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TOS significates "Type of service" and represents the 2nd byte in the IP datagramm. TOS usually refers to "Quality of Service" in packet networks.
Traditionally, the first three IP precedence (-> RFC 791) bits were supposed to be used in TOS Application Routing (RFC 1583-> OSPF, IS-IS) but no application really supports it. The TOS field has then been redefined as the Differentiated Services Code Point (DSCP-> RFC 2474) which consists of the first 6 bits and 2 bits used for a TCP mechanism called Explicit Congestion Notification (ECN) defined in RFC 3168.
The value 160 (Binary 10100000) means IP precedence 5 (Binary 101) or DSCP Class Selector 5 (Binary 101000 = 0x28).
In order to obtain low-delay, low-jitter, low-loss service Expedited Forwarding should be used instead (= 184):
| IP Prec | IP Prec Bin | DSCP Class | DSCP Bin | DSCP Hex | DCSP Dec | TOS value (snom) |
| 0 | 000 | Best Effort | 000000 | 0x00 | 0 | 0 |
| 1 | 001 | CS 1 | 001000 | 0x08 | 8 | 32 |
| AF11-Low | 001010 | 0x0A | 10 | 40 | ||
| AF12-Medium | 001100 | 0x0C | 12 | 48 | ||
| AF13-High | 001110 | 0x0E | 14 | 56 | ||
| 2 | 010 | CS 2 | 010000 | 0x10 | 16 | 64 |
| AF21-Low | 010010 | 0x12 | 18 | 72 | ||
| AF22-Medium | 010100 | 0x14 | 20 | 80 | ||
| AF23-High | 010110 | 0x16 | 22 | 88 | ||
| 3 | 011 | CS 3 | 011000 | 0x18 | 24 | 96 |
| AF31-Low | 011010 | 0x1A | 26 | 104 | ||
| AF32-Medium | 011100 | 0x1C | 28 | 112 | ||
| AF33-High | 011110 | 0x1E | 30 | 120 | ||
| 4 | 100 | CS 4 | 100000 | 0x20 | 32 | 128 |
| AF41-Low | 100010 | 0x22 | 34 | 136 | ||
| AF42-Medium | 100100 | 0x24 | 36 | 144 | ||
| AF43-High | 100110 | 0x26 | 38 | 152 | ||
| 5 | 101 | CS 5 | 101000 | 0x28 | 40 | 160 |
| Expedited Fwdg | 101110 | 0x2E | 46 | 184 |
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