[Fwd: questions]

[Jim Boyle <jimpb@nc.rr.com>]

I was probably a little off base in implying that these questions will 
generate an omnibus of requirements.  They are good questions, but I 
still do wonder if they will provide concrete and prioritized 
requirements (including identifying non-starters).

Here I've modified Rob's questions to incorporate some of my thoughts 
(delimited with a <Jim> </Jim>) and Avri's comments( <Avri> </Avri>).
I hit Avri's multi-provider, but not the fate-sharing (though it is 
important in context of protection) nor the pre-established -v- event 
driven.  I think the latter is more a fallout of ability of approaches 
to meet functional requirements (e.g. all connections restored in 45ms).

Sorry I didn't have time to spell check - off to the beach.  Talk to you 
all Monday PM.

regards,

Jim

-------- Original Message --------
Subject: questions
Date: Wed, 20 Jun 2001 13:18:06 -0700
From: Rob Coltun <rcoltun@redback.com>
To: tewg-dt@ops.ietf.org

A. Definitions

1. In determining the specific requirements, the design team should
precisely
    define  the concepts "survivability", "restoration", "protection",
    "protection switching",
    "recovery", "re-routing" etc. and their relations. This would enable the
    requirements doc to describe precisely which of these will be addressed.

    In the following, the term "restoration" is used to indicate the broad
    set of policies and mechanisms used to ensure survivability.


B. Network types and protection modes

1. What is the scope of the requirements with regard to the types
    of networks covered? Specifically,  are the following in scope:

    -  Restoration of connections in mesh optical networks
       (opaque or transparent)
    -  Restoration of connections in hybrid mesh-ring networks
    -  Restoration of LSPs in MPLS networks (composed of LSRs overlaid on a
       transport network, e.g., optical)

    (What other network types should be covered?)
	<Jim>
	(is commonality of approach, or optimization of approach more important?)
	</Jim>

2.  What are the requirements with regard to
     the protection modes to be supported in each network type covered?
     (Examples of protection modes
     include 1+1, M:N, shared mesh, UPSR, BLSR, newly defined modes
     such as P-cycles, etc.)

3.  What are the requirements on local span (i.e., link by link)
     protection and end-to-end protection, and the interaction between them?
     E.g.: what should be the granularity of connections for
     each type (single connection, bundle of connections, etc).

C. Hierarchy

1. Vertical (between two network layers):
    What are the requirements for the interaction between restoration
    procedures across two network layers,
    when these features are offered in both layers?
    (Example, MPLS network realized over pt-to-pt
    optical connections.) Under such a case,
    (i) Are there any criteria to choose which layer should provide
        protection?
    (ii) If both layers provide survivability features, what are the
        requirements to coordinate these mechanisms?
<Jim>
    (iii) How is lack of current functionality of cross-layer 
cooridnation currently hampering operations?
     (iv) Would the benefits be worth additional complexity associated 
with routing isolation (e.g. VPN, areas), security, address isolation 
and policy / authentication processes?
</Jim>


2. Horizontal (between two areas or administrative subdivisions within
    the same network layer):
    What are the criteria that trigger the creation of protocol or
    administrative boundaries pertaining to restoration? (e.g., scalability?
    multi-vendor interoperability? what are the practical issues?)
<Avri> multi-provider? </Avri>
<Jim> should multi-vendor necessitate hierarchical seperation? </Jim>

    When such boundaries are defined,
    (i) What are the requirements on how protection/restoration is
        performed end-to-end across such boundaries?
    (ii) If different restoration mechanisms are implemented on two sides of
       a boundary, what are the requirements on their interaction?

<Jim>
   What is the primary driver of  horizontal hierarchy?
    - functionality (e.g. metro -v- backbone)
    - routing scalability
    - signalling scalability
    - current network architecture, trying to layer on TE ontop of 
already hiearchical network architecture
    - routing and signalling

   For signalling scalability, is it
    - managability
    - processing/state of network
    - edge-to-edge N^2 type issue

    For routing scalability, is it
    - processing/state of network
    - are you flat and want to go hierarchical, or already hierarchical?
    - data or TDM application?
</Jim>

D. Policy

1. What are the requirements for policy support during
protection/restoration,
    e.g., restoration priority, preemption, etc.

E. Signaling Mechanisms

1. What are the requirements on the signaling transport mechanism
    (e.g., in-band over sonet/sdh overhead bytes, out-of-band over
    an IP network, etc.) used to communicate restoration protocol
    messages between network elements. What are the bandwidth and
    other requirements on the signaling channels?

2. What are the requirements on fault detection/localization mechanisms
     (which is the prelude to performing restoration procedures)
     in the case of opaque and transparent optical networks?
     What are the requirements in the case of MPLS restoration?

3. What are the requirements on signaling protocols to be used in
    restoration procedures (e.g., high priority processing, security, etc).

4. Are there any requirements on the operation of restoration protocols?

E. Quantitative

1. What are the quantitative requirements (e.g., latency) for completing
    restoration under different protection modes (for both local and
end-to-end
    protection)?

F. Management

1. What information should be measured/maintained by the control plane at
    each network element pertaining to restoration events?

2. What are the requirements for the correlation between control plane
    and data plane failures from the restoration point of view?