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Foundry NetIron M2404C and M2404F Metro Access Switches
Configuring HQoS (Rev.03)
QoS/HQoS Implementation
© 2008 Foundry Networks, Inc.
Page 17 of 98
ACL-based
Filtering
802.1p/DSCP->FC+Color OR
Port->FC+Color OR
Flow (classified)-> FC+Color
OR
Dest. MAC->FC+Color
(FC maps to egress queue…)
Single-Rate me
802.1p marking/DSCP
remarking
Local Switching: traffic
goes back to Service
side
Replication for
multicast traffic
SP/WRR (or mixed)
scheduler per port
Shaper per port
SP/WRR
8 queues per access port
Color-aware WRED/TD per
queue
Shaper per queue
32MB deep buffering
Figure 10: QoS in Local Switching Path
Once traffic enters the device, it is
classified
according to various classification criteria, defined as
Access Control Lists (ACLs), which are defined per SAP (access port or VLAN). Up to 256
conditions can be defined on most access ports. The conditions can be based on various parameters
from the Ethernet and IP header, including IP and MAC addresses, Ethertype, VPT, IP Protocol, IP
ToS, UDP/TCP Ports and some ICMP and IGMP parameters.
Thus, the ACL mechanism is a very flexible and powerful classification tool, which determines the
traffic flow and allows further QoS actions to be performed per flow. The following actions can be
performed:
•
Flow filtering
, which allows protecting the device and other network resources from being
attacked by traffic of unwanted origin or type, which in turn frees more resources for
recognized traffic and increases its QoS.
•
Mapping to Forwarding Class (FC) and Color
. FC will determine one of 8 egress queues
(per port), while the Color (Green or Yellow) will be used to determine WRED dropping
probability. The mapping can be performed in “trusted” or “un-trusted” mode.
o
Trusted
mode means the Provider trusts the Customer’s edge equipment to mark the
traffic using VPT/DSCP, and the device maps either VPT or DSCP (as configured) directly
to FC and Color.
o
Un-trusted
mode means the FC and Color will be determined according to other fields in
the Ethernet/IP headers, as specified by the ACL.
•
Policing
. A Single-Rate Three-Color Marker (SRTCM) is implemented per Access Control
Group (a group of ACLs or flows). It allows changing the initial mapped Color of traffic
exceeding the specified thresholds (CIR, CBS and EBS). Currently the only action that can be
performed on the excess traffic is marking it Yellow, which means that this traffic is likely to
be dropped later by WRED/Tail-drop in the case of congestion or over-subscription.