|It is very convenient to be able to use one's personal
address, i.e: firstname.lastname@example.org, for both email and SIP communications (IP
telephony, presence, video conferencing etc), just by changing the application prefix. For
DNS is the mechanism for determing the IP address, port and transport of the host to which a SIP request is sent.
DNS provides two different record types that controls SIP requests: SRV and
NAPTR. The SRV resource record allows DNS administrators to use several servers, located on differnet
places, for a single domain. The NAPTR record is a way for the called domain to specify which protocol it prefers a SIP request to