Terminology: "Split horizon"

Terminology: "Split horizon"

Post by ian » Thu, 24 Jul 2003 03:20:50



I'm familiar with the term "split horizon" in matters to do with
routing, but also came across it today to do with DNS. Is "split horizon
DNS" an industry-accepted term, or just the invention of one individual?
I have never seen it before now.

I am writing some material on split DNS, and need to get the terminology
right.

Ian

--

 
 
 

Terminology: "Split horizon"

Post by Barry Margoli » Thu, 24 Jul 2003 03:25:32




>I'm familiar with the term "split horizon" in matters to do with
>routing, but also came across it today to do with DNS. Is "split horizon
>DNS" an industry-accepted term, or just the invention of one individual?
>I have never seen it before now.

>I am writing some material on split DNS, and need to get the terminology
>right.

I've generally heard this called either "split DNS" or "split-brain DNS".
I've never before today heard "split horizon" in the context of DNS, and
maybe the other poster was simply confusing the two terms.

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Terminology: "Split horizon"

Post by ian » Thu, 24 Jul 2003 14:39:38




Quote:

>I've generally heard this called either "split DNS" or "split-brain DNS".
>I've never before today heard "split horizon" in the context of DNS,

Me neither -- I thought I may have missed something.

Quote:> and
>maybe the other poster was simply confusing the two terms.

I guess so. The other poster is generally most emphatic in stating the
"facts", so I assumed he knew what he was talking about :-))

Ian
--

 
 
 

Terminology: "Split horizon"

Post by Peter Pentch » Thu, 24 Jul 2003 20:41:30





> >I'm familiar with the term "split horizon" in matters to do with
> >routing, but also came across it today to do with DNS. Is "split horizon
> >DNS" an industry-accepted term, or just the invention of one individual?
> >I have never seen it before now.

> >I am writing some material on split DNS, and need to get the terminology
> >right.

> I've generally heard this called either "split DNS" or "split-brain DNS".
> I've never before today heard "split horizon" in the context of DNS, and
> maybe the other poster was simply confusing the two terms.

I believe the term "split horizon DNS" was coined - or at least popularized -
by Prof. Daniel J. Bernstein in the documentation and rationale of his
djbdns package - <URL:http://cr.yp.to/djbdns.html>.  However, I just tried
a Google search on "split horizon" DNS, and it seems that its usage has been
slowly seeping across the 'Net, even into non-djbdns-related fora :)

G'luck,
Peter

 
 
 

Terminology: "Split horizon"

Post by Jonathan de Boyne Pollar » Thu, 24 Jul 2003 21:32:52


I> Is "split horizon DNS" an industry-accepted term, or just
I> the invention of one individual?

Is Google not working ?

I don't know who invented the term "split horizon DNS", but
one of the earliest users, according to Google Groups at
least, was Paul Vixie, back in 1994.  It's been used a fair
amount during the intervening nine years.

There are earlier uses of the term "split horizon" relating
to IP routing and not DNS that go back even further to 1988,
and I suspect that the term simply carried over from the one
to the other.

Another possibility (which I don't suspect) is that it is
indeed the invention of one individual, and that that
individual is Paul Vixie.

The original etymology of "split horizon" apparently stems
from the world of sextants.  (Ironically, the analogy from
"split horizon update" to the world of sextants is rather
more contorted than the analogy of "split horizon DNS" is.)

"Split brain DNS" is a newer term (first occurring some
years after Paul Vixie first used "split horizon DNS") and
one less often used according to Google Groups.  The
surgical procedure to which it alludes is somewhat drastic
and definitely ugly, and I suspect that it's used mainly by
those who didn't understand "split horizon DNS" straightaway
when they first saw it because they've never encountered a
sextant.  (-:

 
 
 

Terminology: "Split horizon"

Post by Jonathan de Boyne Pollar » Thu, 24 Jul 2003 21:56:16


BM> I've never before today heard "split horizon" in the
BM> context of DNS, [...]

My goodness!  Where have you _been_ during the last nine
years ?

 
 
 

Terminology: "Split horizon"

Post by Matt Curti » Fri, 25 Jul 2003 08:33:39



Quote:> My goodness!  Where have you _been_ during the last nine years ?

As far as I can tell, he's been earning the right to be accorded
significantly more respect than you can be bothered to show.

I don't think I've heard the term "split-horizon DNS" more than once
or twice, either.  So some subset of DNS users came up with some
bizarre name that barmar didn't remember seeing.  Big deal.  It's not
like he doesn't understand this stuff.

A little more Google usage suggests that "split-horizon DNS" is almost
as infrequently used as "split-brain(ed)? DNS".  A search for the
literal term returns fewer than 700 hits.  A Google search for "split
DNS" returns over 6,000.  "Split-brain DNS" returns almost 500, and
"split brained DNS" returns around twenty.

--
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Founder, Interhack Corporation +1 614 545 HACK http://web.interhack.com/
Author of /Developing Trust: Online Privacy and Security/ (Apress, 2001)

 
 
 

Terminology: "Split horizon"

Post by Richard J. Sexton (At wo » Fri, 25 Jul 2003 23:25:26


Quote:>A little more Google usage suggests that "split-horizon DNS" is almost
>as infrequently used as "split-brain(ed)? DNS".  A search for the
>literal term returns fewer than 700 hits.  A Google search for "split
>DNS" returns over 6,000.  "Split-brain DNS" returns almost 500, and
>"split brained DNS" returns around twenty.

And "braindead dns" gives 4 hits.

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1. Snapshot routing and "split horizon"

        Now i heard that if two branch offices shares one ISDN interface at the
        central site will lead to the following situation.

        Branch office A dials in and sends its local routing info as well as
        recives the backbone routing.

        Branch office B then dials in to the central site and send its local
        info.  Branch office B will at this moment also recive all backbone
        routing but NOT the routing info deliverd by branch office A.

        Is this last statement true?

   It's not clear.  It may or it may not, depending on the exact details
   of the configuration.  Note that snapshot is irrelevant in this case.

For me this depended on which router had connected to the central site last
8-) It was never a reliable thing.

        If so this will mean that branch A and B may not talk to each other
        via the Central site.

   That's not clear.  A and B may well have default (either statically or
   advertised from the backbone) and use this to communicate.

Having been well down this track 12 months ago, locally advertised defaults
and statics seem to be the only way to get a reliable connection. Whilst I
have had IP working between A & B using a RIP/EIGRP/Static fudge, I
wouldn't recommend anyone actually deploy this unless it was a "butt saver"
;-) It was never really dynamic.

        If iv got this right is it possible to turn split horizon of in
        this case?

    If you like.  "no ip split-horizon".  Not recommended.

I tried this with eigrp/rip hacks and it didn't help. We eventually went to
Frame-Relay :-)

Jon

2. LotusNotes -> Oracle connection

3. Barclays PC Banking panic

4. Help wanted!!!!********"""""""""///////

5. Visio 2002 Version Property

6. """seeking telecom consultant per diem basis""""

7. AxMSFlexGrid CellPicture Transparency

8. Confused by the term "Rom Monitor", "RXBOOT", "Bootstrap"

9. "ignored", "deferred" vs "drops"

10. modems from "Cardinal," "Zoom," and "Evertex"

11. ??? "Unofficial IP Address" --- "Proxy Server" VS "Windows2000Server" ???

12. "security", "authentication" and "other stuff".