Weight; Shortcomings - HP 7102dl - ProCurve Secure Router Configuration Manual

Weight

The router also assigns each conversation a weight based on the IP prece-
dence value of its packets (see Figure 8-3). The rate at which that conversation
gets serviced is proportional to the conversation's assigned weight, preventing
high-weighted interactive traffic such as Telnet from being starved out by high-
volume, lower-weighted traffic.
To determine how much bandwidth is allocated to a conversation, the
ProCurve Secure Router compares its IP precedence value to the sum of all
IP precedence values for conversations on the interface (adding one to these
values so that routine traffic is not entirely starved out). WFQ uses the
following formula:
(IP precedence value +1)/sum of all (IP precedence values +1)
On the ProCurve Secure Router, WFQ is enabled by default on all WAN
interfaces with E1 bandwidth or less. You must set the threshold, or number
of packets, allowed in a queue. (By default, the threshold is 64 packets.)

Shortcomings

A closer examination of the formula WFQ uses to allocate bandwidth reveals
how WFQ becomes less useful as an interface supports more conversations.
First, examine a situation in which WFQ functions well. Most traffic is routine
and the interface supports few subqueues. Network control traffic is given IP
precedence 7 and traffic to a server is given IP precedence 4. The PPP 1
interface supports 5 queues, three with a precedence of 0, one with 4, and one
with 7. When needed, traffic to the server is guaranteed over one-fourth of the
bandwidth and network control traffic is guaranteed half. Traffic with a higher
precedence receives relatively more bandwidth. (See Table 8-3.)
Table 8-3. WFQ Example 1
Subqueue Precedence
1 0
2 0
3 0
4 4
5 7
Total —
Setting Up Quality of Service
Precedence + 1
1
1
1
5
8
16
Configuring WFQ
Weight
.0625
.0625
.0625
.312
.5
1
8-15