queue time doesnot match

[maya davidson]

Hello, 

I have a network topology as below:

R2 - R3 - R4
         |
         R1

My bandwidth are 100Mbps, queue sizes are 1000 packets, fifo
and I am sending 12500 frame/second and 1000byte each frame , 
from R2- R3 
and another one R1-R3
Loss is around 1.96% for both flows, but the delay is 0.007s for the first flow and 0.4s for the second flow, 
which in theory i can calculate the queuing time as below, 
queue sizes / (bandwidth / packetsize * 😎 = 0.08s

the R2 and R3 are from 9200 cisco and R1 c1111 

I don't know where I am getting wrong that with the same configs i am getting delays which none of them are correct. 

Thanks for your help in advance

[CaroleMay]

The discrepancies in delay and packet loss in your network setup can be attributed to several factors:

1. Flow Calculations: You're sending 12,500 frames per second, each 1,000 bytes, which saturates the 100 Mbps link between R2 and R3, leading to potential queuing delays.
2. Queue Size and Delay: The calculated queuing delay of 0.08 seconds (80 ms) aligns with your theory, but the 0.4 seconds delay for the R1-R3 flow suggests R1 may be a bottleneck.
3. Router Performance: The Cisco C1111 router (R1) may have lower processing capabilities compared to the Cisco 9200 series (R2 and R3), causing increased queuing and processing delays.
4. Packet Loss: The 1.96% packet loss indicates that incoming traffic may exceed R1's processing capacity, leading to dropped packets.

Recommendations:

• Check R1 Configuration: Optimize R1's settings and consider increasing buffer sizes or implementing QoS to prioritize traffic.
• Monitor Resource Utilization: Check CPU and memory usage on R1 to identify potential overload issues.

By addressing these factors, you can improve the performance and reduce delays and packet loss in your network.