I've just installed a WSUS onto our network, and I'm currently doing the initial sync. I've found that WSUS does not seem to be talking to an Akamai cache, but rather with MS directly. This is contrary to what I've always thought regarding Windows Update traffic.

Tcpdump of our WSUS server doing initial sync... As you can see it's speaking with 65.55.194.221. For me to speak to this IP, I have to go over international transit links. Which is of course not ideal.

8:42:31.279757 IP 65.55.194.221.https > XXXX.XXXX.XXXX.XXXX.50888: Flags [.], seq 4379374:4380834, ack 289611, win 256, length 1460
18:42:31.279759 IP 65.55.194.221.https > XXXX.XXXX.XXXX.XXXX.50888: Flags [.], seq 4380834:4382294, ack 289611, win 256, length 1460
18:42:31.279762 IP 65.55.194.221.https > XXXX.XXXX.XXXX.XXXX.50888: Flags [.], seq 4382294:4383754, ack 289611, win 256, length 1460
18:42:31.279764 IP 65.55.194.221.https > XXXX.XXXX.XXXX.XXXX.50888: Flags [P.], seq 4383754:4384144, ack 289611, win 256, length 390
18:42:31.279793 IP XXXX.XXXX.XXXX.XXXX.50888 > 65.55.194.221.https: Flags [.], ack 4369154, win 23884, length 0
18:42:31.279888 IP XXXX.XXXX.XXXX.XXXX.50888 > 65.55.194.221.https: Flags [.], ack 4377914, win 23884, length 0
18:42:31.280015 IP XXXX.XXXX.XXXX.XXXX.50888 > 65.55.194.221.https: Flags [.], ack 4384144, win 23884, length 0

And yet, if I ping download.windowsupdate.com it seems to resolve to a local (national) Akamai node, just fine:

root@some-node:~# ping download.windowsupdate.com
PING a26.ms.akamai.net (210.9.88.48) 56(84) bytes of data.
64 bytes from a210-9-88-48.deploy.akamaitechnologies.com (210.9.88.48): icmp_req=1 ttl=59 time=1.02 ms
64 bytes from a210-9-88-48.deploy.akamaitechnologies.com (210.9.88.48): icmp_req=2 ttl=59 time=1.10 ms

Why is this? And how can I change that (if possible)? I know that I can manually specify a WSUS source to sync with instead of pick the default MS Update like I currently have... But it seems like I shouldn't have to do this.

NOTE: I've haven't confirmed if a WUA speaks with Akamai, just looking at WSUS as all WUAs will use our internal WSUS from now on.

We'll be looking to join an IX shortly with the hopes of peering with an Akamai cache and have very fast access to Windows Updates. Before I let this drive my motivations for an IX at all I want to first confirm it's actually possible for WSUS to speak with an Akamai cache.

I know this is somewhat networking related, but I feel like it has more to do with WSUS than anything, so someone who knows WSUS better than me will likely be able to figure this out.