Replication Traffic from Other Sites Test

Used in the Active Directory to express proximity of network connection, a site is defined as an IP subnetwork. A site consists of one or more subnets (unique network segments). Client machines use site information to find nearby DCs for logon operations. The Active Directory uses site information to help users find the closest machine that offers a needed network or a third-party service.

The Active Directory provides two methods of replication within the Active Directory environment: intrasite replication and intersite replication. Intrasite replication is replication within an Active Directory site. It is based assumption that the IP subnets within a site are well connected and that bandwidth is considered freely available and inexpensive. Because of this assumption, data is sent without compression. 

Inter-site replication is replication between Active Directory sites. It is based on the assumption that the WAN is connected by slower links, so it is designed to minimize traffic rather than CPU cycles. Before being sent out, data is compressed to about 10% to 15% of original volume.

By monitoring the replication data flowing into each site, the Replication Traffic from Other Sites test helps determine the nature of the inbound traffic handled by every site - whether inter-site or intrasite, and reveals what type of inbound traffic is high on a site. Using this information, administrators can determine whether or not the replication data has been compressed enough to optimize bandwidth usage, and accordingly decide if more data compression is required at the source.


This test applies only to Active Directory Servers installed on Windows 2008 or above.

Target of the test : An Active Directory or Domain Controller on Windows 2008 or above

Agent deploying the test : An internal agent

Outputs of the test : One set of results for every Active Directory site that is being monitored

Configurable parameters for the test
Parameters Description

Test period

This indicates how often should the test be executed.


The IP address of the machine where the Active Directory is installed.


The port number through which the Active Directory communicates. The default port number is 389.

Measurements made by the test
Measurement Description Measurement Unit Interpretation

DRA inbound before bytes compression

Indicates the original size of inbound compressed replication data (kilobytes per second before compression, from DSAs in other sites).



DRA inbound after bytes compression

Indicates the compressed size of inbound replication data (kilobytes per second received after compression, before DSAs in other sites).


To save bandwidth on the network connection, the bridgehead servers in each site compress the traffic at the expense of additional CPU usage.

A high value for this measure indicates that the bridgehead server is receiving high inter-site inbound replication traffic.

Replication traffic is compressed down to about 40 percent when replication traffic is more than 32 KB in size.

DRA inbound bytes not compression

Indicates the number of incoming bytes replicated per second that were not compressed at the source (that is, from DSAs in the same site).


A high value for this measure indicates that the intra-site replication traffic is high.

Compressing the replication data adds an additional load on the domain controller server. Uncompressed replication traffic preserves server performance at the expense of network utilization.