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FierceTelecom.com continued from page 5 Level 3 Makes its Point with Ethernet Santitoro said. “There are two different OAM standard drafts right now, one [G.8113.1] that is based on Y.1731, the ITU-T approach, and the other [G.8113.2] is the more MPLS-centric IETF approach. There are some incompatibilities between the two that need to be resolved.” Santitoro added that it is possible for MPLS-TP to include two different OAM models. “You could have both in the standard and say carriers may use one or the other, but that could lead to interoperability problems if carriers are interconnecting,” he said. “PBB- TE has the advantage of having a single OAM standard, and only one layer of OAM to manage.” The standards delay may appear to put MPLS-TP at a disadvantage in terms of market adoption, but COE has not been deployed widely enough yet for that to be the case. Though Overture Networks does not currently support COE, Prayson Pate, chief technology officer at Overture, said MPLS-TP still has the leverage of well-developed MPLS market behind it. “The IETF is an interest- ing group in that their standards usually reflect what people are actually using, rather than trying to define what they should use,” he said. “The IETF’s work on MPLS-TP reflects a market for MPLS that is already mature, and that the big carriers are already using this technology, and will continue to use it in the future.” The standards race may not be much of a race at all, which might be part of the reason why several COE vendors feel the need to support both standards in their future equipment platforms. Further supporting the likelihood for both standards to be viable is the tendency of the Metro Ethernet Forum, which created the specifications for supporting Carrier Ethernet services, to be agnostic when it comes to infrastructure technology architectures. “It was a great decision by the MEF to focus on service attributes rather than technology,” Santitoro said. “The MEF is technology agnostic, and they care more about Ethernet as a service.” He added that the MEF is working on its own specifications to support future cloud services. l BY DAN O’SHEA � Throughout the telecom service provider sector, the need to draft Ethernet in service of point to point transport network applications is becoming increasingly apparent. The movement toward standardized Connection-Oriented Ethernet (COE) provides carriers with an architectural approach and different options for doing just that. COE is gradually making its way into transport networks, though deployment has yet to become widespread. Still, service providers are taking some of the notions inherent to COE—point-to-point connections, deterministic service quality, ease of management—and applying them to the transport services they are delivering to customers. These services include backhaul for mobile carriers, as well as backhaul for wireline broadband in business and residential markets. Another emerging application is data center interconnection for fast growing segment of cloud service providers. It turns out that COE technologies—the Ethernet-centric provider backbone bridging— traffic engineering (PBB-TE) standard, and the multi-protocol label switching-centric MPLS—transport profile (MPLS-TP) standard, which still has a couple operations, administration and maintenance kinks to be worked out—are not the only options these carriers have for addressing their point to point application needs. “We are not currently using Connection-Oriented Ethernet in our network, but we do provide COE services to our customers by doing point-to-point private virtual circuits over MPLS,” said Ted Wagner, senior director of product management at Level 3 Communications. “We also can deliver the same sort of quality Ethernet experience over SONET. For now, we can meet the needs of ourselves and our customers for point to point without using Connection-Oriented Ethernet per se.” Wagner said that Level 3 does not necessarily see a clear delineation between point-to-point Ethernet and other architectural methods for using Ethernet. When the company looks at using Ethernet to satisfy various applications, it is in terms of deploying it over MPLS, which eases the routing complexity between network end points. “We use Ethernet over MPLS both for the flexibility it gives us, and the mix of applications it can support.” Mobile backhaul, business broadband and data center interconnection are among some of Level 3’s chief applications for point to point Ethernet, according to Wagner. Level 3’s comfort level with Ethernet in transport applications may not be so typical in the service provider market, since the company probably has much less of older technologies like ATM and Frame Relay deployed in its network than some of the other Tier 1 carriers. But, its use of Ethernet is evidence of how the large service providers have been getting more accustomed to working with Ethernet over the several years by putting their trust in Carrier Ethernet service guidelines from the Metro Ethernet Forum (MEF), as well as new Ethernet technology schemes from vendors. Wagner noted that some carriers, including their customers have been very quick to adopt Ethernet, but that other companies may still be moving more deliberately into the Ethernet era. “Some companies just haven’t seen a compelling reason to move that quickly,” he said. “It depends on what your needs are.” That position also pretty much explains where Level 3 is in thinking about using standard COE architectures like PBB-TE or MPLS-TP. Wagner said that while Level 3 has not deployed these technologies up to this point, the company does continue to track their evolution. “I don’t think we are going to use them anytime soon, but we are always looking for ways to improve our infrastructure and how we support our services,” Wagner said. “I’m not sure if that will happen via MPLS or something else. What we’re always looking for are new ways to scale and to lower costs.” l 7 April 2012 April 2012 8
