Special Considerations For Cbwfq With Multilinks - HP 7102dl - ProCurve Secure Router Configuration Manual

Setting Up Quality of Service
Configuring CBWFQ
Next, apply the QoS map to the logical interface for the connection on which
you want to enable CBWFQ. Move to the interface configuration mode context
and enter:
Syntax: qos-policy out <mapname>
For example:
ProCurve(config)# interface frame-relay 1
ProCurve(config-fr 1)# qos-policy out Class

Special Considerations for CBWFQ with Multilinks

Multilink protocols such as Multilink PPP (MLPPP) and Multilink Frame Relay
(MLFR) increase the total bandwidth of a connection. Although the bundle of
carrier lines acts as a single logical connection, each carrier line is physically
separate, and you should remember this as you allocate the interface's band-
width. Carrier lines may go down and alter the bandwidth actually available.
For example, an MLPPP connection with two T1 lines provides 3.0 Mbps of
bandwidth. You can allocate up to 75 percent of this bandwidth, or 2.25 Mbps,
to the interface's classes. You could allocate 300 Kbps (10 percent) to Class 1,
600 Kbps (20 percent) to Class 2, 600 Kbps to Class 3, and 750 Kbps (25 percent)
to Class 4. However, if one of the lines fails, the connection will only have 1.5
Mbps of bandwidth to provide the 2.25 guaranteed. If Class 3 and Class 4 are
already consuming their full minimum bandwidth (1.35 Mbps), traffic from
Class 2 will not be able to receive its guaranteed level of service.
You should consider allocating bandwidth to the multilink connection as if it
had one carrier line less than the total. This is particularly true when the
multilink is designed more to provide redundancy than to increase a connec-
tion's bandwidth.
N o t e
Even when you assign bandwidth to classes as a percentage, the router assigns
it as an absolute value of the bandwidth normally available on the interface.
This means that when one or more lines in a multilink bundle goes down, the
router does not automatically readjust the bandwidth allocated to various
classes.
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