[cisco-voip] Comfort noise RTP

[Seth McGuinness]

Hello All, 

 

We have a customer complaining about Comfort Noise generating from our
Cisco AS5400, strange thing is that the packet traces suggest that the
request for comfort noise generation comes from the client SIP invite, I
can't see where this is the case in the invite.

 

Client invite 

 

No.     Time                  Source     Destination Protocol Length
Info

1 2013-08-07 09:21:34.500695  10.10.1.1  192.168.1.1 SIP/SDP  1131
Request: INVITE sip:+197831111111149 at 192.168.1.1;user=phone, with
session description

 

Frame 1: 1131 bytes on wire (9048 bits), 1131 bytes captured (9048 bits)

Ethernet II, Src: WwPcbaTe_11:11:11 (00:0f:1f:11:11:11), Dst:
BrocadeC_22:22:22 (00:1b:ed:22:22:22)

Internet Protocol Version 4, Src: 10.10.1.1(10.10.1.1), Dst: 192.168.1.1
(192.168.1.1)

User Datagram Protocol, Src Port: sip-tls (5061), Dst Port: sip (5060)

Session Initiation Protocol

    Request-Line: INVITE sip:+197831111111149 at 192.168.1.1;user=phone
SIP/2.0

    Message Header

    Message Body

        Session Description Protocol

            Session Description Protocol Version (v): 0

            Owner/Creator, Session Id (o): - 1375863694 1375863694 IN
IP4 10.10.1.1

                Owner Username: -

                Session ID: 1375863694

                Session Version: 1375863694

                Owner Network Type: IN

                Owner Address Type: IP4

                Owner Address: 10.10.1.1

            Session Name (s): -

            Connection Information (c): IN IP4 10.10.1.1

                Connection Network Type: IN

                Connection Address Type: IP4

                Connection Address: 10.10.1.1

            Time Description, active time (t): 0 0

                Session Start Time: 0

                Session Stop Time: 0

            Media Description, name and address (m): audio 33870 RTP/AVP
8 0 18 101

                Media Type: audio

                Media Port: 33870

                Media Protocol: RTP/AVP

                Media Format: ITU-T G.711 PCMA

                Media Format: ITU-T G.711 PCMU

                Media Format: ITU-T G.729

                Media Format: DynamicRTP-Type-101

            Media Attribute (a): rtpmap:8 PCMA/8000

                Media Attribute Fieldname: rtpmap

                Media Format: 8

                MIME Type: PCMA

                Sample Rate: 8000

            Media Attribute (a): rtpmap:0 PCMU/8000

                Media Attribute Fieldname: rtpmap

                Media Format: 0

                MIME Type: PCMU

                Sample Rate: 8000

            Media Attribute (a): rtpmap:18 G729/8000

                Media Attribute Fieldname: rtpmap

                Media Format: 18

                MIME Type: G729

                Sample Rate: 8000

            Media Attribute (a): fmtp:18 annexb=no

                Media Attribute Fieldname: fmtp

                Media Format: 18 [G729]

                Media format specific parameters: annexb=no

            Media Attribute (a): rtpmap:101 telephone-event/8000

                Media Attribute Fieldname: rtpmap

                Media Format: 101

                MIME Type: telephone-event

                Sample Rate: 8000

            Media Attribute (a): fmtp:101 0-15

                Media Attribute Fieldname: fmtp

                Media Format: 101 [telephone-event]

                Media format specific parameters: 0-15

            Media Attribute (a): sendrecv

            Media Attribute (a): silenceSupp:off - - - -

                Media Attribute Fieldname: silenceSupp

                Media Attribute Value: off - - - -

 

 

Our response

 

No.     Time                       Source         Destination
Protocol Length Info

2       2013-08-07 09:21:41.862610 192.168.1.1    10.10.1.1
RTP      60     PT=Comfort noise, SSRC=0x8FED3F6, Seq=28259,
Time=1374861414 

 

Frame 7: 60 bytes on wire (480 bits), 60 bytes captured (480 bits)

Ethernet II, Src: BrocadeC_22:22:22 (00:1b:ed:22:22:22), Dst:
WwPcbaTe_11:11:11 (00:0f:1f:11:11:11)

Internet Protocol Version 4, Src: 192.168.1.1 (192.168.1.1), Dst:
10.10.1.1(10.10.1.1)

User Datagram Protocol, Src Port: 19578 (19578), Dst Port: 33870 (33870)

Real-Time Transport Protocol

    [Stream setup by SDP (frame 1)]

    10.. .... = Version: RFC 1889 Version (2)

    ..0. .... = Padding: False

    ...0 .... = Extension: False

    .... 0000 = Contributing source identifiers count: 0

    0... .... = Marker: False

    Payload type: Comfort noise (13)

    Sequence number: 28259

    [Extended sequence number: 93795]

    Timestamp: 1374861414

    Synchronization Source identifier: 0x08fed3f6 (150918134)

    Payload: 48

 

In our RTP Comfort noise payload type 13 in frame(2) it states that the
Stream has been setup by SDP in frame 1, I can't see this in frame 1, it
has silence suppression turned off and annexb=no, the RTP stream is
G.711 anyway, I left out the whole capture for brevity. Has anyone come
across this? Any suggestions appreciated and apologies if I post this in
the wrong place!

 

Cheers 

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