Re: [manet-dlep-rg] DLEP multicast address

[Teco Boot <[e-mail]>]

Op 13 nov. 2013, om 21:08 heeft Stan Ratliff (sratliff) <[e-mail]> het volgende geschreven:

> +1. Henning's right; there's no need to go to the IEEE, IMO… 
> 
> Seems like the issue for us is how to scope discovery. Is it
> 
> (a) a single-hop operation, exploiting link-local MCAST, or 
> (b) a potentially multi-hop operation, utilizing some sort of site-local or other MCAST technique/address?
> 
> I'm leaning to making it link-local (1-hop) myself. Note that does *NOT* preclude multi-hop DLEP operation over a TCP socket; it just means that multi-hop DLEP sessions would rely on a-priori configuration. There are *lots* of other issues that are going to confound, confuse, and otherwise screw-up multi-hop DLEP… ;-) Given the amount of characters typed over lesser issues, I don't know how far we want to go into multi-hop DLEP at this juncture. Suffice it to say my position is to write the spec in such a way as to avoid *precluding* it, but not to attempt to describe it. Multi-hop DLEP *can* work, given a careful network design (including a careful addressing policy). But I do not believe it will "generalize" down to something that warrants a section in the spec.  

I think you mix up multi-hop L2 and multi-hop L3.

Teco


> 
> Stan
> 
> On Nov 13, 2013, at 2:45 PM, Henning Rogge <[e-mail]> wrote:
> 
>> Why should we need to ask IEEE? Just use the standard IP mac addresses
>> for the linklocal IPs.
>> 
>> The Modem can filter them based on IP content out of the bridge.
>> Henning Rogge
>> 
>> On Wed, Nov 13, 2013 at 7:31 PM, Teco Boot <[e-mail]> wrote:
>>> 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
>> 
>> 
>> 
>> -- 
>> We began as wanderers, and we are wanderers still. We have lingered
>> long enough on the shores of the cosmic ocean. We are ready at last to
>> set sail for the stars - Carl Sagan
> 
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