FierceTelecom.com Connection-Oriented Ethernet Strategies for Next-Gen Networks BY MiCHAEl kENNEDY � Connection-Oriented Ethernet (COE) is designed to provide packet-centric services that meet the needs of Next-Gen transport solutions while maintaining the attractive operational features of SONET/SDH designs. COE is used in the access and preaggregation portions of the network particularly where low cost, guaranteed performance and high security are required. Primary applications include mobile backhaul, Ethernet private line business services, wireline broadband backhaul, and for some peering links in wholesale networks. Operational simplicity is a high design priority because thousands or even tens of thousands of network links may be deployed. Requirements for highly skilled engineers and technicians should be minimized to achieve low cost at massive scale. COE is a fusion of connectionless Ethernet and SONET/SDH design features. Ethernet features include Layer 2 aggregation, statistical multiplexing, and flexible bandwidth granularity. These features support cost efficient aggregation of traffic flows while maintaining bandwidth guarantees for high priority traffic. Familiar concepts such as the Metro Ethernet Forum’s (MEF) Committed Information Rate (CIR) and best efforts service are maintained. This provides guaranteed quality of service (QoS) for high priority services just like SONET. However, it provides better economic performance than SONET by providing capacity for best efforts service during periods of slack capacity. Bandwidth granularity in one Mbps increments also provides more efficiency than SONET’s 50 Mbps bandwidth increments. As a variant of Ethernet, COE has the low cost of Ethernet products versus the high cost of SONET and TDM products. For example, the cost to equip and deploy a 100 Mbps Ethernet service is about the same as the cost to equip and deploy a 1.5 Mbps T1 service. COE maintains some SONET-like features. QoS is deterministic and precise. Bandwidth is reserved. Service conforms to a five 9s availability requirement and the protection path is provided within 50ms of a circuit failure. Security is at the highest level service runs over a point-to-point (or multipoint) Layer 1 link. COE is implemented through Ethernet-centric and MPLS-centric approaches. The Ethernet-centric approach is a high performance implementation of Carrier Ethernet. However, as its name implies it is connection-oriented. Ethernet bridging is disabled. No Spanning Tree Protocol or MAC address learning/flooding are employed. Ethernet paths are static and provisioned by a management system—this makes protection path performance deterministic (predictable). Label-based frame forwarding is used and designed to eliminate the scaling limits of original VLAN schemes. This approach makes COE more like SONET which dominates metro networks today. Most importantly this approach provides a smoother transition for SONET-trained operations personnel. The MPLS-centric approach to COE employs MPLS Transport Protocol (MPLS-TP). This approach brings MPLS to access networks. In-band operation administration and maintenance (OAM) is introduced into MPLS OAM. This replicates the transport-centric operations familiar to TDM operators and provides a simple mechanism for validating that the data path is operational in the network. MPLS-TP supports restoration mechanisms based upon a static backup path. This is like the Ethernet-centric approach and differs from the dynamic control plane approach used by MPLS in core networks. MPLS-TP employs pseudowires for multiservice transport. This is particularly important in mobile backhaul applications where 2G, 3G and 4G technologies share many cell sites thus, TDM, ATM and Ethernet services must be supported in the same transport link. This is accomplished by establishing three OAM layers; one for Ethernet, ATM or TDM; a second for the pseudowire; and finally a MPLS Label Switched Path. Advocates for the Ethernet and MPLS centric approaches of course are quick to point out what they see as short comings of the other approach. My view is that the perceived short comings are primarily dependent on the approach to the market taken by the systems vendor and by the service provider’s business and operational requirements. For example, Ethernet-centric advocates point to MPLS-TP’s three OAM layers as an example of operational complexity and as being less than optimal for Ethernet service delivery and transport. MPLS-centric advocates point to the Ethernet-centric approach’s lack of multiservice capabilities and incompatibility with MPLS. Furthermore, Ethernet-centric advocates observe that many transport organizations lack MPLS expertise. Also, the lack of IP functionality in Ethernet-centric COE is seen as a strength by Ethernet-centric advocates and a weakness by MPLS-centric advocates. These differences can be resolved by evaluating each approach in the context of actual deployments. First, an avowed rationale of the MPLS-centric camp is to extend MPLS across the network end-to-end. MPLS-TP is needed to accomplish this because some aspects of MPLS are incompatible with access network requirements. For example, the large number of access nodes compared to the core network makes routing algorithm used in the core computationally infeasible in access networks. Service providers whose goal it is to extend MPLS end-toend in their networks will not see the need to train the transport organization as a barrier to adoption of the MPLS-centric approach. As a second example, many service providers are deploying packet optical transport (POT) systems in their networks to cost effectively handle TDM and Ethernet traffic. The Ethernet-centric approach’s lack of a multiservice capability is not a weakness for POT deployments. COE, despite the approach, is essential to achieving the low cost, high performance, and security required by leading edge services including mobile and broadband backhaul, and business Ethernet services. l Michael Kennedy is a regular FierceTelecom columnist and is Principal Analyst at ACG Research—www.acgresearch.net. He can be reached at mkennedy@acgresearch.net. 9 April 2012 April 2012 10
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