TP-Link TL-R600VPN Configuration Manual page 66

Configuring Preferences
When Other is selected, the following page will appear.
Figure 5-5 Other Protocols
Protocol Number
3) (Optional) Enter a brief description of this service type to make identifying it easier.
4) Click OK.
Note:
A service type entry that is being referenced by a rule cannot be deleted.
Specify the protocol number of the packets. Packets with the protocol
number field matched are considered as the target packets.
Service Type Configuration
Configuration Guide 58