Troubleshooting guide

REVIEW DRAFT—CISCO CONFIDENTIAL
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Cisco Wide Area Application Services Configuration Guide
OL-26579-01
Chapter 1 Introduction to Cisco WAAS
Benefits of Cisco WAAS
Optimized Read and Write Caching
The common file services feature in Cisco WAAS maintains files locally, close to the clients. Changes
made to files are immediately stored in the local branch WAE, and then streamed to the central file
server. Files stored centrally appear as local files to branch users, which improves access performance.
CIFS caching includes the following features:
• Local metadata handling and caching—Allows metadata such as file attributes and directory
information to be cached and served locally, optimizing user access.
• Partial file caching—Propagates only the segments of the file that have been updated on write
requests rather than the entire file.
• Write-back caching—Facilitates efficient write operations by allowing the data center WAE to
buffer writes from the branch WAE and to stream updates asynchronously to the file server without
risking data integrity.
• Advance file read—Increases performance by allowing a WAE to read the file in advance of user
requests when an application is conducting a sequential file read.
• Negative caching—Allows a WAE to store information about missing files to reduce round-trips
across the WAN.
• Microsoft Remote Procedure Call (MSRPC) optimization—Uses local request and response caching
to reduce the round-trips across the WAN.
• Signaling messages prediction and reduction—Uses algorithms that reduce round-trips over the
WAN without loss of semantics.
WCCP Support
The Web Cache Communication Protocol (WCCP) developed by Cisco Systems specifies interactions
between one or more routers (or Layer 3 switches) and one or more application appliances, web caches,
and caches of other application protocols. The purpose of the interaction is to establish and maintain the
transparent redirection of selected types of traffic flowing through a group of routers. The selected traffic
is redirected to a group of appliances. Any type of TCP traffic can be redirected.
The WCCP v2 protocol has a built-in set of beneficial features, for example, automatic failover and load
balancing. The router monitors the liveness of each WAE attached to it through the WCCP keepalive
messages, and if a WAE goes down, the router stops redirecting packets to the WAE. By using WCCP,
the branch WAE avoids becoming a single point of failure. The router can also load balance the traffic
among a number of branch WAEs.
Cisco WAAS supports transparent interception of TCP sessions through WCCP. Once WCCP is turned
on at both the router and the branch WAE, only new sessions are intercepted. Existing sessions are not
affected.
PBR Support
Policy-based routing (PBR) allows IT organizations to configure their network devices (a router or a
Layer 4 to Layer 6 switch) to selectively route traffic to the next hop based on the classification of the
traffic. WAAS administrators can use PBR to transparently integrate a WAE into their existing branch
office network and data centers. PBR can be used to establish a route that goes through a WAE for some
or all packets based on the defined policies.
For more information about PBR, see Chapter 1, “Configuring Traffic Interception.”