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Re: Mirror Negotiation

From: Stephen Lewontin <stevel@siren.osf.org>
Date: Tue, 10 Dec 1996 11:25:55 -0500
Message-Id: <9612101625.AA07047@berlin.osf.org>
To: bmorin@WPI.EDU
Cc: www-talk@w3.org

   An emerging trend on the web is to offer the same information at =
   multiple locations to increase performance, ie mirroring.  This has been =
   done with FTP for years.

   The way this is often done is by offering users a list of mirror sites =
   and having them select one from the list.  However, I do not feel this =
   is a decision that is best made by the user.  How does a user know what =
   mirror is best?  If the sites I frequent are all mirrored, why should I =
   go through the inconvenience of selecting a mirror each visit?

   Mirror selection can be done by the server within the constraints of =
   HTTP/1.0, however I do not feel that this is not a decision the server =
   should be making.  The server does not know where the client is nor is =
   the server in a position to test one or more mirrors to see which is =

   Therefore I see potential in having the client involved in the decision =
   of where to get information. =20

   In all of the flavors of HTTP I've seen, the only grammar for =
   negotiating where information is retrieved from is the simple redirect =
   from the server.  Would it be a good idea to send a list of alternative =
   locations a resource or a group of resources can be acquired so the =
   client can select the fastest location without user involvement?

   Is there anything I'm overlooking?

   Has there been any work in this area?

We are doing work in the area of server replication and
client-side load balancing. We intend to submit a paper to the next
WWW conference on the topic.  One issue that we raise is the need for
a proper name service where clients can find locations for replicated
servers. LDAP, which will be supported by most web browsers may be the

Steve Lewontin
Principal Research Engineer
Open Group Research Institute
Received on Tuesday, 10 December 1996 11:25:40 UTC

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