RE: Updating to RFC6434 to deal with 8200-style header insertion by IPIP

["Manfredi, Albert E" <[e-mail]>]

-----Original Message-----
From: ipv6 [mailto:[e-mail]] On Behalf Of Tom Herbert

> I think the sticking point is going whether a node can blindly
> perform IP-IP encapsulation on packets to arbitrary destinations
> (as opposed to using IP-IP for explicitly tunneling across a
> network).

Interesting thread. My question has been, during this exchange, why should we expect that *any* given payload should be assumed ahead of time, by a source, to be acceptable to a destination? Or if not acceptable, to return a particular ICMP message?

> This requires the assumption that all nodes in the downstream path
> will forward a packet with IP-IP and the added extension headers,
> and that the destination will accept such packets.

Yes. And if the source sends some obscure spreadsheet or word processor format, or streaming media compression algorithm, there's no assumption that the obscure format will be acceptable either.

> The problem is that if a packet is dropped because of the
> encapsulation or EHs and no ICMP error is returned to the
> encapsulator then there is no way to recover. The original source
> host might see packets being dropped on a connection but will have
> no idea why.

As in many other examples of not-very-standard payloads? Is there an expectation that any random host out there should know to be the egress of a tunnel? Or is this the sort of job one expects only or mainly from certain routers, very deliberately configured for such a task?

Bert