Side_1_360

• To provide a framework for real-time provi-
  sioning of optical channels in automatically
  switched optical networks;


• To foster the expedited development and
  deployment of a new class of versatile OXCs;


• To allow the use of uniform semantics for net-
  work management and operation control and
  hybrid networks consisting of OXCs and label
  switching routers (LSRs).

A particular emphasis may be placed on the

support of various protection and restoration

schemes.

3.3 Traffic Engineering Topics

The main components of the MPLS TE control

plane model include (ref. [Jens01]):

• Discovery of resources;


• Dissemination of state information (similar to
  abilities of routing protocols);


• Selection of paths (similar to constraint-based
  routing);


• Management of paths (label distribution, path
  placement, path maintenance, path revoca-
  tion).

Several of the capabilities can be derived from

MPLS by replacing “traffic trunk” with “optical

channel”.

3.4 Optical Transport Networks

A high level architectural model is presented in

[ID_MPLSoptte]. The modelling aspects have

been grouped into a horizontal dimension and a

vertical dimension. The horizontal dimension

refers to special requirements for an Optical

Transport Network (OTN) including considera-

tions such as:

• Type of OTN state information should be
  discovered and disseminated to support path
  selection for optical channels (e.g. attenuation,
  dispersion);


• Infrastructure used for propagating the control
  information;


• Computing constrained paths fulfilling perfor-
  mance and policy requirements;


• Domain specific requirements for establishing
  optical channels and enhancements for MPLS
  signalling protocols for addressing these
  requirements.

The vertical dimension includes concerns when

porting MPLS control plane software onto an

OXC. A potential architecture of an OXC is also

given in [ID_MPLSoptte], see Figure 12.

Looking closer into an OTN as described by

ITU-T, it should be noted that it is itself divided

into layers, including:

• an optical channel (OCh) layer network;


• an optical multiplex section (OMS) layer net-
  work;


• an optical transmission section (OTS) layer
  network.

4 Mobility

4.1 Mobile Routing – Mobile IP

As users and hosts may be moving around and

still want to be connected to a network as if they

were “at home”, the network has to be capable

of supporting this. One issue is mobile routing

where a mobile user (mobile node) may move

while still having a predefined home location

(where a Home Agent, HA, is located).

Mobility support is described in [RFC2002]. The

assumptions made are:

• No additional constraints on the assignment of
  IP addresses;


• The mobile user will not change points of
  attachment very frequently, say less frequent
  than once per second;

Figure 11 Organising
“labels” hierarchically

IP packet packet-switch

time-division

multiplex

lambda

switch

fibre

switch

Figure 12 Potential OXC
system architecture, adapted
from [ID_MPLSoptte]

MPLS control plane

Control adaptation

OXC switch-controller

OXC switch fabric

OXC data plane

OXC with MPLS control plane