Multiple server challenge packets during NTLM authentication

Hello,

While running my tests using tsql client, i found that if server sends
multiple NTLM Challenge packets, then tsql generates a new NTLM AUTH packet
for every Challenge packet. The sequence is as follows :

Client -> Server (NTLM Negotiate packet)
Server -> Client (NTLM Challenge packet)
Client -> Server (NTLM AUTH packet)
Server -> Client (NTLM Challenge packet)
Client -> Server (NTLM AUTH packet)

Is this supported by NTLM protocol ? I tested the same sequence with other
TDS clients(SQL Server Studio) and it threw an error.

Is this a bug ? Can somebody please shed some light on this ?

Thanks,
Vipul