FreeTDS Development Group

["ZIGLIO, Frediano, VF-IT" <Frediano.Ziglio AT vodafone.com>]

> 
> Hi,
> 
> I have the following questions regarding the MS SQL protocol 
> (Client-Server interaction):
> (i) What is the significance of the prelogin packet (TDS Type 0x12)?

Some informations got exchanged:
- client library version
- encryption (is not possible to have encryption without prelogin)
- instance name
- process id (just informative)
see
http://freetds.cvs.sourceforge.net/*checkout*/freetds/freetds/doc/tds_ss
l.html?revision=1.6


> (ii) If I sniff the traffic between a MS SQL Client and 
> Server, this is 
> the first packet that the Client sends on wire and has the TDS Data 
> having the string "MSSQLServer". Any reasons ?

is the default instance name.

> (iii) Also, Is it always the first packet when MS SQL is started?
> 

no, is used from TDS protocol version 8 (from mssql2k), previous do not
use this packet.

> Any inputs/refernces that answeres this questions would be 
> appreciated.
> 
> Thanks,
> Sankalp

bye
  freddy77