@article {3038, title = {Providing and verifying advanced IP services in hierarchical DiffServ networks - the case of GEANT}, journal = {Journal of Communication Systems, Wiley InterScience}, year = {2004}, pages = { 321 - 336}, abstract = {The differentiated services (DiffServ) framework is widely proposed as an efficient method for providing advanced IP services to large-scale networks, with QoS requirements. However, the provisioning of such services in production networks has proved to be more difficult than initially expected, in defining, setting and verifying appropriate Service Level Agreements (SLAs). GEANT, the Gigabit core pan-European research network, on a pilot basis introduced {\textquoteleft}Premium IP{\textquoteright} service, offering bounded delay and negligible packet loss to the European National Research \& Education Networks (NRENs) that it interconnects. However, large scale provisioning of this new service requires the definition of efficient interaction procedures between administrative domains involved and methods for SLA monitoring. This paper focuses on these issues and presents the experience acquired from the early experiments in GEANT, as an example of hierarchical Gigabit multi-domain environment, enabled with QoS provisioning to its constituent NRENs. This model scales more efficiently than the common peering Internet Service provider (ISP) commercial paradigm. Finally, we outline other options that promise QoS, such as Layer 2 VPNs in MPLS backbones, with non-standard (yet) mechanisms.}, author = {Christos Bouras and Afroditi Sevasti and A Liakopoulos and B Maglaris} }