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CCAMP WG - http://www.ietf.org/internet-drafts/draft-pbh-packet-optical-escalation-01.txt
NAME OF I-D:
http://www.ietf.org/internet-drafts/draft-pbh-packet-optical-escalation-01.txt
SUMMARY
This document describes two well-known escalation strategies referred
to as bottom-up and top-down strategies. However, in the context of
the current GMPLS developments, when considering packet-over–optical
networks, a third method can be developed the hybrid strategy which
which is a combination of a top-down and bottom-up approaches.
We start with an initial description of general restoration related
aspects, analyze various restoration schemes and focus on efficient
inter-working between packet and optical layer restoration mechanisms.
This analysis results in potential control protocols enhancements
required to achieve the fast-restoration targets.
RELATED DOCUMENTS
http://www.ietf.org/internet-drafts/draft-ietf-many-gmpls-architecture-00.txt
http://www.ietf.org/internet-drafts/draft-ietf-mpls-generalized-cr-ldp-03.txt
http://www.ietf.org/internet-drafts/draft-ietf-mpls-generalized-rsvp-te-03.txt
http://www.ietf.org/internet-drafts/draft-ietf-mpls-generalized-signaling-04.txt
http://www.ietf.org/internet-drafts/draft-many-optical-restoration-00.txt
http://www.ietf.org/internet-drafts/draft-ghani-optical-rings-01.txt
http://www.ietf.org/internet-drafts/draft-papadimitriou-optical-rings.txt
WHERE DOES IT FIT IN THE PICTURE OF THE SUB-IP WORK
It fits in the CCAMP WG - Control C
WHY IS IT TARGETED AT THIS WG
In the context of packet-over-optical networks, also known Packet–
over-Wavelength (POW) networks, the restoration approach depends on
the service being offered. Restoration can happen either at the
packet layer, the optical layer or both. In the latter case,
coordination between the various restoration schemes is required to
maximize efficiency and to avoid conflicting actions occurring at
different layers. The scope of this memo is to define and extend the
proposed mechanisms for a packet over all-optical network where
packet capable interfaces are only available on O/E/O capable
devices.
JUSTIFICATION
Today multi-layer restoration aspects are not covered by the current
CCAMP or TE WG charters. Since GMPLS - Peer model introduce the
concept of an integrated control-plane in a unified service model
inter-layer mechanism for traffic-engineering and network survivability
can be considered.
In this document, we describe two well-known escalation strategies
referred to as bottom-up and top-down strategies in order to introduce
a third strategy: the hybrid multi-layer restoration strategy applied
to packet-over-optical networks.
When considering packet-over–optical networks, the bottom-up strategy
is the most “used” since coming directly from “digital” transmission
TDM networks. However, along with the current developments in
transmission technologies where all-optical channels replaces SDH/Sonet
circuits (and SDH/Sonet is only use as a framing procedure), switching
capabilities are now concentrated on two layers: the packet and the
optical layer.
>From these considerations, since now the “circuits” are to be considered
as huge pipes, the multiplexing capabilities are concentrated at the
packet layer (i.e. using LSP multiplexing). Depending on the LSP
multiplexing rate and the available discrete bit-rate at the optical
layer, a top-down approach can be considered when for instance the
optical layer does not provide restoration mechanisms or signal
quality monitoring capabilities so that the re-routing must be
performed at the upper-layer.
Nevertheless, it doesn’t seem to be the most efficient way to
perform restoration within the network since for instance, a huge
number of packet LSPs can be multiplexed into a 40Gbps lambda-LSP.
Consequently, if we consider (and when the optical layer enables it)
simultaneous restoration at optical and packet layer then, advantages
of both layers can be combined in order to achieve a faster restoration
comparing to one achieved when using a top-down approach.
This hybrid process can be considered as the best method when for
instance, some of the packet-LSP granularity is comparable to the
one of the optical channel into which they are multiplexed while
the majority of the packet-LSP granularity is very small compared to
one of the optical channel into which they are multiplexed but using
a comparable number of lambda-LSP. In the first case a “top-down”
approach can be considered while in the second case a “bottom-up”
approach can be efficiently considered. Therefore, when a physical
layer failure occurs implying to consider simultaneously both scenarios
then an hybrid packet-optical restoration mechanism is the most
suitable.
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