[dispatch] Comments on draft-jain-dispatch-session-recording-protocol-req-00
Alan Johnston <alan@sipstation.com> Fri, 24 July 2009 18:29 UTC
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Date: Fri, 24 Jul 2009 13:28:58 -0500
From: Alan Johnston <alan@sipstation.com>
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Subject: [dispatch] Comments on draft-jain-dispatch-session-recording-protocol-req-00
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Here are my comments on this draft. Overall, I think this draft is an excellent start at the requirements for this important topic. I look forward to future discussions of charter text so we can get started on the work. Section 2: " Another, related IETF draft is draft-wing-sipping-srtp-key [I-D.wing-sipping-srtp-key], which describes an approach for providing SRTP session keys to a recorder-type server. That draft focuses on the mechanism to provide the SRTP session key, rather than the mechanism to invoke and sustain recording sessions themselves." draft-wing-sipping-srtp-key actually has a lot of discussion, including call flows showing how recording sessions can be established. Also, this document has four recording modes discussed, which I think should be discussed in this document. Two are mentioned without really explaining them, and two others are implied by various requirements. Section 3: " Recording Session: The session created between an RC and RS for the purpose of recording a Recorded Session. The Recorded Session may itself be based on SIP, but it is a separate session from the Recording Session. Recorded Session: A session created between a UAC and UAS that is recorded by the RC and RS systems." These two terms only differ by their tense, yet I think one refers to a signaling session and the other refers to a media session. If so, better terms and definitions are needed. If not, we need a term for the actual recorded media. Also, there are (at least) two sessions here - the one between the UAs and the Recording Session - in a few places I suspect the two are being confused. " Dynamic Recording: Dynamic recording is a mode of recording where the recording sessions are established on an as needed basis. The length of these sessions is typically same as the length of the actual media sessions. Persistent Recording: Persistent recording is a mode of recording where the recording sessions are established at system start-up and kept-alive from that point on. The length of these sessions is independent from the length of the actual recorded media sessions. Persistent recording sessions avoid issues such as media clipping that can occur due to delays in recording session establishment." These terms need more explanation as I can think of multiple things they might mean. For example, when you say "session" do you mean a signaling session or media session? When you talk about avoiding media clipping, do you mean that media is always sent by the RC to the RS regardless of whether there is any media? Figures could use Figure numbers and labels. Also, it would be worth showing which is the RC and which is the RS in them. Section 5 " o REQ-001 The mechanism MUST support the ability to perform persistent (always-on) or dynamic (on-demand) Recording Sessions." I'm not sure that the Persistent and Dynamic Recording as defined above correspond to the Always On and On Demand modes defined in http://tools.ietf.org/html/draft-wing-sipping-srtp-key-04#section-4. " o REQ-002 The mechanism MUST support the ability to perform persistent Recording Sessions, such that the connection and attributes of media in the Recording Session are not dynamically signaled for each Recorded Session before it can be recorded. Call details and metadata will still be signaled, but can be post- correlated to the recorded media. There will still need to be a means of correlating the recorded media connection/packets to the Recorded Session, however this may be on a permanent filter-type basis, such as based on a SIP AoR of an agent that is always recorded, or based on identifiers in the recorded media itself." Without fully understanding Persistent Recording, I can't evaluate this requirement. " o REQ-009 The mechanism MUST support the ability to deliver mixed media streams to the RS. The RS MAY be informed about the composition of the mixed streams through session metadata. Note: A mixed media stream is where several recorded sessions are carried in a single recording session. A mixed media stream is typically produced by a mixer function." I'm not clear what mixed media means here - does it mean a mix of media types - synchronized audio and video from the same session, or do you mean multiple media streams from different sessions? The note seems to indicate that this relates only to a conference call where multiple sources (SSRCs) have been combined into a single RTP session. " o REQ-013 The mechanism MUST support the ability to inject tones into the Recorded Session either from the RS or from the RC." Recorded Session seems to be defined as the media between the RC and RS. Is that where the injected tones should be? Or should then be mixed in the media between the two UAs? " o REQ-021 The mechanism MUST support the ability for the RC to only perform media replication to the RS, without needing to decode or mix audio/video/etc., and without needing to be an RTP agent. This will allow the RC to replicate media at layers below RTP. Clearly, such an RC mode would not be able to provide transcoding, or media injection from the RS back into the Recorded Session." Does this mean that you think that RTP is unsuitable for transporting media between the RS and RC? Clearly it isn't for IM, but I would think that many of the functions of RTP are needed for audio and video media. To understand this requirement will take more discussion. Thanks, Alan
- [dispatch] Comments on draft-jain-dispatch-sessio… Alan Johnston
- Re: [dispatch] Comments on draft-jain-dispatch-se… Leon Portman
- Re: [dispatch] Comments on draft-jain-dispatch-se… Alan Johnston
- Re: [dispatch] Comments on draft-jain-dispatch-se… Roni Even
- Re: [dispatch] Comments on draft-jain-dispatch-se… Labarbera, Chris
- Re: [dispatch] Comments on draft-jain-dispatch-se… Doken, Serhad
- Re: [dispatch] Comments on draft-jain-dispatch-se… Jain, Rajnish
- Re: [dispatch] Comments on draft-jain-dispatch-se… Sanjay Sinha (sanjsinh)
- Re: [dispatch] Comments on draft-jain-dispatch-se… Jain, Rajnish
- Re: [dispatch] Comments on draft-jain-dispatch-se… Doken, Serhad