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For QoS/WMM (EDCA) a mac80211 driver needs to have at least four queues. mac80211 will then program the queues according to the advertised access parameters.
Legend:
- MQ: mac80211 queue
- AC: Access Class
- ACI: Access Class Index
mac80211 queue mapping:
| AC | MQ |
| BK | 3 |
| BE | 2 |
| VI | 1 |
| VO | 0 |
802.11 uses the following number scheme (cf. Table 7-36)
| AC | ACI |
| BK | 01 (1) |
| BE | 00 (0) |
| VI | 10 (2) |
| VO | 11 (3) |
Therefore, we have:
| AC | ACI | MQ |
| BK | 1 | 3 |
| BE | 0 | 2 |
| VI | 2 | 1 |
| VO | 3 | 0 |
Due to internal collisions (we don't really know what this means either) the queue numbering is important, and queue 0 is highest priority, 3 lowest. If your hardware has a different idea of queue priority, you may need to rewrite the queue number, but make sure to do it everywhere mac80211 passes a queue number (conf_tx, skb_get_queue_mapping).
The user priority is used as follows (802.11-2007 table 9-1):
| UP | AC | Priority |
| 1 | BK | Lowest |
| 2 | BK | . |
| 0 | BE | . |
| 3 | BE | . |
| 4 | VI | . |
| 5 | VI | . |
| 6 | VO | . |
| 7 | VO | Highest |
TOS:
mac80211 currently determines the UP based only on the IPv4 TOS field, unless the packet priority is set to 256..263 with setsockopt(SO_PRIORITY), in which case this maps directly to the UP (priority - 256) for testing.
The IPv4 TOS field maps into the UP as follows, but keep in mind that the lowest two bits of the TOS are reserved (or used for ECN):
| TOS | UP |
| 0 - 31 | 0 |
| 32 - 63 | 1 |
| … | |
| 224 - 255 | 7 |
DSCP (RFC 2474):
Alternatively you can set the IP_TOS with setsockopt, then you need to ask how DSCP maps into the UP. DSCP is defined in the Differentiated Services (DiffServ) model as the six most significant bits of the DiffServ(DS) Field.
| DS5 (P2) | DS4 (P1) | DS3 (P0) | DS2 | DS1 | DS0 | ECN | ECN |
The classes of DSCP in wide usage are:
| DSCP Class | Codepoint(s) |
| Default | 0x00 |
| Expedited Forwarding (EF) | 0x2E |
| Assured Forwarding (AF1) | 0xA, 0xC, 0xE |
| Assured Forwarding (AF2) | 0x12, 0x14, 0x16 |
| Assured Forwarding (AF3) | 0x1A, 0x1C, 0x1E |
| Assured Forwarding (AF4) | 0x22, 0x24, 0x26 |
The 3 Precedence bits of DSCP (P2, P1, P0) are used for mapping to 802.1D tags and AC values as:
| P2 P1 P0 | 802.1D | AC |
| 0 0 0 | 0 | BE |
| 0 0 1 | 1 | BK |
| 0 1 0 | 2 | BK |
| 0 1 1 | 3 | BE |
| 1 0 0 | 4 | VI |
| 1 0 1 | 5 | VI |
| 1 1 0 | 6 | VO |
| 1 1 1 | 7 | VO |
Testing:
- Use ping ( with -Q option, see manpage )
- use iperf:
iperf -S 0xE0 -c <IP>
- Use iptables. Example session with 2 iperf streams:
- * iptables -t mangle -A OUTPUT -p tcp –dport 5000 -j DSCP –set-dscp-class “EF”
- * iptables -t mangle -A OUTPUT -p tcp –dport 5001 -j DSCP –set-dscp-class “BE”
