Re: [manet-dlep-rg] DLEP session establishment

OK, looks like my opinion is "in the rough" on this one… 

But I'm still concerned about putting the TCP "server" code into the (probably more) constrained modem device. So, what if we make the *router* issue the Peer Discovery (call it a Peer Advertisement) to an MCAST address/well-known port? That Peer Discovery/Peer Advertisement would contain the unicast IP address/port for the TCP listener. The modem would respond with the TCP SYN…

The router would continue to periodically "strobe" the Peer Discovery/Peer Advertisement ad-nauseum (as much as I hate that approach).

I'm really concerned about modem-side complexity, based on discussions I had a couple of years ago with some radio vendors who were looking at implementing. 

Regards,
Stan

On Nov 12, 2013, at 7:47 AM, "Taylor, Rick" <Rick.Taylor@cassidian.com> wrote:

> Sorry for the delay, I was out of office yesterday.
> 
> My thoughts:
> 
>    Router                                        Modem
>    ===================================================
> 
> 1)                                  TCP socket listen()
> 
> 2)  <--------------------------- Peer Discovery Message
>                              UDP unicast or broadcast?
>                                       + Session Cookie
>                                     + TCP address/port
>           + Alternate reliable protocol endpoint infos
> 
> 3)  TCP connect()
> 
> 4)  Initialize (was Peer Offer) ---------------------->
>    + Session Cookie
> 
> 5)  <----------------------------------- Initialize ACK
>                                       + Session Cookie
>                                + Supported metric TLVs
> 
> 
> My reasoning, often agreeing with others:
> 
> The Modem 'advertises' its DLEP support, and therefore should
> be the one that listens for the TCP connect.
> 
> A cookie passed between the UDP discovery message and the TCP
> connection adds a little security (is this the modem I think I am
> connecting to?)  This could be extended to a full signature TLV
> in a later RFC.
> 
> The Peer Discovery message could carry additional reliable
> protocol endpoint information for non-TCP transports.
> 
> The Initialize ACK is the correct place to put the 'default'
> metric TLVs, and is sent by the modem.
> 
> A 3-way handshake seems safer to me.
> 
> I have a question over whether the Peer Discovery message should
> be unicast to a configured destination, or broadcast to all
> connected peers on a TBD port.  I prefer broadcast as it is more
> ZeroConf, but I can see use-cases for unicast to a configured
> destination for more complex topologies.
> 
> Cheers,
> 
> Rick Taylor
> 
>> -----Original Message-----
>> From: manet-dlep-rg-bounces@ietf.org [mailto:manet-dlep-rg-
>> bounces@ietf.org] On Behalf Of Teco Boot
>> Sent: 11 November 2013 16:29
>> To: Stan Ratliff
>> Cc: DLEP Research Group (manet-dlep-rg@ietf.org)
>> Subject: [manet-dlep-rg] DLEP session establishment
>> 
>> 
>> Op 11 nov. 2013, om 01:55 heeft Stan Ratliff (sratliff)
>> <sratliff@cisco.com> het volgende geschreven:
>> 
>>> Also, as to the Discovery: Here's what I'm writing up as we speak:
>>> 
>>> 
>>> Router
>> Modem
>>> ========================================
>>>                                    <------------------------ Peer
>> Discovery Message
>>> Peer Offer with           ------------------------->
>>> unicast IP addr/
>>> port for TCP connect
>> 
>> So this is multicast reply, telling modem to connect?
>> Why not TCP connect from router to modem? Makes more sense to me, the
>> modem is the peer offering a service.
>> Maybe add a TcpPort TLV in the Peer Discovery, this allows other than IANA
>> assigned ports.
>> 
>> 
>>> 
>>> *Connect on TCP socket. Router has issued TCP "listen",
>>>   modem issues TCP "connect" (e.g. Modem is the TCP "client",
>>>   router is the TCP "server")
>>> 
>>> Now, The modem's UDP socket can be closed.
>> 
>> Please don't.
>> 
>> 
>>> Over the TCP
>>> Socket,
>>>                                   <------------------------- Peer
>> Initialization containing
>>> 
>> TLVs/default values for ALL
>>> 
>> supported metric values - all
>>> 
>> meaning the MANDATORY ones,
>>> 
>> plus any optional metrics (right now,
>>> 
>> just Resources) that are supported.
>> 
>> Yes, here the full set TLV exchange takes place. This should not be in the
>> Peer Discovery. That's why I suggested to put this in the Peer Offer.
>> 
>> 
>>> 
>>> Peer Initialization ACK ---------------------->
>>> MAY contain optional
>>> Layer 3 (address) TLVs
>> 
>> I'm fine with three way handshake, not with this two way. Or use TCP
>> disconnect when modem modem is not willing to accept first message from
>> router.
>> 
>> Teco
>> 
>>> 
>>> .... And, everything from there is basically the same as before.
>> 
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