This read-write integer from 0 to 100 caps the maximum percentage of upstream bandwidth that can be allocated to constant-bit-rate traffic, defaulting to 100. It provides the same kind of protection as its downstream counterpart, but specifically guards upstream capacity, which is typically the more constrained direction on a cable plant. For example, an operator concerned about upstream telephony traffic growth might lower hcxMaxUpstrmCBRAlloc to ensure best-effort upstream data traffic always retains some guaranteed headroom.