Cisco Cisco Expressway Manual De Manutenção
Call signaling SRV records
Call signaling SRV records (and A/AAAA records) are intended primarily for use by non-registered endpoints which
cannot participate in a location transaction, exchanging LRQ and LCF. For each domain hosted by the Expressway,
you should configure a call signaling SRV record as follows:
cannot participate in a location transaction, exchanging LRQ and LCF. For each domain hosted by the Expressway,
you should configure a call signaling SRV record as follows:
■
_Service
is
_h323cs
■
_Proto
is
_tcp
■
Port is the port number that has been configured from Configuration > Protocols > H.323 as the Call signaling
TCP port.
TCP port.
Registration service SRV records
Registration records are used by devices attempting to register to the Expressway. For each domain hosted by the
Expressway, you should configure a registration service SRV record as follows:
Expressway, you should configure a registration service SRV record as follows:
■
_Service
is
_h323rs
■
_Proto
is
_udp
■
Port is the port number that has been configured from Configuration > Protocols > H.323 as the Registration
UDP port
UDP port
Configuring SIP SRV Records
describes the DNS procedures used to resolve a SIP URI into the IP address, port, and transport protocol of
the next hop to contact.
If you want the Expressway to be contactable using SIP URI dialing, you should configure an SRV record for each SIP
transport protocol enabled on the Expressway (that is, UDP, TCP or TLS) as follows:
transport protocol enabled on the Expressway (that is, UDP, TCP or TLS) as follows:
■
Valid combinations of
_Service
and
_Proto
are:
—
_sips._tcp
—
_sip._tcp
—
_sip._udp
(although not recommended)
■
Port is the IP port number that has been configured from Configuration > Protocols > SIP as the port for that
particular transport protocol.
particular transport protocol.
_sip._udp
is not recommended because SIP messages for video systems are too large to be carried on a packet based
(rather than stream based) transport. UDP is often used for audio only devices. Also, UDP tends to be spammed more
than TCP or TLS.
than TCP or TLS.
Example DNS Record Configuration
A company with the domain name
example.com
wants to enable incoming H.323 and SIP calls using URI addresses in
the format
user@example.com
. The Expressway hosting the domain has the FQDN
expressway.example.com
.
Their DNS records would typically be as follows:
■
SRV record for
_h323ls._udp.example.com
returns
expressway.example.com
■
SRV record for
_h323cs._tcp.example.com
returns
expressway.example.com
■
SRV record for
_h323rs._tcp.example.com
returns
expressway.example.com
■
NAPTR record for
example.com
returns
—
_sip._tcp.example.com
and
—
_sips._tcp.example.com
■
SRV record for
_sip._tcp.example.com
returns
expressway.example.com
■
SRV record for
_sips._tcp.example.com
returns
expressway.example.com
195
Cisco Expressway Administrator Guide
Dial Plan and Call Processing