Re: [TICTOC] comments on draft-ietf-tictoc-1588overmpls-04.txt

["Shahram Davari" <[e-mail]>]

Hi Yaakov,

Thanks for your great comments, please see my response inline.

Thx
Shahram

-----Original Message-----
From: Yaakov Stein [mailto:[e-mail]] 
Sent: Monday, March 11, 2013 8:26 PM
To: Shahram Davari; [e-mail]
Subject: RE: [TICTOC] comments on draft-ietf-tictoc-1588overmpls-04.txt

Shahram

A few more comments.

First, I don't like the terminology "both MPLS and MPLS-TP".
MPLS-TP is MPLS too. And in any case "environments" (in the plural).

SD> I have removed such text and replaced it with MPLS/MPLS-TP

"Extensions to signaling protocols (e.g., RSVP-TE) are required"
well, you COULD set them up manually, in which case no extensions are required.

SD> I have changed the text to" If singling is used then extension to signaling is required ...."

Section 5 GAL/ACH -> GAL/G-Ach (and throughout the document you have various mis-spellings of G-Ach)

SD> Done

In section 6.2 you require the Ethernet to be tagged, and in fact to be double tagged.
Since we now have an offset from BoS to the TC, why is this required ?
I realize that we want to limit the number of different encaps to be supported,
but I believe this is too harsh a limitation.
And why must the tagged mode of 4448 be used ?  
You can have tags and still use raw mode.

SD> I made both tags optional and also optional to use Raw or tagged mode

Section 6.3 - If NTP or some new method is used, 
with which part of the packet is the timestamp associated ?
Also "the control and signaling requirements in this document are defined ..."
needs to be removed (they are NOT defined here any more).

SD> I don't understand your comment that says " with which part of the packet is the timestamp associated ?" could you please clarify.

Section 7: technically a TC is not a timestamp, it is a time difference.
Also updating the TC is not time-stamping either.

SD> I have changed the text to state " time-stamping or correction field update"

I see that in Section 8 the recommendation regarding protection switching is SHOULD be used.
As you know I don't agree, but let's see if the WG agrees to this in LC.
Taking my view to the extreme, why outlaw ECMP in Section 9?
I agree with ruling it out, but if you allow protection switching, then why not ECMP?
Properly performed TC will remove the major portion of the delay differences.

SD> We could rephrase as:

" Therefore this specification recommends that protection
   switching SHOULD NOT be used, unless the operator knows that the
   protection switching does NOT have adverse effect on the slave clock."

SD> But both mean the same thing.

Section 11: entropy -> entropy label

Perhaps sections 14 and 15 can be combined. I am not sure which way is better.

SD> Done

If I remember the last meeting correctly, 
we asked for the signaling material to be mentioned in an Appendix.
Here it is in Sections 16 and 17.
I am not sure that this is terrible, but I don't think these belong in the body of a PS draft.

SD> Done, both moved to Appendix

Section 19 ware -> aware, it needs -> they need

SD> Done

I am not sure we need the applicability statement.

SD> Applicability statement removed

In the Acknowledgements: Luca Moniti -> Luca Martini

SD> Done

Y(J)S

-----Original Message-----
From: [e-mail] [mailto:[e-mail]] On Behalf Of Shahram Davari
Sent: 12 March, 2013 02:59
To: Meyer, Peter; [e-mail]
Subject: Re: [TICTOC] comments on draft-ietf-tictoc-1588overmpls-04.txt

Peter,

Good feedback. I will update the draft after the Orlando to include your comments.

Thx
Shahram

-----Original Message-----
From: [e-mail] [mailto:[e-mail]] On Behalf Of Meyer, Peter
Sent: Monday, March 11, 2013 5:49 PM
To: [e-mail]
Subject: Re: [TICTOC] comments on draft-ietf-tictoc-1588overmpls-04.txt

Hi Shahram et al,

Some comments on draft -04.


1) Section 3.  "A generic method is defined in this document that does
not require deep packet inspection at line rate, and can
deterministically identify Timing messages.  The generic method is
applicable to MPLS and MPLS-TP networks."

May want to add that this would apply only to one-step TC (I imagine
that is the point of the correction at line rate).  A two-step TC would
need to do deep packet inspection as it uses sourcePortIdentity &
sequenceId fields for Follow_up or Delay_Resp.


