ZyXEL Communications 5 Series - Manual (Page 429)

ZyWALL 5/35/70 Series User’s Guide
Chapter 24 Bandwidth Management 429
• The Bill class cannot borrow unused bandwidth from the Root class because the Sales
class has bandwidth borrowing disabled.
• The Amy class cannot borrow unused bandwidth from the Sales USA class because the
Amy class has bandwidth borrowing disabled.
• The Research Software and Hardware classes can both borrow unused bandwidth from
the Research class because the Research Software and Hardware classes both have
bandwidth borrowing enabled.
• The Research Software and Hardware classes can also borrow unused bandwidth from
the Root class because the Research class also has bandwidth borrowing enabled.
24.9 Maximize Bandwidth Usage With Bandwidth Borrowing
If you configure both maximize bandwidth usage (on the interface) and bandwidth borrowing
(on individual sub-classes), the ZyWALL functions as follows.
1 The ZyWALL sends traffic according to each bandwidth class’s bandwidth budget.
2 The ZyWALL assigns a parent class’s unused bandwidth to its sub-classes that have more
traffic than their budgets and have bandwidth borrowing enabled. The ZyWALL gives
priority to sub-classes of higher priority and treats classes of the same priority equally.
3 The ZyWALL assigns any remaining unused or unbudgeted bandwidth on the interface to
any class that requires it. The ZyWALL gives priority to classes of higher priority and
treats classes of the same level equally.
4 If the bandwidth requirements of all of the traffic classes are met and there is still some
unbudgeted bandwidth, the ZyWALL assigns it to traffic that does not match any of the
classes.
24.10 Over Allotment of Bandwidth
It is possible to set the bandwidth management speed for an interface higher than the
interface’s actual transmission speed. Higher priority traffic gets to use up to its allocated
bandwidth, even if it takes up all of the interface’s available bandwidth. This could stop lower
priority traffic from being sent. The following is an example.
Table 137 Over Allotment of Bandwidth Example
BANDWIDTH CLASSES, ALLOTMENTS PRIORITIES
Actual outgoing bandwidth available on the interface: 1000 kbps
Root Class: 1500 kbps (same
as Speed setting) VoIP traffic (Service = SIP): 500 Kbps 7
NetMeeting traffic (Service = H.323): 500 kbps 7
FTP (Service = FTP): 500 Kbps 3