Troubleshooting guide

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Cisco Wide Area Application Services Configuration Guide
OL-26579-01
Chapter 1 Configuring File Services
About File Services
One obstacle is created by the file server protocols that operate over the WAN. Common Internet File
System (CIFS), which is the file server protocol for Windows, was designed to operate over a LAN.
Every file operation generates several exchanges of protocol messages between the client and the file
server. This situation is usually not noticeable on the LAN, but quickly causes high latency over the
WAN. Occasionally, this high latency breaks the file server protocol altogether.
Even in cases where the file server protocol is managing to function correctly over the WAN, there are
typically long delays between each transaction. These delays can often cause timeouts in user
applications such as word processing programs, image editing programs, and design tools, which stops
them from functioning correctly.
All of these problems—unreliable WANs, file system protocol compatibility, and user application
compatibility—contribute to an unfriendly work environment that negatively affects the user experience
and diminishes productivity.
The WAAS file services feature overcomes the WAN latency and bandwidth limitations by caching data
on Edge WAEs near the user. This data caching method allows branch office users to access centralized
data at LAN-like speeds over the WAN. The solution is based on several key concepts:
• Use the WAN as little as possible—By minimizing the number of operations that need to traverse
the WAN, WAAS effectively shields users from many of the obstacles that WANs create.
• Use the WAN optimally—The file services feature uses sophisticated caching, compression, and
network optimization technologies, which enable the system to use the WAN optimally.
• Preserve file system protocol semantics—Although WAAS software uses its own proprietary
protocol over the WAN, it leaves the complete semantics of the standard file system protocol
commands intact. This is essential to preserve the correctness and coherency of the data in the
network.
• Make the solution transparent to users—The best solutions are the ones that do their jobs unnoticed,
without interfering with end users’ operations or forcing users to change their ways of doing
business. The WAAS file services solution does not require any software installations, either on the
server side or at the client, and does not require the user to learn anything new. Users derive all the
benefits of having a secure data center without needing to change any of their work habits.
By using the WAAS file services feature, enterprises can consolidate their file servers to a data center
that provides the facilities, IT personnel, and storage devices required to manage the data properly.
Figure 1-1 shows a typical deployment scenario after WAAS file services have been set up.
Figure 1-1 WAAS File Services Solution
Edge WAE
Core WAE
WAAS Central
Manager
Domain
Controller
Domain
Controller
CIFS client
CIFS FS
CIFS client CIFS client
CIFS client
Branch office Data center
WAN
T1, 120 ms RT
CIFS FS
192.168.29.0
192.168.2.0
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