Cisco WAAS Optimizations for Centralized E-Mail Services [Cisco Wide Area Application Services (WAAS) Software]

What You Will Learn

Cisco® Wide Area Application Services (WAAS) enables IT departments to simplify email services infrastructure through consolidation and improve delivery of email services that are already centralized. The optimizations provided by Cisco WAAS provide dramatic throughput improvements for remote-office users when accessing centralized email servers through Messaging API (MAPI), Simple Mail Transfer Protocol (SMTP), Post Office Protocol 3 (POP3), Internet Mail Access Protocol (IMAP), Remote Procedure Call (RPC), and any other TCP-based protocol. This document examines the optimizations provided by Cisco WAAS and describes how Cisco WAAS enables consolidation and acceleration of email services.

Challenge

With IT budgets shrinking and with the need to contain capital expenditures (CapEx) and operating expenses (OpEx), almost every IT department that manages a distributed infrastructure wants to consolidate costly remote-office infrastructure into the data center or onto scalable, virtual branch-office application delivery devices. Furthermore, as the network load created by applications continues to evolve and become larger and more complex, the performance characteristics of the WAN affect application delivery even more. The challenges of data-retention, business-continuance, and disaster-recovery policies and compliance requirements for a highly distributed infrastructure and already overburdened WAN environment exacerbate the problem. Many vendors have attempted to address this problem with point products that do not effectively allow IT departments to take advantage of existing investment in network intelligence.

A centralized IT infrastructure enables OpEx and CapEx savings while streamlining data-protection processes. With Cisco WAAS and the Cisco Wide Area Application Engine (WAE) family of hardware appliances and router-integrated network modules, enterprise IT departments can now safely centralize distributed file, email, and application infrastructure within the data center without compromising the performance expectations of remote-office users (Figure 1).

Figure 1. Centralized and Consolidated Infrastructure with Cisco WAAS

Cisco WAAS is deployed on an appliance or router-integrated network module on each side of the WAN to provide application-specific acceleration and WAN optimization capabilities. Cisco WAAS appliances can be deployed out of the data path or physically in-path in the data center or in the remote branch office, and Cisco WAAS Network Modules (NMEs) can be deployed out-of-path in the branch office. Regardless of the deployment model, Cisco WAAS provides application performance improvements and enables centralization without compromising high availability and scalability by providing intelligent load distribution and fail-through operation.

Cisco WAAS Optimizations for Centralized Email Applications

Cisco WAAS is a multilayer application acceleration and WAN optimization solution that improves application performance over the WAN, thus enabling centralization. Acceleration for email applications and the associated protocols is achieved through Cisco WAAS optimization features such as:

• Transport flow optimization (TFO): TFO provides standards-based, field-proven throughput improvements for TCP-based applications while maintaining packet-network friendliness and safe coexistence with other network nodes communicating using standard TCP implementations. TFO terminates TCP sessions locally and transparently optimizes flows that traverse the WAN, thereby shielding communicating nodes from WAN conditions. TFO includes the following components, each providing specific acceleration for email services:

– Large initial windows: Client email connections more quickly exit the TCP slow-start phase and enter congestion avoidance, thereby allowing quicker startup in email throughput.

– Window scaling: Cisco WAAS transparently increases the TCP message window capacity of optimized TCP connections to allow more data to be in transit across the WAN, thereby improving email throughput.

– Advanced congestion handling: Through intelligent handling of TCP message congestion scenarios, Cisco WAAS can more efficiently retransmit lost data when necessary and return to higher levels of throughput on the network much more quickly, resulting in better email application performance.

