Hypertec ISDN 10T Router - Manual (Page 21)

Concepts and Principles of Operation
14
Dial on Demand
When the ISDN router receives packets from the Ethernet and decides to route packets to the WAN
interface, an ISDN call is automatically made to the remote end, followed by the PPP negotiation. The
PPP connection to the remote router is triggered automatically by the LAN traffic without user
intervention. On the other hand, when the traffic activity over the connection become idle for a certain
period, the ISDN router automatically releases the ISDN/PPP connection.
Bandwidth on Demand
If Multilink PPP is enabled, the router will bring up the second B channel when the traffic activity on
the first PPP channel passes beyond a certain threshold for a certain period, as specified in “1->2 util”
(increase from 1B to 2B), and “ave interval” (average) parameters. The router may also release the
second B channel when the data traffic activity on the second channel has fallen below a certain
threshold for a certain period, as specified in “2->1 util”(decrease from 2B to 1B), and “ave interval”.
128
64
5
secs
5
secs
1
2
3
4
5
Bandwidth
Kbits/sec
A
B
Time (in seconds)
Traffic bandwidth
A = 80% volume of one B-Channel (64 Kbits/sec)
B = 30% volume of one B-Channel (128 Kbits/sec)
Available bandwidth
0 10 20 30 40 50 60
Figure 0-6, Bandwidth on Demand
Bandwidth on Demand occurs dynamically on an 'as needed' basis. Before you begin to set up
Bandwidth on Demand parameters, you need to decide at what point you want the second B-channel to
open. For example, you may want to open the second channel when the first is at 50% of its maximum
throughput. You also need to work out how long you want traffic on the first B-channel to remain at
this percentage level before the second channel opens up. The diagram above illustrates how
Bandwidth on Demand works.
When an ISDN call is made, one B-channel is opened. Point 1 shows when data reaches the traffic load
percentage value. This means that the volume of data has reached the percentage value that you have
set on “1->2 util”. You can configure Hypertec Router to wait for a set length of time before bringing
the second B-channel into operation. In this case, data volume must exceed 80% volume for a certain
length of time, as in “ave interval” before the second B-channel is opened. Point 2 marks the point at
which data volume has exceeded the traffic load percentage value for five seconds. The second ISDN
B-channel now opens automatically, and remains open until data volume drops below a configurable
level as in parameter “2->1 util”. Data is shared equally between the two B-channels. At point 3 in the