[e2e] overlay over TCP

[Coene Lode]

>David P. Reed wrote:
>> The reason not to depend on SCTP is the same reason that UDP isn't 
>> adequate. 
>
>I said DCCP, not SCTP, FWIW, and for a number of reasons.
>

And what might be those reasons????
DCCP will have just about the same deployment difficulties that any other
new transport protocol has to jump through....

>> The social (non-technical) processes of the "internet 
>> community" have labeled anything non-TCP as POISON, KEEP OUT.
>> We have middleboxes and routers that chuck stuff like that on the floor.

Well even the wrong portnumber with TCP could put you up the creek without a
paddle....
Seems the drop-to-floor boxes have already won then... 
So all overlay networks would be welded to TCP for the rest of their
lives.... 

>
>Sure - at that point, you're stuck going over TCP, but then you're also 
>stuck with a few other things:
>
>	- ACK aggregation delays
>	- messages split across packets (lack of fate sharing,
>	  so higher loss rates at the message level)
>	- NATing that will kill interior apps anyway
>		any app the NAT doesn't _already_ know about
>
>> Interop is about allowing everything not explicitly prohibited, but 
>> don't tell that to the "corporate IT" folks, who want to give you 
>> freedom from pesky things like ways to do your job better...  some jerk 
>> with a beard and a technical education knows how and when you should 
>> communicate, and he will let you know what communications technology you 
>> will be allowed to use.   Cisco's firewall division tells him what's OK, 
>> and God (or TPC from the President's Analyst) tells Cisco.
>
>In that case, you're safer doing IP over HTTP (yes, there is such an 
>animal).

And before you know it, all network and transport protocol have a XML
syntax... :-)

Seriously: you can extend TCP or deploy an already existing transport
protocol that gets close to what you want.
If it has to do something similar to UDP then PR-SCTP and/or DCCP might do
the job....
(PR-SCTP: Partial relialability extension for SCTP)
If it should do something similar to TCP, then at present SCTP might be
interesting....
Extending TCP or using SCTP/DCCP functionality is actually the battle
between: 
(1)Put functionality in the transport layer 
Versus
(2)The application should do this functionality because it knows what it is
doing...

(2) Makes sense for some applications, however most applications wouldn't
mind (1) because, if later they find out that the functionality actually
helps them(you never know..), then they don't have to reimplement it in
their own code, they just have to throw a few switches....
 
>
>Joe
>

Yours sincerely,
Lode Coene

Siemens COM
atealaan 34          2200 Herentals, Belgium
E-mail: lode.coene at siemens.com
Tel: +32-14-252081
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