Call Processing Of Sip Dialog Requests - AudioCodes Mediant 4000 SBC User Manual

CHAPTER 22 SBC Overview
If the operation mode is configured in both tables, the operation mode of the IP Group is applied.
Once configured, the device uses default settings in the IP Profiles table for handling the SIP
headers, as mentioned previously. However, you can change the default settings to enable partial
transparency.
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Call Processing of SIP Dialog Requests

The device processes incoming SIP dialog requests (SIP methods) such as INVITE,
SUBSCRIBE,
REGISTER. The process is summarized in the following figure and subsequently described:
The To-header tag remains the same for inbound and outbound legs of the dialog,
regardless of operation mode.
If the Operation Mode of the SRD\IP Group of one leg of the dialog is set to 'Call
Stateful Proxy', the device also operates in this mode on the other leg with regards
to the dialog identifiers (Call-ID header, tags, CSeq header).
It is recommended to implement the B2BUA mode, unless one of the reasons
mentioned previously is required. B2BUA supports all the device's feature-rich
offerings, while Stateful Proxy may offer only limited support. The following
features are not supported when in Stateful Proxy mode:
✔
Alternative routing
✔
Call forking
✔
Terminating REFER/3xx
If Stateful Proxy mode is enabled and any one of the unsupported features is
enabled, the device disables the Stateful Proxy mode and operates in B2BUA
mode.
You can configure the device to operate in both B2BUA and Stateful Proxy modes
for the same users. This is typically implemented when users need to
communicate with different SIP entities (IP Groups). For example, B2BUA mode
for calls destined to a SIP Trunk and Stateful Proxy mode for calls destined to an IP
PBX. The configuration is done using IP Groups and SRDs.
If Stateful Proxy mode is used only due to the debugging benefits, it is
recommended to configure the device to only forward the Call-ID header
unchanged
OPTIONS, REFER, INFO, UNSOLICITED
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Mediant 4000 SBC | User's Manual
NOTIFY, MESSAGE, and