Line Card Vc Limitations - Cisco 10000-2P2-2DC Software Configuration Manual

Line Card VC Limitations

Table 2-1
Parameter
Priority
The number of SAR priority levels and the service categories supported at each priority level vary from
line card to line card. For example, the 1-port OC-12/STM-1 line card supports the four levels of priority
and the service categories listed in
priority and the service categories listed in the table.
The ATM line cards support a maximum number of VCs per priority. That VC limit depends on the VC
limit of the SAR (SAR limit) and the number of priority levels configured.
determine the VC limit per priority level per port for the specified line cards.
Table 2-2
ATM Line Card
1-Port OC-12/
STM-1
4-Port OC-3
8-Port E3/DS3 0 = CBR VCs
Configuring more channels or VCs than there are available priority locations can cause random channels
or VCs to get stuck in the SAR. This occurs when an active channel tries to reschedule itself, but no
priority locations are available. Therefore, the channel cannot find a place to reschedule itself, which
results in a lost event for the channel, and the channel becomes stuck in the SAR.
On the PRE2, when a VC becomes stuck in the SAR, the PRE2 scheduler stops forwarding traffic on
only the VC that is stuck in the SAR; the other VCs still carry traffic. On the PRE3, the PRE3 scheduler
stops forwarding traffic on all the VCs configured on that ATM line card.
For example, suppose a 1-port OC-12 line card at full line rate is configured for four levels of priority
and a 4-port OC-3 line card at half line rate is configured for two levels of priority. By calculating the
maximum number of VCs as described in
Cisco 10000 Series Router Software Configuration Guide
2-2
ATM Service Categories
CBR VBR-rt
0 1
Table 2-2, but the 4-port OC-3 line card supports only two levels of
Maximum Number of VCs per Priority
SAR Priority Levels
0 = CBR VCs
1 = VBR-rt VCs
2 = VBR-nrt VCs
3 = UBR VCs
0 = CBR, VBR-nrt VCs
1 = UBR VCs
0 = VBR-nrt VCs
1 = UBR VCs
Table
Chapter 2
VBR-nrt Shaped UBR
2 3
VC Rate Maximum Number of VCs per Priority
Full line rate SAR limit / 2 / number of priority levels
4 priority system:
65,536 / 2 / 4 = 8192 VCs per priority level
Half line rate SAR limit / number of priority levels
and below
4 priority system:
65,536 / 4 = 16,384 VCs per priority level
Half line rate SAR limit / number of PHYs / number of
and below priority levels
2 priority system:
65,536 / 4 / 2 = 8192 VCs per priority level
per port
Half line rate SAR limit / number of PHYs / number of
and below priority levels
2 priority system:
65,536 / 8 / 2 = 4096 VCs per priority level
per port
2-2, you can configure 8192 VCs per priority level for
Scalability and Performance
Unshaped UBR
None
Table 2-2 describes how to
OL-2226-23