Rate Limiting for Microsoft Robocopy

[rmujeeb81]

Hello All,

We have a requirement to limit traffic to 1 Mbps on WAN links based on a specific source & destination ip address pair. The purpose is to limit the rate to 1 Mbps for a copy operation between a server and client over the WAN. Microsoft Robocopy is being used for copying data which I believe is a TCP based application. Now I need your advice that what could be the best possible solution here for e.g CAR or MQC policing etc ? Keeping in consideration that we need to avoid too many packet drops , our goal is just to limit the bandwith utilization for this specific data copy operation between client and server. As we know TCP is having builtin mechanism to adjust window size so what could be the best possible solution without having too many packet drops and TCP synchronization.

Thanks in Advance.

[Peter Paluch]

Hello,

As for the configuration, the MQC is the standard now so I would suggest using that to accomplish your task. Please note that the MQC is not a particular QoS mechanism; rather, it is only a specific style of configuring and orchestrating the diverse QoS tools.

Regarding your need, I would personally suggest using shaping to limit the traffic bandwidth to 1Mbps for your application. The shaping will allow the excess packets to be buffered rather than dropped. Also, to prevent the TCP from being too aggressive and potentially overfilling your router egress queue and resulting in packet drops, I suggest deploying the RED/WRED to throttle down the TCP flow should it become too greedy.

Also, if that is possible, I would suggest looking into activating the ECN (Explicit Congestion Notification) in the TCP/IP driver of your Windows workstations, and then using ECN-based WRED. The ECN-based WRED will mark packets as being excessive instead of dropping them, and the end applications will react as if the packet was lost by slowing down the transmission rate.

My two cents on this... I hope other friends here having their extensive share of experiences in QoS will share their views as well!

Best regards,

Peter

[rmujeeb81]

Hi,

Actually I have ONLY option to apply QoS at client side not server side. So I can apply policy on WAN router where client sits and I believe traffic shaping can not be configured inbound ?

Regards,

[Peter Paluch]

Hi,

You are right, the shaping can be configured only on an egress port because it requires a buffer to store the excess packets. But I am afraid I cannot help you further right now because I am not sure what is the topology of your network, where are the endpoints located, what is the direction of the flow you want to control, and where is the device located that you want to configure the QoS tools on. Can you provide a simple drawing visualizing this information? Thank you!

Best regards,

Peter

[rmujeeb81]

Hi Peter,

Topology is simple, let me try to elaborate,

Server---Switch----WAN Router 1<---------------------------> WAN Router 2 -----Switch-----Client

client and server are placed at two different locations and both sites are connected through a 4 Mbps IP VPN link. client needs to copy some data from server on daily basis and we want to limit that data transfer ( from server to client ) at WAN Router 2 to 1 Mbps. The traffic flow would be from WAN Router 1 towards WAN Router 2 and we can only change configuration on WAN Router 2 so only option is to configure some QoS feature inbound to WAN Router 2 in order to limit the traffic for this particular operation to 1 Mbps.

Thanks

[jack01reacher]

Hello, when I try to use Robocopy in a batch file to copy from a directory from C drive to my CIFS share, I get "error 5" stating that it can't issue the time-stamp.
Are there any suggestions?

Thanks for your time.

[dannydan]

Perhaps using some other tool like GS Rich Copy 360 would be a good solution as you can have multiple threads (upto 256) and can also schedule the tasks. That way it'll make sure that no packages are dropped and the overall performance will also be increased.

[nicoooolllsssmartin]

That's because RoboCopy doesn't have the time stamp copying feature (and not sure when they are going to update their software with this feature). Try using GS Rich Copy 360. It can copy timestamp and has a file scheduling feature as a bonus, too!