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Network architecture
tools to support
network operator
requirements
Luc Le Beller
FTR&D/DAC
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Optical World D1 - 25/04/01
Outline
Introduction and scope
Generic transport layer structure
Two examples of IP over optical network configurations
Additional architectural components
Service description
Conclusion
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Technical background
Transport network architecture is driven by the following items :
An important diversity of transport network techniques in
the core and the access : SDH, ATM, IP, MPLS, OTN, GbE
The development of control(s) plane(s) in addition to
management(s) plane(s) : from B-ISDN to ASON
A lot of different architectural models coming from the
standardisation : ITU-T, IETF, OIF
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Operator background
Transport network architecture is driven by the following items :
Dynamicity
Transport costs decreased
Monopoly era with reliable voice and LL services demand forecasts is over
Emergence of multiple new services with uncertain needs
Impact of competitors market share and network architecture options
Diversification from raw transport service
Provisioning/reconfiguration time enables differentiation from competition
Transport carriers must differentiate their services and climb on the value chain
 Bandwidth on demand (wavelengths, SDH VCs) : OSP (optical service
provider) i.e. Storm
 Modulation of quality of service (protection levels)
 VPN
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Scope
Full description of the transport network components
G.805 and derived standards, G.8080 and derived standards : very low granularity
Consistent top-down (from the service to the network) and
bottom-up (from the network to the service) description
SG 15 bottom-up approach ; SG 13 top-down approach
General interaction between transport network components
Depending on organisation structure (actors, business units)
Interaction between transport network components and other
networks and services components
Also depending on organisation structure with more actors and business units
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Outline
Introduction and scope
Generic transport layer structure
Two examples of IP over optical network configurations
Additional architectural components
Service description
Conclusion
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Generic Layer Structure
A generic layer structure for transport network, independent of the techniques, is obtained
by combination of the following criteria :
- Does the layer provide flexible connectivity (G.805 sub-network capability) or not ?
- What type of resources in the layer needs to be reserved in response to a client
request for the transport of his (characteristic) information ?
Layer(s) offering flexible connectivity and
not requiring specific resources allocation
for every sub-network is named FW
Layer(s) offering flexible connectivity and
requiring specific resources allocation for
Every sub-network is named SW/XC
Layer(s) offering point-to-point connectivity
is named PHY layer
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FW
SW/XC
PHY
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Transport Network Techniques
FW
IP
SW/XC
PHY
MPLS, ATM VP/VC,
SDH VC-X, ETH MAC,
OTN ODUk/OCh
SDH RS/MS, OTN OTS/OMS
ETH PHY, Optical Fiber
Not only physical !!
It is assumed that a G.805 client/server relationship is existing between all these layers
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One example
IP
IP
FW
a
b
ATM VP/VC
SW/XC
d
a
a
ATM VP
c
e
e
VC-4-4c
e
SDH VC-4/VC-4-4c
e
k
VC-4-4c
e
c
PHY
STM-N/WDM
k
k
STM-4
c
k
k
STM-4
Equivalent G.805 representation of
a, e, k and c client/server relationships
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Outline
Introduction and scope
Generic transport layer structure
Two examples of IP over optical network configurations
Additional architectural components
Service description
Conclusion
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IP over optical configurations
Optical Network
O3
IP Network
IP Network
O2
R6 I6
I4
R4
O1
I5
IP Network
R5
Can both IP adjacencies R4-R6 and R4-R5
coexist on the same I4 interface ?
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Concatenated versus channelised
CONCATENATED : only one
adjacency per interface
FW
IP
CHANNELISED : more than one
adjacency per interface
IP
FW
PHY
PHY
IP
STM-16/OF
SW/XC
SW/XC
IP
OTN
OTN
OTN
OTN
OF
PHY
OF
The SW/CX layer is
supporting the PHY layer !
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Outline
Introduction and scope
Generic transport layer structure
Two examples of IP over optical network configurations
Additional architectural components
Service description
Conclusion
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General processes
For the description of the services telecommunication, it is useful to structure
all the actions required to offer a service in the following (and chronologically) way :
- pre-sales (PSA)
-subscription (SCR)
- invocation (INV)
- assurance (ASU)
- billing (BIL)
This structure can also be applied to the transport network and as example
to the IP over optical configurations where the service is : creation of an
IP adjacency between routeur R4 and R5
IP Network
R6
I6
O3
O2
IP Network
I4
R4
O1
IP Network
R5
I5
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Optical Network
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Operations for conc. and chan. (1)
Operations 1 to 4 are required to create an adjacency between routers R4
and R5
CHANNELISED
CONCATENATED
PSA
1
2
-Routers
localisation
SCR
3
-Interfaces
I4 and I5
installation
4
-Create
optical
channel
-Routers
deployment
Step 4 requires a step 3 :
the same dynamics applies
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PSA
INV
1
-Routers
localisation
2
-Routers
deployment
SCR
3
-Interfaces
I4 and I5
installation
INV
4
-Create
optical
channel(s)
Step 4 can be independent of step 3 :
different dynamics can apply
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Operations for conc. and chan. (2)
Optimized procedure for the
CONCATENATED configuration
PSA
1
-Routers
localisation
2
-Routers
deployment
3
-Interfaces Ix
installation
SCR
Optimized procedure for the
CHANNELISED configuration
INV
4
-Create
opticals
channels
This requires the provisioning of
routers with the maximum capacity
of interfaces
PSA
SCR
1
-Routers
localisation
2
-Routers
deployment
3
-Interfaces
I4 and I5
installation
at maximum
bit-rate
INV
4
-Create
opticals
channels
This requires installation of
interfaces at the highest capacity
! : optimisation is considered from the IP network side
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Transport service definition at
G.805 level
1) Trail service
LIK Y1
Layer Y
TRAIL X
Layer X
A and B : access groups
or sub-networks
B
2) Sub-network
connection service
A
SNC X
Layer X
Note : trail service requires at least one sub-network connection service (except if X is a PHY layer)
Telecommunication service modelling requires other considerations :
additional transport layers, division in actors (partitioning),
control plane components, …
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Conclusion
It has been shown on a basic IP over optical configuration that a technical
choice has great impact on the global architecture.
This was made possible by a network modelisation at a low-level of
granularity, which assembles well defined elementary architectural
components.
Elementary architectural components must continue to be standardised
independently of the technology
There is no need to standardize more global architectural tools
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