Confirming source-routed multicast is dead on the public Internet

Tue Jul 31 22:15:47 UTC 2018

On Tue, 31 Jul 2018 at 23:29, Sean Donelan <sean at donelan.com> wrote:

> Its tought to prove a negative. I'm extremely confident the answer is yes,
> public internet multicast is not viable. I did all the google searches,
> check all the usual CAIDA and ISP sites. IP Multicast is used on private
> enterprise networks, and some ISPs use it for some closed services.
>
> I got sent back with a random comment from a senior official saying "but
> I heard different." I bit my tongue, and said I would double (now
> quadruple) check.
>
> If any ISPs have working IP source-routed multicast on the public
> Internet that I missed, or what I got wrong.  That's what content
> distribution networks (cdn's) are for instead.

AS 2914 is working to fully dismantle all its Internet multicast related
infrastructure and configs. All MSDP sessions have been turned off, we have
deny-all filters for the multicast AFI, and the RPs have been shut down.

For years we haven’t seen actual legit multicast traffic. Also the
multicast “Default-Free Zone” has always been severely partitioned. Not all
the players were peering with each other, which led to significant
complexity for any potential multicast source.

Reasoning behind turning it off is that it limits the attack surface
(multicast can bring quite some state to the core), reduces the things we
need to test and qualify, and by taking this off the RFPs we can perhaps
consider more vendors.

However, as you noted; multicast within a single administrative domain
(such as an access network distributing linear TV), or confined to
purpose-built L3VPNs very much is a thing. On the public Internet multicast
seems dead.

Kind regards,

Job