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4G LTE Network Management: The Reality of Evolved Packet Core Management White Paper July 2012
4G LTE Network Management: The Reality of Evolved Packet Core Management White Paper July 2012
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Executive Summary
The world’s mobile networks are quickly evolving from 3G to 4G technologies, specifically Long Term Evolution (LTE). Over the next few years, LTE will move from initial trials to providing commercial service in each region of the world. The impact on the operators’ business models will be profound as subscribers move from services primarily based on voice and limited data to higher speed data services (including VoIP). This means, in effect, that in a few short years, the majority of revenue for many large operators will come from data services, not voice.
Figure 1: Global Growth in 3G and 4G Subscribers
Source: iGR, 2012
While 3G networks are well understood, the same cannot be said of LTE. Mobile operators are, by definition, very experienced with the Radio Access Network (RAN) layer of the network and this experience and knowledge has been applied to the development of LTE. The RAN, therefore, is not expected to present too many problems.
Based on interviews with mobile operators in North America, Latin America and Europe, iGR believes the same cannot be said of the Evolved Packet Core (EPC). The LTE EPC is relatively complex (even though it is all IP) compared to the 3G SSGN/GGSN/PDSN (the mobile Server Gateway Nodes for UMTS and CDMA networks respectively).
This increased complexity, and the need to maintain the legacy 3G network while migrating to LTE, presents new points of potential failure in the EPC for the operators. Aside from a lack of experience with operating an EPC, the operators are also challenged by the rapidly increasing traffic on the new networks as more consumers move to LTE smartphones, tablets and other devices.
The overall business objectives of the operator dictate that the new LTE network must be efficiently deployed and managed, with reliability being of paramount importance. As revenue shifts from 3G to 4G networks, the operator has little room for error -‐ a failure of
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the EPC means that all services will be unavailable with the resulting loss of revenue. iGR believes there are three issues that need to be addressed when managing the EPC especially when comes to monitoring:
Management of, and access to, the large amounts of data collected for monitoring in the network as it scales beyond the initial deployment. This requires visibility across the entire network.
Mobility and IP knowledge, resources and vendor expertise to analyze and take action on the information collected by the network probes.
Variation in the type of traffic on the network -‐ operators are increasingly seeing more video, audio and application traffic on their networks which makes traffic modeling more difficult.
This paper discusses the issues associated with managing the EPC in further detail, as well as the potential of the network monitoring switch as the solution to allow mobile operators to grow their networks efficiently and cost-‐effectively.
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Move to 4G LTE Networks
The majority of the world’s mobile subscribers today use 3G networks (UMTS/HSPA or CDMA EV-‐DO) that are supported by a number of established vendors for radio and network equipment. While data traffic is growing exponentially, the majority of revenue continues to come from circuit switched-‐based voice services. For the mobile operators, the maturity of the 3G networks means that operational costs are minimized and that competitive pricing is available for network equipment and devices. The operators understand the 3G radio and core networks well, which results in efficient operations.
An important aspect of the 3G network architecture is that the voice and data traffic take different paths from the base station (or base station controller) through the network. As figure 2 shows, the data traffic is routed through two different service nodes -‐ a Serving GPRS Service Node (SGSN) and then a Gateway GPRS Service Node (GGSN). While the majority of revenue is from voice services, this is changing quickly in favor of data traffic. In the next few years, the majority of the world’s mobile operators will get most of their revenue from data. iGR believes this shift will be accompanied by a fundamental change in how mobile networks are built and managed.
Figure 2: Typical 3G Architecture (with UMTS/HSPA)
Source: iGR, 2012
4G LTE
The next evolution for the mobile operators’ networks is from 3G to 4G and specifically to LTE. One main advantage of LTE is that the air interface uses orthogonal frequency-‐division multiple access (OFDMA) which is also used by WiFi and WiMAX networks -‐ as such, the LTE air interface is relatively well-‐understood by the mobile operators. While offering higher-‐speed IP data connections over the air, the mobile operators do not seem concerned about their ability to deploy and maintain an efficient LTE air interface.
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The bigger changes come when moving from 3G to LTE in the EPC. Rather than the relatively simple SSGN/GGSN, LTE uses an all-‐IP packet core that also incorporates some of the mobile management functions previously managed by the base station controller.
While the EPC is all-‐IP and inherently a ‘flat’ network architecture, complexity and additional risk are introduced by new functions and processes in the EPC. Additional points of potential failure mean that the costs of network management may also be higher for the operator unless the EPC is correctly sized, deployed and managed.
To illustrate the nature of the problem, one operator noted to iGR, it took the industry 5 – 8 years to optimize the SS7 network in 2G/3G networks. But the pace of competition and the increasing demand for data means that the EPC must be deployed and optimized in 18 months.
Figure 3: Typical LTE Architecture (with EV-DO 3G)
Source: iGR, 2012
Business objectives
Given the economic and financial constraints on mobile operators today, it comes as no surprise to find that the deployment and operation of LTE is driven by the carriers’ business objectives. LTE will not be deployed simply because it is the next evolution of mobile network technology – there must be sound financial and business reasons.
It is important to note that while the network drives all of the revenue generation for the operator, the network infrastructure is also responsible for a large percentage of the operating cost. The main business objectives for the LTE network can therefore be summarized as follows:
Efficient use of OpEx and CapEx as the LTE, and especially the EPC, is deployed and managed. Since funding is likely to be limited, operators of all sizes around the world are looking to make maximum use of every investment dollar.
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The network performance, especially the LTE, directly impacts customer experience, which is something that no operator can afford to ignore.
Provide QoS at realistic and manageable cost – mobile operators interviewed by iGR in preparation for this paper indicated different approaches to providing a quality experience on the LTE network but all indicated the need to do so efficiently and cost-‐effectively.
Scaling network effectively and efficiently to support growth of both subscribers and data traffic.
Managing network growth with limited spectrum – spectrum is the resource that is most limited and therefore most expensive for the mobile operator to acquire. Making the best use of available spectrum is therefore critical to the operator’s ability to deliver the bandwidth required by the subscriber base.
Consider that if the packet core on a 3G network fails, consumers may be unable to get their email or check the weather but the voice service will still be available. However, with LTE (and especially when Voice over LTE (VoLTE) is deployed), a failure of the EPC means that all services will be unavailable. The impact of EPC problems in some early LTE deployments have been well documented in the press – many other operators fear the same issues in their networks.
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Network management for LTE
As well as building an LTE network, operators must also manage the resulting infrastructure. LTE, especially the EPC, is a major step from the 3G architectures currently in use and is different enough to cause the operator concern.
Evolved Packet Core
Unlike the RAN, the EPC is seen as a major source of potential management issues by the mobile operators. Part of this concern arises from unfamiliarity with the EPC but also from the fact that all of the traffic in LTE is IP and this flows through the EPC. Get the EPC wrong and all of the operator’s LTE business will be impacted.
As part of the research for this paper, iGR interviewed one operator who is testing LTE and took eight weeks to find a problem in the EPC that was significantly slowing traffic. It appears that while the operator had the necessary IP network management tools and probes in the network, the number of interfaces, processes, functions and servers in the EPC meant that the problem was not readily identified. The reality is that the amount of information coming from the EPC overwhelmed the network engineers and complicated their ability to identify the single source of the problem.
What is particularly disturbing is that many of the operators iGR interviewed echoed this type of issue and the difficulty in identifying the problem.
There is little doubt that if this had been a production network (note that the whole LTE network was still in test), the mobile operator would have faced a significant backlash from its subscriber base. This would have seriously impacted the operator’s ability to provide a competitive service and experience, with obvious potential consequences.
Network management issues for the LTE EPC
Based on discussions with the mobile operators, iGR believes the issues with the EPC arise from the following:
The Interface between the new EPC and existing 3G IP core appears to cause some difficulties, especially when handing connections back to 3G from LTE. Once VoLTE is deployed (as an IP multimedia Subsystem – IMS -‐ service) and Circuit-‐Switched Fall Back (CSFB) is implemented, there is concern that these interconnection issues will multiply.
The operators’ relative inexperience with the EPC and how it behaves. While the network managers expect to quickly learn the ‘quirks’ of the EPC, there is a major concern that the intense competition in the industry means that the learning curve will have to be compressed.
As well as the sheer volume of data traffic, EPC network managers must also deal with the signaling (control) plane. The EPC splits the control plane from the traffic
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flow and functions such as the Mobility Management Entity (MME) only deal with signaling traffic. So while the user plane must be correctly sized, the same is also true of the signaling plane – remember that newer smartphones and tablets may initiate 10 or more sessions just on power-‐on. Each session involves multiple signaling requests and commands.
The final major concern surrounds growth and scale. As the IP traffic and signaling grows, so the network management tools must also scale. While configurations vary, most major operators currently have 5 – 20 data centers. But the growth in data traffic means that the LTE network is likely to become more distributed and many operators are expecting to support more than 40 data centers and in a few cases as many as 80 to 100 data centers. It should be noted that the configuration of each data center is the same – the network grows by simply replicating the existing design to deploy additional capacity. But the operator is unlikely to be able to scale management resources at the same rate – the network engineering staffs must necessarily learn to manage larger networks with the same (or slightly more) human resources and expertise.
Management Tools
Based on research with the major mobile operators, iGR does not believe that IP network management tools for the EPC are the main issue – the necessary functionality is available but deploying and operating the tools in a cost effective manner is a challenge. Simply put, the experience, knowledge and expertise necessary to action the data coming from probes at multiple points across the network is currently lacking.
There appears to be an abundance of IP tools, probes and analytical solutions available to the operators from multiple vendors. But while the operators see many IP tool vendors and solutions, it does seem that many lack experience with managing the relatively-‐new mobile all-‐IP networks. The mobility functionality in the EPC (especially around the MME and Home Subscriber Server (HSS) adds a layer of complexity that many vendors fail to appreciate. And while the larger mobile infrastructure OEMs have both the IP tools and necessary mobile experience, their solutions can be expensive. In the case of the smaller mobile operators, these tools can be prohibitively expensive.
