Each Syslog message includes a priority value at the beginning of the text. The priority value ranges from 0 to 191 and is made up of a Facility value and a Level value.
The Facility value is a way of determining which process of the machine created the message. Since the Syslog protocol was originally written on BSD Unix, the Facilities reflect the names of Unix processes and Daemons.
The priority value is calculated using the following formula:
Priority = Facility * 8 + Level
The list of Facilities available:
0 kernel
1 user
2 mail
3 daemon
4 authorization
5 syslogd
6 line printer subsystem
7 news
8 UUCP
9 cron
10 security
11 FTP
12 NTP
13 log audit
14 log alert
15 clock daemon
16 local use 0 (local0)
17 local use 1 (local1)
18 local use 2 (local2)
19 local use 3 (local3)
20 local use 4 (local4)
21 local use 5 (local5)
22 local use 6 (local6)
23 local use 7 (local7)
By default, this value is set to 23 (Local7).