PXB4330 Datasheet, PDF (54/201 Pages) Infineon Technologies AG – ICs for Communications

PXB 4330
Operational Description
Definition of Necessary Traffic Classes:
The ABM allows up to 16 traffic classes to be defined by Traffic Class Table RAM entry
via the registers TCT0 and TCT1, page 93. In this example, there are 3 traffic classes:
• CBR (real-time) = traffic class 1
• GFR (non-real-time) = traffic class 2
• UBR (non-real-time) = traffic class 3
Assignment of the queues to the traffic classes:
Each queue must relate to a defined traffic class according to the Queue Configuration
Table RAM entry via the TrafClass(3:0) bits of the register QCT1, page 6-104.
Figure 4-3 shows that each queue belongs to one of the traffic classes 1..3; for example,
Queue 1 belongs to Traffic Class 1, Queue 2 to Traffic Class 2 (just as for Queue 3) and
Queue 4 corresponds to Traffic Class 3.
Assignment of the Queues (QIDs) to the Schedulers (SIDs):
Every Scheduler possesses a certain number of queues depending on the assignment
by the user of the SID(5:0) bits of register QCT1, page 6-104. In the example, every
ADSL device has four data connections so that four queues per Scheduler are neces-
sary. Each Scheduler of the ABM has one real-time queue and an arbitrary number of
non-real-time queues. For Schedulers #1..#95, indicate that the first queue belongs to
Traffic Class 1, the 2nd and 3rd Queue to Traffic Class 2, and the 4th Queue to Traffic
Class 3. There are 380 (1..380) queues altogether for Schedulers #1..#95. The 96th
scheduler must be able to serve the 95 ADSL devices (95 Schedulers and appropriate
queues). Thus, Scheduler #96 has 95 x 2 = 190 non-real-time queues as every Sched-
uler from #1..#95 possesses two GFR non-real-time queues (GFR has a guaranteed
minimum rate; thus, each GFR queue needs a per VC queueing). The 95 UBR queues
of Schedulers #1..#95 need only one UBR queue at the 96th Scheduler as UBR has no
guaranteed minimum rate. As every Scheduler has only one real-time queue, the 95
real-time queues from Schedulers #1..#95 flow into the one real-time queue of Scheduler
#96. Therefore, Scheduler #96 needs the assignment of 190 (GFR) + 1 (UBR) + 1 (CBR)
= 192 queues (only the queue with QID = 400 corresponds with Traffic Class 1).
In Figure 4-3 the first queue starts with QID = 400 and not with QID = 380 because this
makes it easier to recognize the number of queues belonging to Scheduler #96 (also, it
shows that the assignment is arbitrary within the given borders (only 1023 queues = QID
1..1023 per ABM Core exist)). The restriction of 1023 queues maximum per ABM Core
must be met. The example (Figure 4-3) fulfills this condition:
a) Upstream ABM core:
192 queues (≤ 1023 queues!) are used
b) Downstream ABM core:
380 queues (≤ 1023 queues!) are used
Data Sheet
4-54
09.99