Atm Vc Oversubscription And Atm Line Cards; Atm Over-Subscription-Factor Command - Cisco 10000 Series Configuration Manual

Chapter 15 Oversubscribing Physical and Virtual Links

ATM VC Oversubscription and ATM Line Cards

ATM VC oversubscription controls the allocation of resources that are managed on a line card. If you
enable oversubscription on one port alone, other ports might use more resources than they are supposed
to use, which could result in resource starvation of other ports, causing VC creation to fail. Therefore,
we recommend that you apply VC oversubscription to all ports of an ATM line card.
Table 15-1
IOS Release 12.3(7)XI2 and later releases.
Table 15-1 Active VCs on ATM Line Cards
Line Card Max. VCs per Port
E3/DS3 4,096
OC-3 8,191
OC-12 16,384 (previously 14,436)
1. For 32,768 VCs per module, 4096 of them must be unshaped UBR VCs.
2. For 28,672 VBR, CBR, and shaped UBR VCs, no VCs can be in shaped VP tunnels. If VCs are in shaped VPs, the number of VBR, CBR, and shaped
UBR VCs is 22,204.
3. For 32,764 VCs per module, 4096 of them must be unshaped UBR VCs.
4. For 28,672 VBR, CBR, and shaped UBR VCs, no VCs can be in shaped VP tunnels. If VCs are in shaped VPs, the number of VBR, CBR, and shaped
UBR VCs is 22,204.
You can configure the maximum number of VCs across the ports in any fashion, provided that you do
not exceed the per-port maximum.
Although the maximum number of VBR, CBR, and shaped UBR VCs per E3/DS3 and OC-3 ATM line
card is 28,672 VCs, the router supports a maximum of 22,204 VBR, CBR, and shaped UBR VCs per line
card that you can place within virtual path (VP) tunnels. If you attempt to bring up more than 22,204
VCs in a configuration that includes VP tunnels and VCs (hierarchical traffic shaping configuration), the
VCs might not assign traffic correctly or the VCs might not come up at all. Be sure to limit the number
of configured VBR, CBR, and shaped UBR VCs on an ATM card to less than 22,204 VCs if you place
the VCs in VP tunnels.
For the OC-12 ATM line card, the router supports 16,384 VCs in VP tunnels.

atm over-subscription-factor Command

To oversubscribe ATM virtual circuits (VCs), use the atm over-subscription-factor command in
interface configuration mode. To prevent oversubscription of an ATM VC, use the no atm
oversubscribe command. By default, oversubscription of ATM interfaces and tunnels is enabled.
atm over-subscription-factor {factor}
no atm over-subscription-factor {factor}
OL-7433-09
lists the number of active VCs the ATM line cards support in atm pxf queuing mode for Cisco
Maximum VCs per Module
32,768
32,764
16,384
1
3
Cisco 10000 Series Router Quality of Service Configuration Guide
ATM Virtual Circuit Oversubscription
No. VBR, CBR, Shaped UBR VCs
2
28,672
4
28,672
16,384
15-5