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Configuration Guide
As far as possible, the NMOS specifications make use of automated configuration techniques. Where additional configuration is required this will typically be carried out according to vendor-specific instructions (for example when configuring manual IP addressing). The following examples provide details for configuring aspects of systems which are agnostic to specific implementations.
Unicast DNS provides a more scalable discovery solution for APIs which make use of DNS-SD, as opposed to multicast DNS. Any standard DNS server will support the ability to advertise DNS-SD services. The following examples show how to configure some popular DNS servers to advertise an IS-04 Registration and Query API. Similar configuration can be applied to other server implementations.
The following lines should be included in a Linux BIND DNS zone file.
; These lines indicate to clients that this server supports DNS Service Discovery
b._dns-sd._udp IN PTR @
lb._dns-sd._udp IN PTR @
; These lines indicate to clients which service types this server may advertise
_services._dns-sd._udp PTR _nmos-registration._tcp
_services._dns-sd._udp PTR _nmos-query._tcp
; These lines give the fully qualified DNS names to the IP addresses of the hosts which we'd like to discover
; This example uses a domain of 'dns.nmos.tv'. We recommend using a subdomain of a domain name which you own.
registration1.dns.nmos.tv. IN A 192.168.200.5
query1.dns.nmos.tv. IN A 192.168.200.6
; There should be one PTR record for each instance of the service you wish to advertise.
; Here we have one Registration API (_nmos-registration._tcp) and one Query API (_nmos-query._tcp)
_nmos-registration._tcp PTR reg-api-1._nmos-registration._tcp
_nmos-query._tcp PTR qry-api-1._nmos-query._tcp
; Next we have a SRV and a TXT record corresponding to each PTR above, first the Registration API
; The SRV links the PTR name to a resolvable DNS name (see the A records above) and identify the port which the API runs on
; The TXT records indicate additional metadata relevant to the IS-04 spec
reg-api-1._nmos-registration._tcp SRV 0 0 80 registration1.dns.nmos.tv.
reg-api-1._nmos-registration._tcp TXT "api_ver=v1.0,v1.1,v1.2" "api_proto=http" "pri=0"
; Finally, the SRV and TXT for the Query API
qry-api-1._nmos-query._tcp SRV 0 0 80 query1.dns.nmos.tv.
qry-api-1._nmos-query._tcp TXT "api_ver=v1.0,v1.1,v1.2" "api_proto=http" "pri=0"The following lines should be added to the dnsmasq configuration file, e.g. /etc/dnsmasq.conf.
; These lines indicate to clients that this server supports DNS Service Discovery
; This example uses a domain of 'dns.nmos.tv'. We recommend using a subdomain of a domain name which you own.
ptr-record=b._dns-sd._udp.dns.nmos.tv,dns.nmos.tv ; domain enumeration
ptr-record=lb._dns-sd._udp.dns.nmos.tv,dns.nmos.tv ; legacy browse domain
; There should be one PTR record for each instance of the service you wish to advertise.
; Here we have one Registration API (_nmos-registration._tcp) and one Query API (_nmos-query._tcp)
ptr-record=_nmos-registration._tcp.dns.nmos.tv,reg-api-1._nmos-registration._tcp.dns.nmos.tv
ptr-record=_nmos-query._tcp.dns.nmos.tv,qry-api-1._nmos-query._tcp.dns.nmos.tv
; Next we have a SRV and a TXT record corresponding to each PTR above, first the Registration API
; The SRV links the PTR name to a resolvable DNS name (see hosts file below) and identify the port which the API runs on
; (priority and weight are optional and omitted here)
; The TXT records indicate additional metadata relevant to the IS-04 spec
srv-host=reg-api-1._nmos-registration._tcp.dns.nmos.tv,registration1.dns.nmos.tv,80
txt-record=reg-api-1._nmos-registration._tcp.dns.nmos.tv,"api_ver=v1.0,v1.1,v1.2","api_proto=http","pri=0"
; Finally, the SRV and TXT for the Query API
srv-host=qry-api-1._nmos-query._tcp.dns.nmos.tv,query1.dns.nmos.tv,80
txt-record=qry-api-1._nmos-query._tcp.dns.nmos.tv,"api_ver=v1.0,v1.1,v1.2","api_proto=http","pri=0"
The A records may be configured in the dnsmasq additional hosts file (specified by the -H,--addn-hosts=<file> option).
192.168.200.5 registration1.dns.nmos.tv.
192.168.200.6 query1.dns.nmos.tv.
The entries in the hosts file may omit the domain if two further lines are added to the configuration file:
expand-hosts
domain=dns.nmos.tv
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