#103 authentication: nc is not incremented in a session

[Colaviti]

When using sipp as a client, the nc is not incremented for each request and so, the server rejects the request because it is considered as a replay.

If the same nonce is used for following requests, the nc MUST be incremented.

examples:

SIPP client server
request without credentials ------------>
<----- 401 with challenge
request with credentials (nc=00000001)-->
<----- 401 because bad password
request with credentials (nc=00000001)-->
<----- 400 rejected by server

it should be
request without credentials ------------>
<----- 401 with challenge
request with credentials (nc=00000001)-->
<----- 401 because bad password
request with credentials (nc=00000002)-->
<----- 200 (if right password)
or

INVITE without credentials ------------>
<----- 401 with challenge
INVITE with credentials (nc=00000001)-->
<----- 200
ACK ----------------------------------->

Subsequent REFER with credentials (nc=00000001)->
<----- 400 rejected by server
it should be

INVITE without credentials ------------>
<----- 401 with challenge
INVITE with credentials (nc=00000001)-->
<----- 200
ACK ----------------------------------->

Subsequent REFER with credentials (nc=00000002)->
<----- 200