Subject: [AAA-WG]: [Issue] Server Discovery

From: Pat Calhoun <[email-masked]>
Date: Tue, 5 Jun 2001 15:49:10 -0700

It seems this one fell through the crack :(

Issue nn: Server Discovery Text to change
Submitter name: Pat Calhoun 
Submitter email address: [email-masked] 
Date first submitted: 2001-06-05 
Reference: 
Document: Base 
Comment type: C 
Priority: 1 
Section: 2.6
Rationale/Explanation of issue: 

At the Interim Meeting, Bernard stated that we should adopt the
procedures described in draft-ietf-sip-srv-02.txt. 

Requested change: 

I am not sure what Bernard had in mind. Should we replace the whole
section, including the proposal to use SLPv2, and just use the DNS SRV
proposed in the above draft, or just replace the one section that deals
with DNS SRVs?

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From: Bernard Aboba <[email-masked]>
Date: Tue, 5 Jun 2001 23:45:33 -0700 (PDT)

I don't think we have to remove SLP support. The text in the SIP-SRV draft
specifies how SRV and A records are used in a very detailed way that would
be helpful (for example, how caching is done, etc.). I sent along some
text that could be gleaned from it that I thought would be useful to
insert.

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From: Pat Calhoun <[email-masked]>
Date: Wed, 6 Jun 2001 06:32:55 -0700

> text that could be gleaned from it that I thought would be useful to

Good, that's my preference too. I will take care of this one today. 

Thanks,

PatC

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From: Pat Calhoun <[email-masked]>
Date: Wed, 6 Jun 2001 09:30:34 -0700

All,

Here is my proposed text for this particular issue (specifically, I changed
text in item 3):

2.6  Diameter Agent Discovery

   Allowing for dynamic Diameter agent discovery will make it possible
   for simpler and more robust deployment of AAA services.  In order to
   promote interoperable implementations of Diameter agent discovery,
   the following mechanisms are described.  These are based on existing
   IETF standards.

   There are two cases where Diameter agent discovery may be performed.
   The first is when a Diameter client needs to discover a first-hop
   Diameter agent.  The second case is when a Diameter agent needs to
   discover another agent - for further handling of a Diameter
   operation. In both cases, the following 'search order' is
   recommended:

      1. The Diameter implementation consults its list of static
         (manual) configured Diameter agent locations.  These will be
         used if they exist and respond.

      2. The Diameter implementation uses SLPv2 [28] to discover
         Diameter services.  The Diameter service template [32] is
         included in Appendix A. It is recommended that SLPv2 security
         be deployed (this requires distributing keys to SLPv2 agents.)
         This is discussed further in Appendix A.

         SLPv2 will allow Diameter implementations to discover the
         location of Diameter agents in the local site, as well as their
         characteristics.  Diameter agents with specific capabilities
         (say support for the Mobile IP application) can be requested,
         and only those will be discovered.

      3. The Diameter implementation uses DNS to request the SRV RR [33]
         for the '_diameter._sctp' and/or '_diameter._tcp' server in a
         particular domain.  The Diameter implementation has to know in
         advance which domain to look for an Diameter agent in.  This
         could be deduced, for example, from the 'realm' in a NAI that
         an Diameter implementation needed to perform an Diameter
         operation on.

        3.1 If the destination address is a numeric IP address, the
            requestor contacts the peer at the given address and the
            port number specified in the SRV record or, if not
            specified, the default port (TBD).

        3.2 The results of the query or queries are merged and ordered
            based on priority. Then, the searching technique outlined in
            [46] is used to select servers in order. The requestor
            attempts to contact each peer in the order listed, at the
            port number specified in the SRV record. If none of the
            servers can be contacted, the requestor gives up. If there
            are no SRV records, DNS address records are used, as
            described below.

        3.3 If the destination specifies a port number other than TBD or
            if there are no SRV records, the requestor queries the DNS
            server for address records for the destination address.
            Address records include A RR's, AAAA RR's, or other similar
            records, chosen according to the requestor's network
            protocol capabilities.

            If the DNS server returns no address records, the requestor
            gives up. If there are address records, the same rules as in
            step 3.2 apply.

         Requestors MUST NOT cache query results except according to the
         rules in [47]. Diameter allows AAA peers to protect the
         integrity and privacy of communication as well as to perform
         end-point authentication.  Still, it is prudent to employ DNS
         Security as a precaution when using DNS SRV RRs to look up the
         location of a Diameter agent.  [34, 35, 36]

PatC