White Paper - Virtualizing Small Cell Performance Monitoring
Virtualizing Small Cell
Performance Monitoring
Applying best practices for Carrier Ethernet/IP service assurance to microcell
backhaul networks
Abstract
The exponential growth in demand for capacity in the mobile network is driving mobile carriers and backhaul providers to complement their macro cell deployments with small cell networks. Microcells offer cost-‐effective relief for both bandwidth capacity and radio coverage challenges faced by many mobile operators. As mobile carriers own less and less of their backhaul infrastructure, there are important lessons that can be gleaned from the recent trend by mobile carriers to outsource operation of mobile backhaul network to wholesale providers.
Effective outsourcing requires oversight and active management in order to ensure a high quality end-‐user experience. Performance assurance systems are required for the Carrier Ethernet networks that deliver backhaul services to macro and micro cells alike. These tools provide mobile carriers with the management information they need to effectively leverage the cost advantages and extensibility of a microcell-‐based mobile backhaul network.
The 3 ‘V’s which are: circuit verification; SLA validation; and on-‐going visibility into the performance of the backhaul network require Carrier Ethernet/IP OAM support. Effective performance
management systems include comprehensive instrumentation in the network along with complementary management tools able to summarize thousands of measured data points into concise and actionable performance information. Performance assurance is the key to successfully delivering high quality mobile service.
This short paper outlines an effective strategy that adapts the best practices for performance assurance in macro cell networks, to small cell deployments. Virtualizing the OAM instrumentation enables performance management systems to be applied cost-‐effectively to small cells. This provides the management oversight required to effectively leverage micro cell technology to build out additional mobile bandwidth and extend radio coverage.
Boundless Demand, Limited Supply
The relentless demand for mobile capacity continues to explode around the world, due to both the growth of bandwidth hungry smart phone applications and the new focus on mobile providers who are now competing to deliver the “fastest network”. As smart phone growth continues, in double-‐ digit numbers, the applications running on these devices are increasingly content rich and bandwidth intensive. Thereby demand is outpacing supply.
With capacity demands doubling each year, there will be a need for thirty-‐two (32) times as much bandwidth in 2015 as there was in 2011. While backhaul providers have been quick to adopt new technologies such as Carrier Ethernet to retrofit the macro-‐cell backhaul networks, the sheer magnitude of the problem will eclipse the capacity of even 10Gigabit enabled macro cells.
When shorter radio reach of these ultra high-‐speed radios are taken in to consideration, the need for more cell sites is inevitable. The future is clear. In order to meet demand and coverage needs, a tributary network of micro or small cells must be deployed in order to complement the existing macro cells. Analysts predict that by 2015, without small cell deployments, the capacity supply will fall short of demand by over 50%. In fact, the same analysts predict the need for ten to fifteen microcells for each macro cell site deployed today.
Wholesale Access Rises to Meet the Demand
The initial influx of smart phones saturated legacy macro cell-‐based backhaul networks using TDM transport services. Carrier Ethernet rose to prominence as the solution of choice to relieve the capacity problem at the macro cell. This revolutionary technology shift also brought with it a shift in the traditional business model for delivering backhaul services. Mobile carriers began outsourcing the backhaul network to a growing army of wholesale providers, often referred to as Alternative Access Vendors or AAV’s.
Outsourcing the job of providing backhaul services to thousands of macro cell sites enabled mobile carriers to quickly and exponentially boost their capacity. But managing an outsourced operation brings a new set of challenges. The biggest is maintaining the quality of the service which requires visibility into the performance of each outsourced circuit 24/7/365. Naturally, the mobile carrier is ultimately responsible for the quality of the service, the “high speed 4G LTE networks” they promote, and the end-‐user experience. As such, they must guarantee that the outsourced backhaul network delivers the high quality necessary to meet the demands of smart phone users activities.
Performance Assurance Becomes Mainstream
Mobile carriers realize that they are not only buying Carrier Ethernet backhaul services from a myriad of local providers, but buying a myriad of different services. In order to leverage the
advantages of outsourcing and manage this diversity, a new requirement for intelligent demarcation developed.
Mobile carriers also quickly recognized the need for remotely located tools at the macro cell site to help validate circuit delivery and address this first challenge. As a result Carrier Ethernet operations, administration and maintenance (OAM) technologies in many forms including Network Interface Devices (NIDs), reflectors and other hand-‐held test and turn-‐up tools were deployed.
continuous real-‐time monitoring of the outsourced backhaul network using Carrier Ethernet Service OAM capable demarcation devices like NIDs. Real-‐time performance monitoring following the initial circuit turn-‐up led to the success of the “AAV-‐model” for outsourcing high capacity mobile backhaul by mobile carriers around the globe.
The third, and most daunting hurdle, is dealing with the data overload coming from the NIDs, as well as, literally hundreds if not thousands of OAM sessions. They needed to summarize the multitude of performance data for each circuit and turn it into actionable information about network health.
Ethernet Performance
Measuring Carrier Ethernet Performance
The Metro Ethernet Forum (MEF), the industry body promoting the adoption of Ethernet has defined four Key Performance Indicators (KPIs) for network health. The MEF has standardized on on-‐way metrics, in recognition of the asymmetric traffic patterns in networks. In mobile backhaul networks, 80% or more of the traffic flows from the core where the content resides to the end-‐user devices at the edge. Accurately measuring network performance requires precise measurement of traffic in each direction.
