1 AVIAT NETWORKS FEBRUARY 2011

WHITE PAPER

ETHERNET OAM FOR MICROWAVE BASED NEXT GENERATION NETWORKS

EXECUTIVE SUMMARY The transition from TDM-based transport to Next Generation Networks (NGN) based on Ethernet and IP protocols presents exciting new opportunities for network operators to offer additional services more easily, improve bandwidth efficiency and build a transport infrastructure that will support expansion for years to come. However, the ability to ensure that Ethernet and IP networks can match the availability and reliability of legacy TDM-based networks cannot be taken for granted. Network vendors, mobile operators and wholesale transport providers alike have to take these new challenges very seriously.

Ethernet OAM (Operations, Administration and Maintenance) can help mobile network operators and other transport providers meet the ever-growing demands for increased bandwidth across the backhaul network as well as meeting the equally important demand for quality and reliability of service.

This white paper will look at how Ethernet OAM can help the evolution from TDM to NGN, with a focus on microwave-based NGN radio networks.

ETHERNET OVERCOMING BANDWIDTH LIMITATIONS AND CONGESTION In the past, the solution to network congestion in a TDM-based mobile backhaul network using microwave radio links has most often been resolved by adding more and more bandwidth to the network, using higher capacity TDM microwave radio links. This has significantly changed in the last few years as operators have embraced Ethernet as a proven lower cost per bit transport technology.

The migration from TDM-to-Hybrid to all-Packet microwave is well underway as a result of this shift in direction. In addition, advanced microwave technologies such as cross-polarization interference cancellation (XPIC) and compression techniques have further provided significant bandwidth gains to help overcome the congestion problems. Today, advanced packet microwave systems with such features are increasingly being adopted to address current and evolving bandwidth requirements for 3G, 4G, and beyond.

NGNs require microwave radio links that can respond to changes in as many ways as possible. The transition from TDM- to Ethernet-based microwave radio links is one such way; another is the introduction of Adaptive Coding and Modulation (ACM), dynamically Self Organizing Networks (SON), and other related techniques.

2 AVIAT NETWORKS FEBRUARY 2011

WHITE PAPER

ETHERNET OAM FOR MICROWAVE

HOW ETHERNET OAM HELPS THE NEXT GENERATION NETWORK

With the introduction of an Ethernet centric mobile backhaul network emerges the need to manage and control it. Ethernet OAM is an essential part of the NGN because it allows network operators to monitor and control the network with the same certainty they had with TDM transport. Legacy TDM networks by their nature were very point-to-point centric with very little dynamicity to them. With the advent of Ethernet transport, the ability to layer in new services logically e.g. virtual circuits in addition to physical T1/E1 circuits, brought new challenges such as how to adapt to route changes, congestion and QoS policies, and how to handle changes in link bandwidth due to ACM - in the case of microwave networks.

Key management standards that should be considered when implementing Ethernet OAM for microwave based NGNs include:

• MEF 7.1 - EMS-NMS Information Model

• MEF 17 - Service OAM Requirements and Framework

• RFC 4878 - Definitions and Managed Objects for OAM Functions on Ethernet-Like Interfaces

• RFC 2544 - Benchmarking Methodology for Network Interconnect Devices

• IEEE 802.3ah - Link Layer OAM, Ethernet in the First Mile (EFM)

• IEEE 802.1ag - Connectivity Fault Management (CFM)

• ITU Y.1731 - OAM functions and mechanisms for Ethernet based networks

ETHERNET OAM AND QOS NGNs based on Ethernet and IP-based mobile backhaul networks respond better to sudden changes in mobile backhaul bandwidth demand because they can use Quality of Service (QoS) and path controls to route, differentiate, and prioritize services based on specific needs—for example, video calls demand a lower latency compared to web browsing or email downloading.

A variety of Ethernet QoS controls are available on advanced Ethernet-based microwave radio links, but the result is a plethora of implementation options, because not only are there various algorithms that provide QoS controls, but different methods to identify traffic such as DiffServ, CoS, MPLS EXP, or 802.1p—and the number of levels used to differentiate services may vary between networks and sub-networks.

