Differentiated Service could be used to categorise the type of the network traffic especially when needing to provide Quality of Service (QoS)#. To do that, it uses at least 4 bits to show the 4 types of type of service (TOS), shown at below that the traffic is.
- D: Minimise delay (1000)
- T: Maximise throughput (0100)
- R: Maximise reliability (0010)
- C: Minimise cost (0001)
Note: If the bit is not set, that is the value of binary is 0000, then this means that the traffic should be treated with a standard manner. This is usually the default.
The following table shows the default type of service each protocol is:
| Protocol | TOS |
|---|---|
| ICMP# | - |
| BOOTP | - |
| NNTP | C |
| IGP# | R |
| SNMP | R |
| Telnet | D |
| File Transfer Protocol (FTP)#(data) | T |
| FTP(control) | D |
| TFTP | D |
| SMTP(command) | D |
| SMTP(data) | T |
| DNS# (UDP query) | D |
| DNS (TCP query) | - |
| DNS (zone) | T |