08-18-2009 11:05 PM - edited 03-06-2019 07:18 AM
Hi,
I would like to confirm if I have a policy-map as shown below and if the voice traffic has reached 19 percent of the bandwidth and there is additional voice traffic coming in, these access voice traffic would be dropped isn't it ?
policy-map TEST
class VOIP_Signalling
set dscp af31
bandwidth percent 6
class VOIP_RTP
priority percent 19
set dscp ef
class DEFAULT
set dscp default
Pls advice,
Regards,
InternetB.
Solved! Go to Solution.
08-18-2009 11:36 PM
Hello,
Yes - your VOIP_RTP class is both guaranteed to receive 19% of the bandwidth, and at the same time, it is policed to the same amount. No more than 19% of the interface bandwidth may be used by the VOIP_RTP class and the exceeding traffic will be dropped.
Best regards,
Peter
08-18-2009 11:36 PM
Hello,
Yes - your VOIP_RTP class is both guaranteed to receive 19% of the bandwidth, and at the same time, it is policed to the same amount. No more than 19% of the interface bandwidth may be used by the VOIP_RTP class and the exceeding traffic will be dropped.
Best regards,
Peter
08-19-2009 02:21 AM
"I would like to confirm if I have a policy-map as shown below and if the voice traffic has reached 19 percent of the bandwidth and there is additional voice traffic coming in, these access voice traffic would be dropped isn't it ? "
Not always. The implicit policer only activates when the LLQ contains packets. So it's possible to have LLQ traffic beyond the implicit policed value if there's no congestion. For example, you could have 50% LLQ traffic with another 20% other traffic even with your policy. If you need to guarantee that the LLQ traffic won't ever exceed a certain bandwidth %, you need to add an explicit policer.
08-19-2009 02:53 AM
Joseph,
Thanks again! I'm not sure if these things are written in books. You've obviously got large experiences with the QoS on Cisco boxes. Hat off.
Best regards,
Peter
08-19-2009 03:30 AM
Peter,
This information, I believe, is Cisco documented, but you really have to dig to find it. Actually, if I remember correctly, I thought the same as you until someone else documented this on these forums (where I also find other interesting tidbits from time to time). I then confirmed it by searching Cisco documentation, although I've never actually tested it in a lab.
You're correct, I do have lots of experience with QoS on Cisco boxes and QoS knowledge in general, as I'm often involved in obtaining best network performance across WANs.
Cisco documentation is probably the best, by far, put out by any network vendor. Although, you sometimes have to wade through more than just their primary QoS docs, such as their whitepapers, technotes, and troubleshooting papers. If you do that, you do learn much about what Cisco platforms support, although even then there are some gaps. (I've thought the additional QoS features available on the old 7500s or the FlexWANs or the SIP-200/400 were not really highlighted well. Pretty nice features, as is the new HQF starting with 12.4.20T.)
Again, though, even with all the above, I believe I too discovered this tidbit on these forums.
08-19-2009 04:05 AM
Joseph,
It's great to have you here.
Best regards,
Peter
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