Comment in the source indicates a mis-reading of the standard. Assuming that over a raw socket connection login will be the first message. Standard states that whether login or another mechanism is used is optional. (It is configurable on 3M units and most others). (If used login should be first but it can be spoofed in our implementation anyway)
Use of login should be a configurable option. This may cause problems on flaky connections.
The problem is that the SIP server actually needs an account on the ILS to perform it's operations. So until a login message over the RAW is received, it can not do anything on the ILS.
See the patch I proposed for Bug 7787, it stays in a loop receiving messages (and or garbage) until it receives a login message.
As its not causing anyone major problems and everyone seems happy with things the way they are lets consider this resolved