Research on Wavelength Switched
Optical Networks for the Next 10
years ICT
Session 1 of PhD Academy
Oct. 05, 2011
Xin WANG
TANAKA Lab.
Waseda University
Outline
1.
Background
2.
GMPLS based WSON Architecture
3.
Control Plane in WSON
4.
Research Cases
2
1. Background
Optical network evaluation: opaque  translucent  transparent;
•
• Limitations: physical layer impairments(PLIs), technology and expenditures;
• Study network scenario: translucent WDM networks.
•
•
Transparency
Wavelength Switched Optical Network (WSON, RFC 6163);
Generalized Multi-Protocol Label Switching (GMPLS, RFC 3945);
At several sites, the
signal will undergo
an O/E/O conversion
At each site, the optical
signal will undergo an
O/E/O conversion
O/E/O
O/E/O
O/E/O
O/E/O
WDM router
O/E/O
O/E/O
Optical link (fibres)
O/E/O
O/E/O
Fig. 1 Optical network evaluation
Optical-electronic-optical
Time
3
2. GMPLS based WSON Architecture
•
…
…
Drop
O/E
…
…
…
…
3R Module Pool
O/E
…
MUX
OXC
…
Data plane
…
OSPF-TE;
RSVP-TE;
LMP, etc.
Routing, wavelength
assignment and 3R
regenerator allocation;
• Centralized vs. Distributed.
…
•
•
•
•
…
GMPLS optical control plane:
DMUX
•
MUX/DMUX;
OXC;
O/E transponders;
3R (Reamplifying, Reshaping and
Retiming) regenerator pool:
3R regenerator shown in Fig. 3.
…
•
•
•
•
Optical Control Plane
MUX
Data plane includes:
Management Plane
DMUX
•
Optical control plane locates
between management plane
and data plane，i.e, Fig. 2.
Add
Fig. 2 WSON operating layer
Fig. 3 O/E/O 3R regenerator model
4
3. Control Plane – centralized mode
Central Node
(PCE)
RWA
TED
Advantages:
• Simple;
• No conflict.
Drawbacks:
• No scalability;
• Require real
time state info.
Extended OSPF-TE
OCP
OCP
Node 1
Node 2
RSVP-TE
……
OCP
Node n
Fig. 5 Centralized control plane
5
3. Control Plane – distributed mode
(PCE)
RWA
TED
Advantages:
• Scalable;
• Robust;
Drawbacks:
• Conflict;
• Contention;
• Set-up delay.
OCP
Node 1
OCP
Node 2
Extended RSVP-TE
……
Extended OSPF-TE
OCP
Node n
Fig. 6 Distributed control plane
6
4. Research Cases
Centralized control plane
Combined
(Separated)
RWA
Routing +
Distributed
WA
Connection request will be served one by one in a
central node (NMS) relying on a complete
knowledge of the network.
Advantages:
• Optimizing resource usage;
• No resource assignment conflict;
• Easily being manipulated;
Drawbacks:
• Processing load in the central node would be
very high;
• Highly relying on the accurate network state
information (hard to maintain in large networks);
• Weak scalability and poor survivability;
• Impracticable in realistic large-scale network;
Distributed control plane
RWA calculation is conducted before signalling.
Calculation can be performed either via a path
computing element (PCE) or via a local CSPF
Advantages:
• Calculation of RWA can be either centralized or
decentralized;
• Scalable and survivable;
Drawbacks:
• Highly relying on the accurate network state
information (hard to maintain in large networks);
• High control traffic volume (e.g. OSPF);
• Resource assignment conflict and reservation
contention;
• Poor performance.
Each node provides a candidate path for a connection
demand and the wavelength assignment is performed
along this path in a distributed manner via signalling.
Advantages:
• Calculation of RWA is decentralized;
• Mitigate the influence of inaccurate network state
information
• Scalable and survivable;
Drawbacks:
• Lightpath set-up delay
• Signalling packet also increase control traffic volume;
• Resource assignment conflict and reservation
contention;
Table. 1 RWA processing scheme in WSON
7
Thank you!
Q&A
8