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

[Henning Rogge <[e-mail]>]

I talked with a co-worker from our SDR department.

He said that most SDRs he works with have mid- to high-end ARM/MIPS
CPUs for handhelds and even more powerful ones for vehicle based SDRs.

These devices already have the necessary libraries on board to open
tcp server sockets for other purposes, software complexity for opening
the socket should be no real issue.

The other target platform I have in mind for DLEP are cheap embedded
routers that are converted into DLEP-capable radios with a special
firmware. They also have a full IP stack already present, a TCP server
socket is a non-issue with them either.

Henning Rogge

On Tue, Nov 12, 2013 at 8:59 PM, Stan Ratliff (sratliff)
<[e-mail]> wrote:
> Teco,
>
> On Nov 12, 2013, at 2:05 PM, Teco Boot <[e-mail]> wrote:
>
>> Access list on modem is needed if not on trusted network.
>> (all networks are less trusted these days…)
>>
>> Stan: you have received from multiple sources that modem may have more CPU power and memory than the router. Elect TCP server based on clock speed & memory footprint? As a router vendor, why not taking the easy part?
>
> One additional thought on this topic. In an earlier email on this same thread, you said (in part):
> "...Let’s keep the modem a somewhat dummy device."
>
> I 100% agree with that approach. It's part of what drives me to put "harder" code (like being a TCP server) into the router, not the modem.
>
> Stan
>
>
>>
>> Teco
>>
>> Op 12 nov. 2013, om 19:54 heeft Stan Ratliff (sratliff) <[e-mail]> het volgende geschreven:
>>
>>> That's fair. Also not what I was driving at, so my apologies. It goes back to my contention that TCP server code is "arguably more complex" than client code, and therefore, we should endeavor to put the TCP client code in the modem.
>>>
>>> Regards,
>>> Stan
>>>
>>> On Nov 12, 2013, at 1:47 PM, Henning Rogge <[e-mail]> wrote:
>>>
>>>> I don't think defending against spoofed IP packets, Syn-Floods or just
>>>> DDOS should be part of DLEP.
>>>>
>>>> We have other layers for this.
>>>>
>>>> Henning Rogge
>>>>
>>>> On Tue, Nov 12, 2013 at 7:46 PM, Stan Ratliff (sratliff)
>>>> <[e-mail]> wrote:
>>>>> Fair point. Use of TLS would also help. But I don't think any of that defends against a SYN flood….  that requires things like a tight rein on listen depth, etc.
>>>>>
>>>>> Regards,
>>>>> Stan
>>>>>
>>>>> On Nov 12, 2013, at 1:42 PM, Henning Rogge <[e-mail]>
>>>>> wrote:
>>>>>
>>>>>> If you consider multi-hop connectivity, maybe using a VPN-Box might be
>>>>>> a good idea... let the radio believe its single hop and outsource the
>>>>>> security. ;)
>>>>>>
>>>>>> Henning Rogge
>>>>>>
>>>>>> On Tue, Nov 12, 2013 at 7:40 PM, Stan Ratliff (sratliff)
>>>>>> <[e-mail]> wrote:
>>>>>>> Henning,
>>>>>>>
>>>>>>> I agree, I don't think most networks forward IPv6 link-locals. But, once you consider the problem of allowing multi-hop connectivity, you've got the issue of defending against SYN attacks, etc. IMO, that is yet another reason for putting the TCP server functionality into the *router*, not the modem. The burden on the poor, supposedly resource-constrained modem just gets bigger, and bigger, and bigger…
>>>>>>>
>>>>>>> Regards,
>>>>>>> Stan
>>>>>>>
>>>>>>> On Nov 12, 2013, at 1:36 PM, Henning Rogge <[e-mail]>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> I think most operation systems do not forward linklocal IPv6 addresses...
>>>>>>>>
>>>>>>>> Henning Rogge
>>>>>>>>
>>>>>>>> On Tue, Nov 12, 2013 at 7:30 PM, Teco Boot <[e-mail]> wrote:
>>>>>>>>>
>>>>>>>>> Op 12 nov. 2013, om 19:05 heeft Henning Rogge <[e-mail]> het volgende geschreven:
>>>>>>>>>
>>>>>>>>>> Easiest way to protect yourself against most "long range" attacks is
>>>>>>>>>> to bind the TCP socket to an IPv6 linklocal address.
>>>>>>>>>
>>>>>>>>> There is traffic with IPv6 link local address on the Internet.
>>>>>>>>>
>>>>>>>>> Sent packets with IPv6 link local address should have hopcount=1. Doesn’t completely take away the problem. TTL=255 filter on incoming traffic is stronger (GTSM, RFC 5082).
>>>>>>>>> Use GTSM filter and IPv6 link-local addresses by default?
>>>>>>>>>
>>>>>>>>> Rick and I came up with the idea DLEP can be used between peers multiple hops away. Modem may have an option allowing it.
>>>>>>>>>
>>>>>>>>> Teco
