Siemens HIPATH 8000 User Manual
Page 41
Technical Overview
41
DNS
The phone uses Æ DNS services provided the phones operating system
to perform the following:
• Resolve the IP address of servers that have been configured as names
(DNS A,AAAA records).
• Resolve the IP address of the domain part of users called by URL (DNS
A,AAAA records).
• Identify the location of servers and provide for failover and load balan-
cing (DNS A, AAAA and DNS SRV).
For DNS services to be used on the phone the following must be config-
ured either manually or provided by DHCP:
• Prim DNS IP addr Æ page 207
• Sec DNS IP addr Æ page 212
The Primary DNS server IP address must be configured if DNS is to be
used however the secondary server is optional. The purpose of the sec-
ondary server is to allow a backup DNS server to be used in the system
environment to increase system availability and reliability.
The phone can contact several types of server for different reasons (SNTP,
SNMP, SIP server etc). If a server has been configured by name and not IP
address the phone will provide a DNS lookup to resolve the name to an IP
address when the server needs to be contacted. To optimize network traf-
fic performance the phone caches the result of the normal A and AAAA
record lookups and will not re-issue a request to the DNS server to resolve
that address again until the Time To Live value from the previous lookup
has expired. This mechanism does not currently apply to DNS SRV look-
ups.
If a secondary DNS server has been configured and the primary fails to re-
spond to a request, that request will be re-issued to the secondary DNS
server.
If a DNS Domain Name and one or both of the DNS IP addresses
have been configured, then additionally the following host names
can be entered alternatively to the corresponding IP addresses:
(server, gateway, registrar)
• Download server IP address or DNS name Æ page 183
• SNMP Trap IP address or DNS name Æ page 219
• SNTP server address or DNS name Æ page 219