Mitel 6800 Series Administrator's Manual page 221

For the specific parameter you can set in the configuration files, see Appendix A, the section,
"Backup Outbound Proxy (Global Settings)"
on .
Settings)" page A-91
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 supported.
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.
Note: The phones only generate a 'request' and do not facilitate the 'DNS or SRV service
or provide a response to the requests.
For example, if the phone is configured with sip proxy ip of "ana.mitel.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 (
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
on and
page A-80 "Backup Outbound Proxy (Per-line
startup.cfg
Global SIP Settings
and <mac>.cfg) only.
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