How to check congestion over ATM ....

Unanswered Question
Feb 20th, 2007

Hi,

We have 4 sites connected via ATM and pass VoIP across it.

Each site has a break out point for PSTN over E1s.

We are getting calls routed out the network, presumably due to network congestion.

Our ATM is at about 10% utilisation, so I am assuming it is not the problem.

How can I check on the routers / in Callmanager to find out how many calls are being passed over the ATM and at what point they should be sent outside.

Thanks,

Roy

I have this problem too.
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Paolo Bevilacqua Tue, 02/20/2007 - 05:25

One initial approach is to check if you have packet loss on the ATM network. To do that,

issue "clear counters" on all the routers at the same time. I know you can't do exactly do that at the same time, but just try to make it closer as possible, by using multiple terminals or PCs.

Let the network run one day or two, then check output of "show atm pvc". Your in/out counters should match almost exactly on the corresponding router pairs.

This said, one should look at how your router are configured and what could be triggering the CCM to route off-net.

roy_fisher Tue, 02/20/2007 - 05:31

We do get the following from Ciscoworks, but my predecessor said he was told to ignore them as it's a Ciscoworks thing not an actual problem ...

Now I'm thinking it's maybe not Ciscoworks !

EVENT ID = 0003S6C

ALERT ID = 000021Z

TIME = Tue 20-Feb-2007 09:48:45 GMT

STATUS = Active

SEVERITY = Critical

MANAGED OBJECT = hostname

MANAGED OBJECT TYPE = Routers

EVENT DESCRIPTION = HighQueueDropRate::Component=IF-hostname/1

[AT1/0] [###Cct Ref

xxxxxxxxxx###];Type=DS3;OutputPacketNoErrorRate=553.2792

PPS;DuplexMode=FULLDUPLEX;InputPacketQueueDropRate=0.0

PPS;InputPacketQueueDropPct=0.0

%;MaxSpeed=34000000;OutputPacketQueueDropPct=1.0182385

%;OutputPacketQueueDropRate=5.6916666

PPS;QueueDropThreshold=1;InputPacketNoErrorRate=522.8125

Paolo Bevilacqua Tue, 02/20/2007 - 06:27

Put Ciscoworks on the side for a moment. Log into the router and check the output of "show interface" and "show atm pvc". This will definitely tell you if there is packet drops.

If there is, you can configure QoS to prioritize traffic.

roy_fisher Tue, 02/20/2007 - 06:57

Look OK to me (though that does not count for much !)

4 sites as follows ....

Site 1

VCD / Peak Avg/Min Burst

Interface Name VPI VCI Type Encaps SC Kbps Kbps Cells Sts

1/0.1 ip 1 32 PVC SNAP VBR 23041 23041 1 UP

ATM1/0.1 is up, line protocol is up

Hardware is RS8234 ATM E3

Description: Link to WAN

Interface is unnumbered. Using address of Loopback0 (172.16.32.1)

MTU 4470 bytes, BW 15380 Kbit, DLY 200 usec,

reliability 255/255, txload 27/255, rxload 4/255

Encapsulation ATM

3693063238 packets input, 836279283496 bytes

4234968585 packets output, 2985021406173 bytes

1242098 OAM cells input, 1242059 OAM cells output

AAL5 CRC errors : 2

AAL5 SAR Timeouts : 0

AAL5 Oversized SDUs : 0

AAL5 length violation : 2

AAL5 CPI Error : 0

Last clearing of "show interface" counters never

Site 2

VCD / Peak Avg/Min Burst

Interface Name VPI VCI Type Encaps SC Kbps Kbps Cells Sts

1/0.1 ip 1 32 PVC SNAP VBR 12289 12289 1 UP

ATM1/0.1 is up, line protocol is up

Hardware is RS8234 ATM E3

Description: IPenabled PVC

Interface is unnumbered. Using address of Loopback0 (172.16.96.1)

MTU 4470 bytes, BW 8192 Kbit, DLY 200 usec,

reliability 255/255, txload 6/255, rxload 25/255

Encapsulation ATM

65698888 packets input, 48152269948 bytes

51070492 packets output, 8186070871 bytes

25607 OAM cells input, 25607 OAM cells output

AAL5 CRC errors : 0

AAL5 SAR Timeouts : 0

AAL5 Oversized SDUs : 0

AAL5 length violation : 0

AAL5 CPI Error : 0

Last clearing of "show interface" counters never

Site 3

VCD / Peak Avg/Min Burst

Interface Name VPI VCI Type Encaps SC Kbps Kbps Cells Sts

1/0.1 1 1 32 PVC SNAP VBR 12289 12289 1 UP

ATM1/0.1 is up, line protocol is up

Hardware is RS8234 ATM E3

Description: Link to WAN

Interface is unnumbered. Using address of Loopback0 (172.16.64.1)

MTU 4470 bytes, BW 8192 Kbit, DLY 200 usec,

reliability 255/255, txload 4/255, rxload 8/255

Encapsulation ATM

2461584158 packets input, 1901335110529 bytes

2109706319 packets output, 510523746062 bytes

1416854 OAM cells input, 1416844 OAM cells output

AAL5 CRC errors : 0

AAL5 SAR Timeouts : 0

AAL5 Oversized SDUs : 0

AAL5 length violation : 0

AAL5 CPI Error : 0

Last clearing of "show interface" counters never

Site 4

VCD / Peak Avg/Min Burst

Interface Name VPI VCI Type Encaps SC Kbps Kbps Cells Sts

1/0.1 1 1 32 PVC SNAP VBR 3072 3072 1 UP

CRTC01CO#

ATM1/0.1 is up, line protocol is up

Hardware is RS8234 ATM E3

Description: Link to WAN

Interface is unnumbered. Using address of Loopback0 (172.16.128.1)

MTU 4470 bytes, BW 2048 Kbit, DLY 200 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ATM

852613330 packets input, 214858179060 bytes

862469522 packets output, 226533712205 bytes

5233929 OAM cells input, 5233904 OAM cells output

AAL5 CRC errors : 0

AAL5 SAR Timeouts : 0

AAL5 Oversized SDUs : 0

AAL5 length violation : 0

AAL5 CPI Error : 0

Last clearing of "show interface" counters never

Paolo Bevilacqua Tue, 02/20/2007 - 08:54

Which platform is that? IOS used?

