The Performance barriers created by the WAN:
Bandwidth constraints keep applications from performing well.
Too much data and too small of a pipe causes congestion, packet loss, and backpressure.
Latency impairs application performance in three ways:
-Network latency: The amount of time necessary for a message to traverse the network
-Transport latency: The amount of time necessary for the transport mechanism (TCP) to acknowledge and retransmit data
-Application latency: The chattiness of an application protocol that causes messages to be exchanged across the network
C. Packet Loss, Congestion, and Retransmission
-Packet loss and congestion cause retransmission which hinders application performance and throughput
-Commonly caused by saturated device transmit queues in the network path
The impact of latency and packet lost:
CISCO WAAS (Wide Area Application Services)
The Cisco WAAS solution provides LAN-like performance across the WAN through a combinations of technologies, including:
mitigate latency and bandwidth trough advanced protocol optimization, including read-ahead, message prediction and caching.
Improve behavior of transport protocol to make them more efficient in WAN environment
(message suppression, data distribution, caching, compression)
Minimize the transmission of redundant data patterns trough data redundancy elimination (DRE) and compression
Cisco WAAS operates at both the transport and the application layers. At the transport layer, Cisco WAAS applies TCP transport flow optimization (TFO), Persistent Lempel-Ziv (LZ) Compression, and Cisco WAAS Data Redundancy Elimination (DRE) to minimize latency and bandwidth consumption. At the application layer, Cisco WAAS employs application proxies and caches to reduce latency and minimize data flows over the WAN.
The Cisco WAAS TCP optimization features (TFO, Cisco WAAS DRE, and Persistent LZ Compression) provide optimizations for all applications that use TCP. In addition, Cisco WAAS supports some application-specific acceleration features:
- Operation prediction and batching: These features enable a Cisco WAAS device to transform a command sequence into a shorter sequence over the WAN to reduce roundtrips.
- Intelligent message suppression: Even though TFO optimizes traffic over a WAN, protocol messages between branch-office clients and remote servers can cause slow application response times. To resolve this problem, each Cisco WAAS device contains application proxies that can respond to messages locally so that the client does not have to wait for a response from the remote server. The application proxies use a variety of techniques, including caching, command batching, prediction, and resource prefetch, to increase the response times of remote applications.
- Cisco WAFS Software caching: This feature enables a Cisco WAAS device to reply to client requests using locally cached data instead of having to retrieve this data from remote file and application servers.
Currently, Cisco WAAS supports these types of application-specific functions for Microsoft CIFS and Microsoft Print Services.
Hands-on Lab, #day 3:
Config Guide, and source: