Hi Rishi,
couple of month ago, we were discussing if we might take advantage of
service discovery in Automated Installer (AI) project [1].
Maybe you remember :-)
We have implemented the first phase which uses service discovery over
multicast DNS and now we are in process of enhancing the prototype with
support for service discovery over unicast DNS.
At the time being, we use dns-sd(1M) utility for multicast DNS:
* On AI server side, it is used for registering/advertising the service
* On AI client side, it is used for looking up the service
It is sufficient for proof of concept, but since dns-sd(1M) is only
recommended to be used as testing/debugging tool, as a long term solution,
we would like to create dedicated daemon directly consuming libdns_sd(3LIB)
library taking care of all service discovery tasks.
Meanwhile, we are thinking about how we might implement support for unicast
DNS for now. As far as server side is concerned, we will ask user to
manually
add appropriate PTR and SRV records to the DNS server database. Later
we might be thinking about dynamic DNS update.
With respect to client side, we are thinking if we can continue to use
dns-sd(1M) for looking up the service over unicast DNS.
I have gone through your presentation about Service Discovery and
multicast DNS [2] and in examples, dns-sd(1M) is only used
for testing multicast DNS, dig(1M) and nslookup(1M) are utilized
for testing unicast DNS part.
Since dns-sd(1M) takes domain to browse as parameter, I was wondering
if we could do something like following to look up '_test_service'
instance of '_OSInstall._tcp' service in 'ai-caiman.org' domain.
$ dns-sd -L _test_service _OSInstall._tcp ai-caiman.org
I have tried, but snoop(1M) didn't report any traffic on net
which might be related to this.
I was able to successfully query appropriate PTR and SRV records
using dig(1M) or nslookup(1M) commands. I have added following
records to DNS database for created 'ai-caiman.org' domain:
...
_OSInstall._tcp PTR _test_service._OSInstall._tcp
_test_service._OSInstall._tcp SRV 0 0 46511 tio-nb.ai-caiman.org.
TXT
aiwebserver=tio-nb.ai-caiman.org:46511
...
dig(1M) reports:
$ dig @192.168.100.2 -t ptr _OSInstall._tcp.ai-caiman.org
;; ANSWER SECTION:
_OSInstall._tcp.ai-caiman.org. 86400 IN PTR
_test_service._OSInstall._tcp.ai-caiman.org.
$ dig @192.168.100.2 -t any _test_service._OSInstall._tcp.ai-caiman.org
...
;; ANSWER SECTION:
_test_service._OSInstall._tcp.ai-caiman.org. 86400 IN SRV 0 0 46511
tio-nb.ai-caiman.org.
_test_service._OSInstall._tcp.ai-caiman.org. 86400 IN TXT
"aiwebserver=tio-nb.ai-caiman.org:46511"
...
I have couple of questions here in order to clarify what approach
we might take. Could I please ask you if you might help us understand
what the limitations are and what approach we might take ?
* Can we use dns-sd(1M) for browsing domains/looking up services which
are available over unicast DNS ? If we can, what are the prerequisites
we need to meet in order to make it work ?
* If dns-sd(1M) can't be used, could we take advantage of dig(1M) or
nslookup(1M) commands instead ?
* As far as long term solution is concerned, does libdns_sd(3LIB) support
unicast DNS ? What kind of operations are supported (look up,
register, ...) ?
Thank you very much for your help,
Jan
[1] http://www.opensolaris.org/os/project/caiman/auto_install/
[2] http://atlantic.east/~rs200217/bonjour/mdns-sd.pdf (available only
internally)
