Last Call Review of draft-ietf-avtext-rtp-duplication-04

Request Review of draft-ietf-avtext-rtp-duplication
Requested rev. no specific revision (document currently at 06)
Type Last Call Review
Team Ops Directorate (opsdir)
Deadline 2014-02-04
Requested 2014-01-23
Authors Ali Begen, Colin Perkins
Draft last updated 2014-02-06
Completed reviews Genart Last Call review of -04 by Suresh Krishnan (diff)
Secdir Last Call review of -04 by David Harrington (diff)
Opsdir Last Call review of -04 by Linda Dunbar (diff)
Opsdir Last Call review of -04 by David Harrington (diff)
Assignment Reviewer Linda Dunbar 
State Completed
Review review-ietf-avtext-rtp-duplication-04-opsdir-lc-dunbar-2014-02-06
Reviewed rev. 04 (document currently at 06)
Review result Has Issues
Review completed: 2014-02-06


As a directorate of Ops Area, I have been asked to review “draft-ietf-avtext-rtp-duplication-04”. 

Here are my comments:




Section 3.2 Spatial Redundancy:

The section describes that a source uses two different IP addresses for duplicated streams. But it fails to describe

how the receiving end know if the packets with different Source Addresses are from the same source?

In later session, it is described to use SSRC to merge two sessions. But

How to prevent two different sources using the same SSRC?


The last sentence: 

I don’t think that you mean sending streams to different destinations, do you?

Suggest: “Alternatively, destination host could also have multiple IP addresses for an RTP source to send the redundant streams to.”




Section 3.3

This section is really for analyzing the two methods (3.1 Temporal Redundancy and 3.2 Spatial Redundancy), correct?


Suggest to reference 3.1 and 3.2. For example



Analysis of Temporal Redundancy:



Analysis of Spatial Redundancy:




Section 3.4 

Suggest to spell out SDP (is it “

Session Description Protocol”?)




Section 7 Congestion Control Considerations

I don’t think this recommendation is realistic:



The source hosts don’t know the congestion status of the network. Most likely those duplications are used for sources/destinations to get better results for themselves in congested network.



For the following: most network has its protection for link/interface failure. More likely, duplications of sources/destinations are not for protecting hard failure.



I suggest to emphasize that duplication can only make the overall network congest more.