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QoS loss while bandwith utilization is low

msrohman
Beginner
Beginner

Hi All,

I have a Cisco 3900E series router attached to a carrier MPLS provider. The MPLS Ethernet circuit is 100Mbps of CIR bandwidth. However, when the egress traffic of the MPLS interface reaches above 30Mbps, I receive alert notifications that the interface is dropping packets.

I'm not an expert is QoS, but I can't find any reason in the output of the config that would cause the dropping of packets when the bandwidth utilization on the MPLS egress direction is low. Maybe talk to the carrier regarding an interface problem?

!
!
! MPLS Router #1
1
1
policy-map WAN_Egress
class EF
priority 4096
police 4096000 conform-action transmit exceed-action drop
class AF4
bandwidth remaining percent 30
random-detect dscp-based
random-detect dscp 32 171 500 1
random-detect dscp 34 171 500 1
random-detect dscp 36 52 171 1
random-detect dscp 38 52 171 1
class AF3
bandwidth remaining percent 39
random-detect dscp-based
random-detect dscp 24 250 500 1
random-detect dscp 26 250 500 1
random-detect dscp 28 52 250 1
random-detect dscp 30 52 250 1
class AF2
bandwidth remaining percent 16
random-detect dscp-based
random-detect dscp 16 171 500 1
random-detect dscp 18 171 500 1
random-detect dscp 20 52 171 1
random-detect dscp 22 52 171 1
class AF1
bandwidth remaining percent 6
random-detect dscp-based
random-detect dscp 8 171 500 1
random-detect dscp 10 171 500 1
random-detect dscp 12 52 171 1
random-detect dscp 14 52 171 1
class BE
bandwidth remaining percent 4
random-detect dscp-based
random-detect dscp 0 171 500 1
class BGP
bandwidth remaining percent 3
policy-map shape_WAN_Egress
class class-default
shape average percent 85
service-policy WAN_Egress
!
!
!
!
interface GigabitEthernet0/0
description Carrier MPLS - Circuit ID <Omitted>
bandwidth 100000
ip address 162.181.252.222 255.255.255.252
service-policy output shape_WAN_Egress
!
!
IL1MPLS#sh int Gi0/0
GigabitEthernet0/0 is up, line protocol is up
Hardware is iGbE, address is 4c4e.3582.b700 (bia 4c4e.3582.b700)
Description: Verizon MPLS - Circuit ID BCBK0X3T0001
Internet address is 152.181.222.222/30
MTU 1500 bytes, BW 100000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 26/255, rxload 37/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full Duplex, 1Gbps, media type is SX
output flow-control is unsupported, input flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters 7w6d
Input queue: 0/75/0/323 (size/max/drops/flushes); Total output drops: 699931
Queueing strategy: Class-based queueing
Output queue: 0/1000/699833 (size/max total/drops)
30 second input rate 14659000 bits/sec, 5561 packets/sec
30 second output rate 10587000 bits/sec, 4853 packets/sec
30883982639 packets input, 12313394514038 bytes, 0 no buffer
Received 3962 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
2701 input errors, 0 CRC, 0 frame, 2701 overrun, 0 ignored
0 watchdog, 0 multicast, 0 pause input
28939872421 packets output, 10445268282772 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out
!
!

IL1MPLS#sh policy-map int Gi0/0
GigabitEthernet0/0

Service-policy output: shape_WAN_Egress

Class-map: class-default (match-any)
28933568079 packets, 10444882845653 bytes
30 second offered rate 11614000 bps, drop rate 0000 bps
Match: any
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/699833/0
(pkts output/bytes output) 28938324131/10444801344446
shape (average) cir 85000000, bc 850000, be 850000
target shape rate 85000000

Service-policy : WAN_Egress

queue stats for all priority classes:
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/10/0
(pkts output/bytes output) 665301280/78220133742

Class-map: EF (match-any)
665301385 packets, 78220266846 bytes
30 second offered rate 105000 bps, drop rate 0000 bps
Match: ip dscp ef (46)
665301385 packets, 78220267104 bytes
30 second rate 105000 bps
Priority: 4096 kbps, burst bytes 102400, b/w exceed drops: 0

police:
cir 4096000 bps, bc 128000 bytes
conformed 665301297 packets, 78220135919 bytes; actions:
transmit
exceeded 88 packets, 131185 bytes; actions:
drop
conformed 105000 bps, exceeded 0000 bps

Class-map: AF4 (match-any)
0 packets, 0 bytes
30 second offered rate 0000 bps, drop rate 0000 bps
Match: ip dscp af41 (34)
0 packets, 0 bytes
30 second rate 0 bps
Match: ip dscp af42 (36)
0 packets, 0 bytes
30 second rate 0 bps
Match: ip dscp af43 (38)
0 packets, 0 bytes
30 second rate 0 bps
Match: ip dscp cs4 (32)
0 packets, 0 bytes
30 second rate 0 bps
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 0/0
bandwidth remaining 30%
Exp-weight-constant: 9 (1/512)
Mean queue depth: 0 packets
dscp Transmitted Random drop Tail drop Minimum Maximum Mark
pkts/bytes pkts/bytes pkts/bytes thresh thresh prob

cs4 0/0 0/0 0/0 171 500 1/1
af41 0/0 0/0 0/0 171 500 1/1
af42 0/0 0/0 0/0 52 171 1/1
af43 0/0 0/0 0/0 52 171 1/1

