Understanding NetVisor Quality of Service (QoS) Technology
NetVisor switches follow Ethernet standards and hence can parse and extract the 802.1p Class of Service/Priority bits in the received frames. The CoS field represents the least common denominator form of packet marking available to Ethernet devices as it can be used for any type of traffic (whether IP or non-IP). Historically, Arista Networks has used the CoS field across different and heterogeneous generations of hardware. The packet CoS can be trusted or untrusted. When it’s trusted, for simplicity’s sake, CoS values have been mapped 1:1 to the queue numbers in the ASIC, as shown in the table below:
|
CoS Value |
Output Queue Number |
|
0 |
0 |
|
1 |
1 |
|
2 |
2 |
|
3 |
3 |
|
4 |
4 |
|
5 |
5 |
|
6 |
6 |
|
7 |
7 |
For this reason, in the NetVisor OS CLI a queue number is sometimes referred to as ‘CoS’.
For IP packets, NetVisor OS supports also classification based on the 6-bit DSCP field as defined in the IETF standards:
Figure 13-2: DSCP Field with QoS Profiles