Successfully delivering mission critical, performance sensitive services and applications.
In response to escalating performance requirements for critical applications, converged IP networks must become optimized for performance levels. Service Level Agreements (SLAs) that support application solutions are becoming an increasingly common requirement, and SLAs in the IP infrastructure are an essential part of optimizing the network for business.
Network equipment must therefore verify service guarantees, validate network performance, improve network reliability, proactively identify network issues, and react to performance metrics with changes to the configuration and network. Cisco IOS ® IP Service Level Agreements (SLAs) fulfills those needs, creating a network that is "performance-aware".
This white paper illustrates the importance of monitoring both end-to-end IP Service levels and those at the IP layer, in order to provide true application-awareness. With Cisco IOS IP SLAs, Cisco has taken the traditional concept of Layer 2 SLAs, while advancing the IP infrastructure to become `application-aware'.
Enterprises depend heavily on Cisco IOS IP SLAs in order to meet their business objectives. "At DuPont, we use Cisco IOS IP SLAs to verify our outsourced Service Provider SLAs. The technology allows us to understand their delivered network performance, and helps us to negotiate cost-effective SLAs with Service Providers," said Mike Dowler, Global Services Integration Manager, DuPont Telecommunications.
INCREASING IMPORTANCE OF SLAS
Layer 2 circuit-switched networks are the basis of traditional SLAs. These networks must meet a Committed Information Rate (CIR), or minimal guaranteed bandwidth, as well as a minimum guaranteed connectivity rate, which is expressed as a percentage (ie: 99.9%). This SLA is a fixed circuit and point-to-point, in no way indicative of the end-to-end experience of the end-user and their application. Moreover, the SLA goes with the customer following a migration from the legacy circuit(s) to other transport options. In summary, these traditional SLAs are limited and application-unaware.
Figure 1. Traditional SLAs Versus Cisco IOS IP SLAs
IP networks are currently held accountable for carrying all types of applications that require networks and the Internet to provide the appropriate level of service for the appropriate application. These include integrated web, voice, video, and business-critical applications. In order to make real-time network decisions that ensure application Quality of Service (QoS), it is important to measure end-to-end network performance statistics as data traverses the network. This end-to-end measurement is the only way to accurately assess whether the performance statistics are satisfactory enough to support the application(s).
Market Drivers for Enhanced SLAs
Multiple factors drive network convergence and the corresponding need for performance-sensitive networks:
All customers select which applications are business-critical, in terms of their individual needs. Examples include Enterprise Resource Management (ERP), Customer Relationship Management (CRM), Material Requirements Planning (MRP), portals, and client-server applications. In order to meet business objectives, companies must deliver these applications with a high degree of network performance. This can only be accomplished with a dynamic network that measures, adjusts, warns and assists with problem identification and troubleshooting.
Administrators can use a variety of benchmarks, including delay, packet loss, jitter, packet sequencing and connectivity, to gauge the quality of service received by the end user. An IP infrastructure that supports these metrics ensures a successful network-wide rollout of business-critical applications.
Cisco customers can leverage converged networks to route some or all voice traffic over data networks; benefits include the efficiency of IP , flexibility, avoiding tolls, increased cellular traffic, and cost savings.
In exchange for these benefits, administrators must ensure that their network QoS meets voice requirements. Most Cisco customers have met this requirement by over-provisioning and deploying excess bandwidth. This strategy can meet short-term goals; however, networks need improved efficiently, utilizing performance-awareness in order to meet customer demands in today's rapidly changing and competitive global marketplace. Dedicating a single network connection to voice, video, and data traffic reduces network complexity, resulting in measurable cost savings in hardware, software, and management.
As virtual teams, global offices, and telecommuting are become more frequent, there is a corresponding increase in the importance of video and audio services. Examples of emerging applications include:
• Audio and web conferencing tools allow real-time collaboration (ie: Cisco Latitude Communications' MeetingPlace)
• VoIP Phones in home offices enable telecommuters to traverse the company network
• Seamless interface for scheduling and hosting multimedia conferences
• Unified messaging: integration of voice, email, fax, and scheduling into one interface accessible both via voice and online
All of these value-added applications depend on an IP network that can deliver an appropriate level of network performance.
Some of the technologies that have enabled and will continue to fuel the phenomenal expansion of IP VPNs include Generic Routing Encapsulation (GRE), IPsec Multiprotocol Label Switching (MPLS) VPN. VPNs provide the cost effective sharing of infrastructure, while Cisco IOS IP SLAs allows and accelerates the deployment of SLAs across those VPNs.
