Calculation of the Total Reduction Ratio in WAAS

Introduction

This document describes how the total reduction ratio value is calculated in the Cisco Wide Area Application Services (WAAS) software.

Total Reduction Ratio

When you enter a show stat conn command on a Cisco Wide Area Application Engine (WAE), you can see optimized connections and output as shown in this example:

ConnID    Source IP:Port        Dest IP:Port    PeerID               Accel RR
131200    192.168.10.1:58385    10.0.0.100:445  78:e7:a1:a2:00:b0    TCDL  82.3%

The value in the RR column (82.3%) indicates the total reduction ratio. This is effectively the percentage of traffic that did not cross the WAN.

Calculation of the Ratio

Enter the show stat conn conn-id 131200 command in order to reveal more output, as shown in this example:

                                Original            Optimized
                         -------------------- --------------------
Bytes Read:                       787408                92939
Bytes Written:                    401764               117657

Total Reduction Ratio: 82.291%

The Original column reports the bytes received or sent on the LAN segment, and the Optimized column reports bytes received or sent on the WAN segment. Total the columns:

                                Original            Optimized
                         -------------------- --------------------
Bytes Read:                       787408                92939
Bytes Written:                    401764               117657
                               1,189,172              210,596

For this single connection, the amount of bytes that went across the WAN (210,596) is significantly less than the amount of bytes that went out the WAN (1,189,172).

To calculate the reduction in traffic (the total reduction ratio), use this formula:

1 - (total optimized bytes/total original bytes)

In this example, the calculation is 1 - (210596/1189172) = .82290535 or 82.291%.

If the amount of optimized bytes is greater than the amount of original bytes, you see a total reduction ratio of 0.00%.