Subject: RE: Comments on Applicability Statement

From: "Lai, Wai S (Waisum), ALSVC" <[email-masked]>
Date: Wed, 4 Apr 2001 07:56:34 -0400

Jim,
   Please clarify the intent of the MPLS-TE Applicability Statement.
Is it to document implementation experience only (in which case, the
Statement would be no more than a TEIMP), or to include also what is
needed for proper operation?
   Regarding your comment on point (A), what you rephrased reflects
today's environment.  Given that RSVP-TE and CR-LDP are intended to be
functionally similar, as described in their respective Applicability
Statements, please explain the significance or the relevance.
   Regarding your comment on point (D), admission control takes many
forms.  For example, it is performed today by administrative means in
static provisioning in SP environments.  Moreover, work done on RSVP
in Intserv has demonstrated the need for such a mechanism.  So, again,
the Applicability Statement should include what is needed for proper
operation of TE.
Thanks, Wai Sum.

-----Original Message-----
From: Jim Boyle [mailto:[email-masked]]
Sent: Tuesday, April 03, 2001 10:28 AM
To: Lai, Wai S (Waisum), ALSVC
Cc: [email-masked]
Subject: Re: Comments on Applicability Statement

On Mon, 2 Apr 2001, Lai, Wai S (Waisum), ALSVC wrote:

> The "Applicability Statement for Traffic Engineering with MPLS" draft is
an
> excellent summary of MPLS TE issues.  To broaden its coverage, I propose
> below some further points (A, B, C, D) for consideration.  Your feedback
> would be appreciated.
> Thanks, Wai Sum.
> 
> -----------------------------------------------------------------------
> 
> (A) In Section 1, 2nd paragraph, add the following after the 2nd sentence:
> 
> Another signaling protocol that performs similar functions is CR-LDP, the
> applicability of which is described in
> G. Ash, M.K. Girish, E. Gray, B. Jamoussi, and G. Wright,
>    "Applicability Statement for CR-LDP", work in progress, July 2000.

In similar, do you mean that CR-LDP has been "developed and deployed in
scale, and in a multi-vendor environment", or do you mean "Another
signalling protocol that intends to perform similar functions is CR-LDP
[CR-LDP-REF], though it hasn't been deployed in scale".

> 
> -----------------------------------------------------------------------
> 
> (B) After Sub-section 3.3, add a new Sub-section:
> 
> 3.4 Re-optimization after restoration
>  
> After a network failure, a new set of LSPs can be calculated that optimize
> the performance of the new topology. This re-optimization is complementary
> to the fast-reroute operation used to reduce packet losses during routing
> transients under network restoration.  Traffic protection can also be
> accomplished by associating a primary LSP with a set of secondary LSPs,
> hot-standby LSPs, or a combination thereof.

probably wouldn't hurt to highlight the increased role after failures.

> 
> -----------------------------------------------------------------------
> 
> (C) After Sub-section 4.2, add two new Sub-sections:
 > 

We have no section 4.2.  These are important aspects, the value of the
measurements one can get off an MPLS TE network.  But again, in order to
try to hold the line on conciseness, we need to figure out a way to touch
on that in less words.

> 4.3 Capacity
Engineering Aspects
> 
> Traffic engineering has a goal of ensuring traffic performance objectives
> for different services.  This requires that the different network elements
> be dimensioned properly to handle the expected load.  More specifically,
in
> mapping given user demands onto network resources, network dimensioning
> involves the sizing of the network elements, such as links, processors,
and
> buffers, so that performance objectives can be met at minimum cost.  Major
> inputs to the dimensioning process are cost models, characterization of
user
> demands and specification of performance objectives.
> 
> In using MPLS, dimensioning involves the assignment of resources such as
> bandwidth to a set of pre-selected LSPs for carrying traffic, and mapping
> the logical network of LSPs onto a physical network of links with capacity
> constraints.  The dimensioning process also determines the link capacity
> parameters or thresholds associated with the use of some bandwidth
> reservation scheme for service protection.  Service protection controls
the
> QoS for certain service types by restricting access to bandwidth, or by
> giving priority access to one type of traffic over another.  Such methods
> are essential, e.g., to guarantee a minimum amount of resources for flows
> with expected short duration, to improve the acceptance probability for
> flows with high bandwidth requirements, or to maintain network stability
by
> preventing performance degradation in case of a local overload.
> 
> 4.4 Network Measurement Aspects
> 
> To ensure that the QoS objectives have been met, performance measurements
> and performance monitoring are required so that real-time traffic control
> actions, or policy-based actions, can be taken.  To characterize the
traffic
> demands, traffic measurements are used to estimate the offered loads from
> different service classes and to provide forecasting of future demands for
> capacity planning purposes.  Forecasting and planning may result in
capacity
> augmentation or may lead to the introduction of new technology and
> architecture.
> 
> -----------------------------------------------------------------------
> 
> (D) In Section 5, add the following paragraph to end of the 4th paragaph:
> 
> Connection-oriented mode of operation allows the use of admission control
at
> the connection or flow level to avoid QoS degradation at the packet level.
> This is a form of preventive control to ensure that the QoS requirements
of
> different service classes can be met simultaneously, while maintaining
> network efficiency at a high level.  However, it requires proper network
> dimensioning to keep the probability for the refusal of connection/flow
> requests sufficiently low.    
> 

Is this from MPLS TE in a service provider network?  Or from experience in
ATM/FR networks or in simulations.  I'd like to keep the focus of the
applicability statement to real experience with MPLS TE in SP
environments.  I feel nervous about saying something is applicable, where
there are no war-scars to show either way that it is or not.

---

From: Jim Boyle <[email-masked]>
Date: Wed, 4 Apr 2001 07:49:59 -0600 (MDT)

Wai Sum, yes.  It should include what is needed for proper
operation.  More precisely, it should be a statement of applicability of
mpls and traffic engineering in service provider networks.  Where is it
applicable, and how.  And what are some of the gotchas and complexities
that come along as baggage.

It shouldn't, in my estimation, make comments as to how something untested
might be applicable, or highlight something tangential (such as intserv,
or operation of phone or atm networks, or even simulation results) that
might have some relevance. There is enough experience deploying traffic
engineering techniques in operational IP networks that the applicability
statement should be based on that.

What do others think?

Jim

---

From: Alan Hannan <[email-masked]>
Date: Wed, 4 Apr 2001 07:48:14 -0700

> might be applicable, or highlight something tangential (such as intserv,

 ..

> What do others think?

  Agreed.

> > [CR-LDP-REF], though it hasn't been deployed in scale".

  I posit that CR-LDP has not been deployed in scale.

  -alan