Subject: (ngtrans) templin-isatap-dhcp-00 comments

From: Pekka Savola <[email-masked]>
Date: Sun, 16 Mar 2003 13:53:21 +0200 (EET)

Fred, others,

A few quick comments on the draft.

2. ISATAP DHCP Option

   The ISATAP DHCP option carries two lists. Each list may contain zero
   or more 32-bit IPv4 addresses or DNS (RFC 1035 [4]) fully-qualified
   domain names (FQDNs). The elements in each list MUST NOT include a

==> add a note to Introduction and refer to KEYWORDS RFC2119

   mix of IPv4 addresses and FQDNs; instead, the data type for each list
   is identified by an 'enc' byte in the DHCP option. The ISATAP DHCP
   option has the following format:

    Code   len   enc      Potential Router List
   +-----+-----+-----+-----+-----+-----+-----+-----+--
   | TBD |  m  |  x  |  p1 |  p2 |  p3 |  p4 | p5  | ...
   +-----+-----+-----+-----+-----+-----+-----+-----+--
     ... |  n  |  y  |  d1 |  d2 |  d3 |  d4 | d5  | ...
      ---+-----+-----+-----+-----+-----+-----+-----+--
     ... | len   enc        DHCPv6 Server List
      ---+
==> why not use the classic bit/byte notation..? I found this quite
confusing to read..

   As can be seen in the figure, the ISATAP DHCP option encodes 'm'
   octets of Potential Router List entries of encoding type 'x' followed
   by 'n' octets of DHCPv6 Server List entires of encoding type 'y'.
==> s/entires/entries/

   When an 'enc' byte has a value of 0, the list contains a sequence of
   zero or more labels comprising FQDNs encoded exactly as specified in
   ([3], section 3.1). When an 'enc' byte has a value of 1, the list
   contains zero or more IPv4 addresses encoded exactly as specified in
   ([3], section 3.2). The 'len' and 'enc' fields for both the Potential
   Router List and DHCPv6 Server List are always present (i.e., even if
   one or both lists are empty).

==> this is very confusing (due to overloading of len + enc vs m/n + x/y)

   ISATAP nodes use the elements encoded in the Potential Router List
   exactly as specified in ([1], section 7.3.1).

   When the elements encoded in the DHCPv6 Server List are IPv4
   addresses, they are used by ISATAP nodes to construct link-local
   ISATAP addresses exactly as specified in ([1], section 5.1). When the
   elements encoded in the DHCPv6 Server List are FQDNs, they are used
   by ISATAP nodes in DNS queries to obtain IPv4 addresses for
   link-local ISATAP address construction as specified above.

==> why is it named "DHCPv6 Server List"?  Is the intention to construct the
_node_'s ISATAP address, or tell the DHCPv6 server address so it can be
contacted?  Probably the latter, but it isn't said anywhere!

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings

---

From: "Fred L. Templin" <[email-masked]>
Date: Sun, 16 Mar 2003 07:00:06 -0800

Pekka,

Not sure if anyone is still reading this list, but thanks for the 
comments. As
to your last question, yes - the second list is to provide addresses of 
DHCPv6
servers configured for the site so that ISATAP nodes can contact them. I
agree that this could have been made more clear and agree on the other
points for clarification as well.

Fred
[email-masked]