Differentiated Services (Diffserv) and Real-Time Communication
draft-ietf-dart-dscp-rtp-10

Thank you for doing this work. It's excellent, and valuable.

I have a small number of editorial questions.

In this text:

1.  Introduction

   The results of using multiple DSCPs to obtain different QoS
   treatments within a single network 5-tuple (e.g., reordering) have
   transport protocol interactions, particularly with congestion control
   functionality. 

This is probably perfectly accurate, but I find it confusing. I think my problem is that the sentence sounds like the sender's goal was to cause problems with transport protocol mechanisms. I think it means 

- senders use multiple DSCPs to obtain different QoS treatments within a 5-tuple

- a side effect of using multiple DSCPs is that packets with different DSCPs will often be reordered

- this side effect causes problems with transport protocol mechanisms that expects largely in-order delivery, particularly with congestion control functionality

Am I reading this correctly?

In this text:

2.1.  RTP Background

   The STUN and TURN protocols were originally designed for use of UDP,

I’m not sure what “for use of UDP” means. Is this “to use UDP as a transport”?

   however, TURN has been extended to use TCP as a transport for
   situations in which UDP does not work [RFC6062].  When TURN selects
   use of TCP, the entire real-time communications session is carried
   over a single TCP connection (i.e., 5-tuple).

http://tools.ietf.org/html/rfc7350 has been published recently, defining DTLS as a transport for STUN. Is that in any way relevant to this section?

I feel horribly pedantic for even asking this, but in this text:
3.2.  Traffic Classifiers and DSCP Remarking

   DSCP markings are not end-to-end in general.  Each network can make
   its own decisions about what PHBs to use and which DSCP maps to each
   PHB.  While every PHB specification includes a recommended DSCP, and
   RFC 4594 [RFC4594] recommends their end-to-end usage, there is no
   requirement that every network support any PHBs 

would this be “support any PHBs beyond Default Forwarding”?

In this text:

5.1.  DiffServ, Reordering and Transport Protocols

   Transport protocols provide data communication behaviors beyond those
   possible at the IP layer.  An important example is that TCP [RFC0793]
   provides reliable in-order delivery of data with congestion control.

is there a better reference for TCP than RFC 793? Isn’t that a version of TCP that does NOT have congestion control? Perhaps draft-ietf-tcpm-tcp-rfc4614bis-08 ...

Alternatively, if you dropped “with congestion control”, you might still be making your point … reliable, in-order delivery is beyond what IP does.