Acceleration 102: Asymmetric or Symmetric?

Transcription

1 F5 White Paper Acceleration 102: Asymmetric or Symmetric? Both asymmetric and symmetric acceleration technologies can deliver great benefit to your users. But how and where do you deploy them? by Peter Murray Technical Marketing Manger

2 Contents Introduction 3 Acceleration Topology Types 5 Asymmetric Acceleration 6 Asymmetric Acceleration Misconceptions 6 Asymmetric Acceleration Functions 7 Asymmetric Acceleration Benefits 8 Symmetric Acceleration 10 Deploying Symmetric Acceleration 11 Data Center to Data Center Deployment 11 Large Branch and Regional Office Deployment 11 Symmetric Web Acceleration 12 Symmetric Acceleration Using Client-based Acceleration Software 12 The Wonder Widgets Symmetric Solution 13 The Combined Wonder Widgets Solution 15 Tying it All Together 17 Conclusion 18 2

3 Introduction This paper is the second in a series. The first, Acceleration 101, describes acceleration features and terms. This paper focuses on topology options for deploying acceleration features in an Application Delivery Network (ADN). Acceleration is an excellent technology for overcoming the limitations inherent in today s networks and applications. An application acceleration solution can significantly reduce application response times improving the chances for success for application rollouts; increasing user productivity; and increasing revenues from e-commerce sites by minimizing abandoned transactions or shopping carts due to slow page loads, failed transactions, or error messages. You can deploy acceleration asymmetrically, symmetrically, or in combination. Where you deploy asymmetric and symmetric acceleration features depends largely on the geographic distribution of your organization s members and customers. Table 1 summarized the acceleration features described in the Acceleration 101 white paper ( acceleration-101-wp.pdf), and illustrates how each can be deployed in a network. Feature Asymmetric Deployment Symmetric Deployment Benefit Server Load Balancing X Ensures users access the best performing information source at that moment. Global Server Load Balancing X Ensures that users access the highest-performing site at that moment. Decreases transmitted data: Compression X X Asymmetric compression condenses web data for transmission to a browser. Data Deduplication X Symmetric compression condenses any data for transmission to a remote acceleration device. Replaces previously-sent data with dictionary pointers, minimizing transmitted data and ensuring rapid user response time. Also ensures data is current and delivered only to authorized users. 3

4 Feature Asymmetric Deployment Symmetric Deployment Benefit Increases TCP performance: Asymmetric optimization aggregates requests for any TCP protocol to reduce connection processing. TCP Optimization X X It optimizes TCP processing for TCP/IP stacks that increases client-side connections to speed web page downloads. Symmetric optimization aggregates transactions inside tunnels that connect acceleration devices. Web Browser Object Caching X Manipulates HTTP responses to increase browser caching and decrease HTTP requests. Remote Web Object Caching X Reduces client response times by serving web objects directly from a remote device rather than from a central server. Non-Web Object Caching X Reduces client response times by serving files directly from a remote device rather than a central server. HTTP Protocol and Web Application X Manipulates web requests and responses to increase HTTP and web application efficiency. Optimization Table 1: Acceleration feature deployment Asymmetric acceleration uses a centrally located acceleration device to perform optimizations that increase performance for all users connected to that data center. Some asymmetric optimizations, such as TCP optimization and load balancing, are useful for many applications and protocols. Others, like web acceleration are application-dependent. Regardless, no special software is required for client systems; asymmetric acceleration uses techniques that do not affect endpoint devices. 4

