WAAS (Wide Area Application Services) has been introduced to market few years ago. It was used to increase performance of low bandwidth links with high delays or jitter. Main disadvantage of this solution was that it required at least 3 components -central manager and two accelerators which could be external or as a router module. But it was all hardware solution. With introduction of WAAS Express introduced in IOS 15.1(2)T some form of acceleration can be provided on software basis.

WAAS Express is enabled by license and all it require is lots of RAM memory. It’s recommended to maximize RAM memory in router before enabling it – if you don’t have enough memory WAAS process won’t start. WAAS Express does not require additional hardware, but disadvantage of that is you can only perform OSI Layer 4 optimization.

Central Manager in this deployment model is not required but it’s recommended. There are two reasons for using Central Manager (version 4.3 or above). First one is centralized management of infrastructure, so all changes are made in one place. Second reason is DRE (Data Redundancy Elimination) which inspects TCP traffic and identifies patterns within the data flow. Once patterns is identified, redundant patterns can be safely replaced by small signatures therefor consuming much less bandwidth. Without Central Manager routers with WAAS Express can only use TCP Flow Optimization (TFO) which optimize TCP sessions and Lempel Ziv (LZ) Compression.

Enabling WAAS Express is pretty simple:

Router(config-if)# waas enable 

Yes, that’s all required configuration 🙂 WAAS Express can be enabled on all interfaces supported by ISR G2 including subinterfaces, dialers, tunnels and virtual-templates. And unlike “grown up” WAAS it does not require WCCP or PBR to forward the packets.

The default policy should be enough for most environments, but if necessary it can be modified using the Cisco Common Classification Policy Language (C3PL). The WAAS Express default policy is generated when WAAS Express is enabled for the first time, and is named waas_default.

WAAS Express is software solution so it consumes CPU for optimization, which affects all services enabled on router. By default CPU threshold for WAAS process is 80% but it can be adjusted. To check what is maximum recommended number of connections and bandwidth supported on ISR G2 platform refer to documentation.