User's Manual

Chapter 28 Bandwidth Management
ZyWALL USG 20/20W User’s Guide
457
Maximize Bandwidth Usage Effect
With maximize bandwidth usage enabled, after each server gets its configured
rate, the rest of the available bandwidth is divided equally between the two. So
server A gets its configured rate of 300 kbps and server B gets its configured rate
of 200 kbps. Then the ZyWALL divides the remaining bandwidth (1000 - 500 =
500) equally between the two (500 / 2 = 250 kbps for each). The priority has no
effect on how much of the unused bandwidth each server gets.
So server A gets its configured rate of 300 kbps plus 250 kbps for a total of 550
kbps. Server B gets its configured rate of 200 kbps plus 250 kbps for a total of
450 kbps.
Priority and Over Allotment of Bandwidth Effect
Server A has a configured rate that equals the total amount of available
bandwidth and a higher priority. You should regard extreme over allotment of
traffic with different priorities (as shown here) as a configuration error. Even
though the ZyWALL still attempts to let all traffic get through and not be lost,
regardless of its priority, server B gets almost no bandwidth with this
configuration.
Finding Out More
• See Section 7.5 on page 120 for an example of how to set up web surfing
policies with bandwidth restrictions.
• See DSCP Marking and Per-Hop Behavior on page 299 for a description of DSCP
marking.
28.1.3 Bandwidth Management Examples
Bandwidth management is very useful when applications are competing for limited
bandwidth. For example, say you have a WAN zone interface connected to an
ADSL device with a 8 Mbps downstream and 1 Mbps upstream ADSL connection.
Table 129 Maximize Bandwidth Usage Effect
POLICY CONFIGURED RATE MAX. B. U. PRIORITY ACTUAL RATE
A 300 kbps Yes 1 550 kbps
B 200 kbps Yes 2 450 kbps
Table 130 Priority and Over Allotment of Bandwidth Effect
POLICY CONFIGURED RATE MAX. B. U. PRIORITY ACTUAL RATE
A 1000 kbps Yes 1 999 kbps
B 1000 kbps Yes 2 1 kbps