5 Symmetric acceleration requires either two acceleration devices with one at each end of a network link, or a central acceleration device and client software that operate together to perform acceleration functions for the client. Organizations can deploy acceleration technology features asymmetrically, symmetrically, or both, depending on several factors. While there is a debate in the industry (mostly by vendors that offer one solution or the other) over whether asymmetric or symmetric acceleration provides the best performance improvement and which represents the best ROI, the truth is that both methods benefit users. The best deployment topology for your Application Delivery Network depends on many factors, including the location(s) in which your users reside, your organization s ability and willingness to deploy and maintain devices in remote offices, the applications you want to accelerate and your budget. This paper uses Wonder Widgets, Inc., the example company introduced in the Acceleration 101 white paper to illustrate how a typical company can benefit from asymmetric and symmetric acceleration. Acceleration Topology Types In the Acceleration 101 white paper, the Wonder Widgets team researched acceleration technology and found that many acceleration features are worth implementing to solve their needs. In fact, they were already using some acceleration features. Now, Kristina, the Wonder Widgets CIO, and her team are investigating where and when to implement additional acceleration technologies in their network. Application acceleration deployment can be configured asymmetrically, symmetrically, or in combination. Before examining each acceleration topology, it is important to review the benefits that any organization should consider when determining the need for an acceleration solution: Improving WAN-based application performance accelerates application adoption and increases user productivity Decreasing variable burst costs associated with Content Delivery Network (CDN) services can decrease monthly telecommunications charges Deployment flexibility reduces ongoing maintenance costs and increases user satisfaction Accelerating SSL-encrypted application traffic increases application performance and organizational security 5

6 Improving existing server capacity eliminates or delays the need to expand data centers and reduces power and cooling costs Decreasing bandwidth utilization improves efficiency of existing capacity and may eliminate the need for expanded capacity Kristina s team realizes that their company s unique challenges greatly affect whether they deploy an asymmetric acceleration topology, symmetric acceleration topology, or a combination. During their weekly staff meeting, they decide to begin investigating asymmetric acceleration. Asymmetric Acceleration Bruno, the network architect, knows that the industry referred to asymmetric acceleration as just acceleration until symmetric acceleration devices appeared on the market. For example, a server load balancer qualifies as an early version of an asymmetric acceleration device because it improves application performance for all users by spreading user load across multiple servers or other devices like firewalls or access controllers, and requires only one device in the data center. A newer example is a web acceleration device, which compresses web traffic, caches static objects, and manipulates HTTP and web application behavior. Asymmetric acceleration requires only one device to accelerate applications and reduce network traffic across public network links where latency, packet loss, Quality of Service (QoS) issues, and application throughput cannot always be controlled. Application response times, which can be completely satisfactory when an application is run over a LAN, may become intolerable when users access the application across a link that suffers from high latency or low bandwidth. An asymmetric acceleration device can dramatically improve performance and reduce response times, making the application run as if it was being served locally. Asymmetric Acceleration Misconceptions An associate from another company tells Bruno that asymmetric acceleration is really only for web-based (HTTP or HTTPS) traffic, and cannot modify browser behavior. Bruno is surprised, as he has just read how asymmetric acceleration is useful for much more than web traffic, so he decides to investigate further. 6

7 He finds out that some asymmetric acceleration products can do far more than accelerate web traffic. They can balance server load, optimize TCP, and apply and enforce QoS for any application running over TCP. Furthermore, some asymmetric solutions can also offload server-side SSL processing for any application running over TCP. These features can dramatically improve application performance. Although Bruno s associate mentions that centralized acceleration solutions can t influence inbound WAN traffic because these solutions do nothing to modify a browser s behavior, Bruno has already learned that some acceleration devices can modify server response content to enable more simultaneous connections to a single URL. The acceleration device modifies an HTTP response by slightly changing the URLs in the response so a browser can open more simultaneous connections, as described in the Acceleration 101 white paper. In addition, some acceleration devices can rewrite HTTP headers to modify browser behavior. Some can modify cache headers to tell browsers to cache an object, even though the application identifies the content as non-cacheable. A company logo, a line on the web page, or a background color, for example, may be static but marked as non-cacheable. The acceleration device modifies the object header to mark the content as cacheable. These features can significantly reduce or eliminate unnecessary traffic, whether due to inefficiencies in the HTTP protocol or in application implementations. They provide the first level of relief for an organization s overburdened WAN links and can often reduce utilization enough to ensure significantly better application response for all remote locations. Asymmetric Acceleration Functions Asymmetric acceleration combines protocol-level optimizations and applicationlayer acceleration techniques to improve response times. It helps overcome problems caused by distance and protocol or application implementation inefficiencies by making protocols more efficient. For example, an asymmetric acceleration device can: Reduce server-side TCP connections by aggregating multiple client-side connections into fewer server-side connections Increasing the number of client-side connections to speed web page building Compress content, allowing a proxy to offload compression while enabling the device to perform other actions on the uncompressed content 7

