Subject: [Int-area] Specification of inbound destination addresses for failover and load balancing via DNS

From: "Greg Daley" <[email-masked]>
Date: Mon, 11 Jan 2010 09:31:30 +1100

Hi,

There's been some interest for a while in controlling inbound
connections
to IPv6 application servers, which allows use of separate blocks of
Provider Aggregatable IP addresses while retaining policy control for
client path selection.

In environments where a single set of server addresses are in use, BGP
routing provides path specification for packets inbound to an
application server.

Where multiple sets of addresses, path selection is effectively
undertaken by 
a client's destination address selection, which typically occurs at name
resolution.

Existing host (A and AAAA) lookup mechanisms provide no automated
failover and only
round robin load balancing mechamisms.  Lookup mechanisms for specific
services (MX and
SRV) have means by which allow specified address selection on clients,
with more
sophisticated failover and loadbalancing.

An experimental mechanism which extends SRV records to hosts (rather
than specific 
services) is presented in draft-daley-dnsext-host-srv-00.txt.  I am
seeking Int-Area
interest and review on this document.

Please reply or discuss on list if this is interesting or requires
specific improvement.

Authors:

  Greg Daley
  Raymond Ng

Title:   
   Use of DNS SRV records for host selection

URL:
   http://tools.ietf.org/html/draft-daley-dnsext-host-srv-00

Abstract:

   Where multiple application servers are able to receive inbound
   connections from clients, it is desirable provide some policy control
   over client behaviour.  This specification allows application service
   providers to provide addresses of multiple servers in response to DNS
   queries, while specifying failover and load balancing behaviours.

   Multiple servers are specified using existing protocol mechanisms for
   DNS Service records (SRV).  An experimental record definition is
   described, which can be implemented on existing systems.

Greg Daley
Security Consultant
NetStar Australia Pty Ltd

E-mail: [email-masked]
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