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

[Joe Touch <[e-mail]>]

When I call them (multihomed) hosts, I never would assume that the experiment you propose would work. However, if I limit the paths to go through only one of those boxes, treating it as the host it is, everything works fine.

That’s why it IS a host. And why I don’t need new rules to understand or explain it.

Joe

> On Jan 17, 2019, at 3:46 PM, Tom Herbert <[e-mail]> wrote:
> 
>> 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