05-07-2007 12:09 AM - last edited on 03-25-2019 03:15 PM by ciscomoderator
Hi to all,
I have some questions about LLQ on ATM PVCs.
The config output is from the CPE (Cisco 878):
controller DSL 0
mode atm
line-term cpe
line-mode 2-wire line-zero
dsl-mode shdsl symmetric annex B
line-rate auto
interface ATM0
bandwidth 1536
no ip address
load-interval 30
no atm ilmi-keepalive
max-reserved-bandwidth 100
!
interface ATM0.100 point-to-point
bandwidth 1280
ip address 172.16.1.1 255.255.255.0
pvc 8/80
protocol ip 172.16.1.254
ubr 1536
encapsulation aal5snap
service-policy output QOS_VOIP
max-reserved-bandwidth 75
I there possible, that it do not work on UBR connections.
Howewer it seems that works:
HOST#sh policy-map interface
ATM0.100: VC 8/80 -
Service-policy output: QOS_VOIP
Class-map: VOIP (match-all)
18769209 packets, 1317687321 bytes
30 second offered rate 0 bps, drop rate 0 bps
Match: access-group 100
Queueing
Strict Priority
Output Queue: Conversation 72
Bandwidth 384 (kbps) Burst 9600 (Bytes)
(pkts matched/bytes matched) 18769210/1317687404
(total drops/bytes drops) 0/0
Class-map: class-default (match-any)
34018060 packets, 12074991095 bytes
30 second offered rate 40000 bps, drop rate 0 bps
Match: any
Queueing
Flow Based Fair Queueing
Maximum Number of Hashed Queues 64
(total queued/total drops/no-buffer drops) 0/271/0
Has anyone a Link of how configure LLQ on ATM PVCs?
Regards,
Thomas
05-07-2007 01:27 AM
Hi,
it seems configured correctly, but UBR 1536 does not give a chance to the service policy to kick in - there is no congestion to do so.
You should find the real value of the upstream PVC and test in presence of congestion.
UBR or other service category should not make a difference.
Hope this helps, please rate all useful posts using the scrollbox below!
05-07-2007 02:35 AM
Hi,
the "real upstream" is 1536 ATM (1280 kbit/s real IP traffic without ATM overhead).
The line is G.SHDSL symmetric.
The CIR is a weightless factor , because the ATM Net is ours, and there is no congestion.
What do you mean about this?..
Regards,
Thomas
05-07-2007 02:51 AM
Hi,
LLQ, like any other priority mechanism, will start working only when there is congestion (backpressure). When there is no congestion, packets are sent out immediately and never queued.
So to test if your QoS is working, you need to generate congestion and verify that voice has no issues, eg you can look at the codec jetter statistics available on the router, etc.
Note: the command
protocol ip 172.16.1.254
is not necessary on point-to-point subinterfaces.
Hope this helps, please rate post if it does!
05-07-2007 04:31 AM
Hi,
I think "Queueing Strict Priority" shows that LLQ is already working.
Regards,
Akhtar
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