Class-map: AF3 (match-any)
3586210901 packets, 1183469359266 bytes
30 second offered rate 1127000 bps, drop rate 0000 bps
Match: ip dscp af31 (26)
3585758519 packets, 1183433565392 bytes
30 second rate 1127000 bps
Match: ip dscp af32 (28)
0 packets, 0 bytes
30 second rate 0 bps
Match: ip dscp af33 (30)
0 packets, 0 bytes
30 second rate 0 bps
Match: ip dscp cs3 (24)
0 packets, 0 bytes
30 second rate 0 bps
Match: ip dscp cs6 (48)
452382 packets, 35794530 bytes
30 second rate 0 bps
Match: ip dscp cs7 (56)
0 packets, 0 bytes
30 second rate 0 bps
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/48/0
(pkts output/bytes output) 3586210847/1183469341453
bandwidth remaining 39%
Exp-weight-constant: 9 (1/512)
Mean queue depth: 0 packets
dscp Transmitted Random drop Tail drop Minimum Maximum Mark
pkts/bytes pkts/bytes pkts/bytes thresh thresh prob

cs3 0/0 0/0 0/0 250 500 1/1
af31 3585758519/1183433565392 0/0 0/0 250 500 1/1
af32 0/0 0/0 0/0 52 250 1/1
af33 0/0 0/0 0/0 52 250 1/1
cs6 452382/35794530 0/0 0/0 32 40 1/10

Class-map: AF2 (match-any)
1013725 packets, 79070842 bytes
30 second offered rate 0000 bps, drop rate 0000 bps
Match: ip dscp af21 (18)
1013647 packets, 79062019 bytes
30 second rate 0 bps
Match: ip dscp af22 (20)
75 packets, 8025 bytes
30 second rate 0 bps
Match: ip dscp af23 (22)
3 packets, 798 bytes
30 second rate 0 bps
Match: ip dscp cs2 (16)
0 packets, 0 bytes
30 second rate 0 bps
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 1013725/79070842
bandwidth remaining 16%
Exp-weight-constant: 9 (1/512)
Mean queue depth: 0 packets
dscp Transmitted Random drop Tail drop Minimum Maximum Mark
pkts/bytes pkts/bytes pkts/bytes thresh thresh prob

cs2 0/0 0/0 0/0 171 500 1/1
af21 1013647/79062019 0/0 0/0 171 500 1/1
af22 75/8025 0/0 0/0 52 171 1/1
af23 3/798 0/0 0/0 52 171 1/1

Class-map: AF1 (match-any)
0 packets, 0 bytes
30 second offered rate 0000 bps, drop rate 0000 bps
Match: ip dscp af11 (10)
0 packets, 0 bytes
30 second rate 0 bps
Match: ip dscp af12 (12)
0 packets, 0 bytes
30 second rate 0 bps
Match: ip dscp af13 (14)
0 packets, 0 bytes
30 second rate 0 bps
Match: ip dscp cs1 (8)
0 packets, 0 bytes
30 second rate 0 bps
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 0/0
bandwidth remaining 6%
Exp-weight-constant: 9 (1/512)
Mean queue depth: 0 packets
dscp Transmitted Random drop Tail drop Minimum Maximum Mark
pkts/bytes pkts/bytes pkts/bytes thresh thresh prob

cs1 0/0 0/0 0/0 171 500 1/1
af11 0/0 0/0 0/0 171 500 1/1
af12 0/0 0/0 0/0 52 171 1/1
af13 0/0 0/0 0/0 52 171 1/1

Class-map: BE (match-any)
24681042074 packets, 9183114150844 bytes
30 second offered rate 10380000 bps, drop rate 0000 bps
Match: ip dscp default (0)
24681042084 packets, 9183114151263 bytes
30 second rate 10380000 bps
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/699785/0
(pkts output/bytes output) 24680342294/9182672703383
bandwidth remaining 4%
Exp-weight-constant: 9 (1/512)
Mean queue depth: 0 packets
dscp Transmitted Random drop Tail drop Minimum Maximum Mark
pkts/bytes pkts/bytes pkts/bytes thresh thresh prob

default24680342298/9182672705569 635709/425290037 64076/16155575 171 500 1/1

Class-map: BGP (match-any)
0 packets, 0 bytes
30 second offered rate 0000 bps, drop rate 0000 bps
Match: access-group name BGP
0 packets, 0 bytes
30 second rate 0 bps
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 0/0
bandwidth remaining 3%

Class-map: class-default (match-any)
0 packets, 0 bytes
30 second offered rate 0000 bps, drop rate 0000 bps
Match: any

queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 5455984/360094944
!
!

Thanks in advance for your help.

-Mike

3 Replies 3

Joseph W. Doherty
Hall of Fame Master Hall of Fame Master
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Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages wha2tsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

What is alerting you to the drops and what is measuring the 30 Mbps?  (NB: it's not uncommon for many measurement tools to use measured rates that are "long" term averages, often over 5 minutes, but queues can overflow down at the ms level.)

We run LiveAction. It monitors QoS class, bandwidth, & interface loss. It also monitors bandwidth as well. We're polling for 5 minutes. SNMP provides the data. I had it polling for 1 minute last month. I would still see the alerts.

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages wha2tsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Well, there's lots of milliseconds within a minute.  I suspect your "low" utilization vs. drops has much to do with that.

Also, a queue depth of 64 is rather shallow for even 100 Mbps.

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