cn8237 Mindspeed Technologies, cn8237 Datasheet - Page 178

• Manufacturer Part Number: cn8237
• Description: Atm Oc-12 Servicesar Plus With Xbr Traffic Management
• Manufacturer: Mindspeed Technologies

6.0 Traffic Management
6.2 xBR Cell Scheduler Functional Description
Figure 6-11. Another Possible Scheduling Priority Scheme with the CN8237
6.2.7 Guaranteed Frame Rate
6-22
VBR_OFFSET
HIGH
LOW
=3
Priority
Levels
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
GFR is a new service category defined by the ATM Forum to provide an MCR
QoS guarantee for AAL5 CPCS-PDUs (or frames) not exceeding a specified
frame length. This class of service is designed specifically to use the UBR service
category. A GFR service connection is thus treated as UBR with a guaranteed
MCR.
using both the VBR1 scheduling procedure (for the MCR rate value) and a UBR
priority queue, thereby providing fair sharing for all GFR connections to excess
bandwidth. The VBR1 queue priority (the PRI field in the SEG VCC table entry)
must be set to a higher priority than the UBR queue (the GFR_PRI field in the
SEG VCC table entry). The priority level entered in the GFR_PRI field can only
be one of the lower eight scheduling priorities. This establishes the condition
where those GFR connections sharing the same GFR_PRI would fair-share any
excess bandwidth above the MCR limits. Call control must not oversubscribe
MCR on GFR channels and other rate-guaranteed services.
The CN8237 implements GFR by scheduling or shaping the connections
Tunnel A
nrt-VBR
rt-VBR
ABR
UBR
Mindspeed Technologies
Example of Multi-Service Tunnels
Tunnel B
rt-VBR
nrt-VBR
UBR
ABR
ATM OC-12 ServiceSAR Plus with xBR Traffic Management
Tunnel C
nrt-VBR
rt-VBR
UBR
ABR
™
Tunnel D
nrt-VBR
rt-VBR
ABR
UBR
28237-DSH-001-C
CN8237
8237_066