Tom,
Only a few companies can control both client and server sides.
However, ISPs might be able to control the STB at the client side and the
middleboxes in their networks.
This may be a relatively easy way to deploy MPTCP technology rather than
updating clients or servers.
Yoshi,
I think you're focusing too much on the benefits of this solution and
not considering the cost. We've seen time and time again that when
middleboxes get involved in transport layer operations they break the
end to end nature of TCP and that leads to problems. Middlebox
involvement in TCP is one of the major source of protocol ossification
on the Internet.
We've spent a long time fighting with middleboxes during the design and
implementation of MPTCP and I know the problems that they cause. Most of
the problems we have with middleboxes today come from the fact that they
are not explicit in the architecture. A client cannot explicitly request
the creation of a TCP connection through a specific middlebox that would
provide service to this client. All middleboxes are implictly deployed
in the network and they process/interfere with traffic without the
consent of the client. On servers, some middleboxes (e.g. load
balancers) are part of the infrastructure and the server are informed
about their presence.
The proposed converters change this approach by making the conversion an
explicit (opt-in) service that can be requested by the client. If the
client does not request the conversion service, then there is no
interference from the middlebox. This is a different approach which
could in the long term provide new benefits that go beyond the simple
conversion service.
MPTCP is just one feature of TCP that we might want
do deploy there are many others. If this solution hampers use and
deployment of those, then I don't believe this is a reasonable
tradeoff regardless of what the benefits are.
Since the conversion service is explicitly requested by the clients,
they can opt-out this service when it is not required anymore (e.g.
MPTCP is supported on servers) or when they wish to use a feature that
is not supported by the converter.
Olivier
