[manet-dlep-rg] DLEP multicast address

[Teco Boot <[e-mail]>]

Changed subject.

Op 13 nov. 2013, om 17:37 heeft Taylor, Rick <[e-mail]> het volgende geschreven:
> 
>> 
>> Sending the multicast from router to modem (and having the TCP server on
>> router) adds some complexity on the modem, in that this multicast packet
>> shall not be forwarded over the modem link (e.g. RF path). Cannot be done
>> with L2 MAC filter, as this would block a set of multicast addresses. The
>> filter has to block the assigned IANA DLEP multicast address.
>> LLDP better fits our requirement for discovery. It doesn't take away the
>> need for the multicast Peer_Discovery. On the other hand, LLDP is not
>> widely implemented, I think. And would be bridged on modems that doesn't
>> support it.
> 
> I agree, but I imagined Peer_Discovery being link-local multicast/broadcast.  You are right that a multi-hop scoped multicast is a nightmare.

Link-local is not sufficient. We need L2-link-local multicast address. We have to go to IEEE802 to allocate such. Even then, it takes ages to get it implemented.

The best we can do is specify the modem MUST NOT forward the DLEP link-local multicast packets to the link to the remote nodes. If the modem has an ethernet bridge function (as devices I have), this DLEP link-local multicast filter MUST NOT be implemented on the ethernet ports.

I’m still puzzled how it can work with cascaded devices, for example to connect a satcom system somewhere further away from the router using an Ethernet extender. Maybe use DLEP link-local for the local attached device and configure something on router (keep the satcom modem a dummy device) to reach the satcom modem with a unicast Peer_Discovery.


> 
> And yes, perhaps we should be using mDNS/Bonjour for discovery rather than re-inventing the wheel here.

Not these ones. These shall be forwarded to remote nodes, to keep existing stuff going.


> 
> Should we put in some text: "Unless there is an alternative discovery protocol in use, such as a-priori static configuration or mDNS, then Peer_Discovery messages SHOULD be sent every X seconds to the link-local multicast address”

Or:
The Router SHOULD send Peer_Discovery messages every Peer_Discovery_Interval seconds to the DLEP assigned link-local multicast address on DLEP enabled interfaces. Alternative mechanism may be used, such as a-priori static configuration or alternative discovery protocol.
The Modem initiates a DLEP TCP connection on reception and successful validation of a DLEP Peer_Discovery message, either received with a DLEP assigned link-local multicast address or on a Modem configured unicast address.

This unicast Peer_Discovery packet is a disadvantage of having TCP server on the router. If one finds an improvement, I’m all ears.


Teco