QOS assistance

Unanswered Question
Dec 15th, 2009

Hi All,

In the place I work we have about 8 workstations and several servers in our local network. We have a Cisco router with an ISDN connection, upload bandwidth speed is 860, behind the router is a cisco switch connected to another cisco switch by trunk port connection. We have established VPN connections with other branches through IP Sec , VoIP calls etc... The most important applications we are using is email, voip (skype, astrisk,cisco phones) , emails and ssh. Unfortunately sometimes we are experiencing some issues regarding our network traffic, the Internet connection seems to be very slow and the VoiP sound quality is very bad. I'm trying to solve this problem using QoS but I'm very new on these and that's why I need some assistance. Reading various articles regarding this subject I tried the bellow configuration but doesn't seem to make a difference.. I have a couple of questions were I couldn't find any answers on the net :

1) Is QoS applied only on Routers or Switches or both and why ?

2) If QoS will be managed by the Router on which interface side should be applied ?

     on the interface facing the Internet (ATM / Dialer ) or the users side ? 

     The service service-policy should be input or output ?

3) A real case scenario were I can test the connection before and after the QoS settings like a benchmark tool ?

Any help would be highly appreciate, bellow I have part of my configuration to be considered.


ip access-list extended iax2

permit udp any any eq 4569


class-map match-any VOIP

match protocol rtp audio

match protocol skype

match protocol sip

match protocol skinny

match access-group name iax2

class-map match-any WEB

match protocol http

match protocol imap

match protocol secure-http

match protocol ftp

match protocol smtp

match protocol pop3

class-map match-any VIDEO

match protocol rtp video

match protocol rtsp



policy-map MyPolicy

class VOIP

  priority percent 20

  set dscp ef

class WEB

  bandwidth remaining percent 70

class VIDEO

  bandwidth remaining percent 20

class class-default


interface ATM0

bandwidth 860

no ip address

ip nbar protocol-discovery

no atm ilmi-keepalive

dsl operating-mode adsl2+

service-policy output MyPolicy

#show ip interface brief

Interface                  IP-Address      OK? Method Status                Protocol

FastEthernet0              unassigned      YES unset  down                  down

FastEthernet1              unassigned      YES unset  down                  down

FastEthernet2              unassigned      YES unset  up                    up

FastEthernet3              unassigned      YES unset  up                    down

BRI0                       unassigned      YES NVRAM  administratively down down

BRI0:1                     unassigned      YES unset  administratively down down

BRI0:2                     unassigned      YES unset  administratively down down

ATM0                       unassigned      YES NVRAM  up                    up

ATM0.1                     unassigned      YES unset  up                    up

Vlan1                      x.x.x.x   YES NVRAM  up                    up

Tunnel0                   x.x.x.x    YES NVRAM  up                    up

NVI0                       unassigned      NO  unset  up                    up

Dialer0                    x.x.x.x   YES IPCP   up                    up

Virtual-Access1            unassigned      YES unset  up                    up

Virtual-Access2            unassigned      YES unset  up                    up

Tunnel1                    x.x.x.x    YES manual up                    up

Tunnel2                    x.x.x.x    YES manual up                    up

I have this problem too.
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Marwan ALshawi Sun, 12/20/2009 - 17:34

to answer your questions:

1. the Qos works end to end what i mean end to end is that your traffic must be marked by the end device or your lan switch then based on that marking your router will be able to distinguish the type of traffic and give it different treatment accordingly

however in you case you are using NBAR for traffic calcification which use L3 - L7 traffic recognition builtin in the IOS

for example when you say match rtp audio this will look on udp port ranges 16383 to 32767 and  so on

in other words if you need qos on your switch you will need it for marking re marking traffic

in your router you will need the Qos policy for traffic prioritizations

for example VOIP will be in LLQ with priority command which means VOIP traffic will be serviced first in case of congestion

traffic class configured with bandwidth command will have a garnteed bandwidth in the event of interface congestion but do not serviced first like LLQ

2. as i mentioned above the router will control your qos policies for LLQ or CBWFQ and so on

in the router you can not use a policy map in the input direction with queuing commands like priority or bandwidth because this is not Handeled first by the software queue

however in the input direction you can police you traffic limit it to certain amount of bandwidth

in your case you need it output direction to use the queuing mechanisms

and it need to be on the WAN output interface

3. i would recommend you after applying the qos do the folioing show command and see if your traffic is mark or using your policy or not

show policy-map int [the interface where your policy applied]

you can see all the classes and you can see how much traffic matched or droped in each class

also if you can see if the number of traffic under one of the classes still 0 this mean either the marking incorrect or no traffic in that class

good luck

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