Enterasys Networks X-PeditionTM manual Configuration per Interface, Vpn

Mechanisms Providing QoS

WRED. Traffic marked with a lower drop probability is assigned a higher MaxP, and bigger thresholds for MinTh and MaxTh than traffic marked with DSCP values having a higher drop level. Because higher drop DSCPs have a lower MinTh, as the queue grows, the XSR starts discarding them earlier than low drop DSCPs. Also, the XSR drops them more often because they have a higher drop probability (MaxProb). The end effect is that packets marked with high-drop DSCP values are discarded more frequently.

Note: Drop Tail and WRED cannot be used on the same queue simultaneously - queue-limitand random-detectare mutually exclusive. If random-detectis set on a queue, queue-limitcannot be set as well until WRED is removed.

The XSR treats RED as a subclass of WRED because it becomes equivalent to RED when all DSCP or precedence values have the same minth, maxth, and maxprob values. While you can implement RED by configuring WRED, RED may still be configured by itself using the random-detectcommand as illustrated in the following example. These two configurations are equivalent - both configure RED with MinTh=10, MaxTh=20 and MaxProb=1 although the first uses random-detectwhile the second uses WRED.

XSR(config)#policy-map ppwe

XSR(config-pmap<ppwe>)#class bus

XSR(config-pmap-c<bus>)#random-detect 10 20 10

XSR(config)#policy-map ppwe

XSR(config-pmap<ppwe>)#class bus

XSR(config-pmap-c<bus>)#random-detect dscp-based

XSR(config-pmap-c<bus>)#random-detect dscp default 10 20 10

Configuration per Interface

QoS can be configured on both LAN and WAN interfaces, sub-interfaces (Frame Relay DLCI, ATM, Ethernet VLAN) , and virtual interfaces (Dialer, VPN). Table 12-2illustrates the options:

Table 12-2 Configuration Options by LAN/WAN Interface

Function	Ethernet	Serial	PPP	MLPPP	FR DLCI	Dialer	VPN
CBWFQ	Y	Y	Y	Y	Y	Y	Y
Priority Queue	Y	Y	Y	Y	Y	Y	Y
Traffic Policing	Y	Y	Y	Y	Y	Y	Y
Random Early Detect	Y	Y	Y	Y	Y	Y	Y
WRED	Y	Y	Y	Y	Y	Y	Y
Traffic Shaping per class	Y	Y	Y	Y	Y	Y	Y
Traffic Shaping per policy	Y	Y	Y	Y	Y	Y	Y
Service Map input	Y	Y	Y	Y	Y	Y	Y
Service Map output	Y	Y	Y	Y	Y	Y	Y

The Dialer interface is a virtual interface in the sense that it does not have a corresponding transmit port (serial or Ethernet). Only after it dials does the dialer interface bind to one of the resources from the dialing pool (Serial port) and establish a data path. Service policy applied to

12-12 Configuring Quality of Service