PBB-TE (802.1Qay PBB (802.1ah) Connectivity Fault (RFC 3031) Management Provider Bridges (802.1ad) VLAN (802.1Q) Ethernet (LAN) 1970s-1990s 2001-2005 2010+ Figure 7.18 CE evolution 7.4.2.3.7.1 MPLS-TP Characteristics The key characteristics of MPLS-TP are as follows [28]: Connection oriented. PWE3 pseudowire architecture. Provides same quality OAM features that are available in SONET/SDH. Physical layer agnostic (can run over Ethernet, SONET/SDH, OTN, WDM, etc.). Service-agnostic (can carry L1, L2, and L3 services). Use of GMPLS3 control plane for service provisioning and management. 7.4.2.3.7.2 MPLS-TP Overview MPLS-TP will use underlying MPLS forwarding mechanism. MPLS-TP will be developed on extending current pseudo-wire and LSP 4 (Label Switched Paths) solutions. MPLS-TP defines concept of MPLS- TP Alert Label (TAL) and Generic Associated Channel (GE ACH). TAL and GE-ACH are the two key components of OAM mechanisms. Alert label (label 14) defined in T-MPLS was reused from MPLS but it is not possible at this point hence MPLS-TP defines TAL (label 13) was envisioned instead. GE ACH will be used as a control channel which will be used to carry OAM and other control messages. T-MPLS has certain similarities with MPLS, such as use of labels and method of forwarding, but there are also differences. Among these, the primary difference is in the manner in which labels are used: while MPLS does label switching along multiple paths for a single flow and assumes bidirectional paths, TMPLS/MPLS-TP neither supports bidirectional paths or spreading the flow into several disjoint paths. T-MPLS/MPLSTP simply sets up one tunnel from source to destination (no stopping at the penultimate (second to last) node as in the case of MPLS). This tunnel, due to its deterministic nature of bandwidth and delay, provides a carrier class solution for transport of any payload (not just Ethernet) [29]. GMPLS is a dynamic control plane that can be applied to both packet switched and optical networks. 4 A Label Switched Path (LSP) is a path th