Re: [dtn-interest] FW: Results of IETF-conflict review for draft-irtf-dtnrg-tcp-clayer-08

Caini Carlo <> Tue, 25 February 2014 10:30 UTC

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Date: Tue, 25 Feb 2014 11:30:06 +0100
To: Vint Cerf <>,"" <>
From: Caini Carlo <>
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Subject: Re: [dtn-interest] FW: Results of IETF-conflict review for draft-irtf-dtnrg-tcp-clayer-08
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Dear Vint and Lloyd,
     In my opinion, the possibility of using TCP 
as convergence layer in a Bundle Protocol DTN 
architecture has many advantages that go beyond 
the mere compatibility with Internet and that can 
be achieved (in some selected but important 
cases) despite the challenges of the links.
To cite an example I have personally 
investigated, consider GEO satellite 
communications. In these the main challenge is 
the RTT of about 600 ms mainly due to the 
propagation time on the satellite link. With such 
a large RTT, TCP New Reno cannot provide 
satisfactory performance, especially in the 
presence of concurrent terrestrial TCP traffic 
(i.e. with short RTTs). The usual solutions are 
TCP splitting PEPs that divide the end-to-end 
paths into three legs: 1) from source to the 
first PEP, 2) between the two PEPs, 3) from PEP 
to destination. TCP splitting PEPs provide good 
performance but violate the end-to-end semantic 
of TCP and are ineffective with IPsec.
By contrast, the BP DTN architecture allows to 
"naturally" split the end-to-end connection into 
3 DTN hops (the same as before), which 
automatically solves the problem of RTT 
unfairness between satellite and terrestrial 
connection; you can use TCP and the first and the 
last, as they have no challenges at all; you can 
use whatever convergence layer you want in the 
intermediate connection (the satellite one), 
included TCP variants specialized for satellite. 
Note that on a link with less than 600ms and 
without (or with just minor disruption) these 
specialized variants of TCP work well (i.e. you 
do not need LTP). In short, in GEO communications 
you can have TCP, by choice, on all the DTN hops, 
with excellent performance. The price to pay with 
respect to PEPs is the lack of transparency, 
because you you need to install and use DTN on 
the end points. It may be worthwhile.


At 10.43 25/02/2014, Vint Cerf wrote:
>there is a lot more TCP and IP network readily 
>available than others so, statistically, this is 
>not a surprise. I anticipate that LTE may prove 
>another supporting environment. Of course, there 
>continues to be work in deep space such as the 
>latest laser comm tests to/from the moon at 600 Mb/s.
>On Tue, Feb 25, 2014 at 4:27 AM, 
><<>> wrote:
>the impression I've gained is that most bundle 
>protocol use is over TCP - that is,
>rather than being a compatibility mechanism, TCP 
>is the dominant transport for the
>bundle protocol.
>Are there any statistics or metrics of use that can shed light here?
>Lloyd Wood
>From: Vint Cerf [<>]
>Sent: 25 February 2014 08:51
>To: Wood L Â Dr (Electronic Eng)
>Cc: dtn-interest
>Subject: Re: [dtn-interest] FW: Results of 
>IETF-conflict review for draft-irtf-dtnrg-tcp-clayer-08
>This makes it possible to support applications 
>end to end over DTN including the Internet.
>It is a compatibility mechanism.
>On Tue, Feb 25, 2014 at 3:23 AM, 
>Congratulations to  DTNRG on reaching the below milestone in getting
>this draft well on the way to being published.
>It's been a long delay since draft-demmer-dtnrg-tcp-clayer-00.txt in October
>2006, but defining how the bundle protocol is carried over TCP will go a long
>way to improving support for networked communications under the very
>difficult disrupted and delay-tolerant network conditions when TCP break...
>um. Ah.
>Lloyd Wood
>From: IETF-Announce 
>On Behalf Of The IESG 
>Sent: 24 February 2014 17:40
>To: Lars Eggert; 
>The IESG; 
>Subject: Results of IETF-conflict review for draft-irtf-dtnrg-tcp-clayer-08
>The IESG has completed a review of draft-irtf-dtnrg-tcp-clayer-08
>consistent with RFC5742.
>The IESG has no problem with the publication of 'Delay Tolerant
>Networking TCP Convergence Layer Protocol'
><draft-irtf-dtnrg-tcp-clayer-08.txt> as an Experimental RFC.
>The IESG has concluded that there is no conflict between this document
>and IETF work.
>The IESG would also like the IRTF to review the comments in the
>datatracker related to this document and determine whether or not they
>merit incorporation into the document. Comments may exist in both the
>ballot and the history log.
>The IESG review is documented at:
>A URL of the reviewed Internet Draft is:
>The process for such documents is described in RFC 5743
>Thank you,
>The IESG Secretary
>dtn-interest mailing list
>dtn-interest mailing list