Qos on 2Mbit link

Unanswered Question
Jun 28th, 2010

Helo,

From our branch office , we have 2 Mbit mpls  link to our head office (10Mbit).

Those 2 Mbit are guaranted for inbound and outbound connections together.

So when Total input and output rate is >2Mbit then congestion occure.

       LAN  ----------   fa0    Branch office  fa1 --------MPLS-------------    Head office  ------ LAN

I have service-policy output Shaper configured on my fa0 interface.

Interface fa0 is shaped to 2Mbit, when output traffic on fa0 will override 2Mbit then service-policy  qos-in get in action.

But situation like that will never happen, because it will be always some input traffic.

For example when we have 0,5Mbit input traffic on interface fa0 and 1,5Mbit output traffic then congestion ocure but service-policy qos-in will never starts(until output traffic >2Mbit).

I would like to execute service-policy qos-in on int fa0 when overall bandwidth (input+output) override 2Mbit.

But I dont have any ID how. Please for help.

Any ideas?

Here is my current config:

class-map match-any voip
match access-group name qos-voip
class-map match-any mail
match access-group name qos-mail
class-map match-any oracle
match access-group name qos-oracle
class-map match-any internet
match access-group name qos-internet
class-map match-any other
match access-group name qos-other
class-map match-any monitor
match access-group name monitor
class-map match-any admin
match access-group name qos-admin
!
!
policy-map qos-in
class voip
  priority percent 20
class poczta
  bandwidth remaining percent 10
class oracle
  bandwidth remaining percent 60
class internet
  bandwidth remaining percent 10
class admin
  bandwidth remaining percent 10
class other
  bandwidth remaining percent 5
class class-default
  bandwidth remaining percent 5
policy-map Shaper
class class-default
  shape average 2000000
  service-policy qos-in

interface FastEthernet0
ip address 192.168.10.1 255.255.255.0
speed auto
service-policy output Shaper


I have this problem too.
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djh278778 Mon, 06/28/2010 - 09:12

Hello,

If your topology is written correctly, it appears that your service policy is on the wrong interface. It should be applied to the outbound direction of the fa1 interface. Traffic inbound to your branch is only coming in at 2Mbit (controlled by your ISP) so there is no need to shape it outbound to your LAN. The only place where I can see a bottle-neck and therefore the potential for congestion is outbound on the interface that faces the MPLS cloud.

Rafal Grabowski Tue, 06/29/2010 - 00:35

Yeah I know that my inbound traffic is only comming ayt ~2Mbit but it's not a point.

The point is that I have to reserve some bandwidth for voip , mission-critical apllication etc. for inbound traffic.

Several times we had situations where sombody in our branch was downloading files from our File server localized at main office.

Without service-policy this one session can fill 100% of bandwith (2Mbit), so there in no more bandwidth for voip and other important services.

My Service-policy qos-in is used to guarantee that each configured traffic class  has a minimal level of bandwidth, thereby preventing starvation for each  configured class of traffic.Physical interface fa0 has 100Mbit, but traffic inbound to my branch is only comming in at max 2Mbit so congestion never occure and policy-map qos-in will not start working.

Congestion management describes how a router or  switch handles each configured class of traffic during times of congestion. If  there is no congestion on the router or switch for that period in time,  congestion management does not come into play. That's why I use policy-map Shaper which main duty is to shape traffic to 2Mbit and let service-policy qos-in doing the rest. That's work if there is no outbound traffic. If there is 0,5 Mbit outbound traffic, inbound traffic can have only 1,5Mbit of bandwidth. Even if I set :

policy-map Shaper

class class-default

  shape average 1500000    //1,5Mbit

  service-policy qos-in

if outbound traffic will be at level >0,5Mbit for example 0,7 Mbit then inbound traffic can have only 1,3Mbit so service-policy qos-in doesn't come into play.

What is the better way to assign bandwidth for important services in such situation?

Tharak Abraham Tue, 06/29/2010 - 01:18

Rafal,

Could you please change the bandwidth of the the Fast Ethernet interface to 2 Mbps manually using the bandwidth command ?

say "bandwidth 2000".

You might have to configure the other end as well if set for auto-neg if its a Switch.

mlund Tue, 06/29/2010 - 04:25

Hi Rafal

I have never heard of a serviceprovider that offers a 2Mlink that counts in both direction. Normally you have 2M in each direction at the same time.

However if this is how it is, You have only one solution. You have to decide what bandwith You want in each direction.

For example, You can choose 1M for each, or maybe 1,2M from headoffice to branch and 0,8 from branch to headoffice, or whatever You decide.

For example if You chose 1,3M to branch then 0,7M to headoffice, it will look like this.

Branchrouter:

fa1 interface must be used because this interface is heading the mpls-cloud towards headoffice.

policy-map shaper

class class-default
  shape average 700000
  service-policy qos-in

interface fastethernet1

service-policy output shaper

In the headoffice router You have to limit the traffic to 1,3M also. This way You can be shure not to overload the link

Headofficerouter:

policy-map Branch-shaper

class class-default
  shape average 1300000
  service-policy qos-in

interface < outputinterface towards mpls-cloud >

service-policy output Branch-shaper

/Mikael

djh278778 Tue, 06/29/2010 - 13:38

Rafal,

I see now what you are trying to do. I misunderstood before and I think it is a great question. I dont know all the details of your end to end network but from what I see, I think that if you want to prioritize Voip etc. coming into your branch LAN, that you should do it from the outbound side of the MPLS facing head office interface. You can also have QOS controlled within the MPLS cloud by your provider depending on your arrangement with them. Unless there is more to your network than you have provided, this method should work fine without the need to shape on your LAN just to create back-pressure. I would still shape on the MPLS facing interfaces as well though.

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