User's Manual

Technical Notes – QoS Features on BES50

Difference Between BES50FE and BES50GE

1. Number of traffic class

BES50FE has four traffic classes, while BES50GE has eight traffic classes.

2. Different ways to configure ACL Based traffic prioritization

BES50FE uses the “QoS Policy” to facilitate ACL based traffic prioritization (see Figure 15: BES50FE

Apply QoS Policy to Ingress Port), while BES50GE uses the “ACL Priority Mapping” to map traffic

matching the ACL to a specified priority index (see Figure 17: BES50GE ACL Priority Mapping).

3. Location of frame/packet re-marking

BES50FE classifies and re-mark CoS/DSCP at the ingress port (i.e. the port in which the Ethernet frame

enters BES50FE) of the switch. In contrast, BES50GE classifies traffic at the ingress port but re-mark

CoS/DSCP at the egress port (i.e. the port in which the Ethernet frame is emitted from BES50GE) of the

switch.

4. IP DSCP re-marking

Both BES50FE and BES50GE support re-marking of the DSCP value of an IP packet. However, there

are subtle differences in terms of how the IP packet is re-marked:

• BES50FE re-marks packets on a per traffic stream level (i.e. all traffic that matches the same

QoS policy configured on a specific ingress port).

• BES50GE re-marks packets on a per port basis, specifically IP packets that are emitted from an

egress port with IP DSCP re-marking enabled.

• BES50FE only re-marks DSCP value of the IP packets that match a “QoS Policy” with an

associated “Set IP DSCP” action.

• If re-marking is enabled on an egress port, BES50GE always re-mark the DSCP value of all IP

packets emitted from that egress port based on the priority index determined by BES50GE.