8 Cache content, offloading servers and increasing performance Mark HTTP objects as static, enabling clients to load objects directly from browser cache Transparently correct HTTP bugs or feature deficiencies Offload SSL, dramatically increasing server performance and offering a simpler repository for certificates Asymmetric Acceleration Benefits Bruno s research tells him that biggest single advantage to an asymmetric acceleration solution is that it can dramatically reduce the Total Cost of Ownership (TCO). An asymmetric acceleration solution requires no point-product in branch or regional offices and requires no additional client software to make the solution work properly. Instead, a single, central device can handle acceleration for all users, making it the ideal first step for improving user experience and reducing traffic for customers, partners, and remote users of corporate applications alike. It also reduces TCO by reducing the ongoing management required for remote devices and software clients. Asymmetric acceleration also helps control costs by increasing server capacity. The acceleration device can offload server operations that are CPU and memory-intensive, freeing the server to perform its primary function serving files. Offloading SSL termination, optimizing TCP/IP connections, and implementing intelligent caching helps increase application server capacity. Often, this enables an organization to delay or even eliminate the need to purchase additional server hardware or deploy additional application software licenses. Asymmetric acceleration also offers benefits to CDN customers. CDN customers can face surprisingly high overage charges when traffic exceeds the contracted monthly service amount. Without an acceleration device, the customer must either suffer potentially huge monthly overage costs or regularly upgrade the agreed monthly service amount (and of course, the cost) to maintain the lowest overall service cost. Deploying an asymmetric solution where the acceleration device correctly marks content as cacheable reduces user requests for content and, therefore, CDN overage charges. Yet another way an asymmetric acceleration device can help control costs is by specifically optimizing web-based applications. Many organizations are moving 8

9 towards web-based application delivery because it simplifies deployment and lowers costs. Even if your organization uses many legacy applications today, it makes sense for you to ensure you know your organization s plans for deploying newer, web-based applications or web-based versions of legacy applications. Chances are, your organization is already evaluating or deploying one or more of the new web-enabled versions of traditional applications that are rapidly replacing legacy software. For example, Microsoft Office SharePoint using the Common Internet File System (CIFS) displaces Windows File Sharing in the enterprise. Some asymmetric solutions can specifically accelerate SharePoint using one central device. Moreover, it s not just Microsoft. BEA, Oracle, and SAP are all examples of legacy application vendors that are moving to web-based clients for which asymmetric acceleration templates are available. Deploying applications with pre-defined templates dramatically speeds deployment and provides dramatic performance gains at a very reasonable cost. This is especially beneficial for users in small remote or branch offices where implementing a symmetric acceleration device is costly and provides less benefit than in a larger office. Kristine and her team realize that placing asymmetric acceleration devices in the Paris office is the best first step for the performance problems Wonder Widgets faces. Asymmetric acceleration devices will immediately improve their customer-facing community application, speed content downloads, reduce CDN charges, and improve application performance both for the web-based community and for web-based employee applications. Kristina directs Bruno to replace their existing Paris-based load balancers with Application Delivery Controllers (ADCs) that also offer web acceleration features. Adding ADCs with web acceleration modules will increase performance and reduce response times for web applications and all other TCP applications accessed by worldwide remote users. Figure 1 (following page) shows how Wonder Widgets, Inc. plans to deploy asymmetric acceleration along with upgraded ADCs as a first step in building an advanced ADN. 9