• Data redundancy elimination (DRE): DRE is an advanced form of network compression that allows Cisco WAAS to maintain a database of byte sequences previously seen traversing the network. This information is used to prevent redundant transmission patterns from traversing the network. For repeated patterns, only pattern identifiers need to be sent, and the original message is then rebuilt in its entirety by the distant appliance. This feature enables significant levels of compression and helps ensure message and application coherency because the original message is always rebuilt and verified by the distant Cisco WAE. Because DRE is application agnostic and bidirectional, it is effective regardless of the direction of traffic flow. Data patterns identified for one application protocol can be reused by other applications, and patterns that have been identified for one direction of traffic flow can be reused to remove redundancy in traffic flowing in the other direction. With DRE, email and attachments are stored as previously seen transmissions, and should redundant segments be identified, such as an email or an attachment that has been seen before, significant levels of compression can be achieved.

• Lempel-Ziv (LZ) compression: LZ compression is a standards-based compression that can be applied to further reduce the amount of bandwidth consumed by a TCP flow. LZ compression can be used in conjunction with DRE or independently. LZ compression can provide from 2:1 to 4:1 compression depending on the application being used and the data being transmitted. This feature is especially helpful for data that has not been previously seen and suppressed by DRE because the pattern identifiers are highly compressible.

• Microsoft Exchange optimization: Microsoft Exchange email relies on the Messaging API (MAPI) messaging interface, used over remote procedure calls (RPCs), to deliver email, calendaring, contacts, and more to Microsoft Outlook users for collaboration and productivity. As with many applications operating over a WAN, Microsoft Exchange performance is constrained by bandwidth limitations and latency found in the WAN. Cisco WAAS provides a number of acceleration services for Microsoft Exchange to improve performance. Unlike other solutions that provide acceleration for Microsoft Exchange, Cisco WAAS acceleration for Microsoft Exchange was developed in conjunction with Microsoft to help ensure protocol correctness and compatibility with all major versions of Microsoft Exchange, without relying on reverse engineering of protocols. The acceleration capabilities provided by Cisco WAAS for Microsoft Exchange include:

– Asynchronous write: Write operations for sending email and attachments are acknowledged locally. Local generation of responses allows clients to fully utilize WAN bandwidth.

– Object read ahead: Objects being fetched from the server, such as email, calendar items, or address books, are fetched at an accelerated rate, with Cisco WAAS prefetching these objects on behalf of the user. This feature helps mitigate the send-and-wait behavior of Microsoft Exchange and Outlook.

– Messages decompression: Cisco WAAS can automatically defer native compression provided by Microsoft Exchange Server and Outlook in favor of Cisco WAAS DRE and persistent LZ compression. Cisco WAAS can also natively decode messages encoded by Microsoft Exchange or Outlook to provide additional levels of compression. Full data coherency is preserved end to end.

– DRE hints: Cisco WAAS provides hints to the DRE compression process based on the message payload, resulting in better compression and overall improvement in DRE efficiency.

– Payload aggregation: Cisco WAAS recognizes many Microsoft Exchange messages that are small in nature and can either batch these messages together for optimized delivery or dynamically adjust DRE and LZ compression to improve compression ratios for these messages.

Email Acceleration Example

When a remote user is sending or receiving email, Cisco WAAS applies the appropriate optimizations to improve the performance of the email application, resulting in reduced bandwidth utilization and dramatically faster remote-office user email performance. Figure 2 shows a common user scenario, described here, demonstrating how Cisco WAAS learns network traffic patterns and optimizes application flows.

Figure 2. Cisco WAAS Email Acceleration Example

1. A user in a remote office connects to a Microsoft Exchange Server and downloads an email that another user from a different remote office has sent. The message includes a 5-MB PowerPoint attachment. Because the Cisco WAAS WAE has never seen this data before, it will begin to learn the traffic patterns from the operation and store the traffic segments locally in its DRE cache. During the operation, the Cisco WAAS WAE will be adding the patterns to its DRE database, and it also will be examining the traffic patterns for repeated sequences and eliminating any redundancy found. In addition to performing pattern matching and redundancy elimination, Cisco WAAS will compress the resulting data in-flight using LZ compression and optimize the TCP connection on behalf of the client and the server. The result of this operation is that:

• DRE identifies new traffic patterns and stores this information locally to eliminate redundancy from future transmissions. DRE may identify and suppress repeated sequences even within the single transfer.

• LZ compression reduces the size of all messages being exchanged between the mail client and server.

• TFO enables the client and server to communicate more efficiently.

• The user experiences superior email performance.

2. The user then opens the attached presentation and saves the file to the desktop. After making several modifications to the file, including adding new images and new slides and deleting slides, the user emails the revised presentation to the original author in the other remote office. The operation is completed with a LAN-like response time, because DRE isolates the changes within network transmissions, sends instructions to the distant Cisco WAAS WAE as to how to rebuild the message in its entirety, and includes only the changed byte patterns. In addition to the high levels of redundancy elimination, LZ compression and TFO are applied. In this way, Cisco WAAS safely isolates changes while eliminating redundancy from network traffic patterns, decreasing bandwidth consumption, and providing high levels of throughput across the WAN. The user's email transfer is significantly accelerated across the WAN.

3. The same user then decides to drag and drop the presentation to a shared folder on the data center's network-attached storage (NAS) device. Cisco WAAS identifies the transmission, and DRE again suppresses the redundant traffic patterns. Because DRE is application agnostic and bidirectional, files transferred through one protocol (in this case, email) help provide compression for transfers for any other protocol (in this case, Common Internet File System [CIFS]). The user again experiences LAN-like performance when accessing the centralized NAS device.

This scenario is one of many in which Cisco WAAS can provide LAN-like application performance while enabling consolidation of email and other servers. In this scenario, if the email were sent to a large group of users in the same location, the download performance of the email for each subsequent user would be LAN-like and require little bandwidth consumption as a result of the optimization capabilities of Cisco WAAS.

Optimized Email Protocols and Applications

Cisco WAAS devices automatically discover one another during the establishment of the client-to-server connection. No explicit configuration for email optimization is required, because the Cisco WAAS WAE devices classify TCP traffic and apply optimizations automatically based on the application protocol. Cisco WAAS provides out-of-the-box, preconfigured optimization policies for a number of email protocols and applications as well as facilities to create new policies if an email application uses nonstandard ports or protocols. The email protocols that Cisco WAAS automatically identifies and optimizes include:

• MAPI: MAPI is used extensively by Microsoft Exchange Server and Outlook clients. Cisco WAAS provides application-specific optimizations for MAPI and the various server and client configurations, including cached mode. Cisco WAAS provides a number of acceleration services for MAPI to help improve performance. This acceleration provides:

– Reduced send and receive times for email messages and improved response times for interactive control operations

– Fast downloads of Microsoft Outlook offline address book (OAB) while significantly reducing bandwidth consumption because this is a redundant transfer across user population

– Fast cleanup of emails from the outbox (in cached mode, email messages will remain longer before they are cleaned from the outbox); Cisco WAAS 4.1 optimizes the send operation, which helps speed cleanup of the outbox

• POP3 and SMTP

• IMAPv4

• IBM Lotus Notes and Notes RPC

• HP OpenMail

• ·Quick Mail Transfer Protocol (QMTP)

• Network News Transfer Protocol (NNTP)

Figure 3 shows the typical improvement achieved by Cisco WAAS for Microsoft Exchange 2003 while sending an attachments of 5 MB and 2 MB over a T1 (1.54 Mbps) line with 250 milliseconds (ms) of round-trip latency.

Figure 3. Cisco WAAS Optimization for Microsoft Exchange and Outlook

Conclusion

Cisco WAAS provides the tools necessary for IT departments to safely centralize distributed email servers within the data center and provide email acceleration to remote-office users, thereby improving the performance of centralized email services in WAN environments. By applying intelligent optimizations such as DRE, LZ compression, and TFO to email application protocols, Cisco WAAS provides remote-office users with a LAN-like experience when working with consolidated email servers.

For More Information

http://www.cisco.com/go/waas

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