Challenges of new approach
As discussed above, the issue is not the availability of suitable IP management tools. For the mobile operator, the main challenge is having the resources necessary to analyze and manage information coming from multiple points in the network.
Based on interviews with the mobile operators, iGR believes that what needs to be addressed for cost effective and efficient management of the EPC is:
Management of the large amounts of information coming from the probes in the network. The reality is that with the need to monitor multiple interfaces throughout the EPC, a large number of probes is needed, each of which generates data for network management. The need to quickly and efficiently analyze this data means
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that the information from the probes needs to be streamlined and organized as much as possible. And as the LTE network grows (with a corresponding increase in the number of data centers), so the amount of data from the necessary probes multiplies.
Education and specifically the need for vendors and resources who truly understand mobility AND IP to analyze and action the data coming from the network probes. For example, as the device moves to the edge of the cell, the connection speed may drop before the device is passed to the next cell. The so-‐called ‘edge of cell’ effects can cause variations in the IP traffic in the core that are not seen in non-‐mobile IP networks.
The variation in the type of traffic also needs to be addressed. Rather than simply relying on voice for future revenues, operators are increasingly seeing more video, audio and application traffic on their networks – this trend will increase. As a result, the mobile operators are building new traffic modeling tools to try and predict network behavior more accurately.
Solutions
One solution to these problems is for the mobile operator to deploy a network monitoring switch. As figure 4 shows, a network monitoring switch consolidates monitoring access to the EPC to provide end-‐to-‐end visibility and enables uninterrupted access to network traffic for the monitoring tools. This allows the mobile operators to get full benefit from their monitoring tools and maximize their investment.
The network monitoring switch provides a number of features that off-‐load compute intensive processing from the network tools:
Filtering -‐ by filtering data in the network monitoring switch, the monitoring tool is freed to perform the work that it was purchased to do. This results in more efficient use of the tool, especially important as the EPC grows. Filtering parameters used by the network monitoring switch in Layers 2-‐4 include MAC source/destination addresses, VLAN and Ethertypes, IP protocol and DSCP/TOS, GTP and MPLS, source/destination IP (IPv4) and UDP, TCP ports.
Load balancing -‐ as the amount of data increases in the EPC, the network data flow is increasing faster than the capabilities of their monitoring tools. A single monitoring tool that previously performed well is now overwhelmed. Through “load balancing” some network monitoring switches have the ability to send data across multiple tools and do it in a way that consistently sends all the data from a particular session to the single monitoring tool. Thus the load balancing feature keeps session data together for better analysis, yet balances the total EPC load across multiple monitoring tools.
Packet de-‐duplication -‐ another form of off-‐loading is the ability of network monitoring switches to remove duplicate packets from EPC data streams, a capability that many tools lack or is prohibitively resource-‐intensive. Off-‐loading duplicate
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packet removal in the network monitoring switch can cut the CPU load of a monitoring tool in half. The bandwidth at the Ethernet port of the tool is also conserved, allowing more data to be provided to the monitoring tool. Thus, as the EPC grows, the same monitoring tools can be used and scaled accordingly.
Packet-‐trimming -‐ packet trimming removes payload data from the packet, leaving the header information, prior to sending the packet to monitoring tools. As a result, the monitoring tool can receive a far greater amount of network data from the EPC, which again becomes important as the EPC grows.
Figure 4: Example of Network Monitoring Switch
Source: Anue Systems, 2012
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About iGR
iGR is a market strategy consultancy focused on the wireless and mobile communications industry. Founded by Iain Gillott, one of the wireless industry's leading analysts, in late 2000 as iGillottResearch, iGR is now entering its twelfth year of operation. iGR researches a range of wireless and mobile products and technologies, including: smartphones; tablets; mobile applications; bandwidth demand and use; small cell architectures; DAS; LTE; WiMAX; VoLTE; IMS; NFC; GSM/GPRS/UMTS/HSPA; CDMA 1x/EV-‐DO; iDEN; SIP; macro-‐, pico-‐ and femtocells; mobile backhaul; WiFi and WiFi offload; and SIM and UICC.
A more complete profile of the company can be found at www.iGR-‐Inc.com.
Disclaimer
The opinions expressed in this white paper are those of iGR and do not reflect the opinions of the companies or organizations referenced in this paper. All research was conducted exclusively and independently by iGR. This white paper was sponsored by Ixia but Ixia personnel were not involved in the carrier interviews, the ongoing research or in the analysis for this paper.
Ixia’s network visibility solutions provide the ongoing data needed to deliver a high-quality subscriber experience reliably and cost-effectively despite the growing diversity of network technologies, user devices and security threats. As operational complexity increases, network engineers at leading mobile service providers can leverage Ixia’s Anue Net Tool Optimizer® (NTO) suite of network monitoring switches to ensure the end-to-end visibility needed to minimize OpEx, sustain profitability, and safeguard quality and satisfaction.
For more information about Ixia’s Anue NTOVisit http://www.ixiacom.com/products/network_visibilityEmail us directly: [email protected] Us at: (512) 600-7171
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