>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Henning Rogge
>>>>>>>>>>
>>>>>>>>>> On Tue, Nov 12, 2013 at 7:04 PM, Teco Boot <[e-mail]> wrote:
>>>>>>>>>>> TCP 4-tupple is not enough to discard some form of blind TCP connect. There must be some sanity check.
>>>>>>>>>>>
>>>>>>>>>>> Radio must protect itself against syn attack (no data, locked port).
>>>>>>>>>>>
>>>>>>>>>>> Teco
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Op 12 nov. 2013, om 17:21 heeft Taylor, Rick <[e-mail]> het volgende geschreven:
>>>>>>>>>>>
>>>>>>>>>>>> I seem to remember SCTP (which I hold in high regard) uses a cookie for its 4-way handshake on the grounds that it stops some types of spoofing attacks.
>>>>>>>>>>>>
>>>>>>>>>>>> I'll re-read their rationale doc if I can find it.  I was just trying to cover some security considerations here, but it might be misplaced.
>>>>>>>>>>>>
>>>>>>>>>>>> I just wonder whether replying to a broadcast with a IP address by blindly connecting to it without some way of checking what your connecting to is what you expect to be there is 'unsafe' - but you do make a good point about the TCP 4-tuple...
>>>>>>>>>>>>
>>>>>>>>>>>> Rick Taylor
>>>>>>>>>>>>
>>>>>>>>>>>>> -----Original Message-----
>>>>>>>>>>>>> From: Stan Ratliff (sratliff) [mailto:[e-mail]]
>>>>>>>>>>>>> Sent: 12 November 2013 16:04
>>>>>>>>>>>>> To: Taylor, Rick
>>>>>>>>>>>>> Cc: DLEP Research Group ([e-mail])
>>>>>>>>>>>>> Subject: Re: [manet-dlep-rg] DLEP session establishment
>>>>>>>>>>>>>
>>>>>>>>>>>>> Rick,
>>>>>>>>>>>>>
>>>>>>>>>>>>> On Nov 12, 2013, at 10:45 AM, "Taylor, Rick" <[e-mail]>
>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>>> Hmmm... good point about complexity in the radio Stan.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> I'd be okay with flipping the whole discovery process so the router
>>>>>>>>>>>>> advertises and the radio connects.  Making the router maintain the extra
>>>>>>>>>>>>> timer for strobing is probably more sensible.  Obviously some
>>>>>>>>>>>>> recommendation for timing of the strobes is needed.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> The handshake still stays 3-way and that covers most of my concerns.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Any comment on a cookie in the offer?
>>>>>>>>>>>>>
>>>>>>>>>>>>> What is the cookie used for? I was thinking the TCP 4-tuple (Source
>>>>>>>>>>>>> IP/Source Port/Destination IP/Destination Port) is sufficient for any
>>>>>>>>>>>>> correlation.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Regards,
>>>>>>>>>>>>> Stan
>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> I have double checked with the 04 draft, and you have covered the
>>>>>>>>>>>>> broadcast or configured unicast UDP address in the text, so I'm happy.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Rick Taylor
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> -----Original Message-----
>>>>>>>>>>>>>>> From: Stan Ratliff (sratliff) [mailto:[e-mail]]
>>>>>>>>>>>>>>> Sent: 12 November 2013 15:17
>>>>>>>>>>>>>>> To: Taylor, Rick
>>>>>>>>>>>>>>> Cc: DLEP Research Group ([e-mail])
>>>>>>>>>>>>>>> Subject: 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" <[e-mail]>
>>>>>>>>>>>>>>> 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: [e-mail] [mailto:manet-dlep-rg-
>>>>>>>>>>>>>>>>> [e-mail]] On Behalf Of Teco Boot
>>>>>>>>>>>>>>>>> Sent: 11 November 2013 16:29
>>>>>>>>>>>>>>>>> To: Stan Ratliff
>>>>>>>>>>>>>>>>> Cc: DLEP Research Group ([e-mail])
>>>>>>>>>>>>>>>>> Subject: [manet-dlep-rg] DLEP session establishment
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Op 11 nov. 2013, om 01:55 heeft Stan Ratliff (sratliff)
>>>>>>>>>>>>>>>>> <[e-mail]> 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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>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> --
>>>>>>>>>> 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
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> --
>>>>>>>> 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
>>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> 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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>>>> 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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-- 
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