Subject: [Pce] Fwd: Suggestion in draft-wu-pce-pcep-link-bw-utilization regarding MRUP calculation

From: Dhruv Dhody <[email-masked]>
Date: Fri, 24 Jan 2014 18:29:17 +0530

Hi PCErs,

Authors have received a following suggestion to change the description for
the new objective function
Maximum Reserved Under-Utilized Path (MRUP) [
http://tools.ietf.org/html/draft-wu-pce-pcep-link-bw-utilization-01#section-6.2
].

We agree that the use of Maximum reservable bandwidth R(L) would be the
correct way. We plan to make this change in the next revision.

Name: Maximum Reserved Under-Utilized Path (MRUP)

Description: Find a path P such that (Min {(R(Lpi)- ru(Lpi)) /

R(Lpi), i=1...K } ) is maximized.

Regards,
Dhruv

---------- Forwarded message ----------
From: Avantika <[email-masked]>
Date: Fri, Jan 24, 2014 at 12:11 PM
Subject: Suggestion in draft-wu-pce-pcep-link-bw-utilization regarding MRUP
calculation
To: Dhruv Dhody <[email-masked]>, Qin Wu <[email-masked]>, "
[email-masked]" <[email-masked]>
Cc: Udayasree palle <[email-masked]>, "[email-masked]" <
[email-masked]>

 Hi Authors!

I have a suggestion regarding the formula used for optimization using
objective function MRUP in draft-wu-pce-pcep-link-bw-utilization.

As per the draft,

Name: Maximum Reserved Under-Utilized Path (MRUP)

Description: Find a path P such that (Min {(c(Lpi)- ru(Lpi)) /

c(Lpi), i=1...K } ) is maximized.

Let me take the example of below topology,

  100(max reservable BW on each link)

Source                   Destination

A------------------------C

|                        |

|                        |

|                        |

|                        |

B------------------------D

LSP1 : BW 20

LSP2 : BW 20

LSP3 : BW 40

Every time a LSP is established path A-C, the RSVP-traffic flowing through
them, let’s say, is approximately 60% of the current reserved.

After each LSP is established, the output of the formula ((c(Lpi)- ru(Lpi))
/ c(Lpi))

Consider link A-C

LSP1: (20 – 12)/20

LSP2: (40 – 24)/40

LSP3: (80 – 48)/80

Always remains as 0.4.

In my opinion, if instead of using Current Reserved bandwidth, c(L) in
the above formula, if we use Maximum reservable bandwidth on link L,
denoted R(L).

Name: Maximum Reserved Under-Utilized Path (MRUP)

Description: Find a path P such that (Min {(R(Lpi)- ru(Lpi)) /

R(Lpi), i=1...K } ) is maximized.

Consider link A-C

LSP1 : (100 – 12)/100 = 0.88

LSP2 : (100 – 24)/100 = 0.76

LSP3 : (100 – 48)/100 = 0.52

This gives a much clearer reserved utilization for the link.

Also, now if the OF MRUP is used for the path computation:

LSP1 : A-C

LSP2 : A-B-D-C

LSP3 : A-C

Hence we get a more diversified path using MRUP OF.

Please let me know your opinion regarding the same.

Regards,

Avantika