Subject: [Ips] iSNS failover and multi-server configurations

From: [email-masked]
Date: Wed, 4 Feb 2004 18:36:44 -0800 (PST)

The iSNS draft (draft-ietf-ips-isns-21.txt) mentions the concept of backup
servers (especially in the heartbeat PDU) and says it will describe client
interatctions with multiple servers (Section 2.8). However I can't find
any discussion of client interactions in that section.

So can we either have some more text, or some sort of suplimental document
that gives guidelines on how to deal with these concepts? I have a few
questions, and while I can answer them, I want to make sure my answers
agree with everyone else's. :-)

Questions:

1) Say a device is using iSNS heartbeats to find the server. Say it starts
up and can't connect to the primary server (or specifically it is only
hearing messages from a backup server). Say it registers with the backup
server. Now say the primary server comes back on line. What does the
device need to do?

1a) does it re-register its configuration with the new primary server, or
does it assume that the new server synchronized itself before resuming
being hte primary server?

1b) does it need to register SCN requests with the new server? Does it
need to de-register its old SCN registrations?

2) I see that DHCP can indicate multiple servers. But what about SLP in
face of multiple servers? Andy Currid suggested that SLP should only have
the most-senior operational server registered. But what happens when
either a formerly-off-line server comes back on line or an on-line server
goes off-line? SLP does not seem well-suited for "server moved"
notifications. Also, with SLP, if a server fails, what are the security
considerations for the backup server to be able to de-register the server?

Would it be easier for SLP to add a "precedence" attribute and have each
server register with SLP, then have the client perform the same failover
as DHCP and heartbeat do?

Thanks!

Take care,

Bill

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