Re: [pm-dir] Request for an RFC 6390 review of draft-ietf-pce-pcep-service-aware-02

[Dhruv Dhody <[e-mail]>]

Hi Qin, 

 

Thanks for your review of our document.  Comments inline and diff file
attached.

I will also get confirmation from co-authors and contributors if they are
okay with these changes.  

 

From: Qin Wu [mailto:[e-mail]] 
Sent: Friday, February 14, 2014 4:14 PM
To: Dhruv Dhody; [e-mail]; [e-mail]; [e-mail];
[e-mail]
Cc: [e-mail]
Subject: Request for an RFC 6390 review of
draft-ietf-pce-pcep-service-aware-02

 

Hi, authors:

I am assigned Performance Directorate reviewer for this draft.

Here is my review to this draft.

 

This draft uses the link latency, latency variation and packet loss
information for end to end path selection. 

The link latency, latency variation and packet loss metrics are defined in
OSPF-TE draft and ISIS-TE draft and 

used to calculate path metrics described in this draft, e.g., P2P latency
metric, P2P latency variation metric, packet loss 

metric, P2MP latency metric, P2MP latency variation metric. 

 

These calculated path metrics( 6 metrics) are carried in PCEP message using
the same Metric Object with different metric type.  

The calculated metrics are used as constraint for path computation 

 

In this draft, each calculated metric is discussed in each separate section
from metric name, metric description 

perspective to measurement unit, calculation method perspective.

IANA is also requested to register these 6 metric types. Therefore I believe
this draft conforms to RFC6390 guideline.

However I have a few comments regarding these metrics definitions.

1. Section 4, 2nd paragraph says:

"

   This document defines the following optional types for the METRIC

   object defined in [RFC5440].

"

s/defined in [RFC5440]/defined in section 7.4 of [RFC5440]

[DhruvDhody>] Okay, But Metric section is 7.8 in RFC5440
http://tools.ietf.org/html/rfc5440#section-7.8 :)

 

2. Section 4.1 says:

"

   Link delay metric is defined in [OSPF-TE-EXPRESS] and

   [ISIS-TE-EXPRESS].  P2P latency metric type of METRIC object in PCEP

   encodes the sum of the link delay metric of all links along a P2P

   Path.  Specifically, extending on the above mentioned terminology:

 

   - A Link delay metric of link L is denoted D(L).

 

   - A P2P latency metric for the Path P = Sum {D(Lpi), (i=1...K)}.

 

   * T=13(TBA - IANA): Latency metric

"

For people who are not familiar with Metrics Object Format, it is not easy
to figure out what T=13 stands for? Would it be good to add some context
text or

Introduce Metric Object format first.

 

[DhruvDhody>] Done! Check the diff file attached if this is acceptable to
you. 

 

3. Section 4.2 says:

"

   - A Latency variation of link L is denoted DV(L).

 

   - A P2P latency variation metric for the Path P = function {DV(Lpi),

   (i=1...K)}.

"

Why not sum of latency variation metrics of individual links?

[DhruvDhody>] Making it a sum and aligning to
http://tools.ietf.org/html/draft-ietf-mpls-te-express-path-00#section-2.1

Is not a bad idea in my opinion. I need to discuss further with my
co-authors, if there is any objection to that. 

 

4. Section 4.2 says:

"

Specification of the "Function" used to drive latency variation

metric of a path from latency variation metrics of individual links

along the path is beyond the scope of this document.

"

s/drive/derive

 

[DhruvDhody>] sentence removed. 

 

5. Section 4

Section 4.3 says:

"Packet Loss Metric metric type of METRIC Object"

Section 4.2 says:

"P2P latency variation metric type of METRIC

   Object"

For consistency, you may either use "xx Metric metric type" or "xx metric
type of Metric Object".

[DhruvDhody>] Done! 

 

6.Section 4.3 says:

"

   The end to end Packet Loss for the path is represented by this

   metric.

 

   - A Packet loss of link L is denoted PL(L).

 

   - A P2P packet loss metric for the Path P = function {PL(Lpi),

   (i=1...K)}.

"

Is function of packet loss metric of individual link same as function of
latency variation metric of individual link?

If they are not same, please use different function name, e.g., function a
for packet loss, function b for latency variation?

[DhruvDhody>] I have updated this, please check the diff. 

 

Regards,

Dhruv

 

Regards!

-Qin