renumbering and roaming

William Allen Simpson wsimpson at
Tue May 19 11:19:20 UTC 1998

> From: "Michael S. Fischer" <otterley at iPass.COM>
> In message <19980518135928.37530 at>, Karl Denninger writes:
> >That doesn't work; too many of those things must be hard-coded numbers
> >(specifically, the DNS servers).
> What has to be hard-coded besides the DNS servers?  Once you have a
> DNS server assigned (which is typically done by the NAS anyway) the
> rest is simple.
Ideal World:
    Nothing should be hard coded.  Every NAS should support DHCP and
    DHCP INFORM.  Each roaming user simply sends a DHCP multicast /
    broadcast packet, which is intercepted and forwarded by the NAS
    (serial link) or the local router (LAN), and recieves a list of
    services, including DNS.

    This is the direction that many of us in the IETF have been
    advocating for about 11 years....

Real World:
    Although all the early (circa '89-92) NAS's supported BOOTP/DHCP
    relaying, more recent shoe-string NAS vendors are missing it, and
    clients have not universally implemented DHCP.  We have to tell our
    customers the list of local DNS (and other) servers for them to type
    into their configuration (or we use a standard install CD).

    For this latter scenario, a few default universal hardcoded numbers
    would be a great idea!  It would help with legacy clients, it would
    help roaming, and would not hurt as DHCP gets installed base.

    I look forward to reading the internet-draft.  It should require no
    changes to client or server software.

> In our experience, well over 90% of roaming users (which excludes UNIX
> and Mac users) use dynamically-assigned DNS servers.  Clearly this
> approach won't work for those clients that don't support the LCP
> extensions, but we consider this "Best Current Practice."  Those
> clients that can't use dynamic DNS server assignment will have to use
> the home ISP's services.
Speaking as the author of "LCP Extensions", there is no such LCP
extension as "dynamically-assigned DNS servers".

There is a bogus, NDA'd, Mircosoft-only, NetBEUI extension to PPP IPCP,
using numbers stolen from the high end of the option space without
registering with IANA, which is marginally applicable to DNS.

This approach has been officially rejected by the IETF.  It is not a
"best current practice".  It only works with NT servers, which no sane
and stable ISP would use.

> We consider it important to make sure as many NASes and PPP clients as
> possible support dynamic DNS.  About the only major obstacle to that
> is OT/PPP (MacOS) and, to a lesser degree, UNIX.
AFIAK, Dynamic DNS is _only_ supported by Unix, but I have high hopes to
see it on MacOS, now that Vinnie is back at Apple.  I have no idea why
it would be supported by a NAS or PPP client.  I think you have your
terminology wrong....

WSimpson at
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