Subject: (ngtrans) Date: Mon, 9 Apr 2001 10:28:21 -0500

From: "Sandeep Kalal" <[email-masked]>
Date: Mon, 9 Apr 2001 13:56:54 -0700 (PDT)

Hi,
 
I am a novice in the field of IPv6. I have recently joined this forum. I
have following questions:

1. What is the use of having separate Link-Local Unicast address and
Site-Local Unicast address, when nodes can communicate ( on a link or in a
site) by using Aggregatable Global Unicast Addresses.

2. What is the use of IPv4-mapped IPv6 addresses and IPv4-compatible IPv6
addresses? Where can I get information about this?

Please let me know if there is any other way of posting query. 

Thanks,

Sandeep Kalal

---

From: Gilles Diribarne <[email-masked]>
Date: Tue, 10 Apr 2001 15:06:20 +0200

Hi,

> Site-Local Unicast address, when nodes can communicate ( on a link or
> in a site) by using Aggregatable Global Unicast Addresses.

Your question is about the scope.
- The link-local address is valid only on a link. But it's an address
which is autoconfigurable (First step of Stateless Autoconfguration).
It allows a host to determine an address and have at least one. For
example, DHCP client uses only link-local addresses to get another
address.
- Site-local are like 'private IPv4 address'. They can be used if you
want to have private addresses.
You have to use NAT for example to toggle public addresses and
site-local addresses.
- Aggregatable global adrresses are global adresses. They contain TLA,
SLA, ...
It's a public addresses which will be given by an ISPs for example.

>> 2. What is the use of IPv4-mapped IPv6 addresses and IPv4-compatible
IPv6 addresses? Where can I get information about this?
Generally, IPv4-mapped IPv6 address is used when a V6 node wants to
communicate with a V4-only node.
I think you can look at ngtrans rfc and drafts that talks about
translator. SIIT is a good example.

The use of IPv4-compatible IPv6 addresses are used to establish
tunnels.  When a IPv6 node wants to communicate over IPv4, it uses
IPv4-compatibke addresses. This address type is usefull to indicate for
example the tunnel endpoint.
Ex under Linux:  $> route -Ainet6 3ffe:/16 gw ::192.168.52.1
To reach 3ffe:/16, you have to encapsulate your packet into a IPv4 one.

For all the previous question, have a look at RFC 2373 and NGTRANS RFC
and draft.

Regards,
Gilles Diribarne

--
 Gilles Diribarne
 Alcatel Research & Innovation
 [email-masked]
 Tel: +33 (0)1 69 63 46 45      Fax: +33 (0)1 69 63 11 69