QoS / Traffic Shaping: Will cOS Core alter DiffServ tagging?

Last modified on 6 Feb, 2023. Revision 6
Does cOS Core ever add, modify or delete DiffServer tags on packets? The short answer is no.
Up to date for
cOS Core 12.00.xx
Supported since
cOS Core 8.xx
Status OK


Does cOS Core add, modify or delete a packet’s DiffServ tags?


No. cOS Core does not ever add, modify or delete DiffServ tags.

DiffServ with IPsec

In the case of IPsec, the Diffserv bits are copied, as is, from the traffic inside the tunnel to the IPsec connection traffic on the outside

DiffServ with Traffic Shaping

A “Pipe” object in the cOS Core Traffic Shaping subsystem has 8 priority levels available. cOS Core can allocate the priority of a packet by mapping its DiffServ tags to one of these 8 priority levels. This requires enabling the “Map IP DSCP (ToS)” option on the relevant Pipe Rule. Even in this case, cOS Core will not modify the DiffServ tags in the traffic when it allocates the priority in a pipe.

Further Discussion

More discussion of DiffServ with cOS Core can be found at the beginning of the “Traffic Management” chapter of the cOS Core Administration Guide.

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