Survey Result


Below is the result of survey conducted for ACH (Automatic Call Handling
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Result of UA follows that of Proxy

Proxy
Q1A Configuration mechanism that are supported
Web UI 7
XCAP 1
FTP/FTPS/SFTP
0
SOAP 6
CPL 1
CSTA 1
Others 4
Not Applicable 1
Q1B Most commonly supported mechanism for configuration
Web UI 4
SOAP 2
Not Applicable 1
Q2A Status Code used for Indicating DND
406
1
486 5
480 2
600 1
603 1
Others 3
Not Applicable 1
Q2B Status Code used for Indicating Busy
486 7
480 3
600 1
Others 1
Q3 When does ACH initiates when multiple contacts are registered for the target AoR
ASAP 3
When all responds 2
Others 2
Not Applicable 1
Q3A If indicated others for Q3 describe
If a 302 or 603 response is received, then all other contacts are cancelled and the 302/603 is handled. Such responses are considered user initiated/configured. On the other hand, if a 480, 486, 606 etc response is received, then the B2BUA waits for all the other contacts to respond. And then takes a decision.
Depending upon the service instantiated, the UA may generate no response but stop alerting, generate a 486 response which would kill that fork, or a 603 which would kill all forks. 600 would kill all forks and go to voicemail.
Q4 If two different responses were received which can initiate different ACH what then?
A priority list among the response received is followed.
Whichever response arrives first
Priority list is used
Priority on return codes will lead to only one action
The 3xx responses are redirected The 4XX/5XX/6XX responses are canceled
Individual responses are followed until one accepts the request. For example, an INVITE that is 300 redirected by one contact and 180 ringing by another, the redirected contact is handled internally and attempted at the new contact.
SIP response code order of precedence and order of arrival are considered. Upstream proxies may normalize some response codes generated by end clients or gateways into a 480 response code.
Q5 Support for discovering where to configure ACH?
Yes 2
No 5
Q5A How is it done?
Depending on the manufacturer's UA, at least two ways:
IP phone display client "toolbar" for the UA using SOAP
Device Configuration
Q6 Do Proxy/B2BUA execute ACH without routing the call first to the contact?
Yes 8
No 1
Q6A If you answered Yes to Q6, when is it executed?
Call Forward Always.? Call Forward Busy in some cases.
If the provisioned user configuration in the database tells this
(the DB content is normally adjustable via a web interface).
Unconditional forward. Call screening. Not available ( not registered ) Forward
The proxy (app server) is also a B2BUA, if the automatic handling is configured there, it will handle the call.
A contact can be behind another proxy (address configured statically) and hence will route to that Proxy.
For the Call Forward unconditional case.
Screening depending upon other conditions such as time of day, calling party ID, etc.
Q7A How does it treat 6xx response if there are multiple contacts registered for the target AoR?
A 6xx response is considered a terminal failure, equivalent to all other terminal failures. The automatic handling continues as configured (e.g. try another ITSP or CO, forward to operator or voicemail, etc).
As Proxy:? Forward the message. As B2BUA: Treated as final response and no further action performed.
The B2BUA follows configured re-routing rules or have a specific treatment?
Will stop processing further routes. May forward to voicemail for 600 response, or not for 603 response.
Q7B How does it treat 6xx response if other contact outside the domain is registered.
A 6xx response is considered a terminal failure, equivalent to all other terminal failures. The automatic handling continues as configured (e.g. try another ITSP or CO, forward to operator or voicemail, etc).
As Proxy:? Forward the message. As B2BUA: Treated as final response and no further action performed.
The B2BUA follows configured re-routing rules or have a specific treatment?
Certain features allow the proxy to route the call to an alternate endpoint. (e.g. backup SIP trunk on a disaster recovery scenario)
Will stop processing further routes. May forward to voicemail for 600 response, or not for 603 response.
Q8 Is there a way to communicate the current setting of ACH to the UA?
No, the B2BUA hides all of the contact information from the UA and performs all automatic handling silently.
Subscribe/Notify mechanism. Synchronizes the call forward state between the endpoint and the B2BUA server. The phone subscribes for the services it is interested in (e.g., DND, CFA, CFB, CFNA). Notifies are sent either way when the service is modified.
Yes, via uaCSTA
Yes, in some cases. Mechanism varies.
Q9 Does it override the 302 response without considering RFC 4458?
Yes 4
No 5
UA
Q1 Does UA implement ACH
Yes
7
No
2
Q1A If 3xx used for ACH which code?
300
1
301
1
302
7
Not Applicable
2
Q1ex: Does it use RFC 4458?
Yes
2
No
6
Q1B If 4-6xx used which code?
400
1
403
1
404
1
405
1
408
1
415
1
420
1
480
1
481
1
482
1
486
2
491
1
500
1
600
1
603
2
Not Applicable
7
Q2 Can the UA configure the proxy remotely via local UI?
Web UI
5
SOAP
2
CSTA
1
Not Applicable
2
Q3 How does UA indiate DND?
480
1
486
2