Пустые атрибуты медиапотока в SDP ответа на INVITE

[alx]

В ответе на INVITE в описание медиапотока юзер-агент помещает атрибуты rtpmap и fmtp без их значений.
Пример ответа:

11:59:52.004049 IP (tos 0x0, ttl 128, id 7745, offset 0, flags [none], proto UDP (17), length 551)
    192.168.0.10.22530 > 192.168.0.63.5060: SIP, length: 523
        SIP/2.0 200 OK
        Via: SIP/2.0/UDP 192.168.0.63;rport=5060;branch=z9hG4bKcB1gm1KrK4NDj;received=192.168.0.63
        From: "\0xd0\0xa2\0xd0\0xb5\0xd1\0x85\0xd0\0xbd\0xd0\0xb8\0xd0\0xba" <sip:2@192.168.0.63>;tag=gjZ2amjF2HX6S
        To: <sip:2@192.168.0.10:22530>;tag=d8771618
        Call-ID: 5f96dc76-a464-1232-4b97-902b3433882b
        CSeq: 64007531 INVITE
        Contact: <sip:2@192.168.0.10:22530>
        Content-Type: application/sdp
        Content-Length: 148

        v=0
        o=2 59346 59347 IN IP4 192.168.0.10
        s=Flibble Session
        c=IN IP4 192.168.0.10
        t=0 0
        m=audio 30000 RTP/AVP 0 101
        a=rtpmap
        a=rtpmap
        a=fmtp

[san]

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