On 30 December 2014 at 22:49, Måns Nilsson mansaxel@besserwisser.org wrote:
Subject: Re: [SR-Users] Kamailio Active / Active HA. Date: Mon, Dec 29, 2014 at 11:13:34AM +0000 Quoting Ben Langfeld (ben@langfeld.co.uk):
Just a word of caution here, there are several SIP stacks which don't handle SRV lookups correctly. I don't mean to discourage you from this,
but
just to be aware of it. For example, Mobicents only understands SRV
record
sets which return domain names. If you return IPs, Mobicents will go
ahead
and look them up as A records and fail.
I would never, ever, put an IP address in the Target field of a SRV record. The specification says:
Target The domain name of the target host. There MUST be one or more address records for this name, the name MUST NOT be an alias (in the sense of RFC 1034 or RFC 2181). Implementors are urged, but not required, to return the address record(s) in the Additional Data section. Unless and until permitted by future standards action, name compression is not to be used for this field.
RFC2782, p3Pretty clear. A host name there should be, resolved to an AAAA/A record. Mobicents is actually Doing The Right Thing; even though one could claim the Robustness Principle in favour of the more lenient behaviour, it is indeed proper to expect to be able to do DNS AAAA/A lookups on the Target string.
Ah, I was not aware of this. Thanks for pointing it out :)
Further, it is a syntax violation to put an IPv6 Address in the Target field. I made a copy of my zone file and threw in a bogus SRV record. Then I gave it to the BIND 10 syntax checker, which most predictably barfed on it:
ball-empfang:tmp mansaxel$ /usr/local/bind10-0a1/sbin/named-checkzone besserwisser.org bsu bsu:35: warning: 2001:470:28:842:201:2eff:fe48:86aa.besserwisser.org: bad name (check-names) zone besserwisser.org/IN: _knolk._tcp.besserwisser.org/SRV '2001:470:28:842:201:2eff:fe48:86aa.besserwisser.org' has no address records (A or AAAA) zone besserwisser.org/IN: loaded serial 2014122801 OK ball-empfang:tmp mansaxel$ sed -n 35p bsu _knolk._tcp 10 SRV 0 0 567 2001:470:28:842:201:2eff:fe48:86aa
So, dont! ;-)
/Måns, who has a population of specialised IP phone devices that most certainly won't do SRV. -- Måns Nilsson primary/secondary/besserwisser/machina MN-1334-RIPE +46 705 989668 LOOK!! Sullen American teens wearing MADRAS shorts and "Flock of Seagulls" HAIRCUTS!