Re: [Int-area] Middleboxes to aid the deployment of MPTCP

[Olivier Bonaventure <[e-mail]>]

Tom,
>>
>> Do you have in mind such use cases when you referred to the "stateful firewalls model"?
> 
> One of the problems with stateful firewalls (as well as transparent
> proxies) is that they require all packets for a flow to consistently
> traverse the same middlebox device. The middlebox is not addressed by
> the packet, so the assumed requirement is that packets for the flow go
> though the same network node by virtue of routing. 

The proposed converter has one IP address and a reserved port number. 
Packets follow norm routing path towards this address.

> For a firewall in a
> single-homed site to the Internet this works because the firewall is
> the only egress/ingress point to the network. If a site is
> multi-homed, then the hope is that routing of packets in both
> directions will go through the same point. But there is absolutely no
> requirement that network layer packets for a flow are always routed
> the same way, and if routing does change and packets need to flow
> through different points the session breaks. >
> If I'm reading the draft correctly, then it has the same property of
> maintaining transport state in the network so it implies the same
> requirement that all packets for a flow follow the same path.
> Personally,  would find it ironic that a a protocol to allow muli-path
> transport would require the network layer to be single path.

The motivation for the proposed converters is that the destination does 
not support MPTCP. To enable the client to leverage the benefits of 
MPTCP (e.g. in the access networks) the MPTCP connection is terminated 
on the converter. The client uses the different paths between it and the 
converter.


Olivier

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