Subject: Re: [Tsvwg] draft-baker-diffserv-basic-classes-02.txt

From: [email-masked]
Date: Mon, 15 Mar 2004 12:36:06 EST

The subject draft should be progressed as an Informational RFC or BCP.

I have the following comments:

Nits: 

2. 1st Note under Figure 2: "were" should be "where".

2.1 Example 1, first sentence reads bad, with the clause "in their network" 
out of place. Suggest putting this clause after the parenthetical "(quality of 
service)".
Example 2, word "use" should be "using".

2.2 "signal" should be "single" (2 times)

2.2 Final paragraph: 2 references to "EF PDB" appear incorrect, since EF is a 
"PHB". It seems that each should be either "EF PHB" or simply "PDB".

2.3 1st line, "aggregation" should be "aggregated". In the 3rd sentence, 
"service" should be "serviced".

4.1.1 11th paragraph (note): Word "constain" should be "constraint" (2 times)

4.1.1 12th paragraph "in to" should be "into" (one word).

4.1.2 First sentence: "requires" should be "require".

Other:

1.3.1  The 2nd paragraph, which talks about "elestic" traffic, does not apply 
for voice/video streams. While one might argue just how "elastic" these are, 
they can not operate as stated, that is, with the sender adjusting its 
transmission rate due to loss reported from the other end (presuming to mean adjust 
it down) like TCP does.

It is suggested that the first sentence should read: "Application traffic in 
the internet which uses the Default Forwarding class is expected ...", since 
this is the title of the section it is in.

1.3.1 2nd paragraph: In the 2nd sentence, where it says "transferring them to 
another class", it is not clear what "them" refers to. It seems to mean 
"packets". It is unclear what is being described, since it implies that a device 
would not follow the required handling for a DSCP, that is, instead put them 
into a different class (queue). Does this intend to refer to putting packets into 
the "Default Forwarding" queue, even though marked with some (higher) DSCP or 
does it refer to putting packets marked with the "Default Forwarding DSCP" 
into some other (presumably higher) queue?

1.3.1 3rd paragraph refers to "limit delays" as one of the purposes of the 
best effort (default forwarding) service. It seems that this is not true, unless 
it means to "limit delays that might be caused on other non-best effort 
traffic". As stated in the 1st paragraph, Best Effort has no further guarantees.

2. Note after Figure 1 (and several other places)

It should be made clear what "alias" means as in "Class Selector 2 codepoint 
[is] alias of AF11 codepoint". Does this mean "Any packet received with 
DSCP=CS2 is treated as if it had DSCP=AF11" or that AF11 is replaced with CS2 or 
vice-versa?

Figure 1: Why are the CS1 - CS4 values out of order with the other values? 
For example, shouldn't CS2 be grouped with AF21-AF23? Wouldn't this simple 
change make it backwards compatible with the "TOS" bits (which 1.3.4 says the 
current definition is not)?

4.1.1 12th paragraph

Makes a reference to "forwarding of voice packets and signaling packets with 
the same very low delay forwarding service class" (presumably meaning EF). 
Section 4.2.2 notes that peer-to-peer signaling (SIP) should use the "Low latency 
Data service" (which is shown as AF2 in Figure 1). It isn't clear where call 
signaling (SIP) should go, but it certainly needs to be a different DSCP than 
the voice packets.

Mike Pierce