RFC 3550, "RTP: A Transport Protocol for Real-Time Applications", July 2003

Errata ID: 3263
Status: Held for Document Update
Type: Technical
Publication Format(s) : TEXT
Reported By: Pieter Demuytere
Date Reported: 2012-06-18
Held for Document Update by: Robert Sparks

Section 6.4.1 says:

cumulative number of packets lost: 24 bits
   The total number of RTP data packets from source SSRC_n that have
   been lost since the beginning of reception.  This number is
   defined to be the number of packets expected less the number of
   packets actually received, where the number of packets received
   includes any which are late or duplicates.  Thus, packets that
   arrive late are not counted as lost, and the loss may be negative
   if there are duplicates.  The number of packets expected is
   defined to be the extended last sequence number received, as
   defined next, less the initial sequence number received.  This may
   be calculated as shown in Appendix A.3.

It should say:

cumulative number of packets lost: 24 bits 
   The total number of RTP data packets from source SSRC_n that have 
   been lost since the beginning of reception. This number is 
   defined to be the number of packets expected less the number of 
   packets actually received, where the number of packets received 
   includes any which are late or duplicates. Thus, packets that 
   arrive late are not counted as lost, and the loss may be negative 
   if there are duplicates. The number of packets expected is 
   defined to be the extended highest sequence number received, as 
   defined next, less the initial sequence number received. This may 
   be calculated as shown in Appendix A.3.

Notes:

Changed

The number of packets expected is defined to be the extended last sequence number received...

Into

The number of packets expected is defined to be the extended highest sequence number received...

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