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Cisco QOS

Posted on 2012-03-19
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Last Modified: 2012-06-21
Hello, I have been asked to set up QOS on our cisco 881 router for our new phone system, and I was wondering if someone would be able to help as I’m not 100% confident is setting QOS, I understand the basic concept but I am unsure how to set it all up correctly. Any help would be greatly appreciated

Router Bandwidth is 10MB, so I’m planning on giving 50% to the phone system, unless there is a better way?

And this is what I was told required QOS
SIP (signalling) - Class 3, AF31, DSCP: 0x1A, TOS: 0x68 RTP (media) - Expedited Forwarding, EF, DSCP: 0x2E, TOS: 0xB8

So this is my start on the QOS settings

ip access-list extended PhoneSystem
 permit tcp any any range ?????

class-map match-any VoIP
match access-group name PhoneSystem

policy-map MyQoSPolicy
class VoIP
  priority percent 50
  set dscp ef

class class-default
 fair-queue

interface FastEthernet4
bandwidith 10240
 description  WAN Interface to the Internet running at 10240
 ip nbar protocol-discovery
 service-policy output MyQoSPolicy
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Question by:stephenHenderson123
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5 Comments
 
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Expert Comment

by:mat1458
ID: 37737914
You could change your class map a little:

class-map match-any VoIP
 match protocol rtp audio
 match protocol sip

That way NBAR identifies the protocols. It keeps track of the calls' source/destination ports.

How many parallel VoIP calls do you have across the Fast Ethernet 4? Do you really need 50%? Not that it is a problem but ist seems to be a lot since you use a Cisco 881.

I did not understand all your DSCP calculations, from the config I derive that you only want to protect voice and transport bearer traffic as well as signaling in the priority queue.
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Author Comment

by:stephenHenderson123
ID: 37737964
Thanks for the quick reply !!
We will probably max out at about 30 parallel VoIP calls, yes VoIP is the main traffic I want to protect, and everything else can be a free for all. Is 50% an overkill?

Updated Config below

class-map match-any VoIP
 match protocol rtp audio
 match protocol sip


policy-map MyQoSPolicy
class VoIP
  priority percent 50
  set dscp ef

class class-default
 fair-queue

interface FastEthernet4
bandwidith 10240
 description  WAN Interface to the Internet running at 10240
 ip nbar protocol-discovery
 service-policy output MyQoSPolicy
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Accepted Solution

by:
mat1458 earned 500 total points
ID: 37738007
Let's rework it a bit more:

class-map match-any VoIP-bearer
 match protocol rtp audio
class-map match-any VoIP-signaling
 match protocol sip
!
policy-map MyQoSPolicy
 class VoIP-bearer
  priority percent 40
  set dscp ef
 class VoIP-signaling
  bandwidth remaining-percent 10
  set dscp af31
 class class-default
  random-detect
  fair-queue

interface FastEthernet4
bandwidith 10240
 description  WAN Interface to the Internet running at 10240
 ip nbar protocol-discovery
 service-policy output MyQoSPolicy

I assume that you use no larger bandwidth codec than g711. That results in approx. 86Kbps per call on Ethernet. So you are fine with 4Mbps, a little growth included. Be aware that if the amount of calls and the voice bandwidth is growing the priority keyword limits the traffic to the amount you configured.
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Author Closing Comment

by:stephenHenderson123
ID: 37738069
Thanks you that's perfect!!!
I will wait to hear back about conformation about the Codec, I believe its either g711 or g711.1
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LVL 10

Expert Comment

by:mat1458
ID: 37738182
You're very welcome.
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