Re: [shara] draft-thaler-port-restricted-ip-issues-00 - A+P tunneling

[Masataka Ohta <[e-mail]>]

Remi wrote:

> Indeed, if two hosts in a common domain in which they have have
> private IPv4 addresses in addition to their port-restricted
> public addresses, nothing prevents them from using any protocol
> between them with these private addresses (and ICMP in particular).

That's fine.

My point is that plain ICMP just works to/from a host with port
restricted public IPv4 addresses so that you don't have to say
anything about private addresses.

You (and A+P routers) can direct an ICMP echo request/reply packet
to an appropriate tunnel using identifier of echo request and
sequence number of echo reply as destination port number.

It is assumed that sequence number of echo request is restricted
as if it is a restricted source port number. Then, the sequence
number is copied by a destination end host to echo reply and
should act as a restricted destination port number of the reply.

For the restriction, ping command must be modified, but no ICMP
protocol change necessary.

						Masataka Ohta