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Introduction ... 2 Deployment Scenario ... 2 DNS SRV (RFC 2782) ... 3Microsoft Server Configuration ... 4
Mediatrix 1600 Configuration... 7
Introduction
Effective May 6, 2005 – This configuration note is a step-by-step guide to set up DNS SRV in the Mediatrix 1631 E1 PRI VoIP gateway and Mediatrix FXS VoIP gateways in a SIP environment. This will allow Mediatrix
gateways to use a secondary server in case the primary server fails. It defines template configurations for the Mediatrix FXS analog gateways and Mediatrix 1631 digital gateway, which can be adapted with little effort to the network you want to configure.
Deployment Scenario
This configuration note assumes that all gateways are already working within a SIP environment. It also assumes that a working solution is currently in place with one server; a clone server will be added on the network, its only difference with the primary server being the location (IP address). Both servers should share the same database (Registrar database) and work in synchronization. Please contact your server provider to ensure that they support this functionality.
This configuration note will help you to add some configuration on the Mediatrix gateways to contact a backup server in case of failure with the first one or to do load balancing. It will also describe an example of DNS SRV configuration using a Microsoft Server.
This configuration note is not a substitute of the formal product documentation. Please have the following manuals available for reference:
Mediatrix Digital Devices Software Configuration Guide Mediatrix Digital Devices Getting Started Guide
Mediatrix 1104 Administration Manual (SIP version)
DNS SRV (RFC 2782)
Currently, one must either know the exact address of a server to contact it, or broadcast a question. DNS SRV is an extension of the standard DNS server. SRV (Service Record) is a type of entry a network administrator may put into the DNS answers. A DNS SRV is used to get one or more IP addresses of servers, each one having its own weight and priority.
Each server received when using DNS SRV, depending on its weight and priority, can be used as a primary or backup server or can be part of a load balancing system.
For instance, the client requests the SRV for SIP servers in some domain. The DNS server may return the A, B, and C addresses, which are all SIP servers. Each address has a weight and the client must choose one of those three addresses by using a random algorithm that considers the weight.
Microsoft Server Configuration
This section describes how to use a Microsoft 2000 server to answer the DNS SRV request.
The domain name for the Mediatrix unit will be saleslab.mediatrix.com. We will create two SRV records under that domain name: one for the primary server (Primary) and the other for the secondary server (Secondary). Then, under the saleslab.mediatrix.com domain name, you will create two A records to resolve the “primary and secondary” host name for there corresponding IP address.
Step 2:
Create a new SRV record
Using the option “Other New Records” you can create a new SRV record. Select SRV in the Resource Record Type window.
Click the Create Record button.
Change the following parameters for the Primary server (see illustration on next page):
Parameter Value
Service _sip
Protocol _udp (_tcp, if using SIP tcp)
Priority 1 (for the Primary Server)
Port Number 5060
Step 4:
Enter the following information:
Host name IP address
Step 5:
Repeat Step 4 for the second server
Mediatrix 1600 Configuration
Step 1:
DNS Configuration
To configure the DNS server IP address in the Mediatrix 1600 follow these instructions: Mediatrix1600>enable
Mediatrix1600#configuration
Mediatrix1600(cfg) #dns server 62.2.32.5
Step 2:
Penalty Box
To configure the Penalty box feature in the Mediatrix 1600 follow these instructions: Mediatrix1600(cfg) #gateway sip gw-sip (i.e. gateway’s name)
Mediatrix1600(gtw-sip) [sip] #penalty-box-time 300
Step 3:
Transaction Timeout
Mediatrix 1104 Configuration
Step 1:
DNS Configuration
If the IP configuration of the unit is done manually, configure only the IP address of your DNS SRV manually.
If the unit gets its IP configuration from a DHCP server, you can overwrite the value of the DNS server to point the unit to the appropriate DNS SRV server. In the MIB structure of the unit, set the following parameters:
o Set the telephonyDNSOverrideEnable variable to enable.
o Configure the IP address of your primary DNS server in the telephonyDnsStaticPrimaryDns variable.
Step 2:
SIP Server configuration
Configure the SIP server with the FQDN address you created in the Microsoft 2000 server:
Step 3:
Penalty Box
If the Penalty Box is disabled and the SIP servers parameters are provisioned with a DNS SRV query that is defined with a primary and secondary server, the unit will always try the primary server and wait for the timeout as defined in Step 4: SIP Transmission Timeout setting. This causes some delay on all calls when the primary server is not answering.
When the feature is enabled, the unit will wait for the configured time to try again with the primary server, using the secondary server in the mean time.
Mediatrix recommendation:
Parameter Value
sipPenaltyBoxEnable enable
sipPenaltyBoxTime Depends on the average down time. 300 (seconds) is
Step 4:
SIP Transmission Timeout setting
This is to configure the amount of time the unit will wait for an answer from the Primary server before trying the secondary.
