A. Cisco Performance Routing (PfR) complements classic routing technologies by adding intelligence to select best paths to meet performance requirements of applications. The first phase of PfR technology intelligently optimizes application performance over WANs and to and from the Internet. The technology will evolve to help enable application performance optimization throughout the enterprise network to provide an end-to-end performance-aware network.
Cisco PfR selects an egress or ingress WAN path based on parameters that affect application performance, including reachability, delay, cost, jitter, and Mean Opinion Score (MOS). The technology can reduce network costs by load-balancing traffic more efficiently and by increasing application performance without WAN upgrades. Cisco PfR selects a WAN path based on parameters such as load, throughput, and cost of using a path. Classic routing protocols (Enhanced IGRP [EIGRP], Open Shortest Path First [OSPF], Routing Information Protocol [RIP], Border Gateway Protocol [BGP], etc...) generally focus on providing reachability by creating a loop-free topology based on shortest or least-cost or -metric path. Cisco PfR focuses on providing application performance by understanding application requirements and current network performance.
Q. What problem does Cisco PfR solve?
A. As enterprise organizations grow their businesses, there is a demand for real-time application performance, and better application experiences for users. For example, voice and TelePresence applications are becoming integral parts of companies, and performance of these applications is crucial to their success. In order to improve application performance, companies have typically deployed two common solutions: providing additional bandwidth by deploying more network connections, and using application optimization technologies (for example, Cisco Wide Area Application Services [WAAS]). Additional WAN bandwidth may improve aggregate throughput but may not improve delay or loss for critical applications. Application optimization technologies such as Cisco WAAS can improve performance with data-reduction techniques, but fluctuating network performance can still affect applications. Cisco Performance Routing addresses network performance problems by helping the network intelligently choose a path that currently meets the requirements of application performance. In addition, PfR allows the network to choose resources appropriately to reduce operational costs incurred by enterprises.
Q. How will customers benefit from Cisco Performance Routing?
A.
• Bandwidth cost minimization allows companies to minimize traffic sent over expensive links or consolidate multiple flat-rate connections to fewer and lower-cost services.
• Automatic performance optimization reduces engineering operating expenses associated with manual network performance analysis and tuning of the routing infrastructure.
• Reports for traffic distribution and usage before and after route optimization help enterprise customers manage Internet Service Provider (ISP) service-level agreements (SLAs) more effectively because they now have more specific and detailed link-cost reporting than the ISPs.
• The following factors help improve customer satisfaction:
– Users can experience improved response time because automated route optimization in Cisco PfR can detect and route around poorly performing paths by finding an optimal exit path.
– Performance optimization can minimize the effects of network outages because it can monitor them (for example, high latency or packet loss or "black-hole" conditions) and automatically reroute affected traffic classes to an alternative, better-performing path.
Q. What are the primary integration benefits of Cisco PfR?
A.
• Offers traffic optimization based upon the application requirements
• Provides link bundling and, for example, uses only a certain set of links in case of emergency
• Provides inbound and outbound path
• Passively and actively monitors network performance
• Provides dynamic load-balancing functions
• Can use a large variety of interface types
• Is embedded in Cisco IOS® Software switches and routers; no network appliance is required
• Enhances network visibility into performance problems
• Can operate in a monitor-only mode to create better awareness of network performance behavior; in monitor-only mode, PfR can determine the network dynamics based upon policies or SLAs without controlling routes
• Can reroute traffic based on user policy every 3 seconds if desired
• Can be configured by anyone with Cisco IOS Software knowledge; no need for extensive new product training
• Is supported by Cisco Technical Assistance Center (TAC) 24 hours a day
• Is compatible with Network Address Translation (NAT)
• Cisco Technology Partner Fluke Networks (http://www.flukenetworks.com) provides a configuration and management GUI: Cisco PfR Manager
Q. What are the software and hardware requirements for Cisco PfR?
A. Refer to Figures 1 and 2.
Figure 1. Cisco PfR Platform Support
Figure 2. Cisco IOS Software Feature Sets
Q. Is Cisco PfR supported globally?
A. Yes, the Cisco TAC provides global support.
Q. Who is the targeted audience of this solution?
A. Typical businesses using Cisco PfR technology include the following:
• Large, medium, and small enterprises with mission-critical Internet presence
• Enterprises with multiple diverse WAN paths
• Enterprises with remote offices with a primary and backup WAN service
• Small offices with dual Internet connections
Q. How do I deploy Cisco PfR in networks not running internal BGP (iBGP) within the enterprise?
A. To synchronize routing within the enterprise and take advantage of new optimal Cisco PfR routes, route redistribution into the local Interior Gateway Protocol (IGP; for example, EIGRP, OSPF, or RIP) needs to occur. Static routes injected by Cisco PfR are tagged by an identifier that can be specifically redistributed. On the other hand, BGP routes are usually not redistributed into IGP.
