Subject: (ngtrans) Shipworm Questions

From: "Eng Soo Guan" <[email-masked]>
Date: Mon, 8 Oct 2001 18:03:54 +0800

Hi!

I am very interested in the Shipworm draft.  A few points however are not
clear to me.

From the Shipworm Ipv6 address described in Section 4.1.1, if a Shipworm
Client opens 2 FTP sessions using Source Port X and Source Port Y, it needs
to obtain 2 different prefix from a Shipworm Server. Is my understanding
correct?

In Section 4.3.2, when the server replies to a RS, "the IPv6 destination
address is normally set to the IPv6 source address of the RS; if that
address was the unspecified address, the IPv6 destination should be set to
the Shipworm IPv6 anycast address".

In Section 4.2.1, during initialisation, a client sends a Router
Solicitation Message whereby the "IPv6 destination of the RS is the Shipworm
IPv6 anycast address; the IPv6 source is the unspecified address".  In the
same section, when a client receives a router advertisement, it has to check
if the "the IPv6 destination address is equal to the random link local
address picked used in the router solicitation".

My question is where in the Router Solicitation Message is the random link
local address stored? If it is not in the RS, ther Shipworm server will not
the random link local address. Then, how can it send a response with the
destination set to the link local address?

Furthermore, if the IPv6 destination address of the RA sent by Shipworm
Server is the Shipworm IPv6 anycase address, according to Section 4.2.1, it
will be discarded, right?

Subsequent in Section 4.2.1, the client prefix must should be valid based
on:
"- the first 16 bits contain the Shipworm service TLA,
- the next 32 bits are the client's Shipworm mapped address,
- the next 16 bits are the client's Shipworm mapped port."

But the Shipworm mapped address and port will not be known to the Shipworm
Client before teh Router Advertisement (RA) is returned. How did the client
then validate the RA?

Thanx in advnace for helping me with my doubts.

Warmest regards.

Soo Guan, Eng
Centre for Wireless Communications, NUS
http://www.cwc.nus.edu.sg

---

From: Pekka Savola <[email-masked]>
Date: Tue, 9 Oct 2001 21:18:37 +0300 (EEST)

> to obtain 2 different prefix from a Shipworm Server. Is my understanding

No.  Shipworm is a tunnel.  2 IPv4 FTP sessions would indeed use two
ports, but you're just establishing an IPv4 UDP "session" through the
NAT(s) and using that as a transparent tunnel for IPv6.

> destination set to the link local address?

This appears to be a bug, from times when random link local address wasn't
required yet.  The client should use random link local address as the
source (and server in the reply).  Good catch.

> will be discarded, right?

There is no point the RA sent by Server would be anycast address.  Source
yes, but the Client checks destination.

So I'm not sure what you mean.

> Client before teh Router Advertisement (RA) is returned. How did the client

The spec doesn't say that that the packet should be verified as you
understood it; it cannot (as you pointed out).

It just means that basically, TLA must be the shipworm prefix, mapped
address should be sane if the local implementation made it so (e.g.
require non-private address), etc., and the values there should be
configured to the Shipworm Client from the advertisement.

There might be room for a minor clarification on what is actually
considered valid there.

-- 
Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords