Subject: [manet] DLEP Draft 7 Router Initiate Peer Discovery

From: "Cheng, Bow-Nan - 0665 - MITLL" <[email-masked]>
Date: Wed, 24 Dec 2014 15:56:29 +0000

Hi all,

I’ve been a little out of the loop on DLEP recently and looked at Draft 7. One thing I was confused about was the change from Modem initiated peer discovery to Router initiated peer discovery and was wondering what the rational was for the change?

In the past when we’ve operated DLEP, we always had the assumption that 1 DLEP Router/server process could support multiple DLEP modem/client connections off the same Ethernet VLAN (or bridged interface as we were operating it). In this case, it made sense for the modem to initiate the peer discovery because at any time, another modem/radio could be “turned on” and “discover” the DLEP router and initiate a new connection. How would this work with the router initiating the peer discovery? Would the router need to periodically initiate peer discovery so modems that “turn on” can find it? Would this mess up normal DLEP session flow?

Is the implicit assumption now that 1 DLEP router/server process will connect to only 1 DLEP modem/client process? So then, each modem/router would essentially need to be on its own interface or subnet and you would need some sort of virtual interface to gang them all up to the router. In this case, I can understand having the router initiate peer discovery. Maybe I’m missing something.

Any clarification would be of great help. Thanks!!

-Bow-Nan

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From: Henning Rogge <[email-masked]>
Date: Thu, 25 Dec 2014 22:04:17 +0100

On Wed, Dec 24, 2014 at 4:56 PM, Cheng, Bow-Nan - 0665 - MITLL
<[email-masked]> wrote:
> Hi all,
>
> I’ve been a little out of the loop on DLEP recently and looked at Draft 7.
> One thing I was confused about was the change from Modem initiated peer
> discovery to Router initiated peer discovery and was wondering what the
> rational was for the change?

It was a compromise between the authors/design-team in London... both
variants could work, lets not reopen this discussion unless its
absolutely necessary.

> In the past when we’ve operated DLEP, we always had the assumption that 1
> DLEP Router/server process could support multiple DLEP modem/client
> connections off the same Ethernet VLAN (or bridged interface as we were
> operating it). In this case, it made sense for the modem to initiate the
> peer discovery because at any time, another modem/radio could be “turned on”
> and “discover” the DLEP router and initiate a new connection. How would this
> work with the router initiating the peer discovery? Would the router need to
> periodically initiate peer discovery so modems that “turn on” can find it?
> Would this mess up normal DLEP session flow?

You could just keep sending discovery UDP multicasts by the router,
even if you got a session.

No, it would not mess up the session flow because the radios that are
already in session would ignore the incoming multicast.

> Is the implicit assumption now that 1 DLEP router/server process will
> connect to only 1 DLEP modem/client process?

My implementation (as an example) can connect to one DLEP radio per
interface its connected to...

> So then, each modem/router
> would essentially need to be on its own interface or subnet and you would
> need some sort of virtual interface to gang them all up to the router. In
> this case, I can understand having the router initiate peer discovery. Maybe
> I’m missing something.

If you use VLANs to bundle multiple radios to a single router ethernet
port, each of the VLANs would have its own virtual interface in the
router.

Henning Rogge

---

From: "Cheng, Bow-Nan - 0665 - MITLL" <[email-masked]>
Date: Thu, 25 Dec 2014 23:02:10 +0000

Thanks Henning,

Regarding re-opening the discussion on router initiated peer discovery. It
sounds counter-intuitive to me, but I¹m not hard opposed to it.. I was
just wondering the rational behind it was. I suspect that more people may
be confused by this change and was hoping it could be captured somewhere
on the list to point at.

-Bow-Nan

On 12/25/14, 4:04 PM, "Henning Rogge" <[email-masked]> wrote:

>> I¹ve been a little out of the loop on DLEP recently and looked at Draft
>>7.
>> In the past when we¹ve operated DLEP, we always had the assumption that
>>1
>> peer discovery because at any time, another modem/radio could be
>>³turned on²
>> and ³discover² the DLEP router and initiate a new connection. How would
>>this
>> periodically initiate peer discovery so modems that ³turn on² can find
>>it?
>> I¹m missing something.