I think there is an error or at least a misleading statement in the documentation for Distribution Points.
The documentation says that the DPs with the package are sorted according to an algorythm. This includes how near the DP is to the client in a network map. Whether the DP is in the same AD site as the client or not, and whether the DP has BITS enabled
or not. The documentation calls this ranking a "sorting category." It allows for multiple DPs to have the same sorting category. The documentation states "Within each sorting category, the order of distribution points is nondeterministic,
which provides a level of load-balancing for the servers." This is incorrect. When multiple DPs have the same "sorting category" in relation to a group of clients, all clients will access the package from the same DP and no load balancing occurs. The
DP list appears to be provided in alphabetical order withing the same sorting rank, and the client chooses the first DP listed alphabetically - not randomly or non-deterministically.
For example. Take 3 identical clients on a single subnet and three identically configured DPs on a second subnet (all BITS enabled, same AD site, etc.). When the client requests the list of DPs for a package, AD will return the same
list in the same order to all three clients. The clients will choose the DP that is first on the list. All three clients will get the package from the same DP - the first one listed. The documentation suggests that when all DPs have the same
ranking, that the order of the DPs sent to the client is non-deterministic and that the clients will load balance across same ranked DPs. This is not the case. All the load will be on the first listed DP. All clients will get the package
from the same DP. The only reason a client would go to DP #2 is if DP#1 is not available. There is no level of load balancing provided as stated in the documentation unless it is refering to something akin to failover clustering and not load balancing.
I view load balancing to mean that the load is spread out somewhat equally among several DP resources. This is not how DP selection works.
What the documentation says at
http://technet.microsoft.com/en-us/library/bb632366.aspx
Within each sorting category, the order of distribution points is nondeterministic, which provides a level of load-balancing for the servers. So, a client would attempt to connect to any of the distribution points that are enabled with the option
Allow clients to transfer content from this distribution point using BITS, HTTP, and HTTPS on the same IP subnet as the client, and then attempt to connect to any of the distribution points that are not enabled with this option when they are
on the same IP subnet as the client.
Internet-Based Distribution Points
When the client is being managed over the Internet, and requesting content from a site configured for Internet-based client management, all Internet-based distribution points in that site will be returned to the client if they contain the content requested
by the client.
In this scenario, distribution points must be configured with the option
Allow clients to transfer content from this distribution point using BITS, HTTP, and HTTPS, and the selection of a distribution point by the client is nondeterministic.