Q. What is Cisco PfR use of passive monitoring?
A. For passive monitoring, Cisco PfR uses many services built into Cisco IOS Software:
• Cisco PfR builds a list of Top Throughput and Top Latency Talkers.
• Based on the list of learned and configured prefixes, Cisco PfR passively monitors traffic in every flow (on the current exit) to measure latency, packet loss, and reachability.
Q. How does Cisco PfR use active probing?
A. Whereas Cisco PfR uses passive measurement to determine the performance characteristics of the current path, it can use active probing to measure latency and reachability of prefixes on all possible paths. You can configure IP probe packets to take system defaults or configure them in the following ways:
• If active probing is enabled but no other specific probe configuration is created (taking system defaults), Cisco PfR dynamically sends out Internet Control Message Protocol (ICMP) probes to a subset of Top Talker destinations, if such a list exists (if you previously configured Cisco PfR to build a Top Talker list).
• Active probing can calculate the Voice over IP (VoIP) MOS by measuring delay, loss, and jitter of codec realistic probes.
Q. Is prefix splitting supported with Cisco PfR? If so, how is it done?
A. Yes. Prefix splitting means that a more specific route is derived from a prefix (for example, splitting a host route [/32] from a /24 prefix). If you configure a /24 prefix to be optimized but Cisco PfR finds only /16 route in the routing table, it injects a /24 route with the new exit link using the attributes from the /16 route. This injection affects only the internal routes, and this new information is not propagated outside the autonomous system. If you configure a prefix and Cisco PfR finds only a default route for it (from any border router), the following occurs:
• If BGP is not running, a new static route is injected.
• If BGP is running, a new BGP route is injected.
Q. How does the master controller inject a route?
A. Master controller-border router communication is through a Cisco internal mechanism that does not rely on an iBGP session between them. When the master controller determines the best path for a specific prefix (whether learned or user-configured), it sends a route control command to a selected border router that has the best exit. If an exact route (BGP or static) already exists for this prefix, Cisco PfR either changes the local preference for a BGP route or modifies the next hop of a static route. If a route does not exist for this prefix but there is a super route or a default route covering this prefix, the Cisco PfR Master Controller injects a route matching exactly the length of this prefix (called "prefix splitting") by sending a route control command to the selected border router. The border router then redistributes this route internally with its iBGP peers.
Q. Does the master controller have visibility to the border router BGP routing tables that it controls?
A. No, the master controller does not have a copy of the BGP or static routing tables from any of the border routers it controls. When the master controller monitors and controls a prefix and it needs to send a probe to that destination prefix to test for a better performing path, it queries the BGP and static routing tables on the border routers.
Q. What happens if the master controller fails?
A. If the PfR master controller fails, the border routers notice that their internal communication to the PfR master controller is no longer active. The Cisco IOS Software in the PfR border router determines which routes are under Cisco PfR control and withdraws these routes, thereby restoring everything back to normal routing. The network experiences no worse performance than before turning on Cisco PfR.
You can also configure a backup master controller if you need additional PfR master controller availability.
Q. What are the performance effects of Cisco PfR on the border routers?
A. Router performance is negligible with NetFlow or Cisco PfR enabled on the border router(s), except for what is already known about NetFlow without PfR.
Q. What is the difference between PfR and Cisco IOS Optimized Edge Routing (OER)?
A. Cisco Performance Routing takes advantage of the vast intelligence imbedded in Cisco IOS Software to determine the optimal path based upon network and application policies. Cisco PfR is an evolution of the Cisco IOS OER technology with a much broader scope. The application intelligence and end-to-end network strategy of Cisco PfR are significantly broader than that of OER. The initial phase of PfR takes advantage of OER technology extensively to meet emerging application demands on the enterprise network. Over time, PfR technology will be significantly expanded beyond OER.
Q. Is Cisco PfR configuration difficult?
A. Basic Cisco PfR configuration is very simple, as shown in Figure 3.
Figure 3. Cisco PfR Configuration
Q. What does the sys-logging for Cisco PfR look like?
Q. Do I need to understand IP-SLA comprehensively?
A. When the master controller and border routers are identified and configured, Cisco PfR can use IP SLA technology without additional human interaction; this feature keeps PfR technology implementation simple.
The activation of IP SLA and active monitoring occurs without any interaction or awareness of the person configuring PfR.
The border router sends the IP SLA results to the master controller, which makes intelligent routing decisions based on its policy configuration; this process happens without knowledge of IP SLA technology.
The master controller has various show commands to check the IP SLA information comprehensively.
Q. Does PfR work only with BGP?
A. No, actually the simplest configuration for border routers is based on static route entries.
