Re: [dispatch] Fwd: I-D Action: draft-johnston-dispatch-osrtp-00.txt

"Hutton, Andrew" <> Wed, 04 November 2015 13:31 UTC

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From: "Hutton, Andrew" <>
To: Laura Liess <>
Thread-Topic: [dispatch] Fwd: I-D Action: draft-johnston-dispatch-osrtp-00.txt
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Date: Wed, 04 Nov 2015 13:30:57 +0000
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Subject: Re: [dispatch] Fwd: I-D Action: draft-johnston-dispatch-osrtp-00.txt
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Agree with Laura what we are doing here is aligning existing implementations that already exist in the field and document that in and RFC so that we can move forward with regard to deployment of SRTP in SIP Trunking environments.

Currently RFC 5763 is not supported at all in this environment and I have not heard a single voice in support of using SDP capability negotiation for SIP Trunking.

Moving forward with the draft is our best chance of seeing SRTP start to be deployed with SIP Trunking.


On 4 Nov 2015, at 19:52, Laura Liess <<>> wrote:

Hi Roni,

[MMUSIC-SDP<>] is now RFC 5939 and it seems to be a MUST for implementations of the  RFC 5763 (SRTP with DTLS).

At Deutsche Telekom we plan to connect SIP-PBXe in the near future using SRTP with SDES.  We are not aware of any existing SIP-PBX which supports RFC 5763, most existing SIP-PBXs suport different flavors of the kaplan-draft. RFC 5763 seems to be too complex so that PBX vendors are not willing to support it, at least in connection with SDES. This is also the case for our service provider call control vendors.  So, a less complex mechanism is needed for best effort SRTP.

Thank you

2015-11-04 5:05 GMT+01:00 Roni Even <<>>:
In my view this approach contradict section 6.11 of RFC5763

Best Effort Encryption

   [RFC5479] describes a requirement for best-effort encryption where
   SRTP is used and where both endpoints support it and key negotiation
   succeeds, otherwise RTP is used.

   [MMUSIC-SDP] describes a mechanism that can signal both RTP and SRTP
   as an alternative.  This allows an offerer to express a preference
   for SRTP, but RTP is the default and will be understood by endpoints
   that do not understand SRTP or this key exchange mechanism.
   Implementations of this document MUST support [MMUSIC-SDP<>].

From: dispatch [<>] On Behalf Of Alan Johnston
Sent: Wednesday, July 08, 2015 2:03 PM
Subject: [dispatch] Fwd: I-D Action: draft-johnston-dispatch-osrtp-00.txt


Many of us have been talking about "Best Effort SRTP" for many years, and there are a number of deployments.  In addition, the IMTC has recommended it, and the SIP Forum would like to recommend it in SIPconnect 2.0 which for the first time includes SRTP media.  With the publication of RFC 7435 (, the IETF has endorsed this approach as Opportunistic Security (OS), so it would be nice to bring standards in line with industry practice.

Comments on the draft, "An Opportunistic Approach for Secure Real-time Transport Protocol (OSRTP)" and the best way forward are most welcome!

- Alan -

---------- Forwarded message ----------
From: <<>>
Date: Mon, Jul 6, 2015 at 1:48 PM
Subject: I-D Action: draft-johnston-dispatch-osrtp-00.txt

A New Internet-Draft is available from the on-line Internet-Drafts directories.

        Title           : An Opportunistic Approach for Secure Real-time Transport Protocol (OSRTP)
        Authors         : Alan Johnston
                          Bernard Aboba
                          Andy Hutton
                          Laura Liess
                          Thomas Stach
        Filename        : draft-johnston-dispatch-osrtp-00.txt
        Pages           : 8
        Date            : 2015-07-06

   Opportunistic Secure Real-time Transport Protocol (OSRTP) allows
   encrypted media to be used in environments where support for
   encryption is not known in advance, and not required.  OSRTP is an
   implementation of Opportunistic Security, as defined in RFC 7435.
   OSRTP does not require advanced SDP extensions or features and is
   fully backwards compatible with existing secure and insecure
   implementations.  OSRTP is not specific to any key management
   technique for SRTP.

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