408 vs 504 Response for INVITE

1. Brekeke Product Name and version:
ONDO Sip Server

2. Java version:
1.6

3. OS type and the version:
Windows XP

4. UA (phone), gateway or other hardware/software involved:
SIP Client

5. Select your network pattern from

6. Your problem:
Hi,
Suppose ONDO SIP Server is unable to forward an INVITE to its destination then will it respond with 408 or 504 ??

It will response with "504 Server request timeout"