4 ms·

This seams like someone configured multicast (smart!) in the hotel but did not use multicast-aware switches or did not turn on IGMP snooping. So the switches re

This seams like someone configured multicast (smart!) in the hotel but did not use multicast-aware switches or did not turn on IGMP snooping. So the switches retrieved the package, did not know it was multicast and delivered it as broadcast to all connected endpoints. > By default, a network switch which is not configured to use IGMP will forward Multicast traffic to all switchports on the switch. Devices will be responsible for filtering out the traffic that they do not want to receive. https://service.shure.com/Service/s/article/multicast-and-igmp-in-depth?language=en_US https://service.shure.com/Service/s/article/multicast-and-ig...

richardwhiuk 6y ago
And they haven't VLAN separated whatever is playing the elevator music, which would be standard practice.
- cimnine 6y ago
  Yes. Yet maybe the switches aren't VLAN aware either. Then – as far as I understand – VLANs would not have helped here either.
  - imadethis 6y ago
    IP multicast only works over the broadcast domain, so VLANing off the speakers would work. You’d need multicast routing enabled on your routers to move multicast traffic between VLANs.
    - fulafel 6y ago
      IP multicast routing and internetworking is a thing. There used to be working one to many internet TV based on multicast in the 90s (was called Mbone). There's contemporary experimental use of routed multicast on public internets too (see eg https://meetings.internet2.edu/2019-technology-exchange/detail/10005525/ https://meetings.internet2.edu/2019-technology-exchange/deta...) edit: seems the IETF are currently in process of deprecating any-source multicast and recommending people focus on keeping single-source multicast working well in as many networks as possible: https://datatracker.ietf.org/doc/rfc8815/ https://datatracker.ietf.org/doc/rfc8815/
      - navaati 6y ago
        Oh, IP TV you get from you ISP in France today is totally multicast based ! Not on public internets tho, yes, that's limited to the ISP network.
      - rkeene2 6y ago
        I was on the local MBone segment at the NASA base (though a Navy installation) I worked at in the late 90s. It pretty much worked like you would expect, some interesting things that happened: - Multicast frames caused our FDDI switches to reboot, had to filter everywhere those were used - When setting up our local CoffeeCam, we used Multicast video stream -- this would have been accessable from anywhere (which would cause a security incident, no one can know when the Rear Admiral drinks coffee) so we were careful to monitor outbound advertisements and used a low TTL - SDR, VIC, VAT, RAT, and all those other tools for doing multicast stuff worked but were very clunky - NASA TV was broadcast over the MBone and times they would go to break in other broadcasts were continued to stream, I think various cameras were available
- iso1631 6y ago
  igmp snooping would be standard practice too
vlan0 6y ago
Even then, unless they restrict the multicast groups, all it takes is join from the client to receive the traffic.
- jandrese 6y ago
  True, but it would be difficult for a random device to discover the group in the first place if they aren't being forwarded the packets. But really, this would just add one more layer of complication that doesn't buy you anything. It's not like this is security data. This is the kind of application where keeping it simple can help the reliability.

richardwhiuk 6y ago

And they haven't VLAN separated whatever is playing the elevator music, which would be standard practice.

cimnine 6y ago
Yes. Yet maybe the switches aren't VLAN aware either. Then – as far as I understand – VLANs would not have helped here either.
- imadethis 6y ago
  IP multicast only works over the broadcast domain, so VLANing off the speakers would work. You’d need multicast routing enabled on your routers to move multicast traffic between VLANs.
  - fulafel 6y ago
    IP multicast routing and internetworking is a thing. There used to be working one to many internet TV based on multicast in the 90s (was called Mbone). There's contemporary experimental use of routed multicast on public internets too (see eg https://meetings.internet2.edu/2019-technology-exchange/detail/10005525/ https://meetings.internet2.edu/2019-technology-exchange/deta...) edit: seems the IETF are currently in process of deprecating any-source multicast and recommending people focus on keeping single-source multicast working well in as many networks as possible: https://datatracker.ietf.org/doc/rfc8815/ https://datatracker.ietf.org/doc/rfc8815/
    - navaati 6y ago
      Oh, IP TV you get from you ISP in France today is totally multicast based ! Not on public internets tho, yes, that's limited to the ISP network.
    - rkeene2 6y ago
      I was on the local MBone segment at the NASA base (though a Navy installation) I worked at in the late 90s. It pretty much worked like you would expect, some interesting things that happened: - Multicast frames caused our FDDI switches to reboot, had to filter everywhere those were used - When setting up our local CoffeeCam, we used Multicast video stream -- this would have been accessable from anywhere (which would cause a security incident, no one can know when the Rear Admiral drinks coffee) so we were careful to monitor outbound advertisements and used a low TTL - SDR, VIC, VAT, RAT, and all those other tools for doing multicast stuff worked but were very clunky - NASA TV was broadcast over the MBone and times they would go to break in other broadcasts were continued to stream, I think various cameras were available
iso1631 6y ago
igmp snooping would be standard practice too

vlan0 6y ago

Even then, unless they restrict the multicast groups, all it takes is join from the client to receive the traffic.

jandrese 6y ago
True, but it would be difficult for a random device to discover the group in the first place if they aren't being forwarded the packets. But really, this would just add one more layer of complication that doesn't buy you anything. It's not like this is security data. This is the kind of application where keeping it simple can help the reliability.