2) Section 4.  "An MPLS domain can serve multiple customers.  This means
that the MPLS domain (maintained by a service provider) may provide
timing services to multiple customers, each having their own Timing
domain.  Therefore LER BCs need to interact with multiple grandmasters,
and consequently multiple time references."

This should be re-phrased.  It switches from an optional situation ("may
provide timing services") to mandatory situation ("LER BCs need to
interact").   Some words such as "in such a deployment scenario, ...."
and replace "can" with "may".   We have seen at ITU at least (with
participation from operators BT, FT, DT, CMCC, AT&T, Sprint, etc.) that
this multiple operator domain case was not useful enough to be included
in standardization process for Telecom networks.


3) Section 19.  "For transporting such peer delay measurement messages a
single-hop LSP SHOULD to be created between the two adjacent LSRs
engaged in peer delay measurement to carry peer delay measurement
messages. Other methods such as PTP transport over Ethernet MAY be used
for transporting peer delay measurement messages if the link between the
two routers is Ethernet."


This new statement to handle peer-delay (which in earlier drafts did not
have a communication path listed), also allows a BC to be embedded in an
LSR with a communication path between BC's as a single-hop LSP
(mentioned March 22, 2012 in my feedback to draft -03, subject "[TICTOC]
Updated 1588 over MPLS draf-03").

Architecture diagrams Figure 1 and Figure should be updated to reflect
the possibility of either BC or TC implementation.   Section 18.2 and
section 18.3 and section 21 should also be updated to reflect the
possibility of either BC or TC.  I understand the RFC is intended to be
generic and not targeted only at TC.



4) Section 20.  "When the MPLS network (provider network) serves
multiple customers, it is important to maintain and process each
customers clock and Timing messages separately from other customers to
ensure there is no cross- customer effect.   For example if an LER BC is
synchronized to a specific grandmaster, belonging to customer A, then
the LER MUST use that BC clock only for customer A to ensure that
customer A cannot attack other customers by manipulating its time."

This seems much more applicable to the TC LSR and should be stated.
>From section 4 we see the TC uses the primary synchronization domain
(that of the service provide) to correct PTP messages.



5) Section 20.  "Timing messages (as opposed to regular customer data)
SHOULD not be encrypted or authenticated on an end-to-end basis."  I
think there is a security draft in parallel being developed that may be
relevant to that statement.



Regards,
Peter


-----Original Message-----
From: [e-mail] [mailto:[e-mail]] On Behalf
Of [e-mail]
Sent: February 23, 2013 2:23 AM
To: [e-mail]
Cc: [e-mail]
Subject: [TICTOC] I-D Action: draft-ietf-tictoc-1588overmpls-04.txt


A New Internet-Draft is available from the on-line Internet-Drafts
directories.
 This draft is a work item of the Timing over IP Connection and Transfer
of Clock Working Group of the IETF.

	Title           : Transporting Timing messages over MPLS
Networks
	Author(s)       : Shahram Davari
                          Amit Oren
                          Manav Bhatia
                          Peter Roberts
                          Laurent Montini
	Filename        : draft-ietf-tictoc-1588overmpls-04.txt
	Pages           : 36
	Date            : 2013-02-22

Abstract:
   This document defines the method for transporting Timing messages
   such as PTP and NTP over an MPLS network.  The method allows for the
   easy identification of these PDUs at the port level to allow for port
   level processing of these PDUs in both LERs and LSRs.

   The basic idea is to transport Timing messages inside dedicated MPLS
   LSPs.  These LSPs only carry timing messages and possibly Control and
   Management packets, but they do not carry customer traffic.

   Two methods for transporting Timing messages over MPLS are defined.
   The first method is to transport Timing messages directly over the
   dedicated MPLS LSP via UDP/IP encapsulation, which is suitable for
   MPLS networks.  The second method is to transport Timing messages
   inside a PW via Ethernet encapsulation, which is suitable for both
   MPLS and MPLS-TP networks.


The IETF datatracker status page for this draft is:
https://datatracker.ietf.org/doc/draft-ietf-tictoc-1588overmpls

There's also a htmlized version available at:
http://tools.ietf.org/html/draft-ietf-tictoc-1588overmpls-04

A diff from the previous version is available at:
http://www.ietf.org/rfcdiff?url2=draft-ietf-tictoc-1588overmpls-04


Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/

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