Subject: [lmap] WGLC on draft-ietf-ippm-lmap-path

From: Brian Trammell <[email-masked]>
Date: Thu, 24 Apr 2014 16:56:53 +0200

Greetings, all,

This begins a Working Group Last Call on draft-ietf-ippm-lmap-path-02, "A Reference Path and Measurement Points for LMAP". (I'm cross-posting this to LMAP, so that the LMAP WG can have a chance to review as well, given that this document is applicable to both WGs.)

WGLC will run until Thursday 15 May 2014. Please review the document and provide comments to [email-masked].

Many thanks, best regards,

Brian Trammell

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From: Charles Cook <[email-masked]>
Date: Thu, 24 Apr 2014 11:03:50 -0600

Brian,

This is the first time I have read the draft, so I have several
comments.  Most of my comments are asking for clarifications to be added
to the text.  Here are my comments:

Section 5
   The numbering for measurement points (mpNNN ) allows for considerable
   local use of unallocated numbers.

Is the numbering (mpNNN) arbitrary?  Should there be rules so that it is
known where the mp is based on the number?

   o  Some use the terminology "on-net" and "off-net"  when referring to
      Internet Service Provider (ISP) measurement coverage.  With
      respect to the reference path, tests between mp100 and mp190 are
      "on-net".

"on-net" and "off-net" are terms relative to the perspective of the
network of interest.  Mp100 and mp190 would only be "on-net" relative to
the Access Service Provider.  They would be "off-net" relative to a
Transport Service Provider.  There is probably a better way to address
"on-net" and "off-net".

   o  Widely deployed broadband access measurements have used pass-
      through devices[SK]  (at the subscriber's location) directly
      connected to the service demarcation point: this would be located
      at mp100.

What is [SK]?

   o  The networking technology used at all measurement points must  be
      indicated, especially the interface standard and configured speed.

Please explain why the "must".  A person doing an end-to-end measurement
does not care what the technology is.  However, if the measurement
result is to be compared to another measurement result, it is essential
that the technology is known in order to understand whether the results
are comparable.  If the "must" is to facilitate comparability, we should
add that to the bullet.

   o  If it can be shown that a link connecting to a measurement point
      has reliably deterministic or negligible performance , then the
      remote end of the connecting link is an equivalent point for some
      methods of measurement (To Be Specified Elsewhere).  In any case,
      the presence of such a link must be reported.

"negligible performance" does not make sense.  You never want
performance to be negligible.  Clarification is needed here on what
conditions result in an intermediate point being equivalent to the
remote end.

   o  Many access network architectures have a traffic aggregation point
      (e.g., CMTS or DSLAM ) between mp100 and mp150.  We designate this
      point mp120, but it won't currently fit in the figure.

Maybe more examples are needed.  When I first looked at the mp figure, I
assumed that mp150 would be a DSLAM or OLT.  Are you saying the mp150 is
an NPE (Network Provider Edge) switch?

   o  In the case that a private address space is used in an access
      architecture, then mp100 may need to use the same address space as
      its remote measurement point counterpart , so that a test between
      these points produces a useful assessment of network performance.
      Tests between mp000 and mp100 could use private address space, and
      when the egress side of a CGN is at mp150, then the private
      address side of the CGN could be designated mp149 for tests with
      mp100.

When you say "remote measurement point counterpart" that sounds like it
should be between mp800 and mp900.  Some clarification as to the example
being discussed is needed.  It appears that rather than a remote
counterpoint, that you are talking about two devices in the same private
network. 

   o  Measurement points at Transit GRA GWs are numbered mpX00  and
      mpX90, where X is the lowest positive integer not already used in
      the path.

This is not consistent with the drawing.  mpX00 could be mistaken for
mp000 or mp100.  Consider starting at mp200 and incrementing to mp290. 
***My real comment is that I believe it would be much clearer to have a
section detailing the numbering rules to ensure consistency.

6.  Translation Between Ref. Path and Tech .  X

What is "Tech."?  May be better to spell out.  I don't recall seeing
"Tech." defined.  After further reading, this should probably be
"Technology".

   Subsc. -- Private -- Private -- Access -- Intra IP -- GRA -- Transit
   device     Net #1     Net #2    Demarc.    Access     GW     GRA GW
   mp000                            mp100      mp150    mp190    mp200
   |--UE--|------------CPE/NAT--------|-------|BRAS -|------|
                                      |----Access Network--|
   |_______Un-managed sub-path________|__Managed sub-path__|

Where you have BRAS is where the DSLAM would be.  The BRAS would
typically be behind the GRA GW and sometimes behind the Transit GRA GW. 
Only if a distributed BRAS is used would it possibly be at mp150.

Because of the variety to topologies that could be used, it may be
useful to consider mps at domain boundaries.  These could be Domain mps,
and Intra-Domain mps.  We may need some more thinking in regarding the
identification of measurement points.

Also, why does "Access Network" need to be shown?  

Section 7
   Subsc. -- Private -- Private -- Access -- Intra IP -- GRA -- Transit
   device     Net #1     Net #2    Demarc.    Access     GW     GRA GW
   mp000                            mp100      mp150    mp190    mp200
   |--UE--|------------CPE/NAT--------|------|-CGN-|------|
              Wi-Fi      wired        |---Access Network--|

          |-Shared--|RT|------Dedicated------| RT  |-----Shared------...
   |_______Un-managed sub-path________|_Managed sub-path__|

I have been asking why we need to indicate "Access Network".  From the
figure for the example is Section 7, I'm thinking rather than say
"Access Network" maybe it should be "DSL" or "GPON" to indicated the
technology.  "Wired" would be 1000BASE-T.  That would make this row in
the figure the Technology row in defining the path.

Thanks for your efforts in putting together this draft.

Regards,
Charles Cook

On 4/24/2014 8:56 AM, Brian Trammell wrote:
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-- 

Charles Cook 
Principal Architect
Network
5325 Zuni Street; Suite 224
Denver, CO  80221
Tel:  303.992.8952  Fax:  925.281.0662
[email-masked]