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Community Member

Question on Auto QOS

we know that after issue Auto QOS command on router, it  will perform a number of tasks which includes:

1, Classify the IP traffic with RTP and audio codec payload type (RFC 1890) as VoIP bearer traffic.
2, Mark VoIP bearer traffic with DSCP EF and VoIP signaling (control) traffic as AF31.
3, Map the Layer 3 marking to the corresponding Layer 2 marking if applicable.
4, Remark traffic that is marked DSCP EF or AF31 to DSCP 0 if the traffic is not classified as VoIP bearer or signaling (control) traffic.
5, Treat all other non-VoIP traffic types as best effort QoS (excluding control traffic such as routing protocol updates and BPDUs).
6, Put VoIP bearer traffic into a strict priority LLQ with guaranteed bandwidth to accommodate voice traffic.
7, Put VoIP control traffic into a non-priority queue with a minimum bandwidth guarantee to ensure no packet loss.
8, Enable LFI and compressed RTP (cRTP) for link speeds of less than 768 kbps.

but when I check on the router after issue the auto qos command I do not find any class map try to classify the RTP or control signal. I was expecting to see such as class-map RTP,  match protocol RTP;  policy-map RTP-VOICE, class RTP set dscp ef... etc... instead I see the following:

class-map match-any AutoQoS-VoIP-RTP-Trust
  match ip dscp ef
!
class-map match-any AutoQoS-VoIP-Control-Trust
  match ip dscp cs3
  match ip dscp af31

without mark those packet with DSCP value at first place, how to match it.  I can understand that some packet from switch might has COS value attached, but what about the traffic orignated from local router such as H323 singalling, if this is H323 Gateway.   any suggestion?

1 ACCEPTED SOLUTION

Accepted Solutions
Green

Question on Auto QOS

Hi,

This is correct for AUTO-QOS

class-map match-any AutoQoS-VoIP-RTP-Trust
  match ip dscp ef  -------- This is matching Cisco RTP
!
class-map match-any AutoQoS-VoIP-Control-Trust
  match ip dscp cs3 ----- Thes 2 are matching Cisco phones Signalling set by the CUCM or the CUCME
  match ip dscp af31

For H323 you have ensure that the QOS is set on your dial peers that use VOIP

E.G.

!

dial-peer voice 11 voip

description *** VOIP DP TO CUCM SUB 1 ***

preference 1

destination-pattern 7.....

voice-class codec 1

voice-class h323 1

session target ipv4:172.16.16.16

incoming called-number .

dtmf-relay h245-alphanumeric

ip qos dscp cs3 signaling

ip qos dscp ef media

no vad

!

This would be the same for a SIP dial peer with the addition of

!

dial-peer voice 11 voip

session protocol sipv2

For MGCP you mark the MGCP protocol as follows

!

mgcp

mgcp ip qos dscp ef media

mgcp ip qos dscp cs3 sig

!

HTH

Alex

Please rate useful posts

Regards, Alex. Please rate useful posts.
2 REPLIES
Green

Question on Auto QOS

Hi,

This is correct for AUTO-QOS

class-map match-any AutoQoS-VoIP-RTP-Trust
  match ip dscp ef  -------- This is matching Cisco RTP
!
class-map match-any AutoQoS-VoIP-Control-Trust
  match ip dscp cs3 ----- Thes 2 are matching Cisco phones Signalling set by the CUCM or the CUCME
  match ip dscp af31

For H323 you have ensure that the QOS is set on your dial peers that use VOIP

E.G.

!

dial-peer voice 11 voip

description *** VOIP DP TO CUCM SUB 1 ***

preference 1

destination-pattern 7.....

voice-class codec 1

voice-class h323 1

session target ipv4:172.16.16.16

incoming called-number .

dtmf-relay h245-alphanumeric

ip qos dscp cs3 signaling

ip qos dscp ef media

no vad

!

This would be the same for a SIP dial peer with the addition of

!

dial-peer voice 11 voip

session protocol sipv2

For MGCP you mark the MGCP protocol as follows

!

mgcp

mgcp ip qos dscp ef media

mgcp ip qos dscp cs3 sig

!

HTH

Alex

Please rate useful posts

Regards, Alex. Please rate useful posts.
Community Member

Question on Auto QOS

thanks Alex !

you are correct,  the RTP and control signal protocol from other source such as phone will be matched with the auto qos,  and DSCP value for signalling traffic such as H323 generated locally can be changed via dial peer.

FYI,   I have just found out that " All voice packets on the routers are marked by default (this can be overridden by the dial peer), signaling with AF31 and media with EF. Calls that match the default dial peer 0 should also have this behavior."  I have tested on the wireshark, it is corrected.

click the link for more details:

http://www.cisco.com/en/US/tech/tk652/tk90/technologies_tech_note09186a008010fed1.shtml

once again thanks for your prompt reply, cheers

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