Enterasys Networks Security Router X-PeditionTM - Manual (Page 306)

QoS Policy Configuration Examples
12-24 Configuring Quality of Service
As an example, tunnels with ESP and 3DES encoding will add 44 bytes (or more) overhead.
Padding for 3DES may add eight more bytes. Calculate the shaper rate with this formula:
ShaperRate = LineRate * ( 1 - OverHead/(OverHead +AvgPktSize))
The table below summarizes the shaper rate as a percentage from the line rate for different
average packet sizes and tunnel modes. The larger the packet, the lesser tunnel overhead effect.
QoS Policy Configuration Examples
Simple QoS on Physical Interface Policy
The following QoS example configures Class1 with these characteristics on the Serial 1 /1
interface: a minimum of 200 Kbps of bandwidth are expected to be delivered to this class in the
event of congestion, and the queue reserved for this class can enqueue 40 packets before tail drop
is employed to handle additional packets.
Class2 is specified with these characteristics: a minimum of 300 Kbps of bandwidth are expected to
be delivered to this class in the event of congestion. For congestion avoidance, RED packet drop is
used, not tail drop. The default class is configured with a maximum of 20 packets per queue which
are enqueued before tail drop is used to handle additional packets.
Begin by creating Class1 and Class2 and matching their respective parameters:
XSR(config)#class-map class1
XSR(config-cmap<class1)#match access-group 136
XSR(config-cmap<class1)#exit
XSR(config)#class-map class2
XSR(config-cmap<class2>)#match ip precedence 2
Create the policy map:
XSR(config)#policy-map policy1
XSR(config-pmap<policy1>)#class class1
XSR(config-pmap-c<class1>)#bandwidth 200
Tunnel ESP Tunnel 20 bytes NA 24 bytes 44 bytes
Tunnel AH Transport NA 24 bytes NA 24 bytes
Tunnel ESP Transport NA NA 24 bytes 24 bytes
Table 12-4 Tunnel Shaper Rates
Packet Size TunnelAH Tunnel ESP TransAH TransESP
64 0.592593 0.592593 0.727273 0.727273
128 0.744186 0.744186 0.842105 0.842105
380 0.896226 0.896226 0.940594 0.940594
1084 0.958801 0.958801 0.977099 0.977099
Table 12-3 Overhead on IPSec Tunnels
Tunnel Type Mode
Tunnel
IP
Header
AH (HMAC) ESP+3DES
Total
Overhead