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

[Joe Touch <[e-mail]>]

> On Jan 18, 2019, at 7:39 AM, Tom Herbert <[e-mail]> wrote:
> 
>> On Thu, Jan 17, 2019 at 9:24 PM Joe Touch <[e-mail]> wrote:
>> 
>> 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,
> 
> You just stated a new rule. In order for these devices to work we need
> to "limit the paths to go through only one of those boxes".

Sticking a phone in a pot of dirt doesn’t make it a houseplant.

Putting these devices where hosts don’t work doesn’t make them routers or anything else.

The rules are simple. If it is a host , it must be run like a host.

If the only way it runs correctly is to act like a host, it is a host.

The Internet doesn’t have a rule that says you can do anything you want. Play by the rules or the system doesn’t work.

> If a user
> deploying a network doesn't follow this rule they will be in a world
> of hurt when things start to fail.

Exactly like sticking the phone in a pot of dirt ruins the phone.

> Even if someone understands the
> rule, consistently routing flows in even a moderately complex network
> is a hard problem.

Yes, when you keep sticking phones in pots of dirt, it’s hard to use the phones.

> This is one reason why transport layer proxies are
> popular. They are hosts, addressees of packets, in the network that
> terminate transport layer protocols and don't require consistent
> routing (but they do entail other complexities).

Non-transparent proxies force users to treat the boxes as hosts, and magically everything starts working again.  Go figure.

Joe

> 
> Tom
> 
> 
> Tom
> 
> 
>> 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
>>