[asterisk-bugs] [JIRA] (ASTERISK-21150) UDPTL Error Correction Scheme Negotiation Issue, Asterisk copies the Error Correction Scheme from T38 offer from remote peer even if UDPTL error correction scheme is set to NONE for that peer in sip.conf

[NITESH BANSAL (JIRA)]

    [ https://issues.asterisk.org/jira/browse/ASTERISK-21150?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=203592#comment-203592 ] 

NITESH BANSAL commented on ASTERISK-21150:
------------------------------------------

Hi Matt,
According to me, if EC scheme is set to NONE is sip.conf, it means that you explicitly state that no error correction scheme should be used.
Whereas in case of FEC/Redundancy, i think it is best to keep the code as it is, because if EC is cofigured to FEC or Redundancy, it means that you want 
to use some kind of error correction if possible.
I don't think anyone would configure EC to NONE in their sip.conf and still want to use ERROR CORRECTION depending on the offer from peer, the use case which we had
was also related to testing a T38 call without any error correction, so we cpnfigured EC to NONE in our sip.conf.

Regards,
Nitesh Bansal

                
> UDPTL Error Correction Scheme Negotiation Issue, Asterisk copies the Error Correction Scheme from T38 offer from remote peer even if UDPTL error correction scheme is set to NONE for that peer in sip.conf
> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: ASTERISK-21150
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-21150
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Channels/chan_sip/T.38
>    Affects Versions: SVN
>         Environment: x86_64 Debian Squeeze Distro
>            Reporter: NITESH BANSAL
>            Assignee: NITESH BANSAL
>            Severity: Minor
>         Attachments: do-not-use-ec-from-offer-if-configured-ec-is-none.patch
>
>
> Scenario: Asterisk receives a T38 invite which proposes some error correction scheme, Asterisk copies the error correction scheme from the offer and puts it in 200 OK. This behaviour does not change even if UDPTL error correction scheme is set to NONE for this peer.
> Expected Output: Asterisk should respond with no error correction scheme if this peer has t38_udptl error correction scheme set to NONE.
> Below is the reference from T38 spec:
> """"T38FaxUdpEC is negotiated only when using UDPTL as the transport. This parameter can have
> one of three values (see also Table D.2): t38UDPNoEC, t38UDPRedundancy, or t38UDPFEC. If
> the answering endpoint supports the offered error correction mode, then it shall return the same
> value in the answer, otherwise a different value shall be returned""""

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