NEC IPASOLINK 400 Installation And Provisioning page 78

The Qos processing of frames consists of four phases from ingress port (e.g. Ethernet port) to egress port
(e.g. modem port). The process is similar in the reverse direction but the QoS settings may be totally
different (Figure 68).
1) Incoming or ingress frames are classified into an internal priority value ("IC" in Figure 68) based on
 customer VLAN-tag L2 priority (p-bit) value or
 customer L3 priority value (IPv4 tai IPv6 DSCP) or
 MPLS Exp –priority value.
The classification is to internal priority. In this phase, if a VLAN tag is added, the CoS value is copied or if
missing, the CoS value is based on the internal priority classification.
In the Port Based QoS –mode the VLAN-tag priority is copied as such from the internal priority. In this
mode VLAN-frames can be classified internally based on IP v4 or IP v6 DSCP-priority using the default
mapping: VLAN CoS value is not used but the DSCP value. The outer tag CoS value is always copied from
the inner tag, however. (This will change in a later version). If the ingress frame has no tag, the CoS value is
the internal priority.
In the Equipment Based QoS mode the VLAN tag p-bit will always decide the internal priority over any L3
priority and it can be mapped as wanted to the internal priority (single profile for all ports). If the frame has
no VLAN tag, it is possible to select IP v4 Precedence, IP v4 DCSP, IP v6 DSCP tai MPLS Exp –value based
internal priority which is also the VLAN tag CoS value. In this mode the classification is common to all ports
of the IDU.
The third available mode is VLAN ID Based QoS Mode. Internal priority is based on the VID only, nothing
else.
Note that the ingress frame priority classification into internal priority is also applicable to the modem port.
2) In the second phase, the frame is Ingress Policer classified based on outer tag CoS value (original or
added tag). "PO" in Figure 68. Ingress Setting tab (Figure 69).
Total 16 Policer profiles can be added. Define CIR (Committed Information Rate), EIR (Excessive Information
Rate, i.e. tolerance above CIR) as well as EBS (Excessive Burst Size, EBS kbyte) and CBS (Committed Burst
Size, CBS kbyte). The burst sizes and the rates define when the frame is marked Yellow or Red (and dropped
immediately).
Note. RFC4115 implementation in iPasolink is such that PIR (Peak Information Rate) = CIR+EIR is the limit
when the frames are marked Red based on the EBS setting. As an example CIR = 100 Mbit/s and EIR = 50
Mbit/s will transmit almost 150 Mbit/s continuously.
78