Finally, RFC8325 is here. RFC8325 contains lot of content for the wireless geeks, especially a mapping table for correct DSCP/PHB (Layer-3 QoS marking) to user priority (Layer-2 QoS marking).
Until now, there are different mapping schemes in the field. Some of them result in incorrect mapping of wireless frames to wireless queues especially for voice traffic. Microsoft Windows is a good example for this. MS (and others) simply use the three most significant bits of the DSCP value for the user priority value. For example:
DSCP 46 equals 101110 in Bit – the three most significant Bits are 101, which is 5 (UP). A frame with UP 5 is mapped to the AC_VI (video) queue. However, a DSCP value of 46 should be a voice packet and mapped to the AC_VO (voice) queue.
So for example Cisco and other vendors have different mapping tables to overcome this and other issue.
Hopefully with RFC8325, the different behaviors of the operating systems and platforms will be harmonized in the future.
Here’s a quick overview of the RFC8325 mapping scheme, compared with other schemes.
The differences from RFC8325 are highlighted in red.
So surprisingly, RFC8325 differs from the currently implemented Cisco model in some points. It is surprising, because RFC3825 is written by three guys and two of them are Cisco.
Let’s wait and see when the RFC8325 changes are implemented in the AireOS builds. The default mapping is used by Microsoft for example
|IETF Diffserv Service Class||PHB (DSCP)||UP Mapping
(e.g. 802.1p, MS)
|Network Control||CS7 (56)||7
|Network Control||CS6 (48)||7
|Multimedia Conferencing||AF41 (34)
|Real-Time Interactive||CS4 (32)||4||4||4|
|Multimedia Streaming||AF31 (26)
|Broadcast Video||CS3 (24)||4||3||3|
|Low-Latency Data||AF21 (18)
|High-Throughput Data||AF11 (10)
|Low-Priority Data||CS1 (8)||1||1||1|