Subject: [ippm] I-D ACTION:draft-ietf-ippm-bw-capacity-01.txt

From: [email-masked]
Date: Fri, 11 Nov 2005 15:50:01 -0500

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the IP Performance Metrics Working Group of the IETF.

	Title		: Defining Network Capacity
	Author(s)	: P. Chimento, J. Ishac
	Filename	: draft-ietf-ippm-bw-capacity-01.txt
	Pages		: 16
	Date		: 2005-11-11
	
Measuring capacity is a task that sounds simple, but in reality can
   be quite complex.  In addition, the lack of a unified nomenclature on
   this subject makes it increasingly difficult to properly build, test,
   and use techniques and tools built around these constructs.  This
   document provides definitions for the terms 'Capacity' and 'Available
   Capacity' related to IP traffic traveling between a source and
   destination in an IP network.  By doing so, we hope to build a common
   language that can be used when discussing and analyzing a diverse set
   of current and future estimation techniques.

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---

From: Joseph Ishac <[email-masked]>
Date: Fri, 11 Nov 2005 20:01:01 -0500

A new version of the capacity draft is available.

With this revision we have hopefully addressed all of the comments and
outstanding issues that were raised.  So, please take a moment to read
the draft and comment.

For those who were familiar with the previous version(s) a changelog follows:

Major changes from draft-ietf-ippm-bw-capacity-00

* The paragraphs surrounding the definition of IP layer bits were
  cleaned up.
* Better explanation of the interval times
* Made the interval a little clearer in the definitions.
* Added a section to specify a correctly formed packet
* Section added for BTC

Thanks!

-Joseph

---

From: "Patrik Arlos" <[email-masked]>
Date: Mon, 21 Nov 2005 13:52:09 +0100

Hi Joseph, Philip: 

In your definition of Nominal Physical Link Capacity (NPLC), you state that
it 'does not vary with time'. I do not think that it holds for wireless
channels. The argument being that the signal interference can change quite
rapidly, and at some point the sending speed has to be altered to compensate
for the interference. Cf. the different speeds of 802.11 or UMTS. However,
from the following discussion, the time varying behaviour of the NPLC is not
interesting. Since it only acts as the upper limit of the capacity, i.e.,
C(t,t+I)<NomCap (t,t+I). Furthermore, if the desire is to define capacity at
the IP layer the behaviour of the underlying technologies should not matter.

How about using 'hop' instead of 'link' in the IP layer terminology? A hop
involves a sender, a receiver and a set of link layer links. I do think that
is would resolve some other problems as well, for instance when virtual LAN
(VLAN) is used a 'hop' might cover multiple physical links, without any IP
layer treatment. I.e., from the IP layer's viewpoint there is a direct
connection to the destination.

For instance, let S and D denote the IP address of the sending and receiving
entities, respectively. The path between S and D is described as sequence of
hops. A hop covers all communication entities involved in the transfer of an
IP packet between two logically adjacent entities. Via the number of hops
(hop count) we can identify the number of networks that has to be traversed
in order to reach D from S. The number of hops is only dependent on the IP
layer configuration, not the underlying configurations. For example, if S
and D are located on the same IP network, then hop count is zero. A hop
count of one would mean that the IP traffic passes one router to reach the
destination. 

/Patrik

Patrik Arlos

SE/BTH/Sweden

+46 (0)455-385654

> -----Original Message-----

> From: [email-masked] [mailto:[email-masked]] On Behalf Of

> Joseph Ishac

> Sent: den 12 november 2005 02:01

> To: [email-masked]

> Subject: Re: [ippm] I-D ACTION:draft-ietf-ippm-bw-capacity-01.txt

> For those who were familiar with the previous version(s) a changelog

> follows: