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- To: email@example.com
- Subject: questions
- From: Rob Coltun <firstname.lastname@example.org>
- Date: Wed, 20 Jun 2001 13:18:06 -0700
- Delivery-date: Wed, 20 Jun 2001 10:14:48 -0700
- Envelope-to: email@example.com
1. In determining the specific requirements, the design team should
define the concepts "survivability", "restoration", "protection",
"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?)
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).
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
(ii) If both layers provide survivability features, what are the
requirements to coordinate these mechanisms?
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?)
When such oundaries 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?
1. What are the requirements for policy support during
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?
1. What are the quantitative requirements (e.g., latency) for completing
restoration under different protection modes (for both local and
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?