[Planetlab-devel] IPv6 support for MyPLC

[McGeer, Patrick C]

Aaron,
There are two effects here:
(1) Alternate implementations of existing services; and
(2) Tunneling everything over http on port 80 because firewalls block
other ports.

For (1), it's clear that where port number is an alias for service name
(53, 110, 25, 80, etc...) using familiar ports and alternate IP
addresses is pretty clearly the right thing to do.  For (2), nobody is
very enthusiastic about tunneling everything over port 80 -- but what
choices have we?  If local admins are going to adopt the policy of
everything-not-compulsory-is-forbidden, which they are, we pretty much
have to do this.

To take one example, I discovered today that I'm going have to tunnel
pings over 80, because one organization that I work with blocks ICMP in
operation.  Very hard to do network measurement without pinging, but
we're going to have to do it...(and don't ask me why people block pings
-- habit, probably)

-----Original Message-----
From: Aaron Harwood [mailto:aharwood at csse.unimelb.edu.au] 
Sent: Tuesday, November 07, 2006 7:02 PM
To: McGeer, Patrick C
Cc: Bound, Jim; Marc E. Fiuczynski; devel at lists.planet-lab.org
Subject: Re: [Planetlab-devel] IPv6 support for MyPLC


On 08/11/2006, at 12:50 PM, McGeer, Patrick C wrote:
> As to why people want their own IP addresses, it's because they want 
> to attach services to well-known ports.  For example, there are at 
> least three collaborative DNS services I know about, and all three 
> would love to use port 53.  Similarly, lots of people want 80,

Hi  all,
Just wondering, while this is what developers want, whether it would be
desirable in the long term. Well known ports exist because they supply a
well known service; which is expected to work in a certain way.
Perhaps a broader statement is to say that developers want their
services to become well known and widely used; attaching to a well known
port and using a protocol that is associated with that port is a design
choice that facilitates their goal. If the service happens to be a "new
and improved" version of an already existing well known service (like
your example above) then this facilitates integration, as well. To some
extent, and just for arguments sake, the use of IPv6 may lead to a
situation where the IP address is the main "address" of the service;
with port number being used to select support services for the primary
service assigned to that IP address.
If we promote overloading of port numbers then we might see a
degradation of interoperability which might not be a desirable outcome.
--aaron