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Re: Proxies and gethostbyname

From: Jeffrey Mogul <mogul@pa.dec.com>
Date: Mon, 27 Apr 98 11:39:15 MDT
Message-Id: <9804271839.AA08355@acetes.pa.dec.com>
To: http-wg@cuckoo.hpl.hp.com
    Clarification is needed on what error is to be returned if a Proxy
    times out looking up a hostname.  The spec is silent on what is a
    very common failure.

    My current opinion is that returning 504 Gateway Timout is correct,
    but that clarification to the spec is in order.  But other options
    include introducting other error codes, or less likely, some other
    existing error code.
    
Before we charge off on a detailed discussion of what to do when a
proxy times out on a DNS translation, we might want to consider whether
is error is part of a larger class.

For example,
	what if the proxy has no route to the server?  (i.e.,
	it gets a "host unreachable" error).  This may also
	be a transient error (cf. the paper in USITS '97 on
	the observed routing instability in the Internet).  Is
	this the same as a "504 Gateway Timeout"?
	
I'm not sure whether there are any other errors in this class.
But if these are the only two that we can think of, perhaps
the proper name for the error is

	504 Temporarily Unable to Forward Request

with an entity body that explains the reason in more detail.
I.e., the relevant question is not "was this a timeout or not?"
but "is the error (probably) transient or is it permanent?"

If people think that these cases are actually different enough
to warrant separate error codes, then I think we ought to add
a "No route to next-hop server" code if we add a "DNS timeout" code.

-Jeff
Received on Monday, 27 April 1998 11:43:12 EDT

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