10 Sales San Diego VPN Beijing BIG-IP Local Traffic Manager Internet or VPN Servers VPN Sales WANJet Sales Enterprise Manager Firewalls BIG IP Global Traffic Manager VPN Load Balancing and Asymmetic Acceleration BIG IP Local Traffic Manager Bangalore Database Servers Blade Servers Paris Figure 1: Asymmetric acceleration configuration example Symmetric Acceleration Next, Bruno and Anne, the application architect, investigate symmetric acceleration, which is a more recent technology than asymmetric acceleration. It requires either an acceleration device at both ends of a WAN link or the combination of a central acceleration device and acceleration software on client systems. It is most often associated with WAN Optimization Controllers (WOCs). Like asymmetric acceleration, symmetric acceleration combines protocol-level optimizations and application-layer acceleration techniques to improve response times. It also uses either data deduplication or caching to position the data closer to users at the far end of a remote link. For example, when used in a arge regional branch office, this results in faster response times for clients and reduced bandwidth utilization over WAN links. 10

11 Both Bruno and Anne are concerned about the cost of deploying symmetric acceleration in every office. Although users in small offices can benefit from symmetric acceleration, the benefit can come at a price beyond the means of many organizations. However, monthly data transport costs associated with WAN-based communication, especially high-speed links that span large distances, often exceed total application and network hardware costs by significant margins. Accelerating all WAN traffic between larger branch offices and the data center or between selected regional offices and the data center generally offers the next best return on investment after an asymmetric deployment. Bruno and Anne decide to investigate where to deploy symmetric acceleration. Deploying Symmetric Acceleration Now that they better understand symmetric acceleration, the Wonder Widgets team looks more deeply into symmetric acceleration. Symmetric acceleration deployments generally fall into the following categories: Data center to data center data replication Backup and branch office acceleration for all protocols, or Branch office acceleration for static web content Each scenario, when deployed effectively, has its benefits. Data Center to Data Center Deployment One of the largest bandwidth consumers and performance bottlenecks for many organizations is real-time data replication and backup. Some symmetric solutions boost replication performance between data centers by a factor of 7x (700 percent). The bandwidth reduction and the productivity benefits achieved from accelerating business-critical functions can prevent the organization from paying ever-increasing WAN bandwidth charges and deliver ROI in a matter of months. Large Branch and Regional Office Deployment TCP optimization, compression, data deduplication, and remote data caching can improve performance for corporate , legacy applications and other file-sharing applications. These features can accelerate any TCP protocol traffic between large offices and corporate data centers. In larger branch and remote 11

12 offices, accelerating all application traffic enables higher productivity and lowers transaction costs for all users. Using a symmetric solution also enables local users to back-up data to a central repository, simplifying backup strategies and lowering branch-office hardware costs. Accelerating all protocols for users within a geographic region can be another good use of symmetric acceleration. Users within a region can connect through the regional office using a VPN and share both the symmetric acceleration device with the regional office and the higher-speed link with the central data center. This approach enables an organization realize the benefit of the acceleration device across all regions, even if the office is relatively small. Remote users get the advantage of having content cached locally plus the benefit of having transactions terminated regionally, greatly reducing application problems caused by latency. Symmetric Web Acceleration Users in larger branch or regional offices and users that connect directly to regional offices can achieve high performance increases from symmetric web acceleration devices. Static web content is cached as users access it from a remote office so over time, most static content resides in the remote office. Users in the remote office access the static content from the local cache, but those connecting to the remote access via VPN gain even more. Instead of dealing with the high latency and low bandwidth of a direct connection to a data center, users connect to the regional office through a VPN and access the content cached in that office. VPN connections by these users to data centers also benefit from the TCP optimization, caching, and data deduplication the remote acceleration device offers. Symmetric Acceleration Using Client-based Acceleration Software A recent form of symmetric acceleration uses a Software-based WAN Optimization Controller (SoftWOC), which is client-based software hat performs compression, perform or assists with caching, optimize TCP, and in some cases, provides universal remote access via SSL. Some SoftWOCs can even perform these actions for all TCP protocols, not just HTTP/HTTPS. The SoftWOC client communicates with a central device, performing similar functions to those supplied by a remote symmetric acceleration device. The advantage to a SoftWOC client is that individual remote users can achieve performance gains individually. SoftWOCs that integrate application acceleration and secure access simplify user access, deployment, and client management. 12

