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New Member

Time-based rate-limit - Is it possible?

I'm using ATM UBR, so no way to use traditional QOS, as UBR has 0 bandwidth regardless of the actual size of the PVC.

Rate-limit works fine, but I would like to add a time-range to it, so that, for example, WSUS gets only a small slice of bandwidth during business hours, but has full access after hours.

Any help would be greatly appreciated.

2 ACCEPTED SOLUTIONS

Accepted Solutions
Hall of Fame Super Gold

Re: Time-based rate-limit - Is it possible?

Yes, use time-based ACL. I suggest you do traffic-shaping rather than rate limiting.

Hall of Fame Super Gold

Re: Time-based rate-limit - Is it possible?

Hi, in the router, there is no thing such "true xBR".

The only thing that differentiates traffic management in a router, is the transmit priority of a VC, that have defaults according to the class of service, or you can set your own.

Of course, VBR still obeys the traffic paramenters, and the sophisticated but little used ABR, the feedback machanism.

All other classes, UBR, UBR+ and CBR, are substantially the same thing for a transmitting router.

See the white paper that I wrote when I was with Cisco:

http://www.cisco.com/en/US/tech/tk39/tk51/technologies_tech_note09186a00800c69bb.shtml

Consequently, as long you find a configuration n that allows you the wanted MQC, doesn't matter for example if one side has CBR (or UBR), and the other has VBR-rt or VBR-nrt with PCR=SCR.

Hope all that makes sense :)

12 REPLIES
Hall of Fame Super Gold

Re: Time-based rate-limit - Is it possible?

Yes, use time-based ACL. I suggest you do traffic-shaping rather than rate limiting.

New Member

Re: Time-based rate-limit - Is it possible?

Thanks very much for your response.

As I said earlier, can't use traffic shaping. UBR has 0 bandwidth available, so no way to police as you would any other interface that has bandwidth available to allocate. Rate-limit looks like my only option.

I'm proficient with time-range, rate-limit and policy-based routing, just having trouble putting them together.

New Member

Re: Time-based rate-limit - Is it possible?

I think I have it figured out. Was over-complicating it trying to tie it in with policy-based routing. For anyone interested, here's the config:

interface ATM1/0.4 point-to-point

description << DATA to Chicago >>

ip address 10.x.x.x 255.255.255.252

rate-limit output access-group 121 512000 640000 768000 conform-action transmit

exceed-action drop

pvc Chi-DATA 4/53

ubr 3044

oam-pvc manage

encapsulation aal5snap

!

!

access-list 121 permit ip host 10.a.b.c any time-range WSUS_time

!

time-range WSUS_time

periodic weekdays 6:00 to 17:00

!

Thanks again for your help.

New Member

Re: Time-based rate-limit - Is it possible?

Correction, that rate-limit command should have been this:

rate-limit output access-group 121 520000 98304 196608 conform-action transmit

exceed-action drop

Had to re-read the burst and max burst help to set them properly.

Hall of Fame Super Gold

Re: Time-based rate-limit - Is it possible?

Hi,

I recommend you use traffic shaping instead of rate limiting.

The reason is that you will be limiting bandwidth usage anyway, but the users will have best performances, due to no sudden TCP drops. Even with a burst configured on rate limiting, traffic shaping resembles more a true circuit with queuing.

One more suggestion, if you want to squeeze a bit more out of you ATM, use encap vcmux instead of snap.

New Member

Re: Time-based rate-limit - Is it possible?

Yeah, I get that, but I can't apply traffic shaping to my interface. Class-based traffic shaping requires a policy map and the router rejects any attempt to add any of the associated commands to an interface with 0 Kb bandwidth. Nothing to allocate, therefore no way to add the command.

Generic traffic shaping is also not an option, as this command is not even available on my router. It is a 3845 running 12.3(14)T Enterprise Services.

If you're aware of another way to do it, I'd be glad to hear it.

Since the goal I'm going for is to throttle WSUS, I don't care if it suffers TCP resets in the process. It can catch up or restart after hours. This isn't user or customer facing so it isn't really causing a problem except for the guy who administers WSUS and decides to push Windows updates during the day.

Thanks.

Hall of Fame Super Gold

Re: Time-based rate-limit - Is it possible?

Hi,

for example you can configure PVC as UBR+ where you have a MCR and PCR. In reality, you could also configure it as VBR-nrt w/ 0 burst, or CBR, and it would not make a difference, except that it would make cisco QoS happy and allow configuration.

The reason why you can configure any ATM service class, is that from the ATM point of view, network doesn't care how the endpoint send cells, as long PCR is never exceeded.

Hope this allows you a better QoS beside the limiting/shaping issue.

Super Bronze

Re: Time-based rate-limit - Is it possible?

Other options might be usage of CBWFQ with a hiarchal policy with parent shaper and/or using 12.4(20)T (which I think CBWFQ might handle UBR).

Hall of Fame Super Gold

Re: Time-based rate-limit - Is it possible?

From an initial point of view, one can see the logic that dictated the inability to configure QoS on UBR VC: no L2 guarantees == no L3 QoS is possible.

However, in practice we know that in most cases UBR delivers 100% of data, beside we can always trick with a configuration like the one suggested above.

So I believe that at a certain point, configuring MQC on UBR PVC became possible, but I've lost track a bit of the roadmap have to say.

New Member

Re: Time-based rate-limit - Is it possible?

Ok, so I tried configuring UBR+ and then applying the service policy to the sub interface. Still no go. The router spawns the following error:

GTS : Not supported on this interface

This circuit already has a VBR-rt for video and a CBR for voice (configured as VBR-nrt with equal SCR and PCR). The problem is that the remote router is a 3662 and doesn't support true CBR in the config (and doesn't support UBR+, either).

I guess I can change the voice PVC to true CBR at the head end (assuming this won't cause the remote to have problems), then change the UBR to VBR-nrt, also at the head end, and the normal ATM class of service should still prioritize the traffic allowing CBR the highest priority, the VBR-rt next, and the VBR-nrt last.

I'll have to wait until after hours to test this, but the voice PVC is critical, and I'm worried that having CBR configured at one end, and VBR-nrt at the other end will be a problem.

Hall of Fame Super Gold

Re: Time-based rate-limit - Is it possible?

Hi, in the router, there is no thing such "true xBR".

The only thing that differentiates traffic management in a router, is the transmit priority of a VC, that have defaults according to the class of service, or you can set your own.

Of course, VBR still obeys the traffic paramenters, and the sophisticated but little used ABR, the feedback machanism.

All other classes, UBR, UBR+ and CBR, are substantially the same thing for a transmitting router.

See the white paper that I wrote when I was with Cisco:

http://www.cisco.com/en/US/tech/tk39/tk51/technologies_tech_note09186a00800c69bb.shtml

Consequently, as long you find a configuration n that allows you the wanted MQC, doesn't matter for example if one side has CBR (or UBR), and the other has VBR-rt or VBR-nrt with PCR=SCR.

Hope all that makes sense :)

New Member

Re: Time-based rate-limit - Is it possible?

Hi, don't know if you're still watching this thread or receiving notifications, but I've found that no matter the PVC type, the router will not allow me to configure traffic shaping. I'm thinking it's an IOS issue, but don't have a test router to try it on. I'm currently running 12.3.11T Enterprise Services. Is it possible that this feature is not included until 12.4 and later?

Thanks.

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