WAN Performance Analysis A Study on the Impact of Windows 7

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1 A Talari Networks White Paper WAN Performance Analysis A Study on the Impact of Windows 7 Test results demonstrating WAN performance changes due to upgrading to Windows 7 and the network architecture and performance optimization technologies that can be applied to improve that performance. A Talari White Paper

2 2 Introduction When to migrate and why? This is the question faced by many organizations considering a transition to Windows 7. This is especially true given that many bypassed Windows Vista entirely, instead sticking with the tried and trusted platform. Gartner says most organizations should be eliminating Windows by the end of Michael Silver, vice president and distinguished analyst at Gartner recently stated, "Windows 7 has been getting positive reviews, and many clients report that they have plans to start their production deployments, but there are some that are still undecided about when to start and how quickly to do the migration." For those organizations that rely on a Wide Area Network (WAN), this paper examines how major improvements in the underlying network technologies used in the Windows 7 impact performance over the WAN when compared to Windows. It looks specifically at how the Server Message Block (SMB, often referred to as Common Internet File System, CIFS) protocol version 2.1 in Windows 7 has been enhanced to make it work more efficiently over a WAN. Test Methodology and Results To benchmark the differences in performance we compared the times taken to transfer a 40 Megabyte non- compressible file over a link with 20Mbps of capacity with different round trip times (RTT) ranging from 50ms to 250ms and different packet loss rates ranging from 0% to 5%. The test also looked at how the performance of both Windows and Windows 7 was improved using Talari s Mercury appliances to make the WAN performance more predicable and reliable. The results demonstrated that Windows 7 performs consistently better on the WAN than Windows for file transfers. Using Talari technology improved the performance of Windows by as much as a factor of 7. With Windows 7 plus Talari, however, the results were even more dramatic, with performance improving by as much as 75 times that of Windows. Windows 7 Impact on WAN Round Trip Times Server Message Block (SMB), often referred to as Common Internet File Systems (CIFS), is a client- server protocol that was originally designed to work on small local area networks. As the name suggests it is a block- oriented protocol where the client makes requests and the server responds. This is in contrast with streaming or windowed protocols that can send large amounts of data represented by the window size before requiring some form of handshake to indicate that the data was received successfully. CIFS/SMB is often described as a chatty protocol that requires a large number of request and response sequences to accomplish any given task. Wide area networks introduce latency and severely impact the performance of SMB as the round trip time (RTT) from sending a request to receiving a response is multiplied by a large number of transactions. With Microsoft SMB 1.0 in Windows many IT managers incorporated performance enhancing products into their networks to make SMB 1.0 perform better on the WAN by terminating SMB request and responses locally to hide large round trip times from protocol.

3 3 With Windows 7 and SMB 2.1, Microsoft has made enhancements to the protocol itself to reduce the chattiness. A summary of the specific enhancements can be found in Jose Baretto s Blog. The SMB 2 specification is also available publically on the MSDN website. When comparing the performance of Windows, using SMB 1.0, and Windows 7 using SMB2.1, the results demonstrated that SMB2.1 has effectively fixed the RTT problem. 250 File Transfer Time (s) Win ms RTT, 0% loss 100 ms RTT, 0% loss 250 ms RTT, 0% loss Figure 1 Impact of RTT on the transfer time of a 40MByte non- compressible file over a single 20Mbps link with Windows and Windows 7 The test compared the performance of both Windows and Windows 7 under different network impairments. Specifically we compared the times taken to transfer a 40MByte non- compressible file over a link with 20 Mbps of capacity with different RTT ranging from 50ms to 250ms and different packet loss rates ranging from 0% to 5%. As Figure 1 clearly shows, even with a small RTT of 50ms Windows 7 transferred the 40MByte file 3 times faster than Windows. As the RTT increased the time taken to transfer the same file increased only modestly for Windows 7 whereas the time taken on Windows increases dramatically. In this test, with an RTT of 250ms, Windows 7 is eight times faster than Windows. All shared IP networks exhibit packet loss; in fact it is required for TCP/IP flow control to work. TCP/IP is constantly trying to find the rate at which it begins to see congestion resulting in packet loss by sending more packets than the network can handle. WAN congestion can happen on the first mile and last mile links that often have significantly less capacity than the networks they interconnect, or at routers in the middle of the network where many TCP/IP flows are competing for bandwidth.

4 4 As can be seen in Figure 2, loss has even more impact on the performance of SMB for both Windows and Windows 7. File Transfer Times (s) ms RTT, 0% loss 50 ms RTT, 1% loss 50 ms RTT, 2% loss 50 ms RTT, 5% loss Win 7 Figure 2 Impact of Packet Loss Rate on the transfer time of a 40MByte non- compressible file over a single 20Mbps link with Windows and Windows 7 With just a packet loss rate of 1% the performance of Windows drops by a factor of 4.5 and 8.5 respectively. Windows 7 does a much better job than at zero loss, which impacts this ratio. Overall Windows 7 is much better than Windows under loss. Impact of Talari Appliances on Windows 7 and Windows Performance Enterprises can dramatically improve Windows and Windows 7 performance by incorporating Talari s Mercury appliances into their infrastructure. Talari brings a revolutionary approach to enhancing Enterprise WANs. Unlike other performance enhancing devices that focus on compression application acceleration, Talari optimizes a low cost, higher- bandwidth network fabric for all applications. Talari makes the WAN look to each TCP application as if it were a zero- packet- loss WAN with the occasional bout of jitter- something TCP and TCP- based applications are designed to expect and accommodate without incident. The effect of Talari s loss mitigation technology can be clearly seen in Figure 3 and Figure 4, when comparing the performance of Windows and Windows 7 for the same 40MByte file transfer under both increasing RTT and loss.