Specifically the one-‐way KPI measurements defined by the MEF are:
Frame Delay – the amount of time required for a frame to travel from point A to point Z in one direction. This is then separately measured from point Z back to point A. The sum of the two measurements is round-‐trip or two-‐way frame delay. This is very different than starting with two-‐way delay and dividing in half to approximate one-‐way delay.
Frame Delay Variation – the difference in arrival times between frames being sent from point A to point Z. This metric was known as jitter in the TDM world. It essentially measures fluctuations in network performance. This happens when some frames travel faster than others over the same link.
Frame Loss – this is simply measuring all the frames sent over from point A and then measuring how many have been received at point Z. Any loss is recorded and the number lost compared to the number sent is the frame loss ratio, expressed as a percentage.
Availability – this is a calculation for a given time period that determines – based upon frame delay, frame delay variation and the frame loss measurements – whether or not the service was within the specified operating range or “available”. If any of the other three KPIs is operating outside of the specified operating range, the service is said to be unavailable.
Monthly SLA compliance reporting and on-‐demand dashboards were introduced to provide visibility into the performance of each backhaul circuit. This led to the deployment of Performance
Management (PM) network management systems (NMS) to collect all the raw measurements, summarize, evaluate and display per-‐circuit statistics of circuit health as measured by four industry defined Key Performance Indicators (KPIs) – latency, frame delay variation (jitter), frame loss and service availability using the results of the first three KPIs.
Performance management and service assurance tools that provide the three-‐V’s: Validation at circuit turn-‐up; Verification of service level agreement conformance; and Visibility into on-‐going circuit performance, became essential to the successful operation of a high capacity macro cell using Carrier Ethernet backhaul.
Everything Big is Getting Smaller Now
The management challenges of the outsourced backhaul model provide a glimpse into the future. Mobile carriers will certainly require that same level of vigilance in order to manage the myriad of microcells. In the microcell model, backhaul traffic will be off-‐loaded onto a tributary of public and private network connections. Managing the quality of the service being carried over a distributed and diverse network will necessitate new techniques for measuring performance.
This new approach will need to provide the instrumentation and telemetry to measure the same four KPIs that are being measured at the macro cell, but in a way that is cost-‐effective in a microcell deployment. The first challenge is that in most cases the dedicated demarcation equipment used to instrument the network and provide the accurate one-‐way performance measurements is now no longer an option.
But if even the “big iron” equipment being deployed at the macro cell didn’t have the Carrier Ethernet OAM features required (which drove the demand for NIDs during the Etherization of the macro cells), then we can hardly expect to find these advanced capabilities in the inexpensive access equipment — such as in-‐building picocells deployed in Internet gateways or set-‐top boxes, or even in the slightly more robust femtocell equipment being deployed by telecomm carriers building these tributary microcell networks.
Virtualized Small Cell Performance Management Model
Yet there are techniques that enable the accurate measurement of one-‐way performance and tracking of the four critical KPIs for network health, without requiring new instrumentation or dedicated equipment at every microcell. Virtual-‐NIDs, which respond to delay measurement messages (DMMs) from a centralized monitoring agent called an Actuator, can accurately reflect back the DMM and perform the critical latency calculations.
At the core, the concept of a Virtual-‐NID is a reflector agent that passively responds to remote measurement requests. The intelligence rests in the actuators, which are the active measurement components in a virtual performance management architecture. The actuators can measure hundreds or even thousands of end-‐points and become in essence, proxy OAM agents for the end-‐ points to make up for their lack of OAM capabilities.
The virtualization of OAM instrumentation can be accomplished in a number of ways. Software-‐ based Virtual-‐NIDs integrated directly into microcell equipment is the most economically attractive. Simple OAM reflector software capable of responding to remote measurement requests from the actuator can be easily and quickly integrated into nearly any type of telecom equipment.
Accedian's VisualMETRIX performance portal provides the visibility into a mobile backhaul network.
In order to add OAM capabilities and accelerate the deployment of this functionality in the microcell network, virtual-‐NID implementations using add-‐on hardware “dongles” that can be added to equipment already deployed is becoming an interesting option. The “dongle” fills the gap and provides NID-‐like OAM functionality without requiring a new software load on the microcell device. So while the long-‐term solution is clearly the software-‐based virtual-‐NID, the short term need can be quickly met using lightweight hardware add-‐ons.
Accedian Networks’ Small Cell V-‐NID
TMPerformance Assurance
Accedian has taken its innovative and industry-‐leading macro cell and adapted it for small cell use. The Accedian V-‐NID solution consists of virtualized reflector agents implemented in either software or lightweight hardware-‐based dongles to provide a number of flexible and cost-‐effective remote measurement capabilities applicable in a wide-‐variety of microcell deployments.
The V-‐NID Actuator actively manages the remote V-‐NID reflector agents by sending DMMs and accurately measuring one-‐way performance from the remote devices. At turn-‐up the V-‐NID Actuator verifies connectivity. It continues to measure and collect performance statistics that are summarized and correlated for validating performance of the microcell in terms of its ability to meet the quality of experience of the end-‐user. The results are then made available via the Accedian VisionMETRIX performance portal providing the visibility required to successfully manage the microcell network.
The Accedian V-‐NID solution provides the ultra-‐accurate performance monitoring mobile carriers have come expect in the macro cell deployment, in a cost-‐effective approach that enables it to be applied in the microcell network. This intelligence lets the network operations team perform the on-‐ going optimization required to ensure that the end-‐user has a high quality experience.
For more information about the Accedian small cell solutions, and how Performance Assurance makes small cells better, visit accedian.com
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