![]() Remember that DSCP can only be accessed on IP packets and DSCP value in IP header should be set somewhere (either by client devices or IP mangle rules). When using the new-priority= from-dscp setting, the priority will be 3 low bits of the DSCP value, but when using new-priority=from-dscp-high-3-bits the priority will be 3 high bits of DSCP value. Note that DSCP in IP header can have values 0-63, but priority only 0-7. Priority from DSCPĪnother way of setting VLAN or WMM priority is by using the DSCP field in the IP header, this can only be done by the IP firewall mangle rule with new-priority= from-dscp or new-priority=from-dscp-high-3-bits settings and set-priority action property. The only exception is when the bridge untags the packet, in this situation VLAN priority is not preserved due to the missing VLAN header. RouterOS bridge forwards VLAN tagged packets unaltered, which means that received VLAN tagged packets with a certain VLAN priority will leave the bridge with the same VLAN priority. Remember there are currently 2 sources for this - VLAN tag in packets and received WMM packets. This essentially means that if it is not possible or wanted to classify packets by rules, the configuration of the network must be such that the router can extract ingress priority from incoming frames. Both options require setting up correct rules. There are basically 2 ways to control priority - assign priority with rules with particular matchers (protocol, addresses, etc.) or set it from ingress priority. Note that ingress priority value is not automatically copied to IP mangle priority value, the correct rule needs to be set up to do this. For all other packets ingress priority is 0. Currently, there are 2 sources of ingress priority - priority in the VLAN header and priority from the WMM packet received over a wireless interface. Ingress priority is the priority value that was detected on the incoming packet, if available. Priority can be set to a specific value or taken from the ingress priority using the from-ingress setting. Priority of packets can be set using action=set-priority of IP firewall mangle rules or bridge filter/nat rules. More details can be studied in the IEEE 802.1p specification. MikroTik devices by default are sending VLAN packets (locally generated or encapsulated) with a priority of 0. It is used for implementing QoS on bridges and switches. ![]() The VLAN priority is a 3-bit field called Priority Code Point (PCP) within a VLAN-tagged header and values are between 0 and 7. Other bands will have it enabled regardless of this setting How VLAN priority works WMM support can be enabled using the wmm-support setting. Details can be studied in 802.11e and WMM specifications. WMM works by executing the DCF method for medium access with different settings for each access category (EDCF), which basically means that "better" access category has a higher probability of getting access to medium - WMM enabled station can be considered to be 4 stations, one per access category, and the ones with "better" access category use settings that make them more likely to get chance to transmit (by using shorter backoff timeouts) when all are contending for medium. ![]() "Better" access category for packet does not necessarily mean that it will be sent over the air before all other packets with the "worse" access category. By default, all packets (incoming and locally generated) inside the router have priority 0. To be able to use multiple WMM access categories, not just best effort where all packets with default priority 0 go, priority must be set for those packets. Mikrotik AP and client classifies packets based on the priority assigned to them, according to the table (as per WMM specification): 1,2 - background 0,3 - best effort 4,5 - video 6,7 - voice. AP does not have control over how clients are transmitting packets, and clients do not have control over how AP transmits packets. QoS policy (different handling of access categories) is applied on transmitted packets, therefore the transmitting device is treating different packets differently, e.g. WMM works by dividing traffic into 4 access categories: background, best effort, video, voice.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |