Re: [dtn-security] Newbie seeking some security related advice

["Graham Keellings (Leonix Solutions Pte Ltd)" <[e-mail]>]

Jason Redi wrote:
> Minor comment to Armando's email:
>
>   
>> -----Original Message-----
>> From: [e-mail] [mailto:dtn-
>> [e-mail]] On Behalf Of Armando
>> Caro
>> Sent: Wednesday, May 27, 2009 8:14 PM
>> To: Ivancic, William D. (GRC-RHN0)
>> Cc: [e-mail]
>> Subject: Re: [dtn-security] Newbie seeking some security related advice
>>
>> Ivancic, William D. (GRC-RHN0) wrote:
>>     
>>> I believe DARPA is using DTN for voice networks but I believe the
>>>       
>> disruption is expected to be very quick fades and the like or perhaps
>> that voice simply will not make sense at certain times.
>>
>> I believe you are referring to the work that BBN is doing for the DARPA
>> WNaN program. For this program, we run IP over DTN and use VoIP without
>> modifications to the VoIP application. We are using the BPA as a
>> forwarding engine that works in both connected and disconnected
>> scenarios. VoIP traffic (and other delay sensitive traffic) are only
>> routed/forwarded to destinations that are currently connected, since
>> VoIP doesn't make sense for disconnected destinations. If a node
>> receives VoIP traffic for a disconnected destination, the traffic is
>> dropped.
>>     
>
> As Armando describes, we are currently using streaming voice over BP.
> Individual packets contain 20-100ms of voice, so sending those individual
> buffers in an individual disrupted fashion would not make a whole lot of
> sense.  
> Note that we are also working on providing voice-snippets of 1-10s
>   
Wow! That surely *is* delay tolerant (if not disruption tolerant). You 
have to wait until you have collected 10 seconds of voice at the sender 
before transmitting. That guarantees a lag of over 9 seconds at the 
receiver, or 18+ seconds to get a reply to a question.

I think that I need to rethink :-)   Or,  at least, we can say that such 
delay might be acceptable in some scenarios, but not in others. Nasa 
might have no choice, given the lag inherent in very long range 
transmissions, but I doubt that DARPA can accept multi-seconds delays in 
combat scenarios.

I am looking at a "real time" voice network, where it has been strongly 
"suggested" that I use DTN, but I am thinking that all that it will 
bring to my particular use case is that I don't have to worry about 
"link lost" for a short time bringing down the call.  My personal feel 
is that DTN is not the right tool for the job for a mainly voice based 
short range system where speed of reply is of the essence. I don't see 
that the benefits justify it, but then I don't get to make the decision 
(and if I recommend against it, I probably don't get the contract. Sigh)

Thank you very much for taking he time to reply and for helping me to 
clarify my thoughts.

With best wishes,

Graham


> that could be sent in a disrupted fashion over the network.  But ultimately
> that's just data like any other bundle.  The only real "work" there is in
> the application, not the BP.   
>
> The key point is that voice can either be streaming as little snippets or
> buffered as a big blob.  If it is a big blob, it's just another bundle.  If
> it is streaming, then one needs to make sure you have a BPA/router that adds
> only a minimal amount of additional overhead to the forwarding process.  (as
> Armando says below)
>  
>   
>> One important take-away from this work... the motivation of DTN is to
>> support delay/disrupted scenarios and apps that can operate in that
>> regime, but it is possible to implement a DTN stack that can also deal
>> with time-sensitive traffic.
>>
>> Armando
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