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From: sip-implementors-boun...@lists.cs.columbia.edu
[sip-implementors-boun...@lists.cs.columbia.edu] On Behalf Of hanifa.mohammed
[hanifa.moham...@globaledgesoft.com]
Can a FQDN "p1-cscf.open-ims.test" resolve to 3 IP addresses as below?
1. 172.16.8.10 - UDP and no signal security support
2. 172.16.8.20 - UDP, TCP but no signal security support
3. 172.16.8.30 - UDP, TCP and signal security support [TLS]
We feel that all the resolved IP addresses of an FQDN must be of
same configuration. Pl clarify.
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There is no requirement that all destinations for a SIP domain must have the
same support.
The simplest solution would be to have three A records for the domain name.
The hosts at the three addresses may listen for different protocols. E.g.,
host1 may listen on UDP but not TCP, while host2 listens on both UDP and TCP.
Although in theory this is not allowed, and all SIP elements are required to
listen for both UDP and TCP. But as long as a host provided ICMP "destination
port unreachable" responses for messages to ports that it is not listening to,
there wouldn't be much degradation of service.
A better solution is to use SRV records, which can specify a different set of
destinations for every combination of protocol and security. Approximately:
_sip._udp.p1-cscf.open-ims.test SRV 172.16.8.10 5600
_sip._udp.p1-cscf.open-ims.test SRV 172.16.8.20 5600
_sip._udp.p1-cscf.open-ims.test SRV 172.16.8.30 5600
_sip._tcp.p1-cscf.open-ims.test SRV 172.16.8.20 5600
_sip._tcp.p1-cscf.open-ims.test SRV 172.16.8.30 5600
_sips._tcp.p1-cscf.open-ims.test SRV 172.16.8.30 5600
Of course, IMS may add its own complications; I'm only using the RFC 3263 rules
here.
Dale
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