Hi all.

I have an issue/doubt regarding Via header. The scenario is a FreeSwitch connected to a Mavenir’s IMS; call is generated by FS towards Mavenir’s IMS (it is ok) and release (BYE) is coming from IMS:

Request-Line: BYE sip:gw+ibcf_gateway@192.168.242.42:5060;transport=udp;gw=ibcf_gateway SIP/2.0

Message Header

     [truncated]Via: SIP/2.0/UDP scscf.ims.mnc001.mcc001.3gppnetwork.org:5060;rport;branch=z9hG4bKmavodi-0-4c-bf-2-640020-4df45e927c208f36,SIP/2.0/UDP tas.ims.mnc001.mcc001.3gppnetwork.org:5060;received=192.168.239.37;rport=5060;branch=z9hG4bK

        Transport: UDP

        Sent-by Address: scscf.ims.mnc001.mcc001.3gppnetwork.org

        Sent-by port: 5060

        RPort: rport

        Branch: z9hG4bKmavodi-0-4c-bf-2-640020-4df45e927c208f36

        Transport: UDP

        Sent-by Address: tas.ims.mnc001.mcc001.3gppnetwork.org

        Sent-by port: 5060

        Received: 192.168.239.37

        RPort: 5060

        Branch: z9hG4bKmavodi-0-7e-76-1-ffffffff-3029420078-24076

    Max-Forwards: 69

    From: <sip:+628811451570@ims.mnc001.mcc001.3gppnetwork.org>;tag=mavodi-0-7e-76-1-ffffffff-_000C2939994E-5e0c-a2ac4700-5df-5ae2f6d8-24075

    To: "+628811452131" <sip:+628811452131@192.168.242.42>;tag=HHXppypZBv2aS

    Call-ID: f4973e3c-c4a8-1236-15b0-000c29581a5f

    CSeq: 122076474 BYE

    Content-Length: 0

    P-Access-Network-Info: 3GPP-E-UTRAN-TDD;utran-cell-id-3gpp=5102800640033101

    P-Charging-Vector: icid-value=0.82.760-1524823768.21;icid-generated-at=192.168.239.35;term-ioi=Ioi1;orig-ioi=22345

    P-Charging-Function-Addresses: ccf=ims.mnc001.mcc001.3gppnetwork.org;ecf=ims.mnc001.mcc001.3gppnetwork.org;ccf=ims.mnc001.mcc001.3gppnetwork.org;ecf=ims.mnc001.mcc001.3gppnetwork.org

Status-Line: SIP/2.0 200 OK

Message Header

    Via: SIP/2.0/UDP scscf.ims.mnc001.mcc001.3gppnetwork.org:5060;rport=5060;branch=z9hG4bKmavodi-0-4c-bf-2-640020-4df45e927c208f36;received=192.168.239.36

        Transport: UDP

        Sent-by Address: scscf.ims.mnc001.mcc001.3gppnetwork.org

        Sent-by port: 5060

        RPort: 5060

        Branch: z9hG4bKmavodi-0-4c-bf-2-640020-4df45e927c208f36

        Received: 192.168.239.36

    From: <sip:+628811451570@ims.mnc001.mcc001.3gppnetwork.org>;tag=mavodi-0-7e-76-1-ffffffff-_000C2939994E-5e0c-a2ac4700-5df-5ae2f6d8-24075

    To: "+628811452131" <sip:+628811452131@192.168.242.42>;tag=HHXppypZBv2aS

    Call-ID: f4973e3c-c4a8-1236-15b0-000c29581a5f

    CSeq: 122076474 BYE

    User-Agent: FreeSwitch

    Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, INFO, UPDATE, REGISTER, REFER, NOTIFY

    Supported: timer, path, replaces

    Content-Length: 0

In the 200 OK replied back by FS to the BYE message, part of the ‘Via’ header is “missing”.

According to RFC 3261: "The Via header field values in the response MUST equal the Via header field values in the request and MUST maintain the same ordering".

Is it a expected behavior? Any variable to set in order to get the “original” ‘Via’ header in the answer?

Br. Stefano