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Global SIP Settings
41-001343-02 REV04 – 05.2014 4-61
Use the following procedure to configure backup outbound proxies.
Limitations
The following are limitations with this feature:
• Keep-alive mechanisms shall be limited to IPv4 only.
• Per M5T, RFC5686 is not fully supported although the draft upon which it was based (draft-ietf-sip-outbound-15) is sup-
ported.
SIP Server (SRV) Lookup
The SIP SRV Lookup feature allows you to configure the IP phone to issue a DNS query to retrieve records pertaining to a
SIP proxy, a SIP registrar, or a SIP outbound proxy.
The IP phone issues a DNS query for an SRV record when the IP address of the server is FQDN and the corresponding port
is 0.
For example, if the phone is configured with sip proxy ip of "ana.aastra.com", and sip proxy port of "0", the SRV lookup
may return multiple servers, based on the priorities if one is selected as primary and others are selected as secondary.
However, if the IP address is an FQDN and the corresponding server port is non-zero, then the phone issues a DNS "A"
Name Query to resolve the FQDN into dot notation form.
If the IP address is a valid dot notation and the port is zero, then a default port 5060 is used.
You can configure SRV lookup using the configuration files (aastra.cfg and <mac>.cfg) only. The parameters to use are:
• sip proxy ip
• sip proxy port
Contact Header Matching
When sending SIP packets, the IP Phones observe the Contact header by matching the username, domain name, port, and
transport as referenced in SIP RFC 3261.This is called “strict SIP Contact header matching.” However, in specific networks
(such as behind some SOHO routers), the phone registers with its private address in the Contact, but when the response is
sent back, the router maintains the public side IP address in the Contact header. This causes a non-matching Contact
header and the phone does not accept the new registration expiry timer.
You can set the parameter, “sip contact matching”, which allows the Administrator to specify the method used by the
phone to match the Contact Header. Previously by default, when sending SIP packets, the IP phones observed the contact
header by doing a full URI matching of username, domain, phone IP and port name, and transport (value=’0’). Now the
default value for the “sip contact matching” parameter is to match the username only (value=’2’). This parameter is avail-
able via the configuration files only.
Enabling/Disabling the “Contact Header Matching” Feature
Use the following procedure to enable/disable the “Contact Header Matching” feature
.
Configuration Files
For the specific parameter you can set in the configuration files, see Appendix A, the section, “Backup Outbound Proxy (Global Settings)” on pageA-
68 and “Backup Outbound Proxy (Per-line Settings)” on pageA-77.
Note:
The phones only generate a ‘request’ and do not facilitate the ‘DNS or SRV service or provide a response to the requests.
Configuration Files
For the specific parameter you can set in the configuration files, see Appendix A, the section, “Contact Header Matching” on pageA-60.