[reSIProcate] DNS SRV multiple records and timeouts

[Scott Godin]

Hi Nathan,

As you mentioned grey listed items will only be tried when all other
non-blacklisted results are checked.  This means we will not try the grey
record first.  So new requests should be using the non-greylisted and
non-blacklisted entries.

Some additional points:
1.  Records are only greylisted for 32 seconds.  So after that time
expires, we could end up trying the potentially bad record again, and
repeating the greylist process.  Making the greylist time configurable
would be nice.
2.  If you are creating a client and don't need to load balance your
outbound requests, then you could enable Whitelisting support - this enable
get your client to stick to a good record tree when one is found.  This is
disabled by default, since it breaks load balancing in SIP server
applications.  See  http://www.resiprocate.org/DNS for more info on how to
enable whitelisting (a compile time flag).

Regards,
Scott


On Thu, Aug 15, 2013 at 11:52 AM, Nathan Stratton <nathan at robotics.net>wrote:

> Based on http://www.resiprocate.org/DNS a SRV with two hosts where the
> first host is down that the stack will only greylist it. This seams like a
> redundancy issue since grey lists are only checked when all other
> non-blacklisted results are checked. All incoming requests to that SRV
> record would need to try the bad host over and over before trying the 2nd
> host in the record. Would it not make sense to blacklist a timeout host so
> that the next request would move to the good host?
>
> --
> ><>
> Nathan Stratton                                               Founder, CTO
> Exario Networks, Inc.
> nathan at robotics.net                                     nathan at
> exarionetworks.com
> http://www.robotics.net
> http://www.exarionetworks.com/
>
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