13 However, there are disadvantages to this approach. First, a SoftWOC must be loaded and maintained on every system that will use the technology. External partners, suppliers and commercial web users do not benefit because they do not have the SoftWOC installed on their systems. Second, SoftWOCs can require multiple Gigabytes of local disk storage to cache downloaded content. This means organizations might have to upgrade systems That use a SoftWOC to support the required disk space and memory requirements or limit the SoftWOC to users whose systems meet the requirements. Third, many organizations are loath to load and maintain multiple software clients on the same system, so acceleration and universal access are more of a requirement than a luxury. Finally, a software SoftWOC may cause a security hole due to cached content present on disk. If the majority of your users are in larger offices, or your largest pain point revolves around backup and corporate data replication to a disaster recovery site, chances are that a symmetric solution using two acceleration devices will benefit you most. The Wonder Widgets Symmetric Solution Kristina and her team have decided that symmetric WAN acceleration can be useful for the link between the Paris and San Diego data centers. They will use symmetric acceleration to replicate data between data centers and to accelerate legacy financial applications that reside in Paris and San Diego. Anne suggests they add symmetric web acceleration between Paris and the San Diego office, which serves as the U.S. regional office and houses the secondary data center. Bruno further suggests that they deploy global server load balancing in the Paris office to ensure users are directed to the closest, best performing site. They know that plans are in place to begin serving social networking and entertainment content from both Paris and the San Diego data center, and want to ensure consistent high performance. By using symmetric web acceleration in Paris and San Diego and global server load balancing in Paris, corporate users in the Paris office will benefit from rapid symmetric access to applications in San Diego and vice versa. Anne further suggests they add a stand-alone web acceleration device in the Beijing office. As with deploying the web acceleration devices in Paris and San 13

14 Diego, the Beijing manufacturing team will benefit from rapid symmetric access to the Paris-based web manufacturing application and Asian commercial users will benefit from regional asymmetric web acceleration in Beijing. Kristina agrees and directs Bruno to replace the load balancer in San Diego with an Application Delivery Controller that also offers web acceleration features, and to add a stand-alone web acceleration device in Beijing. Figure 2 shows how Wonder Widgets, Inc. plans to deploy symmetric acceleration. Symmetric WAN Acceleration Sales San Diego VPN WANJet Beijing BIG-IP Local Traffic Manager Internet or VPN Servers VPN Standalone Symmetric Web Acceleration Sales WANJet Sales Firewalls Enterprise Manager VPN Server Load Balancing and Symmetric Web Acceleration Bangalore Database Servers Blade Servers Paris Figure 2: Symmetric acceleration configuration example 14

15 The Combined Wonder Widgets Solution After reviewing the symmetric acceleration recommendations, Bruno realizes that deploying symmetric web acceleration devices in Paris, San Diego, and Beijing enable Wonder Widgets to add another device to both ensure high availability and simultaneously enable a combination of asymmetric and symmetric web acceleration for Wonder Widgets remote users and retail customers. Although web applications are only served from the Paris site currently, web application data is already being replicated to San Diego. This enables San Diego to take over serving the web applications in case of an outage in Paris. Similarly, legacy application data is being replicated to Paris, which could take over if the San Diego site becomes unavailable. Adding geographic server load balancing would enable simpler and faster failover for customers in the event the Paris or San Diego sites went offline. Second, Wonder Widgets can greatly improve performance for remote users by directing web requests to the closest geographic site. Shorter TCP handshaking due to less latency will speed transactions. If the closest geographic site hosts the web application requested by a user, the web application will be served from there and the user will benefit from asymmetric web acceleration. If the web application is served from another site, the user will benefit from asymmetric web acceleration to the closest geographic site as well as from symmetric web acceleration to the site that hosts the web application. Bruno sees that combining asymmetric and symmetric web acceleration would benefit both remote Wonder Widgets workers, especially salespeople and retail users. He suggests to Kristina that they deploy global server load balancing in the Paris office. She agrees and directs Bruno to add geographic server load balancing to the Paris data center. Figure 3 (following page) shows how the combined Wonder Widgets solution offers a combination of asymmetric web acceleration, symmetric web acceleration, and symmetric WAN acceleration. 15

