Re: [Int-area] WGLC on draft-ietf-intarea-frag-fragile-05

[Tom Herbert <[e-mail]>]

On Thu, Jan 17, 2019 at 3:17 PM Joe Touch <[e-mail]> wrote:
>
>
>
> On Jan 17, 2019, at 1:09 PM, Tom Herbert <[e-mail]> wrote:
>
> Joe,
>
> When they attempt to do host processing on packets that don't belong
> to them they're not hosts.
>
>
> They are every host for whose packets they process.
>
> And when they do this, they impose a new
> requirement that hosts do not have which is that packets for some flow
> must consistently the traverse the same intermediate node.
>
>
> It’s not an intermediate node - it’s a host. It’s the same requirement as any host - that a host has one point of attachment to a network for a given IP address.
>
> In any case, as I said previously, reassembly is only specified as an
> operations at destination hosts.
>
>
> And these are destination hosts because of how they behave, which means they need to reassemble (either actually or logically).
>
> It seems like there might be a need
> for in-network reassmbly, or some nodes might be doing it already.
>
>
> It’s not in-network - it’s at a host, but yes, some do reassemble (or its equivalent).
>
> But, in that case we really need the specification of the protocol to
> have a meaning discussion about it.
>
>
> RFC 791 and 1122 provide everything that is needed.
>
> It’s not new, it’s just not an “intermediate” node. Never was.
>
Joe,

You can try this experiment. Provision two stateful firewalls as
egress points of a network. From an internal network network host
connect to an external host of the network. Now changing routing. If
packets to the external network were being routed through firewall A,
changing routing so they go through firewall B. Now take a look at
what happens to packets on the connection. They are dropped at
firewall B because it does not have the connection state that firewall
A has. The connection is no longer viable. You can call these devices
whatever you want, but that doesn't change the fact that stateful
devices in the network, including those that attempt reassembly, break
multi-path.

Tom

> Joe