Please check output of show interface for the main interface. Any drop, as well queueing strategy is indicated there.

roy_fisher Tue, 02/20/2007 - 12:44

Will do, not in work tomorrow, so will post findings on Thursday.

Thanks,

Roy

roy_fisher Thu, 02/22/2007 - 03:51

How's this look to you ?

Total output drops don't look to be a huge percentage .

First two -

sh int atm 1/0

ATM1/0 is up, line protocol is up

Hardware is RS8234 ATM E3

MTU 4470 bytes, sub MTU 4470, BW 34000 Kbit, DLY 200 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ATM, loopback not set

Encapsulation(s): AAL5

1023 maximum active VCs, 1 current VCCs

VC Auto Creation Disabled.

VC idle disconnect time: 300 seconds

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 5657

Queueing strategy: Per VC Queueing

5 minute input rate 36000 bits/sec, 15 packets/sec

5 minute output rate 20000 bits/sec, 14 packets/sec

855333609 packets input, 885989034 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

865260006 packets output, 3580294569 bytes, 0 underruns

0 output errors, 0 collisions, 3 interface resets

0 output buffer failures, 0 output buffers swapped out

sh int atm 1/0

ATM1/0 is up, line protocol is up

Hardware is RS8234 ATM E3

MTU 4470 bytes, sub MTU 4470, BW 34000 Kbit, DLY 200 usec,

reliability 255/255, txload 1/255, rxload 3/255

Encapsulation ATM, loopback not set

Encapsulation(s): AAL5

1023 maximum active VCs, 1 current VCCs

VC Auto Creation Disabled.

VC idle disconnect time: 300 seconds

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters 23w5d

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 159544

Queueing strategy: Per VC Queueing

5 minute input rate 413000 bits/sec, 150 packets/sec

5 minute output rate 188000 bits/sec, 159 packets/sec

2484602076 packets input, 4076778704 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

2130796755 packets output, 3173954929 bytes, 0 underruns

0 output errors, 0 collisions, 2 interface resets

0 output buffer failures, 0 output buffers swapped out

roy_fisher Thu, 02/22/2007 - 03:52

Second two -

sh int atm 1/0

ATM1/0 is up, line protocol is up

Hardware is RS8234 ATM E3

Description: ###Cct Ref xxxxxxx ###

MTU 4470 bytes, sub MTU 4470, BW 34000 Kbit, DLY 200 usec,

reliability 255/255, txload 14/255, rxload 9/255

Encapsulation ATM, loopback not set

Encapsulation(s): AAL5

1023 maximum active VCs, 1 current VCCs

VC Auto Creation Disabled.

VC idle disconnect time: 300 seconds

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 6245796

Queueing strategy: Per VC Queueing

5 minute input rate 1309000 bits/sec, 520 packets/sec

5 minute output rate 1936000 bits/sec, 555 packets/sec

3742088962 packets input, 4139908101 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 1 throttles

0 input errors, 2 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

1939101 packets output, 3830119708 bytes, 0 underruns

0 output errors, 0 collisions, 4 interface resets

0 output buffer failures, 0 output buffers swapped out

sh int atm 1/0

ATM1/0 is up, line protocol is up

Hardware is RS8234 ATM E3

Description: ###Cct Ref IEUK###

MTU 4470 bytes, sub MTU 4470, BW 34000 Kbit, DLY 200 usec,

reliability 255/255, txload 10/255, rxload 11/255

Encapsulation ATM, loopback not set

Encapsulation(s): AAL5

1023 maximum active VCs, 1 current VCCs

VC Auto Creation Disabled.

VC idle disconnect time: 300 seconds

Last input 00:00:10, output 00:00:00, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 2401

Queueing strategy: Per VC Queueing

5 minute input rate 1519000 bits/sec, 448 packets/sec

5 minute output rate 1373000 bits/sec, 424 packets/sec

113135448 packets input, 330360174 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

87565722 packets output, 2195499762 bytes, 0 underruns

0 output errors, 0 collisions, 1 interface resets

0 output buffer failures, 0 output buffers swapped out

Paolo Bevilacqua Fri, 02/23/2007 - 19:38

Right, the drop ratio is not large and beside you have per-VC queuing, supposedly based on LLQ for media traffic, but we haven't seen that piece of your config yet. Probably just a matter of fine tuning to get the best from what is basically sane already.

roy_fisher Mon, 02/26/2007 - 00:34

One thing I have noticed in our configs -

3 sites have an interface level bandwidth statment reflecting 34Mb - then the sub-interface reflects the actual speed.

However 1 site has no interface level statment, just the correct speed on the sub-interface.

I do not believe this is a problem, but any thoughts would be appreciated.

Thanks,

Roy

Paolo Bevilacqua Mon, 02/26/2007 - 07:43

Hi Roy,

In cisco IOS the "bandwidth" stetmente is merely informative and does not affect the way router handles traffic. In case of ATM, it's VC traffic parameters and per-VC queuing that counts.

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