Low Latency Queueing feature not supported in input policy.

[qasimkhans8]

I have setup VOIP QoS on 3845 router and configure it on WAN inter (int fa 0/0/0) going outside. it works when there is congestion on upstream(upload), but if there is congestion on incoming traffic (download) then there is issue in voice (voice breaks). i tried to config separate class-map and policy-map for incoming (download) traffic and applied policy map on WAN inter (int fa 0/0/0) input (incoming) traffic, i get message, "Low Latency Queueing feature not supported in input policy".

is there any way i can reserve bandwidth for incoming (download) traffic for VOIP. following is my config Thanks,

1. class-map match-all ITC-Voice
2.  match protocol rtp
3. class-map match-all ITC-Voice-In
4.  match protocol rtp
6. policy-map ITC-VOIP
7.  class ITC-Voice
8. set dscp ef
9.   priority 1500
10.  class class-default
11.   fair-queue
13. policy-map ITC-VOIP-In
14.  class ITC-Voice-In
15. set dscp ef
16.   priority 1500
18. interface FastEthernet0/0/0
19.  ip address 116.x.x.x 255.255.255.248
20.  ip nbar protocol-discovery
21.  ip nat outside
22.  ip virtual-reassembly in
23.  duplex auto
24.  speed auto
25.  service-policy output ITC-VOIP

[Philip D'Ath]

You can't configure QoS so easily for inbound traffic - because you have already received it before you can do anything.

About the best you can do is, on the interfaces heading towards the inside of the network, either police or shape all non-voice traffic to something like 80% of the WAN circuit size.

The ideal solution, since this is a WAN, is the head end sending traffic into the WAN should have a QoS policy to prevent the branch router circuit from being overwhelmed.

[qasimkhans8]

i did not understand your following lines. why we cannot prioritize inbound traffic with outbound?

The ideal solution, since this is a WAN, is the head end sending traffic into the WAN should have a QoS policy to prevent the branch router circuit from being overwhelmed.

[Philip D'Ath]

You can not prioritise inbound traffic.  You receive a packet from the WAN.  It hits your interface.  And then you process it.  Because you have already received the packed now amounting processing is going to change anything to do with congestion.

However, since this is a WAN, the hub can choose the order to send the packets to the branch.  That will control the order the branch receives the packets.

[qasimkhans8]

Branch Router has its own internet and download need, how can i control it via hub router.

[Philip D'Ath]

I misunderstood when you said when you mentioned WAN.  So if this is a plain INternet connection the only thing you can do is shape or police non-voice traffic on the interface heading towards the inside of your network.

[qasimkhans8]

ok, that is solution, but why we cannot prioritize inbound traffic with outbound? what cisco says about it?

[Joseph W. Doherty]

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Posting

You can do effective QoS across the Internet, between your sites, if you don't use the same ports/links for general Internet traffic unless your ISP is willing to support egress QoS from their device towards yours (and they almost always will not).

You can try to manage ingress traffic downstream, but it often doesn't work well enough.

Many Internet connections are inexpensive enough, you obtain one for just site-to-site traffic, and the other for general Internet traffic.  (NB: if you have site-to-site traffic, you can also use another site's general internet connection.  I.e. not every site needs to have its own general Internet connection.)