16 Asymmetric Web Acceleration Symmetric Web Acceleration Asia Sales Symmetric WAN Acceleration San Diego Global Server Balancing Load Asia VPN Beijing WANJet BIG-IP Local Traffic Manager Internet or VPN Servers VPN Americas EMEA Americas Sales Firewalls WANJet EMEA Sales BIG IP Global Traffic Manager VPN Bangalore Database Servers Blade Servers Paris Figure 3: Combined asymmetric and symmetric acceleration configuration example 16

17 Tying it All Together Kristina looks forward to presenting her team s solution to the next Wonder Widgets, Inc. board meeting. She and her team are confident that they have identified their pain points and potential acceleration solutions. Plans are in place to deploy the acceleration features that will improve performance for external customers, internal users, partners, and suppliers. Reduced WAN traffic and server offload will give them the added capacity they require for future innovation and will lower both capital and operating expenses by simplifying heir application infrastructure. External customers will benefit from asymmetric acceleration, receiving faster web response from Wonder Widgets social networking and content site applications. Wonder Widgets corporate users in Paris, San Diego, and Beijing will benefit from symmetric web optimization, receiving better performance for their shared web applications. Corporate users will also benefit from symmetric WAN acceleration for faster access to legacy applications and remote file access. Wonder Widgets, Inc. remote sales staff and remote workers will also benefit from both asymmetric and symmetric acceleration. Remote staff will log into Paris, San Diego, or Beijing as appropriate to benefit from asymmetric acceleration from wherever they may be. Remote staff will also benefit from symmetric web acceleration between the regional offices and either Paris or San Diego as appropriate. The Wonder Widgets, Inc. example acceleration deployment helps illustrate where it makes sense to deploy asymmetric and symmetric acceleration. Asymmetric acceleration technologies, including server load balancing, global server load balancing, TCP optimization, SSL optimization, web acceleration, and asymmetric caching and compression offer benefits to any user whether they are internal or external to the organization. Symmetric acceleration technologies, including TCP optimization, symmetric compression caching, data deduplication, and SSL offload offer benefits to corporate users in Wonder Widgets, Inc. major branches as well as remote and external users. 17

18 Conclusion Application acceleration is a viable technology with demonstrable benefits. Virtually any organization, its internal users, customers, partners, and suppliers can benefit from the features acceleration and optimization supply. Acceleration is not a one size fits all solution. Features required for one application or location may be inappropriate for another. Some acceleration features are implemented widely while others are limited to one or a small subset of vendors. The most important decisions should be choosing a partner you can trust and choosing the solution gives you the best application acceleration return for the investment you make. Installing an asymmetric acceleration solution as a starting point provides most organizations the biggest bang for the buck, especially for web applications. If your organization shares applications with many small offices, remote users, suppliers, partners, or the public, asymmetric acceleration offers the simplest way to ensure the greatest performance gain for the lowest cost. Even more importantly, implementing asymmetric acceleration for web-based applications, regardless of other solutions, is likely to offer the largest single performance gain you can achieve. Symmetric acceleration offers the next step for companies with large, distributed sites, large data replication/backup requirements, and higher-speed WAN links. When you evaluate a solution, take the time to determine whether a single solution can support both asymmetric and symmetric deployment configurations. Solutions supporting both offer greater flexibility and adapt more rapidly to the volatile environment of both corporate network architectures and public networks, and will ultimately result in the greatest ROI. F5 Networks, Inc. Corporate Headquarters 401 Elliott Avenue West Seattle, WA Phone (888) 88BIGIP Toll-free Fax info@f5.com F5 Networks Asia-Pacific Phone Fax info.asia@f5.com F5 Networks Ltd. Europe/Middle-East/Africa +44 (0) Phone +44 (0) Fax emeainfo@f5.com F5 Networks Japan K.K Phone Fax info@f5networks.co.jp 08/ F5 Networks, Inc. All rights reserved. F5, F5 Networks, the F5 logo, BIG-IP, VIPRION, FirePass, and icontrol are trademarks or registered trademarks of F5 Networks, Inc. in the U.S. and in certain other countries. 18