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Beginner

What is wrong with my config Qos Dropping packets

What's wrong with my Qos policy it's dropping packets

class-map match-any Video
match access-group name Video
!
policy-map Video
class Video
priority percent 20 64000000
class class-default
bandwidth percent 80
policy-map 100MegShape
class class-default
shape average 100000000
service-policy Video

Router1#show int g0/0/2
GigabitEthernet0/0/2 is up, line protocol is up
Hardware is ISR4451, address is
Description: Internet
Internet address is X.X.X.X/30
MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
reliability 255/255, txload 85/255, rxload 60/255
Encapsulation ARPA, loopback not set
Keepalive not supported
Full Duplex, 100Mbps, link type is force-up, media type is RJ45
output flow-control is on, input flow-control is on
ARP type: ARPA, ARP Timeout 04:00:00
Last input 03:08:25, output 00:07:55, output hang never
Last clearing of "show interface" counters never
Input queue: 0/375/0/0 (size/max/drops/flushes); Total output drops: 138802094
Queueing strategy: Class-based queueing
Output queue: 0/40 (size/max)
5 minute input rate 23656000 bits/sec, 4170 packets/sec
5 minute output rate 33446000 bits/sec, 4797 packets/sec
16013576510 packets input, 12173283659397 bytes, 0 no buffer
Received 10 broadcasts (0 IP multicasts)
0 runts, 1 giants, 0 throttles
1 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 0 multicast, 0 pause input
16033085443 packets output, 12127192896452 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
3 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out

Router1#show policy-map interface g0/0/2 output
GigabitEthernet0/0/2

Service-policy output: 100MegShape

Class-map: class-default (match-any)
16173952429 packets, 12286653320874 bytes
5 minute offered rate 35290000 bps, drop rate 1800000 bps
Match: any
Queueing
queue limit 416 packets
(queue depth/total drops/no-buffer drops) 0/138870149/0
(pkts output/bytes output) 16034087603/12115724571160
shape (average) cir 100000000, bc 400000, be 400000
target shape rate 100000000

Service-policy : Video

queue stats for all priority classes:
Queueing
queue limit 512 packets
(queue depth/total drops/no-buffer drops) 0/2690297/0
(pkts output/bytes output) 2417168145/3598268558289

Class-map: Video (match-any)
2419858442 packets, 3602338264015 bytes
5 minute offered rate 5556000 bps, drop rate 0000 bps
Match: access-group name Video
Priority: 20% (20000 kbps), burst bytes 64000000, b/w exceed drops: 2690297


Class-map: class-default (match-any)
13754093905 packets, 8684314974443 bytes
5 minute offered rate 29732000 bps, drop rate 1793000 bps
Match: any
Queueing
queue limit 332 packets
(queue depth/total drops/no-buffer drops) 0/136179852/0
(pkts output/bytes output) 13616919458/8517456012871
bandwidth 80% (80000 kbps)

Cisco IOS XE Software, Version 03.16.05.S - Extended Support Release
Cisco IOS Software, ISR Software (X86_64_LINUX_IOSD-UNIVERSALK9-M), Version 15.5(3)S5, RELEASE SOFTWARE (fc2

8 REPLIES 8
VIP Mentor

Hello,

Hello,

post the full config of your router. What does the access list 'Video' match ?

Try the following:

policy-map Video
 class Video
  priority percent 20 64000000
policy-map 100MegShape
 class class-default
  shape average 100000000 1000000

Beginner

Can you explain what this

Can you explain what this command does?

  shape average 100000000 1000000

thanks

Participant

Shape average from what I can

Shape average from what I can remember attempts to average out the traffic flow using the first value but allow the traffic to burst above that at periods of low traffic rates.  

Beginner

The access list matches two

The access list matches two video servers we have on site.

VIP Expert

What's wrong with my Qos

What's wrong with my Qos policy it's dropping packets

QoS policies often drop packets, in fact, as they are generally used to manage congestion, they often can be used to manage what's dropped.

What's likely happening, often video is very bursty, and such bursts are hitting the implicit LLQ policer limits.  Your class default is also congesting which would can force LLQ queuing, which is often the trigger for a LLQ policer.

I assume you've tried to minimize this by your very large Bc setting.

Is the video real-time or streaming?  The former often will need LLQ treatment, but the latter often does not.

Somethings you might try include first removing the nested policy and parent shaper.  There's no need to shape for 100 Mbps when the interface is physically running at 100 Mbps (which from you posting it appears to be).

Second, increase you overall bandwidth allocation to your LLQ class.  Cisco recommends you don't exceed one third of available bandwidth, but depending on need, I found you can usually go as high as one half and still have effective LLQ.  (You might also change your class default to bandwidth remaining 100 percent.)

Third, as your class default is also suffering from drops, enable FQ.  You many need to increase FQ's queue limit.

If you video is streaming, don't use LLQ, but insure the class has ample bandwidth and buffering to avoid drops.

What the suggestions, above, will try to accomplish, is remediate video drops, and "target" drops against bandwidth hogs in class default.

Highlighted
Beginner

It's real time streaming.

It's real time streaming.

VIP Expert

What's real time streaming?

What's real time streaming?

I.e. it's is "live" or real-time video, or "canned" video.

The former may need LLQ, the latter shouldn't need it.

For both, though, you want to avoid packet drops.

For your posted policy, you shouldn't be able to mix the priority and bandwidth commands for the same class.  Also if you need to bump up the priority Bc, you probably need a larger overall bandwidth allocation.  Further, if video traffic is "live" you shouldn't need to be queuing it.

Basically, for "live" video, your want to insure you have enough bandwidth that the video packets are almost always sent without delay (also again, and without drop).

For "canned" video, you often have multi-second buffer you're working with, so you can queue that traffic, but also again, you don't want to drop any of its packets.

Beginner

Something like this?

Something like this?


class-map match-any Video
match access-group name Video
!
policy-map Video
 class Video
   priority percent 33 64000000
     class class-default

     queue limit 1000
      bandwidth percent 100

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