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LLQ QOS question

Hello,

I was just curious, what happens to the traffic after is starts to get dropped in a specific CLASS-MAP after the buffers get filled up? Does the traffic eventually resumes?  

I know the traffic will start dropping after the buffers fill up in a particular class-map, but what happens after the traffic drops? Does it eventually resumes everything or clears the map and traffic resumes? If so, how long does it take? and what  is the process it takes to get the map flowing again?
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Don JohnstonInstructor
Top Expert 2015

Commented:
Not sure what you mean by "resumes".  

If it's UDP, non-acknowledged traffic, the packets keep getting sent.  You just don't receive any dropped packets until the congestion stops.  If it's TCP traffic, the sender will not receive acknowledgements and will retransmit until it gives up and terminates the session.
Shark AttackNetwork admin

Author

Commented:
Ok, I don't have that traffic at this minute in my network so can't tell you exactly if it's UDP or TCP.

I created a separate class-map for  particular ACL. The ACL contains an IP of an application that is consuming a huge part of the bandwidth to a point that is slowing down their network. I assigned 10% of bandiwdth the that class-map.

Access-list extanded IRON_MOUNTAIN
permit ip 10.10.10.0 0.0.0.255 any

class-map IRON_M
match access-group name IRON_MOUNTAIN

Open in new window

policy-map TRAFFIC_SHAPING
class IRON_M
bandwidth 10%

Open in new window


If that 10% is reached and the buffers for this map are filled up, what will happen?
Don JohnstonInstructor
Top Expert 2015

Commented:
In this case, it's not a buffer issue.  It's bandwidth.  

You've allocated 10% of the bandwidth to this traffic. When the traffic hits that number, packets will be discarded.  You'll probably have plenty of buffer space available but because you're defined bandwidth as your parameter, that's what determines when traffic gets dropped.
Shark AttackNetwork admin

Author

Commented:
and if that bandwidth number is hit, it will keep discarding until it's done sending correct? so it will be sending and discarding at the same time if the traffic number limit is hit at that time? it will not just literally stop the whole sending process, it will just send to get the buffers emptied and it will at the same time fill the buffers and drop other packets if the buffers are full
Instructor
Top Expert 2015
Commented:
The discarding only occurs for packets that exceed 10% of the bandwidth.

Only the sender can stop the traffic.

Forget the buffers. They don't apply to this scenario.  Buffers only factor in when you're doing queuing and thresholds.
Shark AttackNetwork admin

Author

Commented:
thanks!