User's Manual

Technical Notes – QoS Features on BES50

Overview

BES50 provides a number of features to support different Quality of Service (QoS) for different types of traffic.

There are multiple levels of traffic prioritization on BES50 (both BES50FE and BES50GE). Prioritization can be

based on

(1) Default port priority

(2) 802.1p value of the incoming tagged Ethernet frame

(3) IP DSCP of the incoming IP packet

(4) ACL based (using the 5-tuples in IP header: source and destination IP addresses, source and

destination ports and protocol number)

BES50 has pre-defined precedence (or order) when applying these mechanisms. ACL based prioritization has

the highest precedence over the others, and default port priority has the lowest precedence if nothing else has

been configured.

When an incoming Ethernet frame arrives at an ingress port, BES50 first determines the traffic priority/CoS

(value between 0 – 7) based on the L2/L3 information carried in the Ethernet frame and/or the IP header (IP

DSCP, IP addresses, port numbers and protocol number).

Each priority/CoS (basically 802.1p bit value) maps into one of the traffic class (4 classes for BES50FE and 8

classes for BES50GE). These traffic classes are served by a scheduler that can run in either Weighted Round

Robin (WRR) or Strict Priority.

BES50 also provides the capability to mark or re-mark the 802.1p value (CoS) or the DSCP value of the egress

Ethernet frames and/or IP packets. The following table summarizes these two features:

Egress (re) marking

DSCP (IP packets)

Traffic

Prioritization

CoS/1p (tagged

Ethernet frames)

BES50GE BES50FE

Default port

priority

Yes Yes Yes (optional) No

802.1p bit (tagged

Ethernet frame)

Yes Yes Yes (optional) No

IP DSCP

Yes Yes Yes (optional) No

ACL based

Yes Yes Yes (optional) Yes (if the applied

policy has an

associated action

to set IP DSCP

value)