How to connect to Huawei devices

Huawei develops various devices which has nasty bugs in SIP implementation.

Huawei sends patches to Asterisk to cripple Asterisk to support their non-standard SIP implementation but do not fix their own implementations.

One we encountered is then in SIP INVITE message Asterisk sends line:

a=silenceSupp:off - - - - -

Huawei softswitch does not like it and returns error:

Got SIP response 500 "Server Internal Error" back from 80.237.1.70 

Also Hangupcause code 38 which means: NETWORK_OUT_OF_ORDER

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Related links:

• http://lists.digium.com/pipermail/asterisk-dev/2006-March/019067.html
• http://lists.digium.com/pipermail/asterisk-dev/2006-March/019156.html
• http://bugs.digium.com/view.php?id=6669

Provider which uses Huawei insisted we should patch (criple) Asterisk to make to work with their softdwitch. Instead we put middle server between our Asterisk server and their softswitch:

Our main Asterisk <--IAX2--> Patched Asterisk <--SIP--> Huawei softswitch

In /usr/src/asterisk/channels/chan_sip.c we commented lines

    if (!p->owner || !ast_internal_timing_enabled(p->owner))
            ast_build_string(&a_audio_next, &a_audio_left, "a=silenceSupp:off - - - -\r\n")

as it is described in this patch. Recompiled Asterisk and it started to work.