MPLS VPNs, for example, have gained popularity with customers who are familiar with the security and features of Layer 2 connections (ie: Frame Relay or ATM). MPLS VPNs offer a multitude of features, including:
• Security: restrict access to only member routers of the VPN
• Easily configured shared communities of interest or connectivity between customers
• QoS and differentiated services
Customers can easily converge network traffic over the MPLS VPN links when the provider can provision the requested bandwidth and QoS with confidence. The increasing frequency of MPLS VPNs with QoS guarantees requires providers to pay closer attention to network performance. Cisco IOS IP SLAs has specific features that are targeted at MPLS VPN, as well as other VPN environments.
Many enterprises outsource their network and network services from service providers. In the agreement, fees are based upon certain criteria related to network uptime, mean-time-to-repair (MTTR), bandwidth, latency, packet loss, and occasionally jitter. The agreements can also be specific to traffic; for example, SAP (premium), internet (silver) and email (bronze).
The enterprise must track and confirm that the service provider and consultants are meeting the requirements of the agreement. It must deploy technology to track these key network metrics, and then feed that information into an application for report display. These enterprises also need threshold capability, so they can be notified as soon as there is a service level violation.
Service Provider Integration
Global enterprises must support applications that traverse multiple Service Providers. Cisco IOS IP SLAs can provide a standard measurement system to ensure consistent SLA metrics and quality across integrated Service Providers.
It is essential to improve upon traditional SLAs in order to effectively support market drivers, such as business-critical applications, voice, audio/video conferencing, and VPNs. Network equipment that can measure and track the performance metrics of a network and subsequently enforce an enhanced SLA is imperative. The attributes of an improved SLA include:
1. End-to-end coverage: provides both greater reach and more accurate representation of the end user experience
2. Sophistication: statistics (ie: delay, jitter, packet sequence, Layer 3 connectivity, path, and download time) can be broken down to bi-directional and round-trip numbers, which provide a richer vein of data
3. Accuracy: applications that are sensitive to slight changes in network performance require precision of measurement far beyond that of ping testing with multi-millisecond granularity
4. Ease of deployment: large networks can leverage existing equipment features, thus resulting in immense time and cost savings
5. Application-aware: the ability to leverage Layers 3 through 7 simulates the performance statistics for given applications and supports application-aware SLAs
6. Pervasive: network equipment supports a spectrum of hardware, from low- to high-end router and switches, which opens deployment possibilities and flexibility
Many customers are currently recognizing the need for more sophisticated SLAs, which can support application delivery over a converged network. Many Service Providers now provide round-trip delay, packet loss, and connectivity as metrics in their SLAs; however, these SLAs still may not maximize accuracy and efficiency.
The problem with these SLAs is that the VPN Service Provider recommends a contractual cushion, in order to avoid SLA penalties and to ensure that it meets the stated network performance goal. Customers are less likely to rely on this weakened SLA and use the service for deploying a performance-sensitive application. They are also hesitant to deploy a VPN solution that might require multiple Service Providers for global reach, as the combined SLAs would suggest application failure. For example, delay SLA target over the WAN is set as 150 milliseconds when 50 milliseconds is required for a customer to deliver a VoIP solution when factoring in delay at both LAN networks.
To ensure application delivery for customers, SLAs need to be tight. An IP SLA is an SLA that is set very precisely and thus provides a service level that is both realistic and high quality. Service Providers that support improved IP SLAs have the opportunity to increase their business and to successfully rollout new applications. In order to tighten network SLAs, Service Providers need technology that support metrics and accuracy within the IP infrastructure.
In order to build an end-to-end network SLAs, customers need to understand performance expectations for platinum, gold, silver, and bronze levels of traffic out to the customer premise equipment handoff point. The predictability and reliability of a corporation's global intranet can enable unprecedented efficiencies and cost savings.
FULFILLING THE NEEDS
Cisco IOS IP SLAs Introduction
Cisco IOS IP SLAs, a core part of the Cisco IOS Software portfolio, has grown from technology previously known as Cisco IOS Service Assurance Agent (SAA). It performs active monitoring by generating and analyzing traffic to measure performance between Cisco IOS Software devices or to network application servers. Cisco IOS IP SLAs enables functionality beyond the traditional SLAs:
Table 1. Traditional SLAs Versus Cisco IOS IP SLAs
