Subject: [mpls] Comments on draft-ietf-mpls-tp-on-demand-cv

From: "Joel M. Halpern" <[email-masked]>
Date: Thu, 17 Mar 2011 18:30:25 -0400

As the chairs have issued the last call for this, I have taken another 
look at it.

The format description (section 2) has some problems that need to be 
fixed before this goes to the  AD.

Section 2.1.1 is called "DSMAP/DDMAP Based Non-IP Address TLV."  And it 
refers to an "address TLV".
The problem is that RFC 4379 does not actually use the terminology DSMAP 
or DDMAP.  I would not be surprised if somehow these terms are a 
reference to the downstream mapping TLV from RFC 4379, but if so that 
needs to be stated explicitly. Further, 4379 does not refer to the 
contents of the Dowstream Mapping TLV as an "address TLV".  In fact, the 
contents that are being referred to are not a "TLV", as the length is 
implied by the type, not included in the field.  Some clearer reference 
is needed.

Similarly, section 2.2 talks about the Source/Destination Address TLV.
I first assumed that referenced the TLV defined in 2.2.1.  However, the 
text then goes on to talk about 4379 and about the information defined 
in section 2.1.1 (which is not even a TLV.)

Minor:

The information in these source and destination TLVs in 2.2 is not an 
address.  It would be a good idea to call them something else.

Is it worth stating in section 3 that the Pad TLV from 4379 is used when 
needed to meet the padding requirement of the framework?

The wording choice for describing the usage in section 3.3 is a bit 
confusing, appearing as it does after 3.2.  3.2 says that you can use IP 
encapsulation with ACH, and that you use the IP ACH type.  Section 3.3 
then refers to "using On-demand CV via LSP-Ping with the ACH header" 
when referring to messages that will not have IP headers.  But the text 
just finished telling me that I might have an ACH header and an IP 
header.  Some other way of identifying the two cases would be helpful.

There seems to be an inconsistency between sections 3.4.1 and 3.4.2. 
Section 3.4.1 says that if the R flag is set, the egress LSR "SHOULD" 
return reverse path FEC information.  Section 3.4.2 says that if the R 
flag is set, the egress LSR "MAY" return the information.  Which is it?

Yours,
Joel M. Halpern