I would disagree about "no drawback."
The constraints are:
don't invent new transports
have congestion control
and, for an important part of the traffic, do not have retransmission or
significant transmission delay (i.e. perform congestion control by
dropping packets.)
Now, we have SCTP modes and DCCP which can address those needs over IP.
We do not have a defined protocol that runs over UDP that meets those
constraints.
We could just use UDP. But the congestion sensitivity aspect was
actually an important part of the work.
And the scoping (very near, near, or anywhere) was defined in the
negotiation with the IESG to give us bounds on the work and a framework
for making these sorts of decisions.
So ignoring the bounds would be quite inappropriate. And the problem is
not solvable within the waist you have defined.
Which leaves us with either getting the work done, using IP and suitable
transports, or extending a very long process much longer.
Not a good choice.
Yours,
Joel
Jonathan Rosenberg wrote:
Well, if history is any guide, eventually people will in fact want to
run this from someplace a little farther away, and then you're in big
trouble. So, I think the advice remains the same. There is no drawback
to having it over UDP to start with - it works when there are no NAT,
and it can work when there are NAT.
-Jonathan R.
Joel M. Halpern wrote:
However, I would really like to reinforce the point from another note.
There are quite a few contexts where the ability to run a sensible
transport directly over IP is indeed very useful. For example, the
ForCES working group scope is limited (by chart) to the case where the
control element is near the forwarding element. I am not worried
about there being a NAT between those. So SCTP or DCCP over IP is
very relevant.
Yours,
Joel M. Halpern
Jonathan Rosenberg wrote:
I wrote this because of a discussion that happened during behave at
the last IETF meeting in Vancouver. There was a presentation in the
behave working group on NAT ALG for SCTP - when run natively over IP
- and I found the entire conversation surreal. The entire problem
would have been moot if SCTP had been designed to run over UDP and
not IP.
So apparently its not obvious to everyone that you cannot design
protocols natively ontop of IP.
-Jonathan R.
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