5 File Transfer Times (s) Win 7 + Talari Win 7 + Talari ms RTT, 0% loss 100 ms RTT, 1% loss 250 ms RTT, 2% loss 250 ms RTT, 5% loss Figure 3 Impact of Talari s loss mitigation technology on the transfer time of a 40Mbyte non- compressible file over a single 20Mbps link with Windows and Windows x 75.7x 70.0x 60.0x 59.3x Speed-up Factor 50.0x 40.0x 30.0x 20.0x 20.4x to Win 7 + Talari Win 7 + Talari 10.0x 7.0x 2.9x 3.4x 4.1x 2.7x 1.0x 0.9x 1.0x 1.5x 1.0x 1.5x 1.0x 1.4x 0.0x 50 ms RTT, 0% loss 100 ms RTT, 1% loss 250 ms RTT, 2% loss 250 ms RTT, 5% loss Figure 4 Relative impact of Talari s loss mitigation technology on the transfer time of a 40Mbyte non- compressible file over a single 20Mbps link with Windows and Windows 7 compared to Windows alone Loss mitigation is able to help the performance of Windows file transfers by reducing the file transfer times by as much as a factor of 7. With the new protocols in Windows 7, Talari s loss mitigation technology works extremely well for a combined solution that has consistent performance over a wide range of network conditions. This results in reducing the file transfer time by as much as a factor of 75. How Talari Technology Improves WAN Performance In this controlled test only a single link is used so that consistent data could be compared. In real life deployments of Talari technology, diverse sources of bandwidth would allow much of

6 6 the loss to be avoided altogether by favoring the better performing paths. This will result in even better overall file transfer times. In a network with redundant links, Talari combines multiple IP networks into a single network fabric with the aim of increasing the amount of bandwidth available at each remote office location and as a means to provide physical redundancy should any individual link fail. This allows an enterprise to build a WAN that is very reliable and predictable in the way that it performs. This also results in dramatic performance improvements as well as increased reliability. This is because Talari actively uses all available links, monitoring the health and performance of all links in order to make real time adjustments to optimize network performance. There are two key technologies that allow Talari to deliver these benefits. Multipath Network Spectrometry With Multipath Network Spectrometry, the characteristics of every WAN link, network path and traffic flow are monitored precisely and continuously. This yields detailed data about instantaneous loss, latency and jitter throughout the network, allowing for sub- second changes in path selection. Resilient Multipath Connectivity All of the possible paths through the network are monitored and utilized to improve the performance for all applications by maximizing the use of available bandwidth and mitigating the effects of packet loss. Lost packets can be detected and re- transmitted before the higher layer applications respond by scaling back their transmission rates. This delivers predictable performance throughout, regardless of transient congestion or network outages. To TCP/IP based applications, a network using Talari technology looks like a zero loss network with occasional bouts of jitter. With these two underlying technologies, Talari appliances use end- to- end algorithms to match the state of the network with the needs of different traffic types and adapt using real time traffic engineering. This ensures that the optimal path is chosen for every packet. Talari appliances implement QoS and use the class of service information associated with each flow or configured in a policy rule as part of the path selection criteria. Unlike other boxes that implement QoS and can only prioritize which traffic goes out on the local link first; Talari uses this QoS information to choose the path that gets the packet to the destination in the shortest possible time, which is ultimately what matters most.

7 7 Even though packets can follow any number of paths to the destination, the connection between two locations appears as a single highly reliable link called a conduit. In a Talari conduit there can be up to 10 classes of service, and per flow classification inside the appliance determines which class to use for each traffic flow. So there is a lot of flexibility on how the bandwidth is used among real- time traffic, interactive and bulk transfer application flows. The packets within a conduit are also secured using 128- bit AES encryption. This makes it a viable alternative to either add bandwidth to existing private network connections such as MPLS or replace those expensive connections altogether with much less expensive Internet links. Conclusion By fixing the RTT problem in SMB/CIFS, Windows 7 certainly holds one of the keys to building a faster WAN and this fact alone may be reason enough to switch over from Windows sooner rather than later. But as companies move to centralized data centers, backhaul cloud- driven Internet traffic through the WAN to the data center, move more video and voice traffic across their corporate WAN network, and adjust to increasing requirements for document retention, pressure is mounting to continue to increase bandwidth without corresponding increases in cost. Moving to Windows 7 alone will not free up enough bandwidth to accommodate this additional demand. With Talari, companies can add inexpensive Internet connections to increase bandwidth, while still achieving the performance and quality of service they have come to expect from a traditional WAN connection. For example, using Talari, a site with a DSL connection plus a Cable Modem connection, together costing $100 per month can achieve four nines reliable connection back to the data center. Compare this to using an MPLS network with a T1 link at the site costing $750 per month. The key difference is that the remote office now has perhaps 5 to 15 times as much bandwidth, for a fraction of the cost. This is game changing for businesses that rely on applications that run over the WAN as remote offices can benefit from an order of magnitude more reliable bandwidth at a fraction of the traditional cost. References: Jose Baretto s Blog - SMB2, a complete redesign of the main remote file protocol for Windows SMB 2.0 Specification Talari Networks Stevens Creek Blvd. Suite 220, Cupertino CA