However, regardless of the QoS profile, there is a requirement to closely monitor the behavior of the Ethernet network layer similar to how TDM networks are monitored. This is accomplished by leveraging the Ethernet performance management standard (ITU Y.1731) to provide detailed trending and proactive QoS alerts, so the network operator can see how the various QoS profiles affect the microwave radio link capacity utilization. This is essential feedback for network planners tasked with optimization of the mobile Radio Access Network (RAN) because performance data collected from the transport network can now be more integrally tied to performance data from the base station e.g. NodeB in a 3G network, or eNodeB in an LTE network.

3 AVIAT NETWORKS FEBRUARY 2011

WHITE PAPER

ETHERNET OAM FOR MICROWAVE

ETHERNET OAM AND MICROWAVE ACM Recent advances in microwave radio have given rise to Adaptive Coding and Modulation (ACM) solutions, which dynamically change the modulation of the microwave radio link so that the highest possible modulation is used over the prevailing path conditions—to provide highest possible capacity.

With the advent of Next Generation Networks, performance data collected from the RAN alone is no longer enough for network planners. Now the mobile network operator also has to take the bandwidth available from the ACM enabled NGN microwave radio links into consideration, because it is no longer fixed—as it could vary, from 20 Mbps to 60 Mbps in the example shown in Figure 1, below.

If ACM is triggered—perhaps due to a heavy rain fading or perhaps due to a line-of site obstruction, the capacity of a microwave radio link might be decreased for a very short period or possibly for an extended time.

Figure 1 Microwave Adaptive Coding and Modulation

Management tools are needed to provide control and monitoring of an Ethernet microwave network that supports ACM. Leveraging the Ethernet Connectivity Fault Management standard (IEEE 802.1ag) allows mobile network operators to monitor connectivity at the service layer, which allows them to determine if a reduction in microwave radio link capacity has affected a service. With this additional knowledge, the operator might choose to modify the QoS profiles or help them prioritize maintenance work on the link.

4 AVIAT NETWORKS FEBRUARY 2011

WHITE PAPER

ETHERNET OAM FOR MICROWAVE

ETHERNET OAM AND SERVICE LEVEL ASSURANCE Detecting and localizing network faults are critical to maintaining network quality and reliability. Traditional TDM systems provided OAM mechanisms such as AIS (Alarm Indication Signal) and RDI (Remote Defect Indication) alarms to address this need. These became even more sophisticated and comprehensive with the advent of SONET/SDH. As a result, TDM OAM has become the benchmark for high availability networking and maintaining SLAs, for example, supporting the famous “five nines” availability and reliability, and 50 millisecond (ms) recovery times from failures. Next Generation Networks need to provide equivalent levels of availability and reliability.

Ethernet OAM standards provide the tools to achieve these goals, including tools like IEEE 802.1ag and ITU Y.1731 previously mentioned. In addition, these capabilities need to apply to the access portions of the network also. Leveraging the Ethernet in the First Mile (IEEE 802.3ah) standard, operators have the means to monitor and maintain their networks similar to managing TDM-based transport access networks including microwave. Ethernet in the First Mile (EFM) provides the following link monitoring procedures to assist in this:

• Discovery: demarcation point device discovery & loopback capability • Remote failure indication: dying gasp, link fault and critical events • Fault isolation: customer or provider network, unidirectional failures • Port-level loopback: remote or locally activated, layer 1 only, traffic effecting • Performance & Status Monitoring with threshold alarms

CONCLUSIONS As Next Generations Networks evolve to meet the growing demand for transport bandwidth - driven by new services and products such as smartphones and tablet computers - the tools needed to manage NGNs also need to be highly sophisticated to ensure network performance, availability and reliability is guaranteed. Ethernet OAM tools can be effectively implemented throughout the microwave NGN network to meet this requirement, building on familiar operational practices.

Aviat Networks leads the way in terms of the transition from TDM-based networks to Next Generation Networks (NGN) based on Ethernet and IP protocols, beginning with the Eclipse Packet Node, the industry leader in microwave nodal networking. Eclipse Packet Node is fully equipped to support evolving Ethernet OAM features and capabilities as will Aviat Networks’ next generation Packet Node products and solutions - providing a smooth transition for customers migrating from TDM to Ethernet, while desiring to maintain and evolve their existing equipment and network management solutions.

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