I have to admit I was somewhat surprised by the lab test results I’ve published in my previous CB-WFQ post. It looks like we’ve been fed misleading information about (classic) CB-WFQ behavior for years.
Don’t tell me that things are completely different with HQF implemented in IOS releases 12.4(late)T and 15.0. I know that … but 95+% of the installed base do not use those releases.
Let’s see whether you can figure out what my next lab test results showed. I’ve been running three parallel TTCP sessions on ports 5001, 5002 and 5003 across a 256 kbit point-to-point link. Here’s the relevant part of my router configuration:
policy-map WAN class P5001 bandwidth percent 50 class P5002 police rate percent 50 violate-action drop ! interface Serial0/1/0 bandwidth 256 clock rate 256000 ip address 10.0.6.1 255.255.255.252 encapsulation ppp ip ospf 1 area 0 load-interval 30 service-policy output WAN
TTCP is a program that sends meaningless data across a TCP session. It’s a nice load to use in a QoS test, as it uses TCP stack (ensuring it behaves like a real application) but still sends the data as fast as possible (as it spends no time generating it).
What would be your answers to these questions?
- A single TTCP session is running on port 5001. How much bandwidth does it get?
- A single TTCP session is running on port 5002. How much bandwidth does it get?
- Three parallel TTCP sessions are running on ports 5001, 5002 and 5003. How much bandwidth does each session get?
Try to find the answer before reading the solution.