[Nsi-wg] NSI motivation/context

[Guy Roberts]

Below is a re-worked motivation/context
Guy
Network Service Interface
Motivation and Context



In recent years adoption of control plane protocols have allowed network operators to support fast automated creation of connection-oriented circuits within their networks.  These services are being rolled out in research and education networks to support the demanding connectivity requirements of big science projects such as grids.  With increasing international cooperation, the demand for international circuits is also rising requiring inter-operator co-ordination of these services.



Existing providers implement a wide range of technologies (Ethernet, SDH, OTN etc) to deliver connection oriented services.  These connections are built using a variety of control or management planes (MPLS, GMPLS, TMN etc).  Current operational practices typically require cross-network connections to be created by each network separately and the interconnect point to be mutually agreed by manual negotiation between operators.  This process of add-hoc manual creation has proven to be slow and expensive and acts as an inhibitor to service uptake.



While it is possible for all providers to cooperate and run a common control plane (such as GMPLS) the process of agreement between providers and the timescales required to implement this common control plane is likely to be prohibitive.  For this reason, an application-to-provider network service interface is proposed by the NSI-WG.  This should be implemented in a way that allows operators to exchange connection requests while retaining their existing network technology and their exiting control plane.   The interface aims to be able to be rapidly deployed compared to, for example, wide scale deployment of GMPLS eNNI.   The solution should also be readily scalable and support web service based to support network virtualization in grid network service environments.



NSI
The Network Service Interface (NSI) standard defines an interface that will allow a connection oriented service that spans multiple networks to be requested.  The requestor may be either another network operator or an application such as grid middleware. This network service setup requires configuration, monitoring and orchestration of network resources across each network under particular agreements and policies.
The Network Service Interface assumes the existence, in each network, of a Network Service Agent (NSA) which is capable of controlling a set of network resources - for transmission equipment this might typically be a network management system operating in accordance with TMN principles. The NSA is able to authorize, reserve, schedule, instantiate, monitor, teardown, negotiate, and log its resources and the connections which are created from the resources.  The Network Service Interface is then defined as being the interface between a Requestor Agent (for example grid middleware) and the NSA.

To support reservation of resources across multiple operators, the NSI interface must support the following messaging services:

 *   Topology exchange service
 *   Path computation service
 *   Signalling service
 *   Authorization and Authentication service

While the NSI definition does not mandate any standards for implementation of these services within a network operator domain, a standardised exchange of information over the NSI interface is required.   So for example domain internal path computation may be performed by the operators preferred method (such as PCE), however the results of this computation should be exchanged is standardised in NSI.

The NSI interface is intended to be implemented either:

 1.  Between an application layer (for example grid middleware) and an operator service plane layer.
 2.  Between operator service plane layers.


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Guy  Roberts,  Ph.D

Network Engineering & Planning
DANTE - www.dante.net<http://www.dante.net/>
Tel: +44 (0)1223 371 316
City House, 126-130 Hills Road
Cambridge, CB2 1PQ, UK
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