> For the complete documentation index, see [llms.txt](https://prosbcdocs.telcobridges.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://prosbcdocs.telcobridges.com/telecom-references/parameter-reference/packet-network-type-of-service.md).

# Packet Network: Type of Service

Value to store in the TOS (Type Of Service) field of the IP header of RTP packets.

The most recent usage of this field is a six-bit Differentiated Services Code Point (DSCP) and a two-bit Explicit Congestion Notification (ECN).

| 0 \|\| 1 \|\| 2 \|\| 3 \|\| 4 \|\| 5 | 6 \|\| 7   |            |            |            |            |           |           |
| ------------------------------------ | ---------- | ---------- | ---------- | ---------- | ---------- | --------- | --------- |
| DSCP field                           | DSCP field | DSCP field | DSCP field | DSCP field | DSCP field | ECN field | ECN field |

For example, if a TOS value of 144 is used, the DSCP tag will be 36 (if ECN field is not used). Some examples:

| TOS Value | DSCP Value |
| --------- | ---------- |
| 0         | 0          |
| 32        | 8          |
| 40        | 10         |
| 56        | 14         |
| 72        | 18         |
| 88        | 22         |
| 96        | 24         |
| 112       | 28         |
| 136       | 34         |
| 144       | 36         |
| 152       | 38         |
| 160       | 40         |
| 184       | 46         |
| 192       | 48         |
| 224       | 56         |

**DSCP <=> IP Precedence Conversion Table**

| DSCP Name    | DS Field Value (Dec) | IP Precedence (Description)                |
| ------------ | -------------------- | ------------------------------------------ |
| CS0          | 0                    | 0: Best Effort                             |
| CS1, AF11-13 | 8,10,12,14           | 1: Priority                                |
| CS2, AF21-23 | 16,18,20,22          | 2: Immediate                               |
| CS3, AF31-33 | 24,26,28,30          | 3: Flash - mainly used for voice signaling |
| CS4, AF41-43 | 32,34,36,38          | 4: Flash Override                          |
| CS5,EF       | 40,46                | 5: Critical - mainly used for voice RTP    |
| CS6          | 48                   | 6: Internetwork Control                    |
| CS7          | 56                   | 7: Network Control                         |

Wikipedia link: [Type of Service](https://en.wikipedia.org/wiki/Type_of_service)


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