Timers Definitions

You are investigating an Office 365 related performance issue, let's say for simplicity sake with Outlook and Exchange Online. What can you tell from the timers shown on the Office 365 Inspector Tab?

The first thing to know is a small number of sessions running in a number of seconds is not an indication of an issue. The session timers are included in the inspector to provide an overall sense of what is happening in any given session. A session running for 4 seconds is not bad, but needs to be taken into consideration with a wider review of the available data on the session. Usually server responses paint a better picture of what is happening in the Fiddler trace being reviewed.

Elapsed Time

ClientBeginRequest The timestamp the request's first socket Send() operation was serviced by Fiddler.

ClientDoneResponse The timestamp Fiddler completed sending the response to the client.

The Elapsed Time value is displayed in a custom column in the Extension.

Server Think Time

ServerGotRequest The timestamp Fiddler completed sending the request to the server.

ServerBeginResponse The timestamp Fiddler read the first packet of the server's response.

The 'Server Think Time' value is displayed in the Exchange Online inspector tab when checking individual sessions.

Transmit time from the responding server back to Fiddler

ServerBeginResponse The timestamp Fiddler read the first packet of the server's response.

ServerDoneResponse The timestamp Fiddler completed reading the entire response from the server.

This gives you the time it took to get the data out of the Microsoft data center, across the corporate network (LAN) and to the Fiddler proxy running on the client computer the trace was captured from.

Transmit time from Fiddler back to Outlook

ClientBeginResponse The timestamp Fiddler began sending the response to the client.

ClientDoneResponse The timestamp Fiddler completed sending the response to the client.

This gives you the time it took to get the data from the Fiddler proxy to Outlook running on the client computer the trace was captured from.

1st leg from Outlook to the Fiddler Proxy

It is important to note in the round trip from Outlook to the Exchange server and back again, the Fiddler Proxy only knows when it first sees the request. It does not know when Outlook started sending the request and how long it took to arrive at the Fiddler Proxy.

Calling special attention to: ClientBeginRequest The timestamp the request's first socket Send() operation was serviced by Fiddler.

This can be an important point if any filter drivers are present on the client computer which could affect the traffic Outlook sends/receives. -- On this last point think Enterprise level security products, which manipulate network traffic before it even leaves an end users computer.