Example network trace

This article presents several examples of a network trace that captures various handshakes and

authentication sequences during the Transmission Control Protocol (TCP) connection

establishment process between a client application and the SQL Server Database Engine (the

server).

For information about closing connections, see

Trace the network connection close sequence

on the Database Engine.

You can connect to the Database Engine with

authentication (using

or

authentication), or

authentication.

This article also describes Multiple Active Result Sets (MARS) connections. MARS is a feature of

, introduced with SQL Server 2005 (9.x), that allows multiple commands to be

executed on a connection without having to clean up the results from the first command,

before running the second command. MARS is achieved through session multiplexing (SMUX).

This process describes a normal login process using SQL authentication, showing each

step of the conversation between the client and server through a detailed network trace

analysis. The example network trace delineates the following steps:

1. TCP three-way handshake

2. Driver handshake

3. SSL/TLS handshake

4. Login packet exchange

5. Login confirmation

6. Execute a command and read the response

7. TCP four-way closing handshake

This exchange is allocated 1 second regardless of the

setting in the

connection string.

SQL authentication

Login Timeout