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Command Reference Guide
voip name-service verification attempts <number> interval <seconds>
Use the voip name-service verification attempts interval command to configure the Voice over Internet
Protocol (VoIP) name service (VNS) to verify any domain naming system (DNS) changes to the VNS
table. Using the no form of this command disables verification.
Syntax Description
attempts <number>
interval <seconds>
Default Values
By default, the VNS system does not verify DNS changes.
Functional Notes
Voice and media signaling protocols (such as SIP) often rely on DNS in order to ease configuration and
administration of endpoints and also to implement redundancy mechanisms provided by DNS service
records. Because voice and media signaling protocols are often directly coupled to a user experience,
applications are often very sensitive to latency introduced by the DNS mechanism.
AOS voice products rely on the ability to resolve names to one or more service or address records quickly
in order to place a call or register to an external voice server. The DNS server is often not local to the AOS
unit, and it is not guaranteed to be accessible, even when other mechanisms necessary for successful call
completion may be available. A DNS request for a particular host name results in local caching by the AOS
unit, after which the DNS information is quickly available without requiring additional requests. The cache
remains populated until the cached record expires.
The VNS system in the AOS product implements preemptive and persistent caching of DNS records for
voice signaling protocols. The VNS system maintains a table of DNS records in a cache for voice signaling
protocols like Session Initiation Protocol (SIP) and Media Gateway Control Protocol (MGCP). For example,
if a request is generated from a SIP client (such as a SIP trunk or SIP proxy), for which there is a
configured SIP server entity (such as a proxy address or SIP server address), the request is always
serviced from the local DNS cache (rather than from an external DNS server). This ensures that SIP
access to DNS is always available immediately, even during transient DNS outages.
The VNS system in AOS can be configured manually by adding a host to the cache (using the command
voip name-service host on page
DNS cache changes (using the command
<seconds> on page
1458). You can view the VNS cache by using the commands
cache on page 825
and
Command History
Release A4.03
60000CRG0-35E
Specifies the number of consecutive DNS answers that validate a change to
the VNS table. Valid range is 1 to 10.
Specifies the time interval (in seconds) to wait between verification
attempts. Valid range is 1 to 600 seconds.
1456) and by specifying the number of attempts used by VNS to verify the
voip name-service verification attempts <number> interval
show voip name-service name-table on page
Command was introduced.
Copyright © 2012 ADTRAN, Inc.
Global Configuration Mode Command Set
show voip name-service
826.
1458
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