According to industry analysts, Ethernet services are steadily eroding revenues generated from traditional Frame Relay, ATM, and private line services. With cloud-based services revolutionizing user behavior and network resource utilization, Carrier Ethernet is suitably poised to become a strategic technology enabler.
The MEF has laid a strong foundation for Carrier Ethernet based on five key service attributes:
1. Standardized Services
The MEF has standardized three key Ethernet service types:
• E-LINE services to provide secure, point-to-point connections between two business locations
• E-LAN services to enable a LAN on multiple business locations
• E-TREE services to support multicast services
Service providers have been able to innovate on standardized services using the multiple technology options offered by Carrier Ethernet. Several options for building the underlying transport infrastructure to deliver a Carrier Ethernet service are depicted below:
Ethernet over microwave is one of the fastest adopted technologies for backhaul segments. Ethernet over DSL/PON/bonded copper is primarily embraced by the Carrier Ethernet access platforms.
Bandwidth Scalability: Ethernet has evolved over the past 10 years to offer a wide range of interface speeds ranging from 10/100/1000Mbps to 10/40/100Gbps. Features like Link Aggregation and DSL Bonding help carriers to define intermediate bandwidths to enable services on the fly through software controls from their network operation centers.
Network Scalability: Enterprise businesses today demand that networks should be scalable beyond geographical boundaries. Network scalability has been achieved through features like VPLS on MPLS based networks which later evolved into H-VPLS to address deployment challenges. On Ethernet-based networks, Provider Bridging further overcomes scalability limitations, evolving into Provider Backbone Bridging (PBB) with MAC-in-MAC encapsulation for large scale carriers. PBB completely isolates customer MAC addresses which helps to scale the core network.
Services Scalability: The ability of an underlying technology to multiplex services at the same user-network-interface and to have a deterministic network model is the key aspect to scale services. Service multiplexing for Ethernet-based networks initially revolved around PBB and PBB-TE. PBB-TE offers a managed, deterministic connection oriented model which mimics its legacy counterparts such as SONET/SDH closely. This makes it the technology of choice for most carriers. For MPLS-based networks, MPLS-TP provides a similar deterministic network model.
For Carrier Ethernet equipment, reliability simply means replaying the unmatched 50ms restoration capabilities offered by its legacy counterparts. Looking deeper into the network it means much more – quick fault detection, isolation, and recovery.
Fault Detection and Isolation: Ethernet OAM (IEEE 802.3ah, IEEE 802.1ag, ITU-T Y.1731) functionalities are provided by all Carrier Ethernet equipment vendors. To isolate faults at the earliest, silicon vendors include Ethernet OAM features in their hardware itself. This hardware offloading has helped to handle multiple OAM sessions simultaneously and improving the failure detection performance. On MPLS-based networks, the hardware offloading of MPLS OAM features like LSP Ping, BFD, and VCCV, is also gaining popularity in next generation architectures.
Recovery and Restoration: Ethernet ring and line protection as defined by ITU-T G.8032 and G.8031 brings in fast restoration capabilities and is highly cost effective. For MPLS-based networks, features like Fast Reroute and path protection capabilities like LSP protection along with the fault detection capabilities of BFD provide the ability to meet the 50ms restoration requirements.
Reliability: Reliable, intrinsic timing capability is another important feature requirement of Carrier Ethernet equipment. Synch-E (ITU-T G.8262) and IEEE 1588v2 are the timing-over-packet technologies widely used to synchronize clock frequencies across devices in backhaul networks. Today these standard features are available in switch chipsets designed for Carrier Ethernet. However, the success of these protocols lies in their ability to interoperate with different network devices, and phase and frequency synchronization is one of the key focus areas in interoperability forums around the world.
4. Service Management
Service management is characterized by multiple attributes such as service activation, creation, management, and guaranteed quality.
In the age of virtual switching, the flexibility offered by Carrier Ethernet in activating services dynamically and automatically helps carriers to provision services quickly and accurately. With multi-tiered tunnel models, a service may be delivered by touching the lowest tier of a PBB-TE tunnel without disturbing all layers of the network nodes. However, bottlenecks are created when new service models translate into configuration changes of the underlying multi-vendor Carrier Ethernet equipment. Provisioning a new service involves reconfiguring multiple boxes from multiple vendors in the network and each will have its own set of attributes to be provisioned.
Standards bodies like IETF have come up with standards like NETCONF and YANG to address the shortcomings of standard north-bound interfaces like SNMP and CLI in terms of provisioning network configurations. NETCONF allows the management protocol to closely mirror the native functionalities of the device. YANG is used to model configuration and state data manipulated by NETCONF.
OEMs have also come up with specialized products to automate service activation, creation, and management capabilities, which allow carriers to deliver new services rapidly, assure service quality, and maximize service availability. This completely abstracts the complexities of deploying, delivering, and maintaining services across multi-vendor equipment. The software tools use standard protocols like LLDP, EOAM, and CFM for topology and service discovery. Y.1731 is used extensively for performance monitoring to achieve effective service management.
5. Quality of Service
There are many differences in the QoS attributes each market segment looks for. Residential services need high bandwidth and are delay sensitive. Enterprise services are not bandwidth hungry but delay sensitive. QoS attributes of mobile backhaul services are linked with the performance of legacy services. Wholesale services need good quality with low latency.
Carrier Ethernet allows service providers up to 64 levels of service classification. Hierarchical QoS classification and multi-level scheduling hierarchy with shaping at each level, and the capability to dynamically map the hierarchies, are essential QoS functionalities which Carrier Ethernet equipment need to support today.
Today, the focus has shifted more towards the delivery of Carrier Ethernet services between service providers and delivery through Carrier Ethernet exchanges. MEF calls these connection points as External Network to Network Interfaces as described in MEF 26. They are seen as the external demarcation points and at each such point the services and QoS attributes must be passed or mapped appropriately to ensure that end-to-end SLAs are honored.