Node uses one and the rest are default options.
Syslog UDP is set to Input.
If you do a UDP Send, your data will be lost.
If you send 1,000 items, only 555 or 714 will come in. The remaining data will be lost.
Are there any tuning options?
Any indexing errors? Any errors in the serverlog?
Could be the size of your UDP input that is possible to tweak in kernel settings, the default can be to small. We use TCP always because when graylog or the network is down temporary logs are being held and send when connections are back up again.