface chips as T1/E1 framers and ATM circuit emulation devices, all with the aim of making packet and circuit services work well together. The rise of end-to-end Ethernet in the public network would seem to simplify the job for the OEM designing equipment for the enterprise. However, sending out an Ethernet packet to do an isochronous circuit job is not always as simple as might be anticipated.

When Ethernet switches first were employed in the telco central office, existing Layer 2/Layer 3 switches for the LAN were simply scaled up to offer more ports and faster speeds per port, and in many cases that worked just fine. But the development of new standards for packet prioritization and fault resilience, the product of such organizations as IEEE, Internet Engineering Task Force, and Metro Ethernet Forum, has tasked the network-interface OEM with new requirements for service-aware support at the network demarcation point.

OEMs want to offer enterprise customers a platform that can interface to a service provider with Ethernet services in a manner that preserves everything the customer already knows about packet and circuit services. This means that an access system must offer prioritization of traffic that is as fine-grained as necessary for a customer fs mix of voice, data, and video services. It also means the service protection should be similar to that found in Sonet, midband TDM (T1/E1), and Asynchronous Transfer Mode (ATM) services available in the public network.

The advantages of unifying on Ethernet extend to both carriers and their enterprise customers. By relying on Ethernet as the underlying common Layer 2 protocol, service providers not only flatten their own networks, but also allow their customers to enable unified services across multiple operators. One access device thus can link with many operators. Where once a Network Interface Device (NID) was seen as a tunnel and services platform, operating largely at Layer 2, to interconnect User Network Interfaces, the future NID becomes a more manageable and service-aware platform.

In the new NID, hardwired Operations, Administration, and Maintenance (OAM) is a virtual necessity, due to the need for performance management to be accomplished at wire speed at multiple layers in the OSI stack. In addition, network edge devices must be able to handle a mix of fiber-based Ethernet rings and bonded copper, which will continue to be seen at the network edge.

It is also important for the switch at the network edge to support both standard Multi-Protocol Label Switching (MPLS) and the more recently defined transport version, MPLS-TP, as real-world public networks will use a mix of bridging, L2 switching, and routing in the most practical and cost-effective manner possible. It is not necessary for every Ethernet switch to be a full-service router, but providing support for full Layer 3 classification is a necessity.

While an enterprise customer may not fully realize the capabilities introduced by a dedicated management channel for OAM, the software provided with such a platform will allow indirect control and handoff of service prioritization to the primary service provider and an out-of-franchise operator. This means the enterprise customer can "dial up" Service Level Agreements (SLAs) that involve a single provider or multiple providers. In this case, a Hybrid NID enables more complex traffic management through its dedicated management channel. An out-of-franchise operator can relinquish control of the NID UNI to a second operator through a management channel, thus allowing true multioperator SLAs to exist. The key to realizing a true Hybrid NID is to not lock in management to either a local or OOF service provider, but allow the operators to share an negotiate management of services as part of the SLA.

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