Re: [secdir] Review of draft-ietf-payload-rtp-ancillary-06

Shawn M Emery <> Tue, 22 November 2016 07:39 UTC

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To: Thomas Edwards <>, "" <>
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From: Shawn M Emery <>
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Date: Tue, 22 Nov 2016 00:41:52 -0700
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Subject: Re: [secdir] Review of draft-ietf-payload-rtp-ancillary-06
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Hi Thomas,

Sorry for the late reply, was out of the office last week. Comments 

On 11/15/16 10:26 PM, Thomas Edwards wrote:
> Shawn,
> Thanks again for the Security Directorate review of of draft-ietf-payload-rtp-ancillary-06!
> Please see below for a list of your comments, my responses, and my suggested draft changes.
> Comment: “The [security considerations] section goes on to discuss the specific payload data and how to mitigate against attack by first sanity checking said data.  I'm OK with this assertion, except for the integrity check using Checksum_Word.  The nine bit checksum based on summing the nine least significant bits of four out of dozens of possible data fields doesn't seem to provide sufficient coverage for this check.”
> Response: Indeed, the nine bit checksum word does not provide sufficient coverage for a check against attack.
> Draft change: To "Also the Checksum_Word should be checked against the ANC data packet to ensure that its data has not been damaged in transit" add ", "but the Checksum_Word is unlikely to provide a payload integrity check in case of a directed attack."

I think that this addition more clearly states the limitations of 

> Comment: Abstract: Does RTP and SMPTE need to be expanded first?
> Response: Agreed.
> Draft change: Expand RTP and SMPTE in Abstract


> Comment: Is SMPTE ST 291-1 a normative reference?
> Response: I believe yes, due to specific definitions of ST 291-1 data fields specified in the payload, and DID/SDID info in the Media Type parameter.
> Draft change: No change

Other standards track RFCs have referenced SMPTE standards as 
informative.  If you want this to be a normative reference then you will 
need to call this out in the IETF LC.  This allows the community to 
determine if the standard being referenced meets the criteria of a 
stable and vetted point of reference.  Please see RFC 4897.

> Comment: s/an SDI/a SDI/
> Response: SDI is an initialism.  The Chicago Manual of Style states "When an abbreviation follows an indefinite article, the choice of a or an is determined by the way the abbreviation would be read aloud."
> Draft change: No change