Cisco WAAS Part I: WAN Link Optimization: How does WAAS work?

Cisco WAAS Part I:  WAN Link Optimization

“Cisco WAAS is a software and hardware-integrated, cloud-ready WAN optimization and application acceleration solution. WAAS appliances offer outstanding deployment scalability and design flexibility while WAAS software delivers best-in-class application acceleration for the enterprise network.”

Cisco.com

Many companies actually offer the WAN Optimization solutions. I´m not getting into details of why I think that for example Riverbed offers better and more complete solution (at a much higher cost though). I´m a Cisco guy, so I´ll stick to Cisco technologies and tell you about all the advantages Cisco WAAS (Wide Area Application Services) offers you.

WAAS (Wide Area Applications Services) is the name of the technology (software related).

WAE (Wide Area Engine) is the name given to the appliances on which WAAS operates (hardware related)

We sure went a long way since we measured the BW by the baud. Now the LANs are a pretty optimized environment, applications linked to each other, high BWs, and everything seems great… until we reach the WAN, where it’s still about long load times and re-transmissions.

Basically the Applications are written with the focus on how they work and look, the part of how to optimize their transmission is never coded, and it´s up to us. What we actually need is the transparent optimization for the applications on the WAN.

WAAS offers many services, such as Transport Flow Optimization (TFO), Application Specific Acceleration (CIFS, NFS, etc.), SSL, but the actual technological breakthrough is offered by Context-Aware DRE or the Adaptive Cache Architecture.

To understand this we need to understand the two types of Data Traffic:

-       Transactional – moves between clients and servers using the same TCP connection back forward

-       Directional – moves in one direction using one the same TCP connection (Video, backups), and we never had a good solution for this traffic! That’s why WAAS has the ability to recognize the Uni-Directional traffic

So how does it all work then? There are 2 BUCKETS, one for the Data Signature, and another one for the Actual Data. As data is sent – a unique signature for that application is created and saved to the WAAS. For Uni-Directional traffic the WAAS can save the signature and recognize the traffic on the Receiving Side, and Cisco says this gives 10-15% performance increase per flow.

It´s only logical that the WAAS had a vendor-approved and optimized method to treat the specific traffic for each of the most popular applications (SAP, Microsoft, Citrix etc.)

Context-Aware DRE (Data Redundancy Elimination) is used to identify redundant data patterns in application traffic, replacing them with signatures that the Cisco WAAS devices transfer across the WAN to regenerate the original data. The result is optimal usage of WAN bandwidth and improved end-user response time. The Cisco WAAS DRE Cache Architecture is shown below:

In your WAAS network, traffic can be intercepted in these INTERCEPTION MODES:

-       Transparent mode (WCCP or PBR), Used for the application traffic, there are no configuration changes required to the client or the client-server applications. In promiscuous WCCP mode, application traffic is transparently redirected by network elements to the local WAE.

-       Nontransparent (explicit) mode (WCCP Version 2 disabled; applicable only to CIFS traffic when using the legacy file services mode)

-       Inline mode - The WAE physically and transparently intercepts traffic between the clients and the router. To use this mode, you must use a WAE with the Cisco WAE Inline Network Adapter installed.

Transparent traffic interception methods that are supported in your WAAS Network:

WCCP (Web Cache Coordination Protocol) Version 2 - Used for transparent interception of application traffic and Wide Area File Services (WAFS) traffic. Used in branch offices and data centers to transparently redirect traffic to the local WAE. The traffic is transparently intercepted and redirected to the local WAE by a WCCP-enabled router or a Layer 3 switch. You must configure WCCP on the router and WAE in the branch office and the router and WAE in the data center.

PBR - In branch offices, used for wide area application optimization. The branch office router is configured to use PBR to transparently intercept and route both client and server traffic to the WAE that resides in the same branch office.

Inline - Used for transparent interception of application traffic and WAFS traffic

ACE or CSM - Cisco Application Control Engine (ACE) or Catalyst 6500 series Content Switching Module (CSM) installed in the data center for data center application optimization. The ACE or CSM allows for both traffic interception and load balancing across multiple WAE(s) within the data center.

WAAS usually works with interception done on WAN routers on both site:

-       On datacenter site (Core WAAS)

-       On remote site (Edge WAAS)

Traffic between the Client (workstation) and the Server on the datacenter (in our case a NAS Server) will be first intercepted on the WAN router and sent to the Edge WAAS (or Edge WAE). The Edge WAAS will mark the packet (optional TCP field) and send it back to the router that will route the packet through the IP network.

Upon receiving the packet on the Server side, the Core WAAS will see that the traffic has been intercepted on the other side (through the before mentioned optional TCP field).

There are two different roles within WAAS:

-          The WAAS Engine :

o    Realizes the network optimization

o    Contains the configuration optimization
Can be either Edge or Core
Edge WAE = WAE on the Remote site.

o    Core WAE = WAE on the Data Center site (Server).

-          The WAAS Console:

o    Contains the configuration of all policies optimizations

o    Doesn’t perform the optimization

o    Manages everything

Core and edge WAAS is more specifically linked with WAAS 4.0 where you define a WAE near to the file server and a WAE on the remote site. On WAAS 4.1 using fully transparent CIFS optimization, you don’t need to define Core/Edge WAE.