This Technical Report is one of a series of publications that provides an overview of IP-based enterprise
communication involving Corporate telecommunication Networks (CNs) (also known as enterprise networks)
and in particular Next Generation Corporate Networks (NGCN). The series particularly focuses on session
level communication based on the Session Initiation Protocol (SIP) [6], with an emphasis on inter-domain
communication. This includes communication between parts of the same enterprise (on dedicated
infrastructures and/or hosted), between enterprises and between enterprises and public networks. Particular
consideration is given to Next Generation Networks (NGN) as public networks and as providers of hosted
enterprise capabilities. Key technical issues are investigated, current standardisation work and gaps in this
area are identified, and a number of requirements are stated. Among other uses, this series of publications
can act as a reference for other standardisation bodies working in this field.