Halo MCC Network Ports

[Seraph]

Hello 343 community!

Yesterday, I noticed my Xbox One is communicating outbound on UDP port 4379 to a couple of IP address beginning 51.x.x.x whilst playing multiplayer Halo MCC (after running a who.is this/these IP addresses appear to be owned/registered by Microsoft)
Nothing too surprising here, other than this port appears to be undocumented on the official list of ports used by xbox network and I couldn't find a reference for this port from 343 either.
https://support.xbox.com/en-US/help/hardware-network/connect-network/network-ports-used-xbox-live

Also worth noting, I can easily replicate this after turning the xbox off and on again and starting another matchmaking session.

Out of pure curiosity I decided to create a port forward for UDP  port 4379 to my Xbox One to allow inbound connections.

Whilst playing Halo MCC multiplayer matchmaking I started to see traffic on IPv4 and IPv6 port UDP 3479 hitting my Xbox, so clearly it is used for something inbound too!

As this appears to be undocumented, I would love for somebody to explain what this is for so I and the rest of us can configure our firewalls accordingly :)

Thanks.