Ever wondered how rate limits on Distribution Points in ConfigMgr 2012 work? When I one day accidentally updated all the distribution points at a customer site it was time to learn quickly.
There are three modes for rate limits and these are set per Distribution Point. Unlimited sending is self-explainatory, but the pulse mode and the option to limit specific maximum transfer rates per hour are useful in different scenarios.
I´ll explain the limited to specified maximum transfer rates by hour option first, since it was what helped me quickly in my scenario. First of all, there is no native ConfigMgr support for BITS when distributing content to Distribution Points, therefore, ConfigMgr does not monitor the traffic and/or the amount of data going over the link. Instead, it uses the time available for sending and divides the time into time slots where it sends 100% of data. So, for instance, if you use the option to use only 50% of bandwidth during work hours (ie 8AM to 4PM), it will divide the amount of available time into time slots and send 100% of data 50% of the time, and send 0% data the other 50% of the time. This is useful if you don´t want to clog the available bandwidth on the network during work hours or if you need to limit the transfers for some other reason. This can be set per hour for every day, but unfortunately you can´t set it for specific days (as you sort of could in Configuration Manager 2007).
It is also possible to use pulse mode, in which case you can specify the size of the data blocks sent by the site system to the distribution point and a delay in seconds for how often these blocks should be sent. This is useful if you have slow links to your distribution points, but it requires you to calculate how much data is sent. If you set it too low your packages will never be distributed, if you set it too high it will still clog your bandwidth. Notice that these are radio buttons, so you can only choose one option at a time for one specific Distribution Point.
As you can see in my example I set it to transfer only 50% during working hours for all my distribution points, and I immediately saw the effect on my site servers bandwidth.
It is also possible to use the Schedule option on your Distribution Point to restrict what kind of traffic can be sent during different hours of the day. This applies to the priority of content, so say that you have software update packages that you know you want to distribute but everything else can wait. If you set your software update packages to high priority and everything else at medium, then you can effectively block medium priority content from being distributed but let high priority content get distributed by selecting the option Allow high priority only.
You can read more about the different distribution point settings in the Configuration Manager Document Library.