The ability for a node to specify a forwarding path, other 
than the normal shortest path, that a particular packet 
will traverse, benefits a number of network functions, 
for example:

o    Some types of network virtualization, including multi-
     topology networks and the partitioning of network 
     resources for VPNs
o    Network path and node protection such as fast re-route
o    Network programmability
o    New OAM techniques
o    Simplification and reduction of network signalling 
     components
o    Load balancing and traffic engineering

Source-based routing mechanisms have previously been 
specified for network protocols, but have not seen 
widespread adoption other than in MPLS traffic engineering. 
These applications may require greater flexibility and 
per packet source imposed routing than can be achieved 
through the use of the previously defined methods.

The SPRING working group will define procedures that 
will allow a node to steer a packet along an explicit 
route. Full explicit control (through loose or strict
path specification) is gained though a network 
comprising only SPRING nodes, however SPRING must 
interoperate through loose routing in existing networks
and may find it advantageous to use loose routing.

There is an assumed trust model such that any node 
imposing an explicit route on a packet is assumed to 
be allowed to do so, however administrative and trust 
boundaries may strip explicit routes from a packet.

Initial work will focus on SPRING within in a single AS, 
however design decisions must not preclude operation 
of SPRING in across AS boundaries.

SPRING should support both centralised and distributed 
path computation.  

SPRING should both provide support for its use as 
an OAM tool in SPRING enabled networks, and the 
necessary OAM and other management tools needed to 
manage a SPRING enabled network.

SPRING should avoid modification to existing data 
planes in order to remain compatible with existing 
deployments. When a modification is necessary this 
must be undertaken in conjunction with the working 
group responsible for the definition and maintenance 
of that data plane.

Where possible, existing control and management 
protocols must be used to implement the SPRING function. 
Any modification or extension of existing architectures  
or protocols must be carried out in the working groups 
responsible for  the architectures or protocols being 
modified in co-ordination with  this working group, 
but may be done in this working group after  agreement 
with all the relevant WG chairs and responsible Area
Directors.

The SPRING working group is chartered for the following 
list of items:

o Identification and evaluation of use cases for SPRING . 
  These use cases must include a definition of the 
  data plane for the environment in which they are to be 
  deployed.

 o Definition of any new data plane encodings and 
   procedures, required to implement the use cases. Such 
   procedures must include the necessary security 
   considerations.

 o Definition of any new control plane mechanism 
   needed to enable the use cases. Modification to 
   existing control plane protocols must be done in 
   conjunction with the responsible IETF working group.

o Definition of management  plane mechanism needed to 
  manage and operate a SPRING enabled network.

 
The working group will develop the following documents:

o One or more documents describing SPRING use cases.

o Specification of SPRING architecture.

o Specification of any required new procedures to support 
  SPRING use cases.

o One or more data plane extension requirements documents, 
  including documenting the impact on existing deployments
  of the existing data plane.

o One or more control protocol extensions requirements 
  documents.

o Document interworking and co-existence between the 
  new procedures and the existing signalling and routing 
  protocols.

o Inter-operability reports pertaining to the implementation 
  of extensions supporting SPRING.

o Inter-operability reports pertaining to the implementation of extensions
  supporting SPRING.