ITU-T G.8011. - Ethernet virtual private line service (EVPL) - shared-bandwidth E-LINE service (i.e. statistical multiplexing of user traffic) (e.g. VPWS). E-LAN - multipoint-to-multipoint Ethernet service: - EPLAN - dedicated-bandwidth E-LAN service. - EVPLAN - shared-bandwidth E-LAN service (e.g. VPLS). E-TREE (or Ethernet Virtual Private Tree) - point to multipoint Ethernet service. To support slicing using MPLS the identifying fields can be either the 20-bit label (previously called LLSPs) or the 3-bit traffic class field (ELSPs). Using MPLS-TE one can guarantee performance (hard QoS) through resource reservation using RSVP-TE (RFC 3209), or by mapping each slice to a physical channel (e.g. wavelength or fiber). Furthermore, since slicing requires supporting multiple logically self-contained networks over the same transport network (3GPP TS 28.530), the management systems of the mobile (described in Section 6.5) and transport networks need to function in harmony to eco- nomically attain the performance objectives of each slice instance. This will require cross network interconnection, alignment functions and security mechanisms, which have yet to be standardized. 6.6.5.4.5 Resilience High availability mechanisms such as rapid restoration, rings, and FRER are discussed above in the context of the physical layer. In this section we focus on the impact on higher layer protocols. APS requires careful protocol work, planning, and proper configuration. Historically solutions for both linear protection (i.e. protection over general topologies) and ring protection have been employed. 6.6 Transport Network Ethernet, due to its lacking a time-to-live field, disallows rings. Two solution strategies have been proposed: Open loop ring protection methods (e.g. G.8032), wherein at any instant in time one link in the ring is blocked, and upon a single link failure the protocol assures that the failed link is the blocked one. Closed loop ring protection methods, whereby some other mechanism, e.g. adding a TTL field, avoids lo