DNS delegation
How m-cdn updates DNS to steer viewers — by delegating a sub-domain or by scoped write access to your own zone.
Why DNS is in the loop
DNS steering is how m-cdn places a viewer on the right CDN at connection time. To do that, m-cdn needs to update DNS records the moment the best CDN changes — which means it needs a way to write into the zone that serves your playback hostname.
Delegation (recommended)
You point one NS or CNAME record at a sub-domain that m-cdn manages. From then on m-cdn updates records inside the delegated zone directly. This works with any DNS provider, needs no credentials handed over, and keeps the blast radius to just the delegated sub-domain.
BYO zone (full control)
Alternatively you grant m-cdn scoped write access to your own zone — Route 53, Cloudflare, Google or Azure DNS, NS1, or RFC 2136. It's more setup, but the zone stays entirely yours. Either way, record TTL is the key tuning knob: a lower TTL lets m-cdn redirect viewers faster, at the cost of more DNS queries.
What DNS does and doesn't see
Delegation also reveals per-region demand via EDNS Client Subnet — useful placement and demand visibility before the first byte. That is demand only; real quality always comes from CMCD and CDN logs, never from the DNS layer.
Standards & references
- EDNS Client Subnet — RFC 7871
- RFC 2136 — dynamic DNS updates