Subject: (ngtrans) SIIT versus Shipworm versus Isatap

From: "Michael Cole" <[email-masked]>
Date: Tue, 24 Sep 2002 22:23:52 -0400

I think a point that some people are missing is that if somebody does not 
have at a minimum an IPv4/IPv6 version of Internet Explorer, they will not be 
able to connect to some websites. A node that does not have at least that much 
will not be able to use the Internet in the future. A supported dual stack 
implementation (commercial) is $30 a seat which is not too high a price. If it 
were $300 a seat then there would be a problem of having an IPv4 only node 
trying to talk with an IPv6 only node. The only reason why I have not bought a 
dual stack implementation is that some issues such as this are not settled and I 
am not about to buy software twice.

Security is a problem no matter what kind of scheme that you use for 
getting an node with IPv4 hardware to communicate with a native IPv6 node.

One BIG problem with SIIT is that the IPv4 that is translated must be a 
global one which works fine for GM or MIT but not if you are a cable ISP who is 
stuck with using a NAT and assigning RFC 1918 addresses to your customers.

The object of Shipworm and Isatap is to take care of the situation that NAT 
and RFC 1918 have somehow created a situation where the IPv4 plus the port 
number constitutes an ad hoc 48-bit address. In some cases you would need the 
global IPv4 of the site plus the port number plus the user's RFC 1918 address to 
create an ad hoc 80-bit address in order to uniquely identify the user. In some 
other instances you would only need the site's global IPv4 and the node's 
private IPv4.

Even if an ISP is connected ONLY to the 6bone, they still need a way 
to assign an IPv6 address to their customers and get around the problem that the 
customer will likely be connected via IPv4 hardware. I still have not figured 
out how cable companies make money with the market penetration that they do 
have. A lot of people just do not have the kind of money that IBM and GM 
have.

There are a number of ways to translate an IPv4 address to an IPv6:

1. A associative table where one node's IPv4 address is associated 
with that node's IPv6 address. The 2 addresses do not need to be related to each 
other.

2. Derive an IPv6 address from an IPv4 address that is temporarily or 
permanently assigned to a normally IPv6 node. This is what SIIT does. This 
also creates demand for more IPv4 addresses in some instances.

3. Translate the IPv4 address of a node that is connected via IPv4 hardware 
that is in between the node and the 6bone. This is what Shipworm and Isatap do. 
If the port number or a second IPv4 or both need to be included in the IPv6 
translation to identify the user who is sitting behind IPv4 hardware and 
software, then that is feasible. The idea behind Shipworm and Isatap is to use 
the existing IPv4 information which does not use any extra Ipv4 addresses and 
makes both the bookeeping and translation processes as easy and automagic as 
possible.

--- Michael Cole

--- [email-masked] 

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