PXB4330 Datasheet, PDF (41/201 Pages) Infineon Technologies AG – ICs for Communications

PXB 4330
Functional Description
spare
10
9
bandwidth
8
10
7
9
8
7
6
6
5
4
3
2
5
4
3
2
1
1
9
7
6
Scheduler
bandwidth
1 ^{real time}
traffic
connection setup
with guaranteed
cell rates
not reserved
bandwidth
distributed
unused
bandwidth distributed
Figure 3-6 Scheduler Behavior Example
The left column in Figure 3-6 shows the Scheduler load as seen from Connection Ac-
ceptance Control (CAC). New connections are accepted as long as their guaranteed
rates fit the spare bandwidth of the Scheduler. "Guaranteed rate" is defined below.
The center column shows the case in which all Queues 2..10 are filled; that is, all non-
real time connections are sending data. The total non-real-time bandwidth, including the
spare bandwidth, is then distributed to the 9 queues according to their weight. In this
case, two weight factors are defined, 1 and 10.
The right column shows the case of only three queues (6, 7 and 9) filled; all other con-
nections are not sending data at this time. Again, the available bandwidth is fairly
distributed among the queues, still conserving the 1:10 ratio defined by their weights.
Notice that bandwidth of the real-time connections is not affected by bandwidth re-ad-
justments; but, remains constant over time under the assumption that real-time
connections are constantly sending data. If, however, a real-time connection should not
use its bandwidth, the bandwidth would be used immediately by the non-real-time con-
nections. The behavior shown in Figure 3-6 of the WFQ Multiplexer for non-real-time
connections has advantages for both the network operator and for the end user:
• The available bandwidth is always used completely, resulting in optimum usage of
transmission resources
• A user paying for a higher guaranteed rate also obtains higher throughput under all
load conditions.
Data Sheet
3-41
09.99