CN8236EBGB Mindspeed Technologies, CN8236EBGB Datasheet - Page 189

• Manufacturer Part Number: CN8236EBGB
• Description: ATM SAR 155Mbps 3.3V ABR/CBR/GFR/UBR/VBR 388-Pin BGA
• Manufacturer: Mindspeed Technologies

Specifications of CN8236EBGB

• Package: 388BGA
• Traffic Class: ABR|CBR|GFR|UBR|VBR
• Utopia Type: Level 1|Level 2
• Host Interface: PCI
• Maximum Data Rate: 155 Mbps
• Typical Operating Supply Voltage: 3.3 V
• Minimum Operating Supply Voltage: 3 V

CN8236
ATM ServiceSAR Plus with xBR Traffic Management
28236-DSH-001-B
CBR tunnel need to be activated as a tunnel by setting the TUN_ENA( × ) bit(s)
in the SCH_PRI and SCH_PRI2 registers.
scheduling priority assigned. All can be VBR/ABR tunnels. On the other hand,
the system designer can establish four tunnels, each of which has four scheduling
priorities assigned to it, or any combination of tunnels, which includes up to a
total of 16 scheduling priorities. Individual VCCs are assigned to the tunnel by
the host, by setting the PRI field in the VCC table to the priority of the tunnel.
user wishes to enter a priority level higher than priority 7 in PRI0, assign the
difference in values as an offset, in the TUN_PRI0_OFFSET field in the
SCH_CTRL register.
the highest priority level(s) to CBR tunnel(s).
APPLICATION EXAMPLES: Tunnels
and VBR traffic. The host assigns a fixed number of Schedule table slots
to the tunnel to reserve a fixed rate. Each time an assigned slot is
encountered by the Cell Scheduler, it selects a VCC from a round-robin
queue of active VCCs assigned to that priority.
segmenting data. Each gets 1/100th of the CBR bandwidth assigned to the
tunnel. Tunneling enables system-level end users to purchase CBR
services from a WAN service provider. The purchaser can then
dynamically manage the traffic within this leased CBR tunnel as CBR
and/or a combination of other service categories.
independent tunnels. The first tunnel priority five, is through a private
ATM network, perhaps a corporate ATM campus backbone. The other
tunnel, priority six, carries traffic through a public network. This
topology allows the end user to lease reserved CBR bandwidth from an
administrative domain, but manage the usage of the tunnel in an arbitrary
fashion.
the user has established 4 separate tunnels or pipes. Each can have an
equal 1/4 share of the bandwidth available to the port by provisioning
every fourth schedule table slot to one tunnel for each of the four tunnels.
priority in each tunnel is assigned to real-time VBR, the next highest
priority to non-real-time VBR, the third highest priority to ABR, and the
lowest priority to UBR. This in effect establishes four multi-service pipes,
each on equal priority to the others (since the scheduler services each of
the four pipes equally). Thus, the 4 rt-VBR priorities have effectively the
same priority, and so on through the four levels of priority serviced in each
pipe. Number of VBR/ABR priorities is 12. CBR_TUN = 1,
SLOT_DEPTH = 110.
VBR_OFFSET = 3.
Sixteen tunnels can be active at once, if each of these tunnels has only one
The 3-bit PRI0 field allows the entry of only priority levels 0 through 7. If the
If both non-tunnel and tunnel scheduling priorities exist, the host must assign
Figure 6-6
For example, 100 UBR VCCs with PRI = 6 might currently be
In this example, the user has configured the CN8236 to manage two
Figure 6-11
In each of the tunnels, 4 priority levels are assigned. The highest
Highest VBR/ABR Scheduling priority is 15 (that is, PRI = 15). Thus,
Mindspeed Technologies
shows priorities five and six used as CBR tunnels for UBR
illustrates a different use of CBR tunnels. In this example,
™
6.2 xBR Cell Scheduler Functional Description
6.0 Traffic Management
6-21