RE: The internet architecture

["Hallam-Baker, Phillip" <pbaker@xxxxxxxxxxxx>]

Title: Re: The internet architecture

You are wrong.

 

Take SMTP email. Imagine that a company has three mail servers at geographically dispersed locations with independent network connections. With MX records a local failure of IP connectivity does not need to mean total failure of IP connectivity.

 

In fact provided that core DNS is there, and BGP is not borked it is possible to contingency plan for pretty much any outage that does not result in a virtually complete loss of connectivity at the client end.

 

 

A chain is only as strong as its weakest link. The Internet is not a chain, it is a mesh. A mesh is stronger than the weakest link.

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From: Keith Moore [mailto:moore@xxxxxxxxxxxxxxxxxxxx]
Sent: Thu 12/4/2008 4:29 PM
To: Hallam-Baker, Phillip
Cc: Bryan Ford; tae@xxxxxxxx; ietf@xxxxxxxx
Subject: Re: The internet architecture

Hallam-Baker, Phillip wrote:
> I am trying to parse this claim.
>
> Are you saying that the DNS is fragile and raw IP relatively robust?

DNS is layered on top of IP.  So for a large class of IP failures, DNS
won't work either.  And if IP routing fails, DNS is likely to be
irrelevant because the application using DNS won't work anyway.

And in practice, DNS is quite likely to fail due to configuration
errors, inadequate provisioning, outdated cache entries due to
unanticipated changes, brain-damaged DNS caches built into NATs, failure
of registries to transfer a DNS name in a timely fashion, etc.

So it's not a question of whether DNS is less reliable than IP (it is),
or even whether the reliability of DNS + IP is less than that of IP
alone (it is).  It's a question of whether increasing reliance on DNS by
trying to get apps and other things to use DNS names exclusively, makes
those apps and other things less reliable.  And I'd argue that it does,
except perhaps in a world where renumbering happened frequently, at
irregular intervals, and without notice.  And I don't think that's a